METHODS AND DEVICES FOR TREATING ATRIAL FIBRILLATION

[0001] This patent application is a continuation of U.S. patent application Ser. No. 13/086,389, filed Apr. 13, 2011, which claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 61/323,796, filed Apr. 13, 2010, U.S. Provisional Patent Application No. 61/323,801, filed Apr. 13, 2010, and U.S. Provisional Patent Application No. 61/323,816, filed Apr. 13, 2010, the disclosures of each of which are hereby incorporated by reference in their entirety.

[0002] It is well documented that atrial fibrillation, either alone or as a consequence of other cardiac disease, continues to persist as the most common cardiac arrhythmia. Atrial fibrillation may be treated using several methods, including administering anti-arrhythmic medications, and chemical and/or electrical cardioversion. Ablation of cardiac tissue using surgical techniques have also been developed for atrial fibrillation, such as procedures for atrial isolation and ablation of macroreentrant circuits in the atria. For example, the MAZE III procedure creates an electrical “maze” of non-conductive tissue in the atrium that acts to prevent the ability of the atria to fibrillate by creating incisions in certain regions of atrial tissue. In some cases, the MAZE III procedure may include the electrical isolation of the pulmonary veins. While the MAZE III procedure has shown some efficacy in treating medically refractory atrial fibrillation, additional devices and methods of treatment are desirable, especially if they provide advantages over existing techniques.

[0003] Described here are devices, systems, and methods for affecting tissue within a body to form a lesion. Some systems may comprise devices having tissue-affecting elements that are configured to be positioned on opposite sides of a tissue and operated simultaneously to form a lesion in the tissue between them. Some systems may also comprise devices that guide the advancement of the tissue-affecting elements to a target tissue region, devices that locate and secure tissue, devices that provide access to the target tissue, and/or devices that may help position the tissue-affecting elements on one or more surfaces of the target tissue. The methods described here may utilize one or more of these devices, and generally comprise advancing a first tissue-affecting device to a first surface of a target tissue, advancing a second tissue-affecting device to a second surface of the target tissue, and positioning the first and second devices so that a lesion may be formed in the tissue between them. In some variations, the devices, systems, and methods described here may be used to treat atrial fibrillation by ablating fibrillating tissue from an endocardial surface and an epicardial surface of an atrium of a heart. Methods of closing, occluding, and/or removing a portion of the target tissue (e.g., the left atrial appendage) are also described.

[0004] One variation of a system for affecting tissue within a body may comprise a first device and a second corresponding device. The first and second devices may each comprise an elongate member and one or more tissue-affecting elements. The one or more tissue-affecting elements of the second device may correspond to the tissue-affecting elements of the first device. In some variations, the first device may be configured to be placed on a first surface of a target tissue, and the second device may be configured to be placed on a second surface of the target tissue, where the second surface is opposite the first surface. The first and second devices may be configured to operate the tissue-affecting elements simultaneously to form a lesion in the target tissue at least partially therebetween.

[0005] Some variations of the first and second devices may comprise one or more magnetic components. Optionally, the first and second devices may also comprise a longitudinal lumen therethrough. The first and second devices may also comprise one or more temperature sensors. In certain variations, the first and second devices may have a first delivery configuration and a second deployed configuration, where the devices are compressed in the delivery configuration and expanded in the deployed configuration.

[0006] The first and second devices may each comprise one or more pre-shaped curves in the second deployed configuration. In some variations, the pre-shaped curves may have varying radii of curvature, and/or may be spiral or funnel shaped. In some devices, the deployed configuration may comprise one or more curves in one or more planes, and may comprise a ring-structure coupled to an expandable net.

[0007] The tissue-affecting elements of the devices may affect tissue to form a lesion using any suitable mechanism. For example, the tissue-affecting elements may ablate tissue using cryogenic substances, high intensity focused ultrasound (HIFU), radiofrequency (RF) energy, lasers, heat, microwaves, and the like. Some tissue-affecting elements may ablate tissue using a combination of different mechanisms, as suitable for the target tissue.

[0008] Methods of affecting tissue in a body are also described. One variation of a method comprises advancing and positioning a first tissue-affecting device to a first surface of a target tissue, advancing and positioning a second tissue-affecting device to a second surface of a target tissue, where the second surface is opposite the first surface, positioning the first and second tissue-affecting devices so that ablation energy may pass between them, and operating both devices simultaneously to form a lesion in the target tissue. In some variations, advancing the first device may comprise inserting a curved sheath at a location beneath a sternum and advancing the first device through the sheath. Optionally, the method may comprise withdrawing the first and second tissue-affecting devices after the lesion is formed, as well as verifying and assessing the lesion using fluoroscopic, electrical impedance, and thermal imaging techniques. In some variations of the method, the tissue-affecting devices may comprise magnetic components. Tissue-affecting devices may apply a variety of ablation energies, for example, cryogenic, high intensity focused ultrasound, laser energy, radiofrequency energy, heat energy and/or microwave energy. These methods may be used to ablate tissue of the left atrium as part of a procedure to treat atrial fibrillation, but may also be used to target gastrointestinal tissue, as well as cancerous cell masses.

[0009] Methods of forming a lesion in the tissue of a left atrium are also described here. One variation of a method may comprise advancing and positioning a first tissue-affecting device in the left atrium through a puncture or access site in a left atrial appendage, advancing a second tissue-affecting device to an external wall of the left atrium, where the second device is positioned opposite to the first device, operating both devices simultaneously to form a lesion in the atrial wall between them, and isolating the left atrial appendage. Optionally, the method may also comprise positioning the first and second devices with respect to each other using one or more magnetic components, and verifying and assessing the lesion using various imaging techniques (e.g. fluoroscopic, electrical impedance, and thermal imaging techniques). In some variations, the first tissue-affecting device may be advanced over a first guide (e.g., guide wire) into the left atrium to circumscribe the base of a pulmonary vein, and the second tissue-affecting device may be advanced over a second guide (e.g., guide wire) to circumscribe the trunk of the pulmonary vein on the external atrial wall. Additionally or alternatively, the first guide wire and the first tissue-affecting device may be advanced into the left atrium to circumscribe the bases of two or more pulmonary veins, while the second guide wire and the second tissue-affecting device may be advanced over the external atrial wall to circumscribe the trunks of two or more pulmonary veins. In some variations, isolating the left atrial appendage may comprise positioning an occlusion device comprising a rounded disc with one or more grooves circumscribing the outer perimeter of the disc, wherein the disc is sized and shaped to be constrained in an ostium or base of the left atrial appendage.

[0010] Also described here are kits for affecting tissue within a body. One variation of a kit may comprise a first device with one or more tissue-affecting elements and a longitudinal lumen therethrough, where the first device has a first compressed configuration and a second expanded configuration, a second device with one or more tissue-affecting elements and a longitudinal lumen therethrough, where the first and second devices are configured to operate simultaneously to form a lesion that spans at least a portion of tissue between them. In some variations, the kit optionally comprises first and second devices as described above, where the first and second devices also comprise one or more magnetic components and/or one or more temperature sensors. In certain variations, the kit may also comprise a closure member with an elongate body and a distal snare, where the elongate body may comprise a longitudinal lumen therethrough, a piercing member that is configured to be advanced through the lumen of the elongate body, a first and second cannula, and a first and second guide wire.

[0030] The system and methods described herein may be used to affect any portion of tissue within a body to form a lesion, and/or otherwise electrically isolate a portion of tissue. For illustrative purposes, these devices and methods are described in the context of lesion formation in the tissue of the left atrium for the treatment of atrial fibrillation, and may include the closure of the left atrial appendage. For example, methods for affecting tissue to treat atrial fibrillation may comprise accessing the pericardial space of the heart, creating an access site through the left atrial appendage (LAA), advancing a tissue-affecting device intravascularly and/or through the LAA to contact an endocardial surface of the left atrium, advancing another tissue-affecting device via the pericardial space to contact an epicardial surface of the heart, and affecting tissue from either or both the endocardial and epicardial surfaces. In some variations, a LAA access/exclusion device may be used to stabilize the LAA for the advancement of devices therethrough, as well maintain hemostasis by closing and/or opening the LAA during and/or at the conclusion of the procedure. While the systems and methods disclosed here are described in the context of affecting cardiac tissue, it should be understood that these devices and methods may be used to affect a variety of tissues, such as the skin, heart, liver, etc., as well as to treat a variety of conditions, including various cardiac deficiencies, tumors, gastrointestinal deficiencies, etc.

[0031] FIG. 1 depicts a heart (100), with the cavity of the left atrium partially cut away to reveal a portion of the mitral valve (102) and pulmonary veins (104a), (104b), (104c), (104d). Both the right atrial appendage (106) and the left atrial appendage (108) are shown, located on the superior portion of the heart (100). The heart (100) is enclosed by a pericardium (not shown), which is filled with a fluid that may separate it from the heart. The fluid-filled space between the pericardium and the heart is the pericardial space. In a heart affected by atrial fibrillation, tissues associated with one or more of these anatomical structures may pulsate irregularly or asynchronously, and may cause the atrium to contract quickly and/or irregularly. Procedures for the treatment of atrial fibrillation may comprise the electrical isolation of arrhythmic cardiac tissue from other tissue regions. In some variations, devices and methods for treating atrial fibrillation may be directed towards the formation of lesions in the right atrium (e.g. in the proximity of the tricuspid valve annulus, the anterior limbus of the fossa ovalis, and/or the right atrial appendage), and/or lesions in the left atrium (e.g. in proximity of the pulmonary veins and/or LAA). For example, one variation of a method for treating atrial fibrillation in the left atrium may comprise the electrical isolation of tissue(s) at or around or within each of the pulmonary veins, and may optionally include the closure, occlusion, and/or removal of the left atrial appendage. While the devices and methods described below may be used to access, affect, and electrically isolate tissue in the left atrium, similar devices and methods may be used to treat any suitable portion(s) of the heart, e.g., the right atrium, right ventricle, left ventricle, etc.

[0032] In order to access certain portions of the heart, it may be useful to place one or guide elements in the pericardial space around the heart. Various devices may be used to provide access to the pericardial space for the placement of a guide element into the pericardial space for the advancement of subsequent devices to the heart. Some pericardial access devices may be configured to provide an access pathway from an initial access site (e.g., a sub-thoracic region, an intercostal region, etc.). For example, a pericardial access device may comprise a sheath with one or more curves, and one or more needles, guide elements, tissue-piercing elements, etc. to create a pathway through the pericardium to access the pericardial space. In some variations, the one or more needles, guide elements, tissue-piercing elements, etc. may be sized and shaped to correspond with the one or more curves in the sheath. One example of a sheath with one or more curves is shown in FIGS. 17A and 17B. As shown there, the sheath (1702) may have a curved region (1706) between the proximal portion (1704) to the distal portion (1708). The proximal portion (1704) may be connected to a proximal sheath actuator. A sheath actuator may be used to advance the sheath, e.g., along a longitudinal axis, to navigate the distal portion of the sheath, and/or may be configured to cause the curved region (1706) to bend. A cross-section of the sheath (1702) is depicted in FIG. 17B. The sheath (1702) may have one or more longitudinal lumens therethrough, for example, a wire lumen (1710) and an access device lumen (1712). Other variations of a curved or bendable sheath may have any desired number of lumens therethrough, e.g. 2, 3, 5, 8, etc. The wire lumen (1710) may be sized and shaped for passing a wire therethrough. The access lumen (1712) may be sized and shaped to pass a pericardial access device therethrough, for example, any of the access devices described above. In some variations, sheaths may have additional lumens for inserting other devices therethrough, and/or as necessary for accommodating mechanisms that may be used to control the flexion of the curved region (1706).

[0033] The curved region (1706) may have one or more pre-shaped curves, and/or may be flexible or bendable using a suitable actuating mechanism controlled by the sheath actuator at the proximal portion (1704). The curved region (1706) may serve to generally orient the sheath toward the heart upon insertion at an initial access point beneath the sternum, and/or may have a particular radius of curvature to help guide the sheath under the rib cage to the heart. In some variations, the curvature of the curved region (1706) may be locked or fixed, e.g., the curved region (1706) is first actuated to attain a desired degree of curvature, then locked to retain that desired curvature. Suitable locking mechanisms may include, for example, maintaining the tension of a wire that may be inserted through the wire lumen (1710), or immobilizing the hinge mechanisms to a desired configuration. A flexible or soft curved region may be locked into position by fixing the configuration (e.g., curvature, tension, etc.) of the wire within the wire lumen (1710). Some variations of a sheath may have a pre-shaped curve, where the radius of curvature is determined at the time of manufacture, and remains unchanged as the sheath is used. The radius of curvature of the curved region may be adjusted for sheaths that are inserted at different initial access points. For example, the radius of curvature of a curved region of a sheath to be inserted at an intercostal access site may be different from the radius of curvature of a curved region of a sheath to be inserted at a sub-thoracic access site.

[0034] The curved region (1706) may be made of a flexible or bendable material, or may be made of a substantially rigid material arranged in articulating segments that allow for the curved region (1706) to bend when actuated. The curved region (1706) may be integrally formed with the body of the sheath (1702), or may be separately formed and attached to the sheath (1702). For example, the curved region (1706) may be made of polymeric tubing and/or materials such as Pebax®, nylon, fluoropolymers (e.g., PTFE, FEP), polyethelene, Teflon®, polyethylene terephthalate (PET), Tecothane®, etc. In some variations, the curved region (806) may be made of a polymeric tube with reinforced stainless steel or nitinol. Where the curved region (1706) is made of a substantially rigid material, for example, stainless steel, nickel titanium, nitinol, cobalt alloys (e.g. nickel-cobalt, cobalt-nickel-chromium-molybdenum), and/or polymers such as PEEK, polyethylene (HDPE), polyimide, etc., the curved region may be slotted or segmented to allow bending to occur. In some variations, a curved region (1707) may have one or more slots (1705), as illustrated in FIG. 17C. In other variations, the curved region (1706) may comprise a plurality of segments, where the positioning of the segments with respect to each other is controlled by a wire or pivot mandrel. The segments may be coupled together via mechanical hinges and/or living hinges. Sheaths may also comprise multiple curved regions, where each of the curved regions may have the same or different radii of curvature. For example, one curved region may be made of a material with a selected flexibility, while another curved region may be made of a material with a different flexibility. Other curved regions may be slotted or segmented, as appropriate. Different curved regions may be separated by a straight portion of the sheath, or may be contiguous. A plurality of curved regions may help to provide additional maneuverability to navigate the distal portion of the sheath to the targeted region of the heart. Adjusting the tension on a wire through the wire lumen (1710) may alter the curvature of the curved region (1706). For example, increasing the wire tension may cause bending of the curved region (1706), while decreasing the wire tension may cause straightening of the curved region (1706).

[0035] FIG. 17D depicts one variation of a method of using the sheath (1702). The sheath (1702) may be inserted into the subject (1730) at a location beneath the sternum (1722). Prior to insertion, the sheath may be substantially straight, or may be curved, as appropriate. Once the sheath (1702) has been inserted, the curved region (1706) may be adjusted in order to bring the distal portion (1708) close to the surface of the heart (1720). For example, the distal portion (1708) may be navigated underneath the ribs (1728) towards the heart (1720). Once the distal portion (1708) of the sheath (1702) is in a desired location, e.g., an anterior and/or slightly lateral side of the heart, the curved region (1706) may be locked to retain the curvature of the curved region. The location of the distal portion (1708) may be monitored using any suitable imaging modality, for example, ultrasound, fluoroscopy, and the like. In some methods, the location of the distal portion (1708) may be monitored by tactile feedback.

[0036] An articulating sheath such as is shown and described above may be useful for accessing the heart (1720) where the abdomen (1724) of the subject (1730) may limit the angle at which the sheath (1702) may be positioned. Certain subject anatomy, such as a smaller abdomen (1724) may provide a large range of maneuverability for the sheath (1702), while a larger abdomen (1724) may limit the range of maneuverability for the sheath. Providing one or more curved regions may allow the heart to be more readily accessed where subject anatomy limits the range in which the sheath may be positioned. For example, providing one or more curved regions may help to reduce the force that may be required to position the sheath (1702), and may provide additional access paths to the heart in the event the originally planned pathway becomes unavailable.

[0037] Some methods for treating atrial fibrillation may comprise accessing an endocardial surface of the left atrium through the LAA via the pericardial space. Methods that utilize the LAA as an entry port may also comprise closing and/or opening the LAA during the procedure (e.g., to advance devices therethrough) to maintain hemostasis. Optionally, methods may also comprise excluding the LAA at the conclusion of the procedure. Such a device may be used during the procedure to stabilize the LAA so that tissue-affecting devices may be advanced through the LAA into the left atrium, and may be used to at the conclusion of the procedure to permanently close off or otherwise occlude the LAA. One example of a device that may be capable of locating, securing, manipulating, stabilizing, closing and/or excluding the LAA is depicted in FIG. 2. Closure device (200) may comprise an elongate body (202), a handle portion (204) located at a proximal portion of the elongate body (202), an extension (205) located at a distal portion of the elongate body (202), and a distal looped closure assembly (206) distally coupled to the extension (205). While the closure device disclosed below is described in the context of locating, securing, manipulating, stabilizing and/or closing the LAA, it should be understood that the closure device may be used to act on any desirable tissue.

[0038] The elongate body (202) may have any appropriate shape, for example, the elongate body may be substantially straight (as depicted in FIG. 2), or may have one or more pre-formed curves and shapes. The elongate body (202) may have a suitable cross-sectional diameter and longitudinal length to facilitate navigating the closure device (200) through the vasculature to contact the LAA (or other target tissue). The elongate body (202) may be made of one or more flexible or rigid materials, as may be suitable for navigating towards the target tissue. In some variations, the elongate body may be steerable, and comprise steering mechanisms (such as mandrels, articulating and/or living hinges, cables, etc.) that allow a user to steer the elongate body using the handle portion (204). For example, the elongate body may be made of a single integral flexible material with one or more steering mandrels embedded in the side wall of the elongate body, such that bending the mandrel(s) would cause a corresponding deflection of the elongate body, which may help steer the elongate body towards the target tissue. Alternatively or additionally, the elongate body may be made of a plurality of segments that may be connected by articulating and/or living hinges. Each of the plurality of segments may be rigid or flexible. One or more mandrels may be coupled to each of the plurality of segments, and may be used to bend and steer the elongate body towards the target tissue. The elongate body may also comprise locking mechanisms so that after the elongate body is steered to a target location, it may be locked to retain a certain configuration to maintain contact with that target location. The elongate body (202) may comprise one or more working channels (208) that extend from the proximal portion of the elongate body (202) to the distal portion of the elongate body. A variety of devices may be inserted through the working channel in order to manipulate a portion of tissue. Alternatively or additionally, the closure device (200) may be advanced over a guide element using the working channel (208).

[0039] As depicted in FIG. 2, the distal extension (205) may extend distally beyond the distal end of the elongate body (202). This may allow for additional working space as may be suitable for accessing the LAA. For example, the distal extension (205) may extend distally beyond the distal-most portion of the working channel (208) of the elongate body. The length of the distal extension (205) may be selected such that when the base of the LAA is engaged by the distal looped closure assembly (206), the tip of the LAA may be close to (e.g., in contact with) the distal-most portion of the working channel (208). This may allow devices that are advanced through the working channel (208) to directly contact and/or manipulate the tip of the LAA once it exits the working channel.

[0040] The distal extension (205) may be integrally formed with elongate body (202), or separately formed and attached to the elongate body (e.g., by welding, melding, brazing, adhesives, etc.). The distal extension (205) may be made of rigid and/or flexible materials, and may be made of the same or different materials as the elongate body. The elongate body and/or distal extension may be made of polymeric materials such as Pebax®, polyethylene, and/or other thermoplastic materials with various durometers or densities, and/or any polymers that may be tapered or graduated for varying degrees of flexibility. Additionally or alternatively, the elongate body and/or distal extension may be made of metallic materials such as nitinol, stainless steel, etc. The looped closure assembly (206), distal extension (205), elongate body (202), and/or portions thereof may comprise visualization markers, such as fluorescent markers, echogenic markers, and/or radiopaque markers, that permit the closure device to be visualized using a variety of imaging modalities. As with the elongate body (202) described above, the distal extension (205) may also be steerable. In some variations, the distal extension (205) may be steered independently from the elongate body, while in other variations, the distal extension (205) may be steered together with the elongate body. For example, a steering mandrel that may be used to steer the elongate body may also be coupled to the distal extension so that the extension may be steered in concert with the elongate body. Alternatively, there may be a first mandrel for the steering the elongate body and a second mandrel for steering the distal extension independently from the elongate body. Optionally, the distal extension may have one or more pre-shaped curves which may help to navigate the closure device (200) to a target tissue region.

[0041] In some variations, the distal extension (205) may comprise one or more lumens that may extend from the distal-most end of the extension to the proximal portion of the closure device (e.g., to the handle portion). A lumen in the distal extension may slidably retain a portion of the looped closure assembly such that the dimensions of the loop may be adjusted. For example, the lumen of the distal extension (205) may slidably retain the looped closure assembly (206), which may comprise a distal loop (203). The distal loop (203) may comprise a snare loop and a suture loop that may be releasably coupled along the circumference of the snare loop. The distal loop (203) may be made of polymeric materials such as Pebax®, and/or metallic materials, such as nitinol, and/or any elastic, malleable, deformable, flexible material. The portion of the distal loop that extends outside of the extension, i.e., the external portion of the distal loop, may be adjustable using an actuator at the proximal handle portion. Adjusting the length of the external portion of the distal loop (203) may help to snare and/or close, or release and/or open, a LAA or any anatomical protrusion. While the distal loop (203) may have the shape of a circle, it may also have other shapes, e.g., an ellipse, oval, triangle, quadrilateral, etc. In other variations, the looped closure assembly may be configured (e.g. knotted, looped, coiled, etc.) for other functions, such as locating and securing tissue. For example, the looped closure assembly may optionally comprise tissue graspers, hooks, or other such tissue engagement components that may help secure and retain a tissue portion.

[0042] The looped closure assembly (206) may have an expanded (e.g., open) configuration, and a tightened (e.g., closed) configuration, where the circumference of the loop in the tightened configuration is smaller than in the expanded configuration. For example, a distal loop with an elliptical shape in the open configuration may have a length along the minor axis (e.g., the shortest dimension of the ellipse) from about 15 mm to about 50 mm, e.g., about 20 mm, and a length along the major axis (e.g., the longest dimension of the ellipse) from about 15 mm to about 50 mm, e.g., about 40 mm. A distal loop in the closed configuration may have a diameter equivalent to about 5 mm to about 10 mm, e.g., 6 mm. The looped closure assembly (206) may be tightened or cinched to encircle and secure the LAA, and in some variations, may be able to close the LAA after it has been secured, if desirable. Optionally, the looped closure assembly (206) may be releasably coupled to the closure device such that after the LAA is encircled and secured by the distal loop (203), a knot or locking element may be deployed to retain the tension on the distal loop, which may then be released from the closure device. For example, a looped closure assembly may have a releasable suture loop that is tightened over the LAA and then released from the closure device. The tension on the suture loop may be locked so that the looped closure assembly may be proximally withdrawn from the suture loop. Optional closure elements, such as sutures, graspers, clips, staples, and the like, may be included with the looped closure assembly to help close the LAA. For example, additional closure features, e.g., graspers or staples, may be included at the tip of distal extension (205) that may act to secure the LAA. A looped closure assembly may also comprise one or more energy sources distributed along the length of the distal loop, where the energy sources may be used to ablate tissue or induce tissue fusion. Alternatively or additionally, the looped closure assembly (206) may be actuated in conjunction with other devices advanced through the working channel (208) to secure and position the closure device with respect to the LAA.

[0043] Various types of devices may be inserted through the working channel (208) of the elongate body (202) as may be desirable. In some variations, a vacuum device may be inserted through working channel (208), while in other variations, alignment devices, guide elements, grasper devices, visualization devices, ablation devices, and/or cutting devices may be inserted through the working channel. Variations of the closure device may have a multi-lumen elongate body, where each lumen may be a working channel for one or more different devices. For example, the elongate body (202) may have multiple working channels for the insertion of different devices. Additionally or alternatively, the elongate body (202) may comprise working channels for the injection of liquid or gas fluids, as well as the application of therapeutic and/or chemical agents. The working channel (208) may have any cross-sectional shape as may be suitable for the devices to be inserted therethrough, for example, circular, rectangular, etc.

[0044] The closure device (200) may comprise mechanisms to control the bending and/or steering of the elongate body, as well as adjust the length of the distal loop that extends outside of the distal extension. For example, these functions may be controlled by levers and/or knobs at the handle portion (204). The handle portion (204) may comprise a housing (214), a loop actuator (212), and a working channel actuator (210). The housing (214) may enclose at least a portion of the actuators that control the use of the elongate body, the looped closure assembly, and the device in the working channel of the elongate body. For example, loop actuator (212) may regulate the tension on the distal loop of the looped closure assembly, and control the circumference of the external portion of the distal loop, e.g. decrease it to encircle and/or close the LAA, and increase it to release the LAA. In some variations, the loop actuator (212) may be a slider configured to adjust the circumference of the distal loop (203). In variations where the distal loop comprises a releasable suture loop, the loop actuator may also comprise a fob that initially couples the suture loop with the closure device and may be pulled to release the suture loop from the closure device. The working channel actuator (210) may comprise one or more buttons, sliders, levers, knobs, and the like that are configured regulate the operation of the device(s) in the working channel(s) of elongate body (202). For instance, the working channel actuator (210) may be a grasper actuator, and/or vacuum actuator. Optionally, handle portion (204) may also comprise one or more buttons, sliders, levers, and/or knobs that may be used to navigate the LAA access device through the vasculature to access the LAA, for example, by rotating, pulling, pushing, bending, or otherwise manipulating steering mandrels. Other features of a closure device and methods of use are described in U.S. patent application Ser. No. 12/055,213 (published as U.S. Pub. No. 2008/0243183 A1), which is hereby incorporated by reference in its entirety. Another example of a closure device and methods of use are described in U.S. patent application Ser. No. 12/752,873, entitled “Tissue Ligation Devices and Controls Therefor,” filed Apr. 1, 2010, which is hereby incorporated by reference in its entirety.

[0045] As described above, a variety of devices with different functions may be inserted through the working channel(s) of the elongate body of a closure device to secure and/or otherwise manipulate a portion of tissue. In procedures where access to an internal tissue structure may be desired (e.g. accessing a lumen of a hollow organ or vessel), an access device may be inserted through the working channel of the closure device after the closure device has been advanced at or near the target tissue (e.g., by advancing the closure device over a guide element). Access devices may create a way for the internal portion of a tissue to be accessed from outside the tissue. In some variations, access devices may create an incision, puncture, and/or opening, etc., which may be dilated to allow access to devices larger than the initial opening. Optionally, some variations of an access device may also comprise a guide wire that may be advanced into the created access site. One example of such a device is shown in FIGS. 3A and 3B. FIG. 3A shows individual components of one variation of an access device that may be used to access a LAA or other tissue, and FIG. 3B shows the access device of FIG. 3A fully assembled. In this variation, LAA access device (300) comprises an access wire (302), a piercing wire (304), and an actuator portion (306). The access wire (302) may comprise a lumen (303) therethrough, where the lumen (303) may be sized and shaped for the passage of a piercing element therethrough, e.g. the piercing wire (304). The access wire (302) may be made of a metal alloy or one or more polymers that have mechanical properties suitable for threading the LAA access device (300) in the working lumen of a LAA stabilizing device and for guiding the piercing element. The access wire (302) may be made of a variety of materials, including but not limited to nitinol, stainless steel, as well as polymeric materials such as polyethylene, polypropylene and the like. The piercing wire (304) may be threaded through the lumen (303) of the access wire (302), and may comprise a piercing tip (308) at the distal portion. The piercing tip (308) may be used to create a puncture through the LAA. Optionally, the piercing wire (304) may comprise a lumen therethrough for the insertion of other devices, such as a catheter, guide wire, suture, and/or may be used for the infusion of fluids (e.g. gas or liquid fluids). In some variations, the piercing tip (308) may be a needle that is attached to the distal portion of the piercing wire (304). The piercing tip (308) may be separately or integrally formed with the piercing wire (304), and may have a lumen therethrough. The proximal portion of piercing wire (304) may be coupled with the actuator portion (306). The actuator portion (306) may be used to advance and/or withdraw and/or steer and/or rotate the piercing wire (304), and may also be used to maneuver the access wire (302) to access the LAA or other target tissue. The actuator portion (306) may be manual or mechanized, and may contain ergonomic features as appropriate, as well as electrical/mechanical interfaces to receive and execute instructions from a computing device or microcontroller. For example, the actuator portion (306) may be made of a metal alloy and/or one or more polymers that may be shaped to have an ergonomic geometry. The actuator portion (306) may be made of any materials that possess sufficient rigidity, flexibility, durability, etc., to engage and control the mechanisms driving the use of the closure device (200).

[0046] Another example of a device that may be advanced through the working channel(s) of the elongate body of a closure device is a tissue-affecting device. Devices that affect tissue may generally comprise one or more tissue-affecting elements, arranged in various patterns. In some variations, two or more tissue-affecting devices may be positioned along a target tissue, and used to affect the tissue in a desired pattern, where the tissue-affecting elements may be operated simultaneously or sequentially. In some variations, the two or more tissue-affecting devices may be placed across each other on opposite sides of tissue such that the tissue between them is affected. One example of a tissue-affecting device is an ablation device. Ablation devices may be provided for procedures that aim to ablate a portion of tissue that is abnormal, for example, cancerous tissue, or arrhythmic cardiac tissue. While affecting tissue by ablation is described in detail here, tissue may be affected in other ways, including by excision, occlusion, manipulation and the like. As described below, an ablation device may be used to ablate fibrillating atrial tissue, which may help to prevent the conduction of the irregular or asynchronous pulses in one tissue region to another tissue region.

[0047] In some variations, ablation devices may be used to create a lesion in the fibrillating atrial tissue. For the treatment of atrial fibrillation, one or more tissue-affecting devices, such as ablation devices, may be positioned on the endocardial surface and/or the epicardial surface of the left atrium. One example of an endocardial ablation device that may be inserted through a closure device is shown in FIG. 4. Endocardial ablation device (400) may comprise an elongate body (402), a handle portion (404), one or more ablation source(s) (406), and an ablation array (408). The elongate body (402) may be sized and shaped to be inserted through a working channel of a closure device, or any suitable guide cannula or sheath. The elongate body (402) may comprise one or more lumens therethrough, where the lumens may be configured to pass devices or fluids from the proximal handle portion (404) to the ablation array (408) at the elongate body distal portion. The elongate body may have any number of pre-formed curves for ease of navigation to the target tissue, and may optionally be flexible and/or steerable. While the elongate body (402) may be one continuous segment, other variations of an elongate body may be made of multiple articulating segments, and may be made of one or more flexible and/or rigid materials. In some variations, the elongate body may be steerable via a mechanism in handle portion (404), and as previously described for the closure device. In variations where the elongate body is passed through a portion of a closure device, the curvature and steerability of the elongate body (402) may correspond to the curvature and steerability of the closure device. This may help to inform a practitioner of the orientation of the endocardial ablation device with respect to the orientation of the closure device.

[0048] As shown in FIG. 4, the ablation array (408) may be located at the distal portion of elongate body (402). An ablation array may comprise one or more tissue-affecting elements that may be used for ablating and/or otherwise forming a lesion in tissue. For example, the ablation array (408) may comprise magnets (410) and ablation elements (412) that may be arranged, for example, along pre-formed curves or loops of the ablation array (408). The elongate body may also comprise magnets. The magnets may be of any suitable type. For example, the magnets may be rare-earth, electro-activated, or a multi-alloy (e.g. iron, boron, neodymium) magnets. The magnets may also have any suitable size or shape. More generally, the distal portion of an elongate body may have any open-shape or closed-shape geometry, and the magnetic and/or ablation elements may be arranged along the elongate body, ablation array, and/or on a structure at least partially enclosed within the perimeter of a shaped distal portion of the elongate body. In some variations, the ablation elements may themselves be magnetic. There may be any number of magnets (410) having any suitable configuration(s) or pattern(s), placed at any suitable location on the ablation array. For example, the magnets (410) may be arranged in a straight or curved line along the curvature of the ablation array (408), as shown in FIG. 4. Magnets may also be arranged along a length and a width of ablation array. There may be any number of ablation elements (412) as may be suitable to help ensure that sufficient ablation coverage of the target area is provided. For example, there may be 1, 2, 3, 5, 10, 12, 20, etc. ablation elements. In general, ablation elements may be utilize any mechanism and be in any form that conveys the ablation energy/medium to the target tissue. For example, cryo-ablation elements may comprise conduits that may circulate a cryogenic substance in conductive proximity to the target tissue. Ablation elements may be electrodes that ablate tissue via radiation or heat energy. Alternatively or additionally, ablation elements may be outlets or ports that infuse substances that cause necrosis or apoptosis. For example, ablation elements may ablate tissue using one or more methods, such as cryo-ablation, heat ablation, high intensity focused ultrasound (HIFU) ablation, radiofrequency (RF) ablation, laser ablation, or combinations of the listed methods and/or any method that causes necrotic or apoptotic cell and/or tissue death. Some ablation arrays may comprise two or more different types of ablation elements, e.g., 2, 3, or 4 types of ablation elements. In some variations, an ablation array may comprise both RF and cryo-ablation elements. In some variations, an ablation array may comprise RF electrodes and HIFU electrodes. In still other variations, an ablation array may comprise laser emitters and RF electrodes. In some variations, an ablation array may comprise HIFU electrodes, RF electrodes, and cryo-ablation elements. The different types of ablation elements on an ablation array may be activated simultaneously and/or sequentially in the course of ablating tissue. Alternatively or additionally, ablation elements may be sharp elements, e.g. needles, that excise, cut, or pierce tissue, or any combination of the above. For example, an endocardial ablation device may comprise electrode ablation elements and needle ablation elements.

[0049] The shape of the ablation array (408) as shown in FIG. 4 is semi-circular, which may be suitable for circumscribing and ablating around a vascular structure, such as a pulmonary vein, however, other variations of ablation arrays may have other shapes. For example, an ablation array may have a planar structure with a length and a width, with ablation elements arranged along both the length and the width. An ablation array may also be a one-dimensional array, e.g., a linear structure, where the ablation elements are arranged linearly therealong. Indeed, ablation arrays may be any shape suitable for accessing and contacting the target tissue. For example, the semi-circular shape of ablation array (408) may be suited for circumscribing vascular structures, such as veins or arteries, and may be configured to create circular ablation patterns. Ablation arrays may also have a tapered region that may be helpful in accessing and contacting in the lumen of tubular structures, e.g., the inner lumen of a vein. In some variations, an ablation array may have a narrow undeployed configuration and an expanded deployed configuration. For example, an ablation array may be constrained in a sheath for delivery, and may expand into the deployed configuration by removing the sheath. In another variation, a curved ablation array may be retained in a straight configuration by a straightening mandrel for delivery, and may be expanded into the curved deployed configuration by removing the mandrel. Other variations will be described in detail below.

[0050] The ablation array (408) may be made from a flexible or shape-memory material, such that it may be advanced to the target tissue in a substantially straight configuration, and may be deployed and contacted to tissue in a curved configuration. In some variations, the ablation array is made of a different material from the remainder of the ablation device (400), and may have different mechanical properties. For example, the proximal portion (405) of the elongate body may be made of a first material, while the distal portion (407) and/or the ablation array may be made of a second material. Examples of materials that may be suitable for the proximal portion (405) and/or the distal portion (407) of the elongate body may include metal alloys such as nickel titanium alloy, stainless steel, and/or any polymers, such as polyethylene, polyurethane, polypropylene, polytetrafluoroethylene, polyimide, etc., and/or any combinations thereof. In some variations, an ablation array may be integrally formed with the proximal portion of the ablation device, or may be attached via an articulating hinge. The ablation array may also be attached by other mechanical mechanisms, such as a living hinge, pivot joint, ball joint, etc, which may allow the ablation array to move with respect to the proximal portion of the ablation device (e.g., with two or more degrees of freedom).

[0051] The handle portion (404) located at the proximal end of elongate body may comprise actuating elements that control the movement and/or action of the elongate body and ablation array. In some variations where endocardial ablation device (400) is manually operated, the handle (400) may be ergonomic, while in other variations where the device is mechanically/electrically operated, handle (400) may comprise an interface to receive and execute instructions from a computing device. The handle portion (404) may comprise an ablation array actuator (414), which may be used to regulate application of ablation energy/substances to the ablation array to the target tissue (e.g. frequency, duty cycle, magnitude/amplitude, etc.). Additionally, the handle portion (404) may comprise an actuating mechanism that controls the movement (e.g., bending, flexing, etc.) and position of elongate body (402). The handle portion (404) may also comprise an interface to the ablation source(s) (406), and provide a conduit or conduction pathway from the ablation source(s) (406) to the ablation array. For example, the ablation source (406) may comprise a reservoir of cryogenic substances (e.g., for cryo-ablation), which may be transported through a lumen in the elongate body (402) to the ablation array. Alternatively or additionally, the ablation source (406) may comprise a source of radioactive substances (e.g., radioactive seeds or fluids), and/or a light beam source (e.g., for laser ablation), and/or an ultrasound source (e.g., for HIFU ablation), and/or a radiofrequency source, and the like, which may be delivered or transmitted from the handle portion to the ablation array. In some variations, different ablation sources may be used together in the same ablation device.

[0052] Depending on the tissue to be ablated and the desired ablation pattern (e.g. lesion geometry and size) desired, a second ablation device may be provided, where the second ablation device corresponds to the first ablation device. A second ablation device may increase the tissue ablation area and/or may otherwise alter the ablation characteristics of the first ablation device (e.g. by constructive or destructive interference). For the purposes of ablating tissue of a left atrium, a second ablation device may be provided to help ensure that the lesion formed by ablating tissue spans at least portion of tissue that is between them. In the treatment of atrial fibrillation it may be desirable to electrically isolate the fibrillating tissue from other tissues. In some variations, the formation of a lesion that spans the entire thickness of the atrial wall (e.g., from the endocardial surface to the epicardial surface) using one or more ablation devices may improve the electrical isolation of a portion of the atrial wall from other portions of the heart. Accordingly, in some variations, ablation devices may be placed on opposite sides of a tissue wall such that a lesion that spans a substantial portion of the tissue wall between the ablation devices may be formed. In some variations, positioning a first ablation device on an interior wall (endocardial surface) of the left atrium, and positioning a second ablation device on an exterior wall (epicardial surface) of the left atrium opposite to the first ablation device, may help form a lesion that spans at least a portion of the tissue between the first and second ablation devices. FIG. 5 illustrates one variation of an epicardial ablation device (500) that may be used with an endocardial ablation device to form a lesion in the left atrium. The epicardial ablation device (500) may comprise an elongate body (502), handle portion (504), ablation source (506), and an ablation array (508). As shown in FIG. 5, the ablation array (508) may be located at the distal portion of elongate body (502). The ablation array (508) may comprise magnets (510) and ablation elements (512) which may correspond to the magnets (410) and ablation elements (412) of the endocardial ablation device (400). The magnets of the epicardial and endocardial ablation devices attract each other when the ablation arrays are placed on opposite sides of tissue, which may act to align the epicardial and endocardial ablation devices. For example, the magnets (510) may be positioned on the epicardial ablation array (508) such that they may be aligned with the magnets (410) of the endocardial ablation array (408), e.g. magnets (510) may correspond to, or be mirror images of magnets (410). As with the magnets, the ablation elements (512) may correspond to, or be mirror images of the ablation elements (412), or they may be interlaced between the ablation elements (412). In some variations, the alignment and attraction of the magnets may position the endocardial and epicardial ablation devices such that the ablation elements of the ablation devices are aligned across from each other. The shape of the ablation array (508) as shown in FIG. 5 is semi-circular, however, other variations of ablation arrays may have any shape as may be suitable for accessing and contacting the target tissue. In some variations, the shape of ablation array (508) may be a mirror image, or complementary image, of the endocardial ablation array (408). For example, the semi-circular shape of the ablation array (508) may be suited for circumscribing vascular structures, such as veins or arteries. Other variations will be described in detail below. The ablation array (508) may be made from a flexible or shape-memory material, such that it may be advanced to the target tissue in a substantially straight configuration, and may be deployed and contacted to tissue in a curved configuration. For example, ablation array may be advanced to, and contacted with, an external wall of a vascular structure, e.g. artery, vein, heart chamber, and/or atrial appendage. The ablation elements of the endocardial array and the epicardial array may be in communication with each other, so that they may apply ablation energy in a concerted or programmed fashion.

[0053] The handle portion (504) located at the proximal end of elongate body may comprise actuating elements that control the movement and/or action of the elongate body and ablation array. In some variations where the endocardial ablation device (500) is manually operated, the handle (500) may be ergonomic, while in other variations where the device is mechanically/electrically operated, the handle (500) may comprise an interface to receive and execute instructions from a computing device. The handle portion (504) may comprise an ablation array actuator (514), which may be used to regulate application of ablation energy/substances to the ablation array to the target tissue (e.g. frequency, duty cycle, magnitude/amplitude, etc.). In some variations, the handle portion (504) may be in communication with the handle portion (404) of the endocardial ablation device (400), such that ablation energy from both ablation devices may be applied in-phase or out-of-phase to form a desired ablation wavefront and/or profile. Additionally, the handle portion (504) may comprise an actuating mechanism that controls the movement and position of elongate body (502). The handle portion (504) may also comprise an interface to ablation source(s) (506), and provide a conduit or conduction pathway from the ablation source(s) (506) to the ablation array. For example, the ablation source (506) may comprise a reservoir of cryogenic substances (e.g., for cryo-ablation), which may be transported through a lumen in the elongate body (502) to the ablation array. Alternatively or additionally, the ablation source (506) may comprise a source of radioactive substances (e.g., radioactive seeds or fluids), and/or a light beam source (e.g., for laser ablation), and/or an ultrasound source (e.g., for HIFU′ ablation), and/or a radiofrequency source, and the like, which may be delivered or transmitted from the handle portion to the ablation array. In some variations, different ablation sources may be used together in the same ablation device.

[0054] While the ablation devices depicted and described in FIGS. 4 and 5 are shown as having a semi-circular shape, ablation arrays may have other geometries. Ablation and/or other tissue-affecting arrays may have a variety of geometries and sizes as appropriate to accommodate and contact the target anatomical structure. For instance, ablation arrays with various geometries may be suitable for contacting and ablating tissue, especially vascular or cardiac tissue. Several variations of ablation arrays are shown in FIGS. 6A-6F. A side view and front view of a spiral ablation array (600) inserted in the opening of a vascular structure (603) (e.g. pulmonary vein) is shown in FIGS. 6A and 6B, respectively. As shown there, the spiral ablation array (600) may be coupled to the distal portion of an elongate body (602), where ablation elements (604) and magnetic elements (606) are arranged throughout the curves of the array (600) such that they may contact the walls of the vascular structure (603). FIGS. 6C and 6D depict a side view and a front view of a woven ablation array (610), respectively. The ablation array (610) may be attached at the distal portion of an elongate body (612), and may comprise a woven portion (615) and a rim (617) located along a distal perimeter edge of the woven portion. Ablation elements (614) and/or magnetic elements (616) may be arranged throughout the array, for example, along the rim (617) and/or on various locations on the woven portion (615). The size and shape of the woven portion (615) may be configured to position the ablation elements (614) and the magnetic elements (616) in order to accommodate the geometry of the target tissue (613), e.g., where the expanded size and shape of the woven portion may be bent, shaped, molded or otherwise constrained by the geometry of the target tissue. The woven portion (615) may be used as an ablation conduit or array, and may be arranged to be in proximity to target ablation tissue. Alternatively or additionally, the woven portion (615) may help stabilize the array (610) during ablation without occluding the pulmonary vein. The woven portion (615) may be constructed from various fibers, where the density of the weave may be adjusted according to the degree of perfusion desired. The fibers of the woven portion may be made of polypropylene, polyurethane, polyethylene, polytetrafluoroethylene, as well as metal alloys such as stainless steel and/or nickel titanium alloy. The woven portion may be self-expanding or mechanically expanded to fill the lumen or orifice of the vascular structure, and may be adjusted according to the size of the vascular structure. In some variations, the woven portion may be made of a shape-memory material so that the woven array (610) may have a compressed delivery configuration and an expanded deployed configuration. The size of the woven portion may be adjusted to ablate anatomical structures with dimensions of about 8.0 mm to about 30 mm, or about 12.0 mm to about 18.0 mm. Another variation of an ablation array (620) is shown in FIGS. 6E and 6F. As shown there, a tapered spiral ablation array (620) may be coupled to the distal portion of an elongate body (622), where ablation elements and/or magnetic elements may be arranged throughout the tapered spiral ablation array (620). The tapered spiral ablation array (620) may comprise a single continuous flexible backbone that is wound around the elongate body (622). Ablation elements may be distributed along the length of the backbone. In some variations, the backbone of the spiral ablation array (620) may be a wire that is electrically conductive, and may itself be capable of ablating tissue without additional ablation elements. The spiral ablation array (620) may have a first collapsed configuration shown in FIG. 6E, where the ablation array may be closely wound around the distal portion of the elongate body (622), e.g., with a tight radius of curvature. The narrow profile of the array in the collapsed configuration may help navigate the array atraumatically through narrow anatomical structures, and may also be inserted into folded or creased tissue structures. The ablation array (620) may be retained in its collapsed delivery configuration by a sheath that may be slidably disposed over the array (not shown), and/or by retaining tension on the backbone. FIG. 6F depicts a second expanded configuration of the tapered spiral ablation array (620), where removing the sheath and/or reducing the tension on the backbone of the spiral ablation array (620) may allow the backbone to loosen the radius of curvature such that the profile of the array expands. In some variations, expanding the ablation array may act to dilate a narrow tissue structure, e.g., open a folded or creased tissue structure, enlarge a tissue lumen or aperture for the insertion of additional devices, etc. In some variations, the ablation array (620) may help to maintain perfusion during ablation, and may be an alignment reference point for epicardial elements at various locations along the pulmonary veins. The ablation and magnetic elements may be arranged in any of the previously described configurations, and may be arranged to help stabilize the ablation device during the ablation procedure.

[0055] Any of the ablation arrays described above may optionally comprise one or more temperature sensors. Temperature sensors may be used to measure the ablation energy that has been applied to a tissue, and may be used to evaluate the degree to which tissue is ablated. The measurement of temperature changes in the tissue during the application of ablation energy may be used to regulate the duration, power, and/or frequency of the ablation energy (e.g., by providing feedback information to the ablation array and/or ablation array controllers). Monitoring the temperature of the tissue during ablation may also help prevent excessive or harmful damage to peripheral tissues. The one or more temperature sensors may be thermocouples, thermsistors, thermal resistive sensors (RTD), and the like. One example of an ablation array with temperature sensors is depicted in FIG. 6G. Ablation array (630) may comprise an ablation array substrate or housing (634), one or more ablation elements (not shown), one or more alignment magnets (638) and one or more atraumatic temperature sensors (636) on the tissue-facing surface of the ablation array. The alignment magnets (638), temperature sensors (636), and ablation elements may be arranged in any suitable configuration on the tissue-facing surface of the ablation array, for example, the alignment magnets (638) may be arranged such that the ablation elements of two ablation arrays positioned on opposite sides of a tissue may attract each other to align the ablation elements of one ablation array to the other. The atraumatic temperature sensors (636) may be pressed into the tissue (632) without puncturing or piercing it to measure the temperature of the tissue. Another example of an ablation array with temperature sensors is depicted in FIG. 6H. Ablation array (640) may comprise an ablation array substrate or housing (644), one or more ablation elements (not shown), one or more alignment magnets (648) and one or more sharp temperature sensors (646) on the tissue-facing surface of the ablation array. The alignment magnets (648), temperature sensors (646), and ablation elements may be arranged in any suitable configuration on the tissue-facing surface of the ablation array, as previously described. The sharp temperature sensors (646) may be inserted into tissue (642) to measure the temperature of the tissue at a certain depth from the surface of the tissue (642). In some variations, the sharp temperature sensors (646) may pierce or puncture the tissue (642) in order to gain access to deeper tissue regions. The sharp temperature sensors (646) may also have a length that corresponds to the thickness of the tissue, and in some cases, may penetrate through the entire length of the tissue. Temperature sensors that penetrate through substantially the entire thickness of the tissue may provide temperature data across the entire span of the tissue, which may provide an indication of the uniformity of the tissue ablation, as well as provide information about the temperature gradient across the tissue. This may help improve the accuracy of the tissue temperature measurement that is fed back to the ablation array and/or ablation array controllers.

[0056] In the variations depicted in FIGS. 6G and 6H, the alignment magnets and temperature sensors are located adjacent to each other, however, in other variations, the alignment magnets and temperature sensors may be incorporated together in one location. This may help to reduce the overall size of the ablation array, which may reduce the profile of the array for ease of delivery to the target tissue site. For example, an ablation array may have alignment magnets that have a lumen sized and shaped for encapsulating a temperature sensor. FIG. 6I depicts a regions of one example of an ablation array (650) comprising a housing (654), a temperature sensor (656) and an alignment magnet (658) encapsulating the temperature sensor. The alignment magnet (658) may comprise a lumen (657) that is sized and shaped for the temperature sensor (656). The temperature sensor (656) (which may be an atraumatic or tissue-piercing or sharp temperature sensor) may protrude from the lumen (657), or may be flush with the opening of the lumen (657). In other variations, an ablation array may comprise one or more ablation elements that each comprise a lumen such that a temperature sensor may be encapsulated in the lumen. In still other variations, an ablation array may comprise ablation elements, alignment magnets, and/or temperature sensors that may be retracted into a housing of the ablation array. For example, during delivery of the ablation array to the target tissue site, the ablation elements, alignment magnets, and/or temperature sensors may be in a first retracted configuration, such that the profile of the ablation array is narrow. After the ablation array has been generally positioned at the target tissue site, the ablation elements, alignment magnets, and/or temperature sensors may be a second protracted configuration, where the ablation elements, alignment magnets, and/or temperature sensors are capable of contacting the target tissue for alignment, ablation, and/or measurement of temperature.

[0057] As described previously, some methods may include steps to help maintain hemostasis in the course of the procedure for the treatment of atrial fibrillation. For example, in procedures where access to an endocardial surface of the heart is gained using the LAA as a port, it may be desirable to close and/or exclude the LAA to maintain hemostasis and/or help prevent thrombosis. In some variations, a procedure for the treatment of atrial fibrillation may also include the temporary or permanent closure, and/or occlusion, and/or removal of the left atrial appendage. FIG. 7 illustrates one variation of an occlusion device (700) that may be used with the devices and methods described here. The occlusion device (700) may comprise an elongate body (702), an insert port (704) at a proximal portion of the elongate body, and an expandable member (706) at a distal portion of the elongate body. The elongate body (702) may have one or more lumens, for example, a guide wire lumen (708) sized and shaped for passing a guide wire therethrough. The elongate body (702) as shown in FIG. 7 may also comprise one or more side apertures (710) and imaging markers (712). Any number of side apertures (710) may be provided for infusion of any fluid substance, such as a contrast agent or pharmacological agent (e.g., heparin, antibacterial agent, etc.). The imaging markers (712) may be radiopaque or echogenic, etc., as appropriate for the imaging modality used to monitor the position of the occlusion device (700).

[0058] The elongate body (702) may be made from one or more rigid and/or flexible materials. In some variations, the elongate body (702) may be steerable. An insert port may comprise one or more apertures for the insertion of fluids or devices through the elongate body (702). For example, the insert port (704) may comprise a guide wire aperture (714) and a fluid lumen (716). The guide wire aperture (714) and the fluid lumen (716) may each have independent lumens that may merge into one lumen at a bifurcation (717) of the insert port (704), or may each have separate lumens in the elongate body (702). The guide wire aperture (714) may be continuous with the guide wire lumen (708), and the fluid lumen (716) may be continuous with a cavity of the expandable member (706), such that the introduction of fluid into or out of the fluid lumen (716) may expand or constrict the expandable member. Optionally, the insert port (704) may also comprise actuation mechanisms for navigating and adjusting the shape of the elongate body (702), as well as control the motion of a guide wire, and the expansion of the expandable member (706).

[0059] The expandable member (706) may be any structure that comprises a first small profile and a second larger profile, for example, a balloon or an articulating polygonal structure, e.g. rectangular prism or tetrahedron, and the like. The expandable member (706) may be sized and shaped to fit within the guide wire lumen (208) of the closure device (200) so that it may be advanced and/or withdrawn through the lumen (208). In some variations, the expandable element (706) may have a first collapsed configuration, and a second expanded configuration. For example, the rounded expandable element (706) shown in FIG. 7 may have a diameter of about 15 mm to about 30 mm, e.g., 20 mm. The expandable member may be made of various materials, including polymeric and/or metallic materials. Examples of polymers that may be used in an expandable member may include materials such as latex, silicone, polyisoprene, polyethelene. Example of metals and/or metallic alloys that may be used with an expandable member may include nitinol, stainless steel, titanium and the like. The expandable member may be configured to either self expand or be mechanically expanded by an actuator. For example, the expandable member (706) may be transitioned from the small profile to the larger profile by introducing positive pressure or by a mechanical actuation. In some variations, a balloon expandable member may be urged into the larger configuration by applying positive fluid (gas or liquid) pressure into the lumen of the balloon. The expandable member may have any shape and size as appropriate for the target tissue. For example, a round expandable balloon may be used to occlude a vascular structure, such as a vein or an atrial appendage, e.g. LAA.

[0060] Another variation of a device that may be used for occluding the LAA is depicted in FIGS. 18A and 18B. As shown there, an occlusion device (1820) may comprise grooves (1822) in its deployed configuration. In some variations, the closure device may be deployed and positioned at the anatomical ostium of a left atrial appendage (1800). However, the occlusion device (1820) may be positioned at any desired location in the heart. The occlusion device (1820) may have a collapsed delivery configuration, which may enable it to be enclosed within a catheter or sheath and advanced through the vasculature (e.g., from a retrograde approach, or an antegrade transseptal approach) or through a port in the LAA. The occlusion device (1820) may be deployed into its expanded configuration after it is positioned at or near the ostium of the LAA. In some variations, the occlusion device may be a rounded plate or disc comprising one or more grooves circumscribing the outer perimeter. Grooves (1822) may be configured to interfit with a closure element (1810) (e.g., suture loop or snare loop) of a closure device as the circumference of the closure element is reduced, as shown in FIG. 18B. The occlusion device (1820) may be sized according to the desired degree of closure of the left atrial appendage (1800). Once the closure element (1810) has been secured and decoupled from the rest of the closure device (e.g., by cutting or detaching at a breakaway point), the occlusion device (1820) may be reverted to its collapsed configuration and withdrawn from the ostium of the left atrial appendage (1800). The devices and methods described above for closing and/or excluding the left atrial appendage may be included at the conclusion of a procedure that uses the left atrial appendage as an access site. This may be a more expedient method of closing a heart access site than other conventional methods, such as suture stitching, which may be substantially more time-consuming.

[0061] The above-described devices may be used to secure, ablate, and excise a portion of tissue to help alleviate the symptoms of atrial fibrillation. For example, the devices above may be used to secure a LAA, ablate atrial tissue in the proximity of the LAA and the pulmonary veins, and to close, and/or occlude, and/or remove the LAA. While the description below provides methods of securing, ablating, and excising tissue of the left atrium and/or LAA, it should be understood that the methods may be used to perform similar procedures on the right atrium, as well as other vascular structures or organs. Similar methods may also be used to secure, ablate, and excise tissues and/or organs that have one or more cavities therethrough, e.g. stomach, intestine, bladder, etc., for a variety of indications.

[0062] Methods for ablating tissue for the treatment of atrial fibrillation may generally comprise accessing targeted cardiac tissue regions, advancing ablation arrays to the targeted tissue regions, ablating the tissue regions, and withdrawing the ablation arrays once the desired degree of tissue ablation has been attained. Additionally, some methods may include the closure of the left and/or right atrial appendages, which may help reduce the risk of thrombosis and may help maintain hemostasis. Some variations of methods for tissue ablation may comprise ablating the tissue from an endocardial surface, an epicardial surface, or both. Ablation devices may access an endocardial surface of the left atrium intravascularly, and/or through the LAA via the pericardial space. Once the one or more ablation devices have been placed on the endocardial and/or epicardial surface(s), the ablation devices may be activated sequentially and/or simultaneously to achieve the desired degree of tissue ablation. Ablation array activation sequences may be repeated as may be desirable, and may comprise applying ablation energy pulses (from either or both of the endocardial and epicardial ablation arrays) of varying duration, frequency, duty cycle, power, intensity, etc. The ablation array(s) may be re-positioned to ablate tissue at various desired locations. Once all the desired tissue regions have been ablated, the ablation arrays may be withdrawn. In variations where the LAA is used to access the endocardial surface on the left atrium, the LAA may be closed and/or excluded.

[0063] One variation of a method that may be used to electrically isolate tissue in the left atrium and/or LAA is depicted as a flowchart in FIG. 8A. Method (800) may be used to ablate tissue from both epicardial and endocardial surfaces using surgical, intravascular and/or other minimally invasive techniques (e.g., percutaneous, small incisions or ports), and may be used in stopped heart or beating heart procedures. The method (800) may comprise gaining access to the pericardial space (802), for example, using the access devices described above. Optionally, a device may be used to locate and stabilize the LAA (804), for example, the closure device (200) as described above and shown in FIG. 2. Once access into the pericardial space and to the LAA has been established, a device may be used to enter the LAA (806), for example, by creating a puncture in the LAA. Additional devices and methods of using the LAA as an access port to deliver devices into the heart (e.g., to contact and/or affect an endocardial surface of the heart) are described in U.S. Provisional Patent Application No. 61/323,816 filed Apr. 13, 2010, which was previously incorporated by reference in its entirety, and U.S. patent application Ser. No. 13/086,390 entitled “Methods and Devices for Accessing and Delivering Devices to a Heart,” filed Apr. 13, 2011, which is hereby incorporated by reference in its entirety. Various tissue regions in the left atrium (e.g., atrial wall tissue, tissue at or around the base of the pulmonary veins, tissue within the pulmonary veins, etc.) may be accessed from an endocardial side (810). Devices may be introduced into the left atrium through the LAA, for example, an endocardial ablation array may be positioned and placed in the left atrium (812). An epicardial ablation array may be aligned with the endocardial ablation array (814), for example, based on the position of the corresponding magnets on the endocardial and epicardial ablation arrays. The epicardial ablation array may be introduced to the epicardial surface of the heart using the same initial access site as the endocardial ablation array, or may be introduced through a different access site. For example, the endocardial ablation array may be introduced through a right intercostal site, while the epicardial ablation array may be introduced through a left intercostal site. Alternatively, the endocardial and epicardial ablation arrays may both be introduced through a left intercostal site, for example. Additional description of access sites are described below. The endocardial and epicardial ablation arrays may be positioned in order to obtain a particular ablation pattern, after which both ablation arrays may be activated (816). For example, the endocardial ablation array may circumscribe the base of the pulmonary veins, while the epicardial ablation array may circumscribe the trunk of the pulmonary veins. After the desired tissue regions have been ablated, the ablation devices may be removed (818), and the LAA may be occluded, closed, and/or removed (820). Once the LAA has been decoupled from the remainder of the left atrium, all devices may be retracted from the surgical site (822).

[0064] As described previously, the endocardial side of the left atrium may be accessed intravascularly and/or from the LAA via the pericardial space. The access path into the left atrium may be selected based on the targeted anatomical features in the left atrium such that the path length of the catheter and/or ablation devices may be reduced. The access path may also be selected to reduce the maneuvering, manipulating, bending, torquing, etc. that may be required to position the catheter and/or devices at the targeted tissue site in the left atrium. For example, an endocardial ablation device may access the left atrium using either an intravascular retrograde approach or an antegrade transseptal approach. Entering the left atrium via an intravascular antegrade transseptal approach may allow access to the left pulmonary veins while reducing the maneuvering, manipulating, bending, torquing, etc. of the distal portion of the device. Entering the left atrium via an intravascular retrograde approach may allow access to the right and left pulmonary veins while reducing the maneuvering, manipulating, bending, torquing, etc. of the distal portion of the device. Alternatively or additionally, entering the left atrium through the LAA via a pericardial approach may allow access to the right pulmonary veins without much maneuvering, manipulating, bending, torquing, etc. of the distal portion of the device. Any of these approaches may be used to position an endocardial ablation device in the left atrium. In some variations, a first endocardial ablation array may enter the left atrium through an intravascular approach, and a second endocardial ablation array may enter the left atrium through the LAA via a pericardial approach.

[0065] One example of a method (830) that comprises accessing the endocardial surface of the left atrium both intravascularly and through the LAA via the pericardial space is depicted in FIG. 8B. As previously described, an access pathway may be created to the pericardial space (832). A LAA access/exclusion device may be used to locate and stabilize the LAA (834). Once access into the pericardial space and to the LAA has been established, a device may be used to create a LAA access site (836), e.g., by puncturing the LAA, which may allow a device to access the left atrium through the LAA. An intravascular pathway to the left atrium may also be attained by advancing a delivery catheter through the vasculature into the left atrium (838), e.g., using a retrograde or an antegrade transseptal approach. Once the intravascular and/or LAA access pathways into the left atrium have been established, a first endocardial ablation array may be advanced into the left atrium through the LAA (840). The first endocardial ablation array may be positioned at any desired tissue region in the left atrium (e.g., atrial wall tissue, tissue at or around the base of the pulmonary veins, tissue within the pulmonary veins, etc.), such as the tissue along the bases of the right pulmonary veins (842). The first endocardial ablation array may be activated to ablate tissue (844). A second endocardial ablation array may be advanced intravascularly through the delivery catheter into the left atrium (846). The second endocardial ablation array may be positioned at any desired tissue region in the left atrium (e.g., atrial wall tissue, tissue at or around the base of the pulmonary veins, tissue within the pulmonary veins, etc.), such as the tissue along the bases of the left pulmonary veins (848). The second endocardial ablation array may be activated to ablate tissue (850). An epicardial ablation array may be advanced via the pericardial space to a location on the outer surface of the heart (852), for example, a location corresponding to either or both the endocardial ablation arrays (854), and/or along tissue at or near one or more pulmonary veins, e.g., at or around the trunks of the pulmonary veins. Additional variations of advancing and positioning an epicardial device at around the trunks of the pulmonary veins are described below. In some variations, the endocardial ablation array(s) and the epicardial ablation array may be positioned opposite each other using alignment magnets. Once the epicardial ablation array is positioned at the desired location, the epicardical ablation array may be activated to ablate tissue (856). The positioning and activation of the epicardial and endocardial ablation arrays may be repeated as desired. After ablating the desired tissue regions, the ablation arrays may be removed (858). The LAA may be closed with the access/exclusion device (860), and then the access/exclusion device may be removed (862).

[0066] While the steps of the method (830) have been described in the sequence as depicted in FIG. 8B, it should be understood that the steps may take place in an alternate sequence, and certain steps may take place substantially simultaneously. For example, the delivery catheter may be advanced intravascularly into the left atrium (838) before or after the LAA access site is created (836). In some variations, the epicardial ablation array may be positioned on the epicardial surface of the heart (854) before either or both of the endocardial ablation arrays are positioned in the left atrium. The activation of the ablation arrays may occur sequentially or simultaneously. For example, the first or second endocardial ablation array and the epicardial ablation array may be activated simultaneously. Alternatively or additionally, the first and second ablation arrays and the epicardial ablation array may all be activated simultaneously, and/or the first and second ablation arrays may be activated simultaneously without activating the epicardial ablation array. In some cases, the epicardial ablation array may be activated without activating either or both of the first and second ablation arrays. The method (830) involves the use of two endocardial ablation arrays, but in other variations, only one endocardial ablation array may be used to ablate the left and/or right pulmonary veins. The single endocardial ablation array may be advanced intravascularly or through the LAA, as may be desirable.

[0067] The methods described above ablate the tissue of the left atrium and/or pulmonary veins from both the endocardial and epicardial surfaces, either simultaneously or sequentially. Placement of the ablation arrays on both the endocardial and epicardial surfaces may help ablate atrial tissue from both sides. Ablating tissue simultaneously from both sides may help promote the formation of a lesion that spans a significant portion of the thickness of the tissue between the ablation arrays. A lesion that spans a significant portion of atrial tissue thickness may help to electrically isolate fibrillating tissue. The application of ablation energy (e.g., phase, magnitude, pulse sequence, etc.), type of ablation energy (e.g., radiofrequency, laser, high intensity focused ultrasound, cryogenic agents, microwave energy, heat energy, etc.), and the shape and size of ablation arrays may be varied according to the geometry of the tissue and the ablation profile desired. For example, the endocardial ablation array may ablate tissue cryogenically, while the epicardial ablation array may ablate tissue with heat energy. Alternatively, the endocardial ablation array may ablate tissue using heat energy, while the epicardial ablation array may ablate tissue cryogenically. In other variations, the endocardial ablation array may ablate tissue using HIFU, while the epicardial ablation array may ablate tissue using microwaves. The type(s) of ablation energy used and the shape of the ablation array may be selected to limit ablation of non-target peripheral tissue.

[0068] While the methods and devices described here may be used to ablate cardiac tissue, it should be appreciated that the methods and devices described here may be adapted to ablate any tissue from any two tissue surfaces. For example, endocardial and epicardial ablation arrays may be adapted to ablate a tumor cell mass from one or more surfaces. Endocardial and epicardial ablation arrays may also be used to ablate tissue of a hollow organ (e.g., stomach, bladder, lungs, vascular structures, etc.) by positioning them opposite each other on both the inside and outside surfaces. When two ablation arrays are placed on opposite sides of tissue, they may ablate tissue therebetween in any variety of patterns, some of which are shown in FIGS. 9A-9D. These ablation patterns are described in the context of cardiac structures, however, it should be understood that these patterns may be formed in any desirable tissue, as described above. The ablation profile when using both endocardial and epicardial arrays on atrial tissue (900) may vary depending on the type of ablation energy (e.g. cryo-ablation, high intensity focused ultrasound, radiofrequency, laser, etc.). For example, as depicted in FIG. 9A, a first ablation array (908) may be placed on the endocardial surface (904) and a second ablation array (906) may be placed opposite the first ablation array (908) on an epicardial surface (902) of atrial tissue (900). Both the first and second ablation arrays (908, 906) may be simultaneously operated, where the first ablation array (908) and the second ablation array (906) may deliver ablation energy at substantially the same time. In some variations, the ablation arrays are operated to deliver ablation energy in-phase, out-of-phase, or at an offset to form the ablation pattern (910). FIG. 9B depicts an ablation pattern (920) that may arise when epicardial ablation array (916) delivers ultrasound ablation energy (e.g., HIFU) that may be reflected off endocardial array (918) back to epicardial array (916). Similarly, FIG. 9C depicts an ablation pattern (930) that may be formed when endocardial ablation array (928) delivers ultrasound ablation energy that may be reflected off epicardial array (926) back to endocardial array (928). FIG. 9D illustrates an ablation pattern (940) that may arise when both endocardial ablation array (938) and epicardial ablation array (936) reflect the ultrasound ablation energy delivered by the opposite array.

[0069] The ablation pattern created in the tissue may be monitored using one or more one or more temperature sensors on either or both the endocardial and epicardial arrays. For example, as depicted in FIG. 9E, epicardial ablation array (950) and endocardial ablation array (951) may both comprise one or more temperature sensors (952) and alignment magnets (954). Both the epicardial and endocardial ablation arrays may comprise temperature sensors so that a temperature change arising from activating the opposite ablation array may be measured, and may be used to indicate the progress of the ablation of tissue (953). In some variations, a temperature threshold may be set such that reaching or exceeding that temperature will signal an activated ablation array to deactivate. This may be used to prevent excessive or harmful damage to tissue (953). For example, the epicardial ablation array (950) may be activated when the endocardial ablation array (951) is not activated. The temperature sensors of the endocardial ablation array (951) may provide a temperature measurement as a feedback signal to the epicardial ablation array controller. For example, the duration, magnitude, and other characteristics of the ablation energy applied by the epicardial ablation array may be regulated based on the temperature measured by the temperature probe on the endocardial surface of the heart. The activation of the endocardial ablation array (951) may be similarly regulated by temperature feedback using the temperature sensors on the epicardial ablation array. In other variations, temperature sensors may only be provided on an ablation array on one side of the tissue, but not on the ablation array on the other side of the tissue. For example, in the example depicted in FIG. 9F, epicardial ablation array (960) may have one or more temperature sensors (962), while endocardial ablation array (961) may not have any temperature sensors. Both the epicardial and endocardial ablation arrays comprise one or more alignment magnets (964) that may be used to align the arrays with respect to each other across tissue (954). The tissue (963) may be clamped between the ablation arrays, such that the endocardial ablation array (961) acts as a support for the penetration of the temperature sensors of epicardial ablation array (960). The temperature sensors (962) may have a length that spans over a substantial thickness of tissue (963), which may allow the temperature of the middle of tissue (963) to be measured. In some variations, the temperature sensors of an ablation array may span the entire depth of the tissue, as depicted in FIG. 9G. As seen there, the temperature sensors (972) of the epicardial ablation array (970) may span the entire thickness of the tissue (973) and may, in some cases, even contact endocardial ablation array (971). This may allow the temperature gradient across the tissue (973) to be measured. For instance, it may be determined based on the temperature measurement if the tissue is ablated in a uniform manner, etc. Such data may be fed back to an ablation controller to adjust the power, intensity, frequency, magnitude, etc. of the ablation mechanism to attain the desired ablation pattern. As described previously, the temperature sensors may be atraumatic or may be tissue-piercing, as may be desirable.

[0070] One variation of a method for ablating tissue from both the endocardial and epicardial surfaces is depicted in FIGS. 10A-10S. Access to the pericardial space may be attained in a variety of ways, some examples of which are shown in FIG. 10A. Additional examples are described in U.S. Provisional Patent Application No. 61/323,801 filed Apr. 13, 2010, which was previously incorporated by reference in its entirety, and U.S. application Ser. No. 13/086,328, filed on Apr. 13, 2011, entitled “Methods and Devices for Pericardial Access,” which is hereby incorporated by reference in its entirety. As shown in FIG. 10A, a pericardial sac (1002) encases the heart and LAA (1000). Access to the LAA (1000) may be obtained from an initial site located in between ribs, or below the rib cage (1004). For example, the pericardium may be accessed through a right intercostal site (1006), a left intercostal site (1008), or a sub-thoracic site (1010), below the costal cartilages. The pericardium may also be accessed from below the diaphragm. In some procedures, the pericardium may be accessed from multiple sites, for example, from both right intercostal (1006) and left intercostal (1008) sites, the right intercostal (1006) and sub-thoracic (1010) sites, and the left intercostal (1008) and sub-thoracic (1010) sites. Depending on the location of the tissue targeted by one or more of the devices described herein, the access sites may be selected such that the target tissue region may be readily accessed. For example, an access site may be chosen for a particular target tissue region such that the tissue region may be reached by an ablation device without acute bending of the device, and/or excessive device maneuvering, manipulating, bending, torquing, etc. In some variations, an access site may be selected to reduce the path length between the initial entry site and the target tissue. Pericardial access may be monitored and/or confirmed using one or more imaging techniques, for example, fluoroscopy, echocardiography, and endoscopy. Once access to the pericardium has been established and confirmed, an incision or needle puncture may be made in the pericardial sac (1002), where an incision size may be based in part on the size of the device used for entry (e.g., guide wire, cannula, or any of the devices described here). In some variations, a small incision or puncture may be initially made and subsequently expanded by dilators to enable entry of other devices. Entry of any device(s) into the pericardial sac (1002) may also be monitored and confirmed using one or more imaging techniques as described above.

[0071] Various devices may be introduced into the epicardial space via an incision or puncture in the pericardium. FIG. 10B depicts a side view of the LAA (1000) and the left atrium (1003), encased by the epicardium (1001), myocardium (1005), and pericardial sac (1002). Within the cavity of the left atrium (1003), the bases of two pulmonary veins (1007a) and (1007b) may be seen. Devices may be advanced towards the LAA (1000) by inserting guide wire (1014) into a pericardial sac incision (1011). A guide cannula (1012) may be advanced over the guide wire (1014). A guide cannula (1012) and a guide wire (1014) may be steerable and/or pre-shaped according to a desired access route, for example, an access route that enables the penetration of LAA (1000) from between or under the rib cage. In some variations, one or more dilators may be used to insert and position the guide cannula (1012), after which the one or more dilators may be removed. In some variations, the guide wire (1014) may be removed after the guide cannula is positioned. Once in place, the guide cannula (1112) may provide navigational support and guidance to a LAA device, such as the LAA closure device (200) shown in FIG. 2. One method of localizing and stabilizing the LAA (1000) is depicted in FIG. 10C, where a LAA stabilizing device (1020) may be advanced via the guide cannula (1012) towards the LAA to contact the LAA. One variation of a LAA stabilizing device (1020) may contact the LAA (1000) by advancing a vacuum device (1022) through a looped closure assembly (1024). In this variation, the vacuum device (1022) may apply negative pressure which may draw a portion of the LAA (1000) into a collector, for example, one or more lumens, a basket, any woven semi-rigid structure, or a cup (1023), thereby securing the LAA. Some variations of the LAA stabilizing device (1020) may also comprise graspers. Graspers may be advanced through the looped closure assembly (1024) and such that they may secure the wall of the LAA (1000). Optionally, graspers may penetrate or pierce through the LAA wall. After the desired level of LAA stability is attained by activating the vacuum device (1022) and/or graspers, the looped closure assembly (1024) may be advanced over the LAA, and closed over the LAA. In some variations, the looped closure assembly may comprise a snare loop and a suture loop releasably coupled to the snare loop, where the snare loop and the suture loop may be separately tightened, and/or tightened in a coordinated fashion. The suture loop may be released and/or disengaged from the snare loop after the suture loop has been tightened over the neck of left atrial appendage. In some variations, the suture loop may be released from the LAA stabilizing device (1020) after being closed and locked around the LAA. In some variations, the looped closure assembly (1024) may be closed to secure/locate the LAA, and then may be opened to allow devices to be advanced therethrough, and then closed to secure/locate the LAA. The opening and closing of the looped closure assembly (1024) may help to maintain hemostasis during the procedure. Examples of a looped closure assembly and other stabilization and closure devices that may be used with the LAA stabilization device (1020), along with other devices and methods for ensnaring a LAA, are described in U.S. patent application Ser. No. 12/055,213 (published as U.S. 2008/0243183 A1), which was previously incorporated herein by reference in its entirety.

[0072] FIG. 10D illustrates the proximal portion of the LAA stabilizing device (1020), which may comprise one or more ports, for example, a vacuum source port (1021) and a needle port (1030), and actuators (1028a) and (1028b). The vacuum source port (1021) and the needle port (1030) may comprise valves to regulate the passage of devices or fluids through the ports. Actuators (1028a) and (1028b) may activate the looped closure assembly (1024) and the vacuum device (1022), respectively. While the vacuum device (1022) is activated (e.g. applying negative or positive pressure), an access needle (1032) may be inserted into the needle port (1030). The LAA access device (300) as described above and depicted in FIG. 3 may be used here. As seen in FIG. 10E, an access needle (1032) may be advanced through the needle port (1030), through the LAA stabilizing device, and through the vacuum device (1022) to puncture and enter the LAA (1000). Optionally, before or after the LAA is punctured by the access needle, looped closure assembly (1024) may be adjusted, e.g. closed or opened, to control bleeding and/or provide endocardial access to devices. Other hemostatic devices (e.g., valves, plugs, etc.) may be used at or near the needle puncture to control and/or limit bleeding. Once access needle (1032) has penetrated the LAA, a standard guide wire (1031) may be advanced into the LAA, and the access needle may be withdrawn. In some variations, the access needle (1032) may remain in the LAA and left atrium, to maintain the puncture in the LAA and/or left atrium. After the guide wire (1031) is inserted into the LAA and/or left atrium, the vacuum device (1022) may be removed, as shown in FIG. 10F.

[0073] Optionally, LAA stabilizing devices may comprise additional LAA attachment features that may further secure the LAA after it has been stabilized, for example, as depicted in FIG. 10G. As shown there, a distal segment of a LAA stabilizing device (1020′) may comprise a looped closure assembly (1024′) and apertures (1025) through which positive or negative pressure may be applied. Negative pressure may be applied through apertures (1025) to draw the LAA towards the device, further securing and stabilizing it. In this variation, negative pressure may be applied to apertures (1025) after looped closure assembly (1024′) has effectively encircled the LAA, which may help ensure that the LAA is fully stabilized prior to the insertion of access needle (1032). The position of looped closure assembly (1024′) after it has encircled the LAA may be adjusted by applying positive pressure to the apertures (to release the LAA) and negative pressure (to secure the LAA). Alternatively, a distal segment (1019) of the LAA stabilizing device (1020′) may be adapted to help looped closure assembly (1024′) to engage and encircle the LAA. For example, the distal segment (1019) may be advanced towards the LAA. The looped closure assembly (1024′) may then engage a tip portion of the LAA, after which negative pressure is applied to the distal-most aperture, while the remaining apertures remain pressure-neutral. Then, the distal segment (1019) may be advanced towards the LAA, and then the negative pressure in the distal-most aperture is released, immediately followed by the application of negative pressure on the second distal-most aperture. These steps may be repeated, where distal segment (1019) may effectively advance in a step-wise fashion across the LAA by sequentially applying and then releasing negative pressure on each of the apertures (starting from the distal-most aperture and moving proximally), until the looped closure assembly (1024′) reaches the ostium of the LAA. Once the looped closure assembly (1024′) reaches the ostium of the LAA, it may be cinched to secure the LAA, and optionally, negative pressure may be applied on all apertures (1025) to further secure the LAA.

[0074] Various devices may be advanced over the guide wire (1031) to access the internal portion of LAA (1000) and left atrium (1003). The guide wire (1031) may be navigated and controlled by actuator (1028c). Ablation devices may be advanced over the guide wire (1031) to ablate asynchronous tissue for the treatment of atrial fibrillation. FIG. 10H depicts one variation of an endocardial ablation device (1040) as it is advanced over guide wire (1031), through the wall of the LAA and into the left atrium. For example, the endocardial ablation device (400) as described above and depicted in FIG. 4 may be used here. In some variations, an endocardial ablation device may be advanced through the LAA to access the left pulmonary veins. Optionally, an endocardial ablation device may be advanced via an intravascular antegrade transseptal approach to access the right pulmonary veins. As described previously, an ablation device such as the endocardial ablation device (1040) may utilize any tissue-affecting mechanism to create a lesion in the target tissue. Examples of tissue-affecting mechanisms include cryo-ablation, radiofrequency (RF), ultrasound, microwave, laser, any suitable type of photo-ablation using light-activated agents that may trigger cellular apoptosis, heat, localized delivery of chemical or biological agents, and the like. In some variations of an endocardial ablation device, a source (1044) may be a reservoir of one or more cryogenic, chemical, or biological agents, and/or may be an energy source (e.g., laser light source, pulse generator, ultrasonic source, etc.) and may be located a proximal portion of the ablation device (1040). A conductive structure (1041) may provide a conduit for conveying the ablation energy from the source (1044) to the distal portion of ablation device (1040). For instance, the conductive structure (1041) may be a wire, fiber optic cable, lumen, channel, microfluidic channel, etc.

[0075] Ablation array (1042) of the endocardial ablation device (1040) may be integrally formed with the proximal portion of the ablation device (1040), or may be attached via an articulating hinge (1043). In some variations, an ablation array may comprise ablation elements and/or magnetic elements, as previously described above. The endocardial ablation device (1040) may have a first delivery configuration, where the ablation array (1042) has a narrow profile (as shown in FIG. 10H), and a second deployed configuration, where the ablation array (1042) assumes a wider profile (as shown in FIG. 10I). In the delivery configuration, the ablation array (1042) may have a substantially straight linear geometry. In the deployed configuration, the ablation array (1042) may be expanded to have a curved shape, such as a semi-circular shape, to circumscribe the base of pulmonary vein (1007b). The deployed configuration of the ablation array may have any shape that may be configured to accommodate the anatomy of the target tissue to achieve a desired ablation profile. For example, the ablation array may have any of the shapes previously described and depicted in FIGS. 6A-6F.

[0076] Once the ablation array (1042) of the endocardial ablation device is positioned at a region of tissue in the left atrium, e.g. around the base of pulmonary vein (1007b), an epicardial ablation device may be aligned and placed on the epicardial surface of the atrium (1003). A second guide cannula (1052) may be inserted in any of the access sites previously described and depicted in FIG. 10A, and may use the same or different access point from the first guide cannula (1012). The guide cannula (1052) may be advanced to the pericardial space as described previously, and once positioned and stabilized, the guide wire (1050) may be advanced through guide cannula (1052) to track around a target tissue region, e.g. the tissue region directly across where the endocardial ablation array (1042) is positioned, as shown in FIG. 10J. Guide cannula (1052) may have one or more curves, and may vary in length, as suitable for the access site(s) used. Guide wire (1050) may comprise a magnetic component at its distal tip (not shown). The magnetic component may be of any suitable type, size, and shape, for example, the magnet may be a rare-earth, electro-activated, or a multi-alloy (e.g. iron, boron, neodymium) magnet. A guide wire with a magnetic distal tip may facilitate the navigation of the guide wire to the magnetic component(s) of the positioned endocardial ablation device. The epicardial ablation device may be navigated over the guide wire (1050) and through the guide cannula (1052) to the target site, e.g. at or around pulmonary vein (1017b) which is directly across from the base (1007b). In some variations, the epicardial ablation device (500) as described above and depicted in FIG. 5, may be used here. As with the endocardial ablation device, an ablation array (1062) may be attached to the distal portion of the epicardial ablation device (1060), as shown in FIGS. 10K and 10L. In some variations, an ablation array may comprise ablation elements and/or magnetic elements, as previously described with respect to ablation array (508). Similar to the endocardial ablation device (1040), the epicardial ablation device (1060) may have a delivery configuration that has a substantially narrow profile, as seen in FIG. 10K, and a second deployed configuration, where ablation array (1062) assumes a wider profile, as seen in FIG. 10L. In the delivery configuration, the ablation array (1062) may have a substantially straight linear geometry. In the deployed configuration, the ablation array (1062) may have a curved shape, such as a semi-circular shape to circumscribe the trunk of the pulmonary vein (1017b), however, may be any shape to accommodate the anatomy of the target tissue to achieve a desired ablation profile. In the variation of method described here, the tissue around the pulmonary veins may be ablated both epicardially and endocardially. According to this variation, the shape of the deployed configuration of the epicardial ablation device corresponds with the shape of the deployed configuration of the endocardial ablation device, e.g., mirror-symmetric. Once the epicardial ablation device has assumed its deployed configuration, the guide wire (1050) may be withdrawn.

[0077] Endocardial and epicardial ablation devices may comprise alignment features, which may help ensure a particular orientation of one ablation device with respect to another, and may also create an intimate contact between the ablation devices and the tissue to be ablated. In the variation of the ablation devices described here, the attractive forces between the magnets on one or both of the epicardial and endocardial ablation devices may align the devices to one another. FIGS. 10M and 10N show enlarged cross-sectional views of the endocardial ablation array (1042) and the epicardial ablation array (1062) positioned across each other, where the endocardial ablation array may circumscribe the base of a pulmonary vein within the cavity of the left atrium, and the epicardial ablation array may circumscribe the trunk of the same pulmonary vein on the outer surface of the left atrium. As shown in FIG. 10M, the epicardial ablation device may be advanced such that the epicardial ablation array (1062) is positioned approximately opposite the endocardial ablation array (1042), i.e. around the pulmonary vein (1017b) of the left atrium (1003), such as a left pulmonary vein. Endocardial magnetic components (1045) and epicardial magnetic components (1065) may attract each other, drawing the ablation arrays towards each other to form a stable contact with the wall of the left atrium, as shown in FIG. 10N. The magnetic attraction between the ablation arrays may compress the wall of the left atrium against the ablation arrays, which may improve the efficacy of lesion formation in the atrial wall, which may reduce the magnitude of the energy (or the quantity of fluid) needed to ablate the tissue between the ablation arrays. In some cases, arranging the ablation arrays on both sides of the atrial wall may help form a transmural lesion that spans the entire thickness of the wall between the arrays.

[0078] While the devices and methods above are directed towards ablating tissue endocardially and epicardially to form an ablation pattern that circumscribes the base of a pulmonary vein, other ablation patterns and profiles may be also be used for the treatment of atrial fibrillation. Examples of other ablation patterns are schematically illustrated in FIGS. 10O-10P. A cutaway of left atrium (1003) and LAA (1000) reveals the four pulmonary veins (1007a), (1007b), (1007c), and (1007d). FIG. 10O depicts one variation of an ablation pattern (1070) where each of the pulmonary veins are individually circumscribed. FIG. 10P depicts another ablation pattern (1071) where pairs of pulmonary veins are circumscribed, i.e., (1007a) and (1007c) are circumscribed by one lesion, and (1007b) and (1007d) are circumscribed by another lesion. Different pairs of pulmonary veins may be circumscribed together, depending on the profile of electrical isolation that is needed. The shape (e.g., number of curves, radii of curves, etc.) of the endocardial and epicardial ablation arrays may be adjusted such that ablation pattern (1071) may be obtained. For example, the endocardial and epicardial ablation arrays may have an elongated elliptical shape (e.g., where the length is substantially greater than the width) to attain the ablation pattern of FIG. 10P. FIG. 10Q depicts yet another ablation pattern (1072) where all pulmonary veins are circumscribed by a single lesion. In this variation, the endocardial and epicardial ablation arrays may be sized and shaped to circumscribe all of the pulmonary veins. In addition to the lesion patterns described in FIGS. 10O-10Q for pulmonary vein isolation, the endocardial and/or epicardial ablation arrays may be used to create linear lesions through tissue of the left atrium (LA) including: the LA roof line (e.g., along the connection between the right superior pulmonary vein (1007b) and the left superior pulmonary vein (1007a)), the mitral valve isthmis line (e.g., along the connection between left inferior pulmonary vein (1007c) to the mitral valve annulus (1009)), and the posterior LA line (e.g., along the connection between both sets of pulmonary veins across the posterior LA). Other ablation patterns and lesion geometries may be used to obtain a desired degree and profile of electrical isolation. While these ablation patterns have been described in the context of simultaneous ablation of tissue from both the endocardial and epicardial surfaces, it should be understood that these ablation patterns may also be attained by ablating either the endocardial surface or the epicardial surface. In general, any appropriate ablation profile may be achieved for any target tissue by adjusting the size and shape of the ablation arrays on the ablation devices. For example, to ablate a larger volume and/or area of tissue, a smaller ablation array (e.g. an array that ablates a volume of tissue smaller than the desired ablation pattern) may apply the ablation energy multiple times at different tissue regions. Alternatively, a larger volume and/or area of tissue may be ablated by an ablation array that is comparably sized with the desired ablation volume/area, and may be shaped according to the target tissue. In this variation, the ablation energy may only need to be applied once. While the ablation regions around the pulmonary veins have been described, additional ablation targets for the treatment of atrial fibrillation may include other anatomical regions. For example, other tissue regions that may be suitable non-pulmonary vein ablation targets may include the superior vena cava (SVC), LA posterior wall, crista terminalis, coronary sinus (CS), ligament of Marshall, intrarterial septum, and/or any other tissue regions that may trigger atrial fibrillation.

[0079] During and/or after tissue ablation, the progress of the ablation and the lesion size may be monitored and verified. Lesion formation may be monitored functionally and/or anatomically. For example, lesion formation may be monitored by heat transfer measurements, electrocardiography mapping, ejection fraction, local electrogram amplitude reduction and mapping, impedance tomography, ultrasound, fluoroscopy, and other suitable functional metrics or imaging modalities. Based on these measurements and images, the rate, size, and other characteristics of lesion formation may be modified, e.g., by adjusting power and wavelength of the ablation energy, to achieve the desired degree of electrical isolation. In some variations, lesion formation may be measured in terms of the change in the tissue temperature across the thickness of the tissue. For example, endocardial and epicardial ablation arrays may each comprise temperature sensors as previously described may be pressed into the atrial wall tissue to measure the temperature on either side of the atrial wall. In some variations, either the endocardial or the epicardial ablation array has a temperature probe, so that the heat transfer front from the other ablation array may be measured. The temperature probe may also be a separate device that is advanced to the desire target tissue region.

[0080] Once the desired portion of tissue has been ablated (e.g., verified that a lesion of a desired size and shape has been formed), the ablation devices and positioning catheters may be removed. The alignment feature that couples the endocardial ablation array (1042) with the epicardial ablation array (1062) may be deactivated, either mechanically (e.g., by applying a force stronger than, and opposite to, the coupling force) or electrically (e.g., by turning off the electro-magnet). The endocardial ablation device (1040) and the epicardial ablation device (1060) may be removed sequentially or simultaneously, as may be appropriate. The endocardial guide wire (1031) may be kept in place to facilitate the navigation of any additional devices to the left atrium and/or LAA, however, in other variations, the guide wire (1031) may be removed.

[0081] Optionally, a method for the electrical isolation of tissue in the LAA and/or left atrium may comprise a step that electrically isolates the LAA. FIG. 10R depicts an occlusion device (1080) that may be advanced over the guide wire (1031) via a guide wire port (1082) and through a working channel of the LAA stabilizing device (1020) to access the internal portion of the LAA (1000). For example, the occlusion device (700) as described previously and depicted in FIG. 7 may be used here. In some variations, an occlusion device may be configured to deliver contrast and/or therapeutic agents through the guide wire port or an infusion lumen that may extend along the occlusion device from the proximal portion to distal portion. The looped closure assembly (1024) may remain in a closed configuration to stabilize and localize the LAA. The distal portion of the occlusion device (1080) may comprise an expandable member (1086) which may have a collapsed delivery configuration (shown in FIG. 10R) and an expanded deployed configuration (shown in FIG. 10S). Optionally, the distal portion of the occlusion device (1080) may also comprise radioopaque and/or echogenic markers (1085) so that the position of the occlusion device may be detected by imaging. Some variations of an occlusion device may comprise side apertures that provide for the infusion of a contrast agent to enhance visualization of the occlusion device, or the infusion of other agents, including therapeutic agents such as heparin or other anticoagulants, saline, etc. The expandable member (1086) may be expanded by introducing a fluid, e.g. liquid or gas, via a fluid lumen (1084), from a pressurized fluid reservoir (1083). Alternatively or additionally, in other variations of an occlusion device, the expandable member may be mechanically dilated, e.g., by actuating struts. During or after the expansion of the expandable member (1086), the looped closure assembly (1024) may be further tightened around the LAA by actuating tab (1028d). Tightening the looped closure assembly (1024) around the neck of LAA (1000) may block the exchange of any substances between the LAA cavity and the left atrial cavity. In some variations, tightening the looped closure assembly may sever the LAA entirely, such that it is excluded from the left atrium. For example, a releasable suture loop and a snare loop of the looped closure assembly may be tightened to exclude the LAA, and the snare loop may be proximally withdrawn from the suture loop, e.g., after the suture loop is released from the looped closure assembly by further pulling on tab (1028d). The LAA may be extracted from the body by any suitable method, for example, by using negative pressure to secure the LAA into a collector or tubular member, which is then retracted out of the body. Optionally, a debrider may be used to break the excised LAA into smaller portions prior to extraction, which may be suitable for use with a minimally invasive procedure. In some variations, a chemical or enzyme agent may used prior to extraction to break down or soften the LAA for removal.

[0082] As described above, the neck of LAA may be encircled and cinched by a suture snare, however, other mechanisms may be included to close and/or occlude the LAA cavity. As shown in FIGS. 11A-11C, a clip (1100) may be used to close the LAA. Clip (1100) may be advanced through a guide cannula and encircled around a LAA or LAA neck. Subsequently, a mandrel (1104) may be advanced through the guide cannula in the direction of arrow (1006) to urge a collet (1102) onto a clip neck (1103), as shown in FIG. 11A. FIG. 11B depicts that the collet (1102) may continue to be urged in the direction of arrow (1108), until it is completely secured onto the clip (1100), and the LAA enclosed by the clip is tightened. The collet (1102) may be engaged onto the clip (1100) by snap-fit, press-fit, or friction-fit. In some variations, alternate closure mechanisms may be used, such as a cable tie with a ratchet mechanism, a Nitinol cable or loop, and the like. The clip (1100) may be made of shape memory material, such as a nickel titanium alloy, where in the unconstrained configuration, the neck (1103) naturally springs open, and the spring force engages and secures collet (1102). After the collet has secured and closed the clip, the mandrel (1104) may be removed.

[0083] A variety of expandable members may be used to occlude and/or exclude the LAA. For example, an inflatable expandable member, such as a balloon similar to the expandable member (1086), may be used to occupy the LAA cavity, preventing the escape of, or continuing development of, thrombi in the LAA. In another variation shown in FIG. 12A, expandable member (1200) in LAA (1000) may be filled with a hardening material (1202), such as thermal polymers, hydrogels, epoxy, and any suitable hardening materials. The hardening material may initially be a liquid or gel that may be delivered through a lumen (1204) in the occlusion device, and may solidify after being deposited in the expandable member (1200) within the LAA (1000). Alternatively or additionally, an expandable member may be self-expanding, as depicted in FIG. 12B. As shown there, an expandable element (1210) may be an ostial occluder that automatically expands once urged by mandrel (1212) into the LAA cavity. The expandable member may be made of one or more polymeric materials, for instance, polypropylene, polyurethane, polyethylene, polytetrafluoroethylene, and in some variations, may alternatively or additionally include one or more metal alloys such as nitinol, stainless steel, etc., or any shape-memory material. A self-expanding expandable member may be an enclosed structure, such as a balloon, or a mesh-like structure. Mechanisms of self-expansion include shape-memory, thermal expansion, spring-action, and the like.

[0084] While some methods for the treatment of atrial fibrillation may ablate tissue in the left atrium both endocardially and epicardially, other variations of ablating tissue in the left atrium, and subsequently occluding and/or excising the LAA may be used. One example of a method that ablates an endocardial surface of a left atrium is shown in FIG. 13A. Method (1300) may be used to ablate tissue from an endocardial surface using surgical, intravascular and/or other minimally invasive techniques (e.g., percutaneous, small incisions or ports), and may be used in stopped heart or beating heart procedures. The method (1300) may comprise accessing the pericardial space (1302). Optionally, a device may be used to locate and stabilize the LAA (1304), for example, the closure device (200) as described above and shown in FIG. 2. Once access into the pericardial space and to the LAA has been established, a device may enter the LAA (1306) by creating a puncture in the LAA. Access to various tissue regions in the left atrium (e.g., atrial wall tissue, tissue at or around the base of the pulmonary veins, tissue within the pulmonary veins, etc.) from an endocardial side may be established (1310). An endocardial ablation array may be positioned and placed along an endocardial surface of the left atrium (1312). For example, the endocardial ablation array may circumscribe the pulmonary veins to obtain a particular ablation pattern. The endocardial ablation array may then be activated (1314). After the desired tissue has been ablated (e.g., atrial wall tissue, tissue at or around the base of the pulmonary veins, tissue within the pulmonary veins, etc.), the ablation devices may be removed (1316), and the LAA may be occluded, closed, and/or removed (1318). Once the LAA has been decoupled from the remainder of the left atrium, all devices may be retracted from the surgical site (1320). In some variations of methods for ablating tissue in the left atrium, the endocardial ablation device may be advanced intravascularly (e.g., from a retrograde approach, or an antegrade transseptal approach, etc.). Access to the left atrium may be accessed by any method or approach as may be suitable for contacting the targeted tissue region.

[0085] While the method described above uses one endocardial ablation array for ablating the tissue of the left atrium from an endocardial side, other methods may use two endocardial ablation arrays. One example of a method that uses two endocardial ablation arrays for ablating atrial tissue on an endocardial side is depicted in FIG. 13B. As previously described, an access pathway is created to the pericardial space (1332). A LAA access/exclusion device may be used to locate and stabilize the LAA (1334). Once access into the pericardial space and to the LAA has been established, a device may be used to create a puncture in the LAA (1336), which may allow a device to access the left atrium through the LAA. An intravascular pathway to the left atrium may also be attained by advancing a delivery catheter through the vasculature into the left atrium (1338), e.g., using a retrograde or an antegrade transseptal approach. Once the intravascular and/or LAA access pathways into the left atrium have been established, a first endocardial ablation array may be advanced into the left atrium through the LAA (1340). The first endocardial ablation array may be positioned at any desired tissue region (e.g., atrial wall tissue, tissue at or around the base of the pulmonary veins, tissue within the pulmonary veins, etc.), such as along tissue at or around the bases of the right pulmonary veins (1342). The first endocardial ablation array may be activated to ablate tissue (1344). A second endocardial ablation array may be advanced intravascularly through the delivery catheter into the left atrium (1346). The second endocardial ablation array may be positioned along tissue at or around the bases of the left pulmonary veins (1348). The second endocardial ablation array may be activated to ablate tissue (1350). The positioning and activation of the first and second endocardial ablation arrays may be repeated as desired. After ablating the desired tissue regions, the ablation arrays may be removed (1352). The LAA may be closed with the access/exclusion device (1354), and then the access/exclusion device may be removed (1356).

[0086] While the steps of the method (1330) have been described in the sequence as depicted in FIG. 13B, it should be understood that the steps may take place in an alternate sequence, and certain steps may take place substantially simultaneously. For example, the delivery catheter may be advanced intravascularly into the left atrium (1338) before or after the LAA access site is created (1336). In some variations, the second ablation array may be advanced through the delivery catheter into the left atrium (1346) before the first endocardial ablation array is advanced through the LAA into the left atrium. The activation of the ablation arrays may occur sequentially or simultaneously. For example, the first or second endocardial ablation array may be activated simultaneously or sequentially.

[0087] Examples of ablation patterns that may be formed by endocardial ablation method (1300) are shown in FIGS. 14A and 14B. Ablation array (1402) is positioned against atrial wall (1400) on the endocardial side (1404). The ablation energy (1403) may be any mechanism of tissue ablation, as described previously. As depicted in FIG. 14B, the portion of the atrial wall (1405) that is closest to ablation array may be ablated relatively quickly, while the portion of the atrial wall further from the ablation array, e.g. tissue near the epicardial side (1406), may not be ablated. To ablate tissue furthest from the ablation array (1402), a longer exposure to a greater quantity of ablation energy (1403) may be needed. For example, to ablate tissue closest to the epicardial side (1406), radiofrequency or cryogenic delivery may need to be increased, and laser energy and heat may need to be more intense. Additionally or alternatively, the ablation of tissue further from the ablation array (1402) may involve increasing the exposure time of tissue (1400) to the ablation energy (1403). The ablation depth achieved an ablation array may be regulated by adjusting more of the above-described factors, as may be desirable. For example, the depth of tissue that is ablated may be 5%, 10%, 25%, 40%, 50%, 60%, 75%, 80%, 95%, etc. of the thickness of the tissue wall. In some variations, closed system or open system irrigation may be included during the delivery of the energy source to regulate the ablation of tissue adjacent to the ablation array. As described previously a temperature probe may be used to measure temperature changes that may arise from tissue ablation, which may help to regulate the amount of ablation applied to a tissue region.

[0088] Ablation of tissue of the LAA and left atrium may be achieved by epicardial ablation. An example of a method (1500) for epicardial ablation is shown in FIG. 15. Method (1500) may be used to ablate tissue using surgical techniques or intravascular techniques, and may be used in stopped heart or beating heart procedures. As previously described, an access pathway may be created to the pericardial space (1532). An epicardial ablation array may be advanced via the pericardial space to the outer surface of the heart (1534). The epicardial ablation array may be positioned along tissue at or near the trunk of the pulmonary veins (1536). The epicardial ablation array may be activated to ablate tissue (1538). Optionally, the epicardial ablation array may be positioned and activated at different locations on the outer surface of the heart, as may be desirable. After ablating the desired tissue regions, the ablation arrays may be removed (1540). Optionally, a LAA access/exclusion device may be advanced to the LAA via the pericardial space (1542). The access/exclusion device may be used to locate and stabilize the LAA (1544). The LAA may be occluded or excised by the access/exclusion device (1546), and then the access/exclusion device may be removed (1548). Decoupling the LAA from the remainder of the left atrium may help reduce the risk of thrombosis or stroke that may occur in atrial fibrillation.

[0089] FIGS. 19A-19F depict another variation of an access device and method that may be used to position a device on an epicardial surface of the heart, e.g., around a tissue structure such as a blood vessel or the LAA. Access device (1900) or a similar device may be used to place a guide element (1902) or other device around a tissue structure (1904), such as a blood vessel or the left atrial appendage. As shown there, access device (1900) may comprise a cannula (1906), a first guide (1908), and a second guide (1910). First (1908) and second (1910) guides each may comprise a lumen (1912) extending therethrough, and may further comprise a magnetic alignment element (1914) at a distal end thereof. First (1908) and second (1910) guides may be at least partially housed inside cannula (1906), and may be configured to be advanced out of a distal end of the cannula (1906). In some variations, first (1908) and second (1910) guides may be housed in a single lumen (not shown) of cannula (1906). In other variations, first (1908) and second (1910) guides may be housed in separate lumens (e.g., a first lumen and a second lumen, respectively). It should be appreciated that cannula (1906) may comprise any suitable number of lumens (e.g., one, two, or three or more).

[0090] Returning to the figures, cannula (1906) may be advanced to tissue structure (1904), as shown in FIG. 19A. In some variations, the tissue structure (1904) may be the right atrial appendage. Cannula (1906) may be advanced in any suitable manner. In some variations, cannula (1906) may be advanced over a guidewire (e.g., via one or more lumens of the cannula (1906). Additionally or alternatively, one or more portions of the cannula (1906) may be steerable. While shown in FIGS. 19A-19F as being a blood vessel (1905), tissue structure (1904) may be any suitable anatomical structure. In some variations, tissue structure (1904) may be the left atrial appendage.

[0091] Once cannula (1906) is positioned at or near the tissue structure (1904), first guide (1908) may be advanced out of the distal end of cannula (1906), as shown in FIG. 19B. As first guide (1908) is advanced out of the distal end of cannula (1906), it may take on a curved configuration. In some variations, the first guide (1908) has a pre-shaped curved configuration, which may be constrained when it is housed within cannula (1906). In other variations, the first guide (1908) may be steered or otherwise actuated to take on the curved configuration. The first guide (1908) may be advanced such that a distal portion of the guide (1908) curves at least partially around the tissue structure (1904), as depicted in FIG. 19B.

[0092] The second guide (1910) may then be advanced from the distal end of cannula (1906), as depicted in FIG. 19C. As shown there, the second guide (1910) may be advanced toward and may engage the first guide (1908). For example, in variations where the first (1908) and second (1910) guides each comprise a magnetic alignment element (1914), the magnetic alignment elements (1914) of the first (1908) and second (1910) guides may attract each other and hold the distal ends of the two guides in place relative to each other. In some variations, the distal ends of first (1908) and second (1910) guides may be positioned such that the lumens (1912) of the two guides are aligned. In some of these variations, the magnetic alignment elements (1914) of each of the first (1908) and second (1910) guides may hold the lumens (1912) of the two guides in alignment.

[0093] Once the lumens (1912) of the first (1908) and second (1910) guides are aligned, a guide element (1902) may be advanced through the lumen (1910) of first guide (1908) such that it exits the distal end of first guide (1908) and enters the lumen of the second guide (1910) (or vice versa). The guide element (1902) may then be advanced through the second guide (1910) (or the first guide (1908)) and the first (1908) and second (1910) guides may be withdrawn through the cannula, as shown in FIG. 19D. In some instances, both ends (not shown) of the guide element (1902) may extend out from a proximal end of the cannula and/or may extend outside of the body. In these variations, guide element (1902) may be a wire, a suture, yarn, strand, or the like. While FIGS. 19A-19D depict advancing a guide element (1902) through lumens (1912) of the first (1908) and second (1910) guides, it should be appreciated that in some variations, a tube or catheter may be advanced over the first (1908) and second (1910) guides to place the tube or catheter around the tissue structure (1904).

[0094] In some variations, the ends of the guide element (1902) may be pulled proximally to cinch the distal exposed portion of guide element (1902) (e.g., the portion of guide element extending from the distal end of cannula (1906)) around the tissue structure (1904), as shown in FIG. 19E. In variations where tissue structure (1904) is the left atrial appendage (not shown), cinching guide element (1902) around the left atrial appendage may act to close the left atrial appendage (temporarily or permanently). In variations where the left atrial appendage is used as an access port into the interior of the heart, as described hereinthroughout, guide element (1902) may be used to help provide hemostasis by temporarily closing the left atrial appendage around one or more devices placed through tissue of the left atrial appendage. Additionally or alternatively, in some variations, a knot, clip, or clamping structure (not shown) may be advanced over a portion of the guide element (1902) to hold the guide element in place around the tissue structure (1904). In variations where the guide element (1902) is placed around the left atrial appendage, the guide element (1902) may be used to close the left atrial appendage (as described immediately above). For example, a knot, clip, or clamping structure may be advanced over the guide element (1902) to hold it in place such that the left atrial appendage is held in a closed configuration. In some variations, the guide element may comprise a releasable suture loop, where cinching the guide element around the tissue structure (1904) likewise cinches the suture loop around the tissue structure (1905). Once the desired level of tightening is achieved, the suture loop may be released from the guide element, and the guide element may be retracted proximally. To secure the tension in the suture loop, a knot, clip or other clamping structure may be advanced through the cannula to lock the suture loop. In some variations, a suture-cutter or the like may be advanced over a portion the guide element (1902) or suture loop to sever at least a portion of the guide element (1902) or suture loop (e.g., the portions of guide element located proximal to the knot, clip, or clamping structure.)

[0095] Additionally or alternatively, one or more devices may be advanced over the guide element (1902) to place the device at or around the tissue structure (1904). In some variations, one or more ablation devices may be advanced over the guide element, such as ablation device (1918) shown in FIG. 19F. As shown there, ablation device (1918) may comprise one or more ablation elements (1920) and one or more magnetic elements (1922), and may be any of the ablation devices previously described. Additionally or alternatively, access device (1900) may also be used to place measurement electrodes, temperature sensors, and the like at or around the pulmonary veins, the LAA, and/or any tissue structure on the epicardial surface of the heart. The devices and methods depicted in FIGS. 19A-19F may be used in combination with any of the devices and methods previously described (e.g., in combination with the methods depicted in FIGS. 8A and 8B, FIG. 15, etc.).

[0096] Examples of ablation patterns that may be formed by epicardial ablation method (1500) are shown in FIGS. 16A and 16B. Ablation array (1602) is positioned against an atrial wall (1600) on the epicardial side (1604). The ablation energy (1603) may be any mechanism of tissue ablation, as described above. The portion of atrial wall tissue (1600) that is closest to ablation array (1602) may be ablated relatively quickly, while tissue further from the ablation array, e.g. tissue near the endocardial side (1606), may not be ablated. To ablate a targeted tissue furthest from ablation array (1602), such as targeted tissue (1607) depicted in FIG. 16B, a longer exposure to a greater quantity of ablation energy (1603) may be needed. For example, to ablate tissue closest to the endocardial side (1606), ultrasound and radio frequencies may need to be increased, and laser energy and heat may need to be more intense. Additionally or alternatively, the ablation of tissue further from ablation array (1602) may involve increasing the exposure time of atrial wall (1600) to the ablation energy (1603). Depending on the type of ablation energy (1603) and/or the quality of the tissue (e.g., thermal energy conductivity, etc.), greater quantities of ablation energy may successfully ablate the targeted tissue (1607) without burning, charring, and/or coagulation of the tissue closest to the ablation array. For example, ultrasound ablation may be shaped and focused such that more energy is delivered to the targeted tissue (1607) than to the tissue on the epicardial side (1604). In some variations, closed system or open system irrigation may be included during the delivery of the energy source to limit the heating of tissue adjacent to the ablation array, while delivering larger quantities of energy to tissue further away from the ablation array. As described previously a temperature probe may be used to measure temperature changes that may arise from tissue ablation, which may help to regulate the amount of ablation applied to a tissue region.

[0097] Also described herein are systems for affecting tissue within a body to form a lesion. In general, the systems may comprise devices that have one or more tissue-affecting elements, together with additional components that help to locate and secure the target tissue. For example, the system may comprise a first and second device, where each of the devices comprises an elongate member and one or more tissue-affecting elements. The first and second devices may be separate from each other, but have corresponding geometries and sizes so that operating the tissue-affecting elements may form a lesion in the tissue between them. These devices may have any geometry (e.g., size, number of curves, radii of curvature, etc.), one or more configurations (e.g., a delivery configuration and a deployed configuration) and may apply a variety of tissue-affecting mechanisms (e.g., cryogenic substances, lasers, high intensity focused ultrasound, radiofrequency energy, heat, microwave, etc.). The tissue-affecting elements for a given device may deliver a combination of one or more types of tissue-affecting mechanisms. The tissue-affecting elements may be any of the ablation elements previously described. Some devices may also comprise magnetic components so that the attractive force between the magnets may cause the first and second devices to be positioned in a certain orientation with respect to each other, e.g. opposite one another. Systems may also include actuators and controllers that regulate the application of the tissue-affecting mechanisms. For example, tissue-affecting elements may be configured to be operated simultaneously, and/or apply energy to the tissue in a pre-programmed manner. A controller may be coupled to the tissue-affecting elements to synchronize their operation temporally (e.g., to affect tissue in-phase or out-of-phase, synchronously or asynchronously) and spatially (e.g., to affect one region of tissue without affecting another, to affect one region of tissue from more than one surface, etc.). In some variations, a controller may be configured to receive temperature data measured at the target tissue site to regulate the operation of the tissue-affecting elements.

[0098] Some systems for affecting tissue within a body may include devices that aid in accessing and securing the tissue, as well as positioning the tissue-affecting elements with respect to the tissue. For example, some systems may comprise a closure device (such as described above) may be included to locate and secure target tissue, a piercing member, one or more guide cannulas, and one or more guide wires. These devices may be configured to be inserted through, or advanced over, each other, which may be desirable for minimally invasive procedures.

[0099] Although the foregoing invention has, for the purposes of clarity and understanding been described in some detail by way of illustration and example, it will be apparent that certain changes and modifications may be practiced, and are intended to fall within the scope of the appended claims.