Steerable ablation device

[0001] This application is a continuation of U.S. application Ser. No. 11/647,315, filed 29 Dec. 2006, now pending, which is hereby incorporated by reference as though fully set forth herein.

[0002] a. Field of the Invention

[0003] The instant invention relates to ablation devices, methods of using them, and steerable devices for use in medical treatments. In particular, the invention relates to devices used in conjunction with atrial fibrillation procedures and improvements related to the introduction of devices around the heart or at epicardial surfaces.

[0004] b. Background Art

[0005] A number of surgical procedures employ the use of steerable devices, such as catheters. In an atrial fibrillation treatment for ablating cardiac tissues, an alternative to the surgical incisions of the heart is the maze procedure, where transmural ablations of the heart are made within an ablation device. Such ablations may be performed either from within the chambers of the heart (endocardial ablation) using endovascular devices (e.g., catheters) introduced through arteries or veins, or from outside the heart (epicardial ablation) using devices introduced into the chest. Various ablation techniques have been used, including cryogenic, radiofrequency (RF), laser and microwave, to create elongated transmural lesions and block electrical conduction in the atrial myocardium. An advantageous use of transmural ablation rather than surgical incisions is the ability to perform the procedure on the beating heart without the use of cardiopulmonary bypass. Maintaining the proper positioning against the wall of a beating heart can also be difficult. Visualization of endocardial anatomy and endovascular devices is often inadequate and knowing the precise position of such devices in the heart can be difficult, resulting in misplaced lesions.

[0006] Epicardial ablation devices and methods useful for creating transmural lesions for the treatment of atrial fibrillation have been described in U.S. Pat. No. 7,052,493 to Vaska et al. (“Vaska”) and U.S. Pat. No. 6,971,394 to Sliwa et al. (“Sliwa”), both of which are hereby expressly incorporated by reference. Sliwa describes a method of forming a transmural lesion in a wall of the heart adjacent to the pulmonary veins by placing an ablation device through a thoracic incision and then through a pericardial penetration so that the ablation device is disposed in contact with an epicardial surface of the heart. Vaska describes an ablation device and system which may be used to wrap an ablation device around the pulmonary veins at an epicardial location.

[0007] Execution of a contiguous pulmonary vein (PV) isolation procedure can occasionally present considerable challenges to the physician. Difficulties in maneuvering the devices and passing them around anatomical structures, maintaining accurate placement on a beating heart, and avoiding unintended contact with other tissues mean that a high degree of physician skill and experience may be required in some circumstances. What are needed, therefore, are devices and methods which allow for precise introduction and placement of the ablation elements in PV isolation and linear left atrial ablations. More particularly, devices and methods which insure that ablation devices are properly placed or introduced for a PV isolation or mitral isthmus ablation procedure are desired.

[0008] It is desirable to be able to maneuver or steer an ablation cell or device near epicardial surfaces and other areas in surgical procedures without concern for the unintended movement or reaction of the device while in the body. The invention relates to a flexible assembly for use in a region of a medical or surgical device. In preferred embodiments, the flexible region comprises a set of pull wires for controllably moving a treatment end of the device, and elements to separate the pull wires and maintain the integrity of the shaft of the flexible region in order to improve the operating aspects of the device. The devices and methods can be especially useful in ablation treatments, such as ablation at cardiac or epicardial tissues.

[0009] The present invention meets these and other objectives by providing devices, assemblies, and methods for placing and controlling the movement of medical devices. For example, some steerable devices may crimp or twist if deflected too far or deflected suddenly or forcefully. In addition, some flexible device may break if deflected too far. The invention provides a medical device, such as a catheter or shaft for introduction into the body or an assembly therefor, having improved structural properties and steerable characteristics that, in part, addresses these shortcomings in some existing devices. In particular and in one aspect, the invention provides a steerable wand or shaft-type device, or assembly therefor, for controllably introducing and/or positioning an ablation element on a cardiac or epicardial surface. However, the invention is not limited to use in cardiac procedures or with ablation treatments or devices. Instead, the invention relates more generally to deflectable or steerable medical devices that contain a flexible support region that allows a desired degree of deflection and prevents crimping, breaking, twisting or other movements that may effect the controllability of the device.

[0010] Thus, in one aspect, the invention includes an assembly for a steerable device for use in surgical or ablation therapy wherein the device typically has an elongated shaft with a flexible distal region and a generally straight proximal region. In the example of an ablating device, one or more ablation elements or cells are disposed along the distal end of the device, but which need not be part of the assembly itself. A steerable deflection area is defined within the flexible region, and it includes a first anchor member, preferably a ring-shaped or other shape to accommodate the profile associated with the shaft of the device, attached to a distal portion of the flexible distal region. The anchor member has one or more passageways for one or more pull wires extending from the proximal region and one or more actuators to the distal region. The steerable deflection region comprises a coiled or interlocking flex support member designed to permit deflection to a desired angle of deflection and maintain the integrity of the interior and exterior of the device during its use in a procedure. Typically, the proximal region of the elongated shaft contains one or more actuators to control the movement of the steerable deflection region, such that, for example, the distal region and distal end of the device move in response to actuation of the one or more pull wires.

[0011] The invention also includes methods to design and produce flexible assemblies to allow a desired range of controlled motion for a distal end of a device. For example, if the desired range of deflection of the distal end is from a straight to a 60 degree angle, the flexible support member, its structure and composition, can be selected to substantially prevent the flexible region from crimping, yielding, cracking, on its interior or exterior surfaces, and/or substantially prevent blocking or interfering with the movement of pull wires, or twisting or moving in unintended directions or degrees. Thus, the distal end comprising a treatment or diagnostic element can be steered or moved more controllably by a physician using the medical device.

[0012] A particularly preferred embodiment of the invention includes steerable ablation devices having a shaft with a flexible distal region and a generally straight proximal region. One or more ablation cells are disposed along the distal end, which has a steerable deflection degree defined be a region of the device assembly within a designed flexible region. The steerable deflection region has at least one anchor member attached to a distal portion of the flexible distal region, the anchor member having passageways for one or more pull wires extending from the proximal region to the distal region. The steerable deflection region comprises a coiled or interlocking flex support member designed to permit deflection to a desired angle of deflection or range of deflection angles, and at the same time maintain the integrity of the interior and/or exterior of the steerable deflection region to prevent unintended movement, or prevent during multiple maximum deflections and relaxations of the device cracking, breaking, crimping, or yielding in the flexible region. Thus, in particularly preferred embodiments, the interlocking flex support member can be a laser cut metal or polymer formed into a ribbed-like coil, such as those shown in the figures, which maintains the integrity of the flexible region by substantially preventing breaking, cracking, yielding, or crimping of the flexible region over the course of 10 or 20 or 50 maximum deflection and relaxation cycles of the flexible region, for example. The steerable device can have two or more pull wires for deflection of the distal end in at least two directions. In preferred embodiments, the flexible region includes a flexible separating member within the steerable deflection region, where the flexible separating member is disposed in the flexible distal region to maintain the pull wires on separate sides of the interior of the flexible distal region. As described herein, the coiled or interlocking flex support member can be comprised of one or more of a polymer, metal, nitinol, or combination of two or more of these materials. The selection of the material and shape of the coiled or interlocking support member can include pre-formed linear, curved, or curvilinear shapes, for example. The steerable device typically has one or more pull wires actuated by a handle at the proximal end of the device.

[0013] The invention also includes methods of using a steerable device of the invention, such as introducing the flexible distal region and distal end of the device into a body during a surgical treatment and moving the distal end through actuating at least one pull wire. Preferred methods include those where the surgical procedure comprises ablation of cardiac or pericardial tissue, or where the ablation comprises the use of at least one ultrasound ablation element.

[0014] The foregoing and other aspects, features, details, utilities, and advantages of the present invention will be apparent from reading the following description and claims, and from reviewing the accompanying drawings.

[0023] The headings (such as “Brief Summary”) used are intended only for general organization of topics within the disclosure of the invention and are not intended to limit the disclosure of the invention or any aspect of it. In particular, subject matter disclosed in the “Background Art” may include aspects of technology within the scope of the invention and thus may not constitute solely background to the invention. Subject matter disclosed in the “Brief Summary” is not an exhaustive or complete disclosure of the entire scope of the invention or any particular embodiment.

[0024] As used herein, the words “preferred,” “preferentially,” and “preferably” refer to embodiments of the invention that afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful and is not intended to exclude other embodiments from the scope of the invention and no disclaimer of other embodiments should be inferred from the discussion of a preferred embodiment or a figure showing a preferred embodiment.

[0025] FIGS. 1 and 4 depict different views of a preferred embodiment of the invention comprising a flexible distal region 5 of a medical device. This assembly can be incorporated into a catheter, ablation device, or other diagnostic or treatment device and function to more controllably allow the movement of the distal end of the device in response to the physician's actions on a proximal control or actuating end or handle (not shown). Various deflectable medical devices are known and can be made available for adaptation with the present invention, including those of U.S. published patent applications 20050187455 and 20040034348, and U.S. Pat. Nos. 7,052,493 and 6,971,394, each specifically incorporated herein by reference. The device can have a pre-formed curve or curvilinear distal region or distal end for use in particular surgical procedures.

[0026] FIG. 1 shows an exemplary assembly with flexible region 5 composed in interlocking ribbed structure in a flexible support member 3, which can be any of a number of biocompatible metals, polymers, nitinol, shape-memory polymers or metals, or combinations thereof. In practice, the design of the interlocking ribbed structure should account for desired degree of deflection for a particular use. For example, interlocking pointed ends in the coiled or interlocking member 3, as shown in FIGS. 1 and 2, allow for a certain degree of movement before they become prone to crimping or separating. Similar interlocking ribbed structures with balled tips, flattened tips, or alternating tips may allow a greater degree of bending and may be desired for certain uses. FIGS. 10A-C show exemplary laser-cut designs for interlocking ribbed structures that can provide structural support and maintain the integrity of the flexible region during maximum deflection. The designs shown in FIGS. 10A-C correspond to a junction point similar to that shown in FIG. 3, where the points of each of the ribbed coils meet or come together. These structures can be formed by methods known in the art for laser cutting or other computer numerical control milling machines, for example. Alternatively, the interlocking area can be designed so that the two sides interlock when bent to a certain degree, and then can be held in place at that angle or substantially that angle until the area is bent further to release the interlocking A number of geometrical shapes and designs can be incorporated into the interlocking area or ribbed area of the flexible support member. As shown in FIGS. 8 and 9, the assembly can include a designed orientation of the ribbed structure in relation to the direction of deflection allowed in the medical device.

[0027] FIG. 3 depicts an alternative coiled structure for this member 3, which can similarly be made or comprised of metals, polymers, nitinol shape-memory materials. A variety of spring-like structures, braided structures, or coil structures can similarly be used to add structural integrity to the flexible distal region of a device according to the invention.

[0028] FIG. 1 further depicts the arrangement of elements in an exemplary assembly 5. Anchor member 1, here in shape of an anchor ring of the same diameter as the shaft of the device, fits into the distal end 6 of the distal flexible region of assembly. In this embodiment, a single anchor ring is used. The proximal end of the assembly 4 connects to an elongated shaft and optionally terminates in a proximal end handle and actuating elements (not shown). The exterior of the assembly and device can be coated or covered in a number of biocompatible compositions or polymers, as known in the art.

[0029] FIGS. 2 and 3 depict two of the many optional embodiments of the flexible support member 3 and its optional coiled, ribbed, or interlocking structure. The characteristics of this member can be determined by the desired flexibility, desired freedom of movement over a range of deflection angles, and/or desired strength or stress limits or Young's modulus of the material and structure selected. As noted, a number of polymeric, metal, and other material can be selected, and a preferred material is a shape-memory composition such as nitinol. Similarly and as noted above, the designs of FIGS. 10A-C can be used to produce the interlocking structure of a flex support as shown in FIG. 2 or 3, especially if laser cutting productions techniques are employed.

[0030] FIG. 4 depicts an embodiment with two pull wires 10 running through the flexible distal region assembly and the elements of the assembly. While pull wires 10 are shown to extend beyond anchor member or anchor ring 1, the pull wires can terminate at the holes or connection points in the ring in optional embodiments. A central separating member 11 fits into anchor member 1 in slits to effectively separate the interior of the flexible region so that pull wires 10 are held away from each other. The flat, plate shape of separating member 11 is one embodiment, and several other designs are possible especially when more than two pull wires are used. The separating member is typically a flexible element designed to flex and deflect with the assembly. The interlocking ribbed flex support member 12 adds structural stability and integrity to the assembly. The flex support member 12 fits onto, inside, or is integrally formed into the flexible region 3, which fits into the proximal end 1 of the shaft. The proximal end of the flexible region can also contain an anchor member or additional anchor member (not shown) to support or control movement of pull wires 10.

[0031] FIGS. 5 and 6 depict views of each side of the anchor member 1 and its optional features. Slots 21 are designed to hold or fix in a separating position the separating member 11, as shown in FIG. 4. Holes 23 are designed to allow pull wires to pass through and can be contoured to fit a terminating ball or other fixed point at the end of a pull wire. The differing diameters shown on the profile of anchor member 1 allow for the insertion into the flexible region of assembly. The anchor member can optionally be placed at more than one position in a flexible region assembly, such as at each of the proximal and distal end, and at the distal end, the center or intermediate point of , and the proximal end of the flexible region.

[0032] FIG. 7 depicts a proximal end 13 connection point for the flexible assembly, where slots 20 fix the separating member in position, and inserting diameter 16 region fits into the flexible region of assembly. FIGS. 8 and 9 depict the deflection of the flexible distal region to a desired angle.

[0033] The assemblies and devices of the invention can be used in methods to ablate cardiac or epicardial tissue, or other tissue. The flexible region assembly can be designed to allow, for example, about 90 degrees of deflection, or from about 60 to about 100 degrees of deflection, to a distal end and maintain the integrity of the flexible region and control over the movement of the ablating element at distal end. By maintaining the integrity, the interior and/or exterior walls of the flexible region do not crimp, yield, crack, or break at maximum deflection. Alternatively, the interior and/or exterior walls can withstand multiple rounds of maximum deflection and release, such as 10 rounds, 20 rounds, or 50 rounds, without substantially effecting the integrity of the interior or exterior walls by showing signs of crimping, cracking, yielding or breaking Thus, for example, the pull wires can be actuated at a handle at the proximal end of the device to fully deflect the distal end to 90 degrees. The materials used in construction of the flexible region can be shape-memory materials that allow the flexible region to return to a desired position or move a desired angle to ablate tissue as controlled by pull wires. The deflection can be in one, two, or multiple directions with the use of a number of pull wires and connection points of the pull wires to the device or within the flexible region. The angle of deflection in each direction desired, or range of angles, can be selected from any number between, for example, 45 to 90 degrees.

[0034] Although several embodiments of this invention have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this invention.

[0035] All directional references (e.g., upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are only used for identification purposes to aid the reader's understanding of the present invention, and do not create limitations, particularly as to the position, orientation, or use of the invention. Joinder references (e.g., attached, coupled, fixed, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other.

[0036] It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure may be made without departing from the spirit of the invention as defined in the appended claims.