Fixation Anchor Design for an Occlusion Device

[0001] This Application claims the benefit of and priority to U.S. Provisional Application No. 61/700,221, filed Sep. 12, 2012, the entire contents of which are herein incorporated by reference.

[0002] This invention relates to fixation anchors that may be incorporated into the structure of an occlusion device or vascular filter.

[0003] Medical devices implantable within the vasculature are often used to mitigate against blood clots, deep venous thrombosis, and/or pulmonary emboli when anticoagulation therapy is contraindicated. For example, a pregnant woman afflicted with atrial fibrillation may be implanted with a left atrial appendage occlusion device rather than prescribed anticoagulants. Once in place, the device provides scaffolding over which a tissue plug isolating the left atrial appendage may be formed. As another example, an elderly patient having just undergone a major surgery may be fitted with an inferior vena cava filter to mitigate against pulmonary emboli or deep venous thrombosis following surgery rather than prescribed anticoagulants. Once in place, the structure of the filter traps potential harmful blood clots that may occur as the patient recovers from surgery.

[0004] Both types of devices are generally implantable via endoscopic procedures utilizing catheter delivery systems. In general, a catheter carrying the device in a constrained state is advance through the vasculature to the location of device deployment.

[0005] The device is then expanded and anchored in place by various barbs engaging the surrounding the tissue.

[0006] All US patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.

[0007] Without limiting the scope of the invention a brief summary of some of the claimed embodiments of the invention is set forth below. Additional details of the summarized embodiments of the invention and/or additional embodiments of the invention may be found in the Detailed Description of the Invention below.

[0008] A brief abstract of the technical disclosure in the specification is provided as well only for the purposes of complying with 37 C.F.R. 1.72. The abstract is not intended to be used for interpreting the scope of the claims.

[0009] An implantable medical device having barbs that reduce in height and change angle as the implantable device transitions from an expanded state to a constrained state may lessen the risk of injury associated with the removal and/or repositioning of the deployed device. Such a medical device, implantable within and retrievable from the vasculature of a patient, may comprise a main body formed from a plurality of ribs extending radially outwards from a nexus that are capable of transitioning from an expanded state to a collapsed state. The plurality of ribs defines an interior of the main of the body. Within the main body may be positioned a plurality of fixation struts. When the main body is in the expanded state, the fixation struts may extend through and across at least a portion of the interior. An end of each fixation strut may be secured to the main body directly or indirectly via an intermediary structure. A barb end of each fixation strut may exit the main body at a point of egress and project radially outwards from the main body. Each of the fixation struts may be secured to the main body, such that the distance between the point of attachment of the secured end of a fixation strut, and the respective point of egress from the main body of its free barb forming end is greater in the constrained state than in the expanded state, thereby reducing the height the barb end projects from the main body.

[0010] During implantation, the main body transitions from a constrained state to an expanded state. When in the expanded state, the free barb ends of each fixation strut extend radially outward past the outer diameter of the main body. Extending radially outward, the free barb ends of the fixation struts may collectively anchor the implantable medical device in place by engaging surrounding tissue.

[0011] While the inclusion of barbs on an implantable medical device may be beneficial in reducing migration, they may also be burdensome when repositioning and/or removing the implantable medical device. For example, if an implantable medical device is deployed at an inappropriate and/or less than ideal location, it may be desirable to reposition the device to a more ideal location. Moving the implantable medical device in the expanded state, however, may cause damage to the surrounding tissue as a consequence of barbs engaging the tissue.

[0012] Additionally, engagement of the surrounding tissue by barbs may cause complications when an implantable medical device is removed. For example, when an implantable medical device has served its function, it may be desirable to remove it as to prevent complications arising from its continued presence within the body. Removal of an implantable medical device may be done by transitioning an implantable medical device to constrained state and recapturing it within a catheter. The transition to the constrained state and/or movement of an implantable medical device into a catheter may cause the barbs to traumatically disengage from the surrounding tissue thereby causing injury and/or other complications. The barbs may also damage the catheter during recapture, which may cause a release of debris from the catheter and/or other complications.

[0013] An implantable medical device embodying the present invention mitigates the risk of such complications, and others, by providing barbs that reduce in height and/or change angle when the implantable medical device transitions from an expanded to a constrained state.

[0014] During a recapture to remove and/or reposition, an expanded implantable medical device embodying the present invention may be drawn into a catheter and/or otherwise transitioned from an expanded to a constrained state. During the transition, the points of attachment of the secured ends of the fixation struts move away from the points of egress of the respective free barb ends. Thus, in the constrained state a greater distance separates a struts point of attachment and its point of egress. Accordingly, in some embodiments, as the implantable medical device transitions from an expanded to constrained state, the main body acts like a tether pulling on the secured ends of the fixation struts reducing the amount and/or changing the angle the barb free ends protrude from the main body. The resulting reduction in height and/or change in angle of the barb free ends may cause an easier and/or less traumatic detachment from the surrounding tissue. In combination or the alternative, the reduction in height and/or change in the angle the free barb ends protrude the main body may lessen damage inflicted on inner surfaces of the catheter utilized for recapture or otherwise reduce the likelihood of complications resulting from damage to the catheter.

[0015] These and other embodiments which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof However, for a better understanding of the invention, its advantages and objectives obtained by its use, reference can be made to the drawings which form a further part hereof and the accompanying descriptive matter, in which there are illustrated and described various embodiments of the invention.

[0031] While this invention may be embodied in many different forms, there are described in detail herein specific embodiments of the invention. This description is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated.

[0032] For the purposes of this disclosure, like reference numerals in the figures shall refer to like features unless otherwise indicated.

[0033] FIG. 1 depicts on potential embodiment of the present invention comprising a main body structure 101. As shown in FIGS. 1A and 1B, the embodiment depicted has an expanded state 101a, FIG. 1A, and a constrained state 101b, FIG. 1B. The outer perimeter, shown by dashed line 102, of main body 101 is larger in the expanded stated than when in the constrained state. Main body 101 is formed from a plurality of ribs 103 extending radially outwards from nexus 104 and defining an interior 109. A plurality of fixation struts 105 are within main body 101. Each of the fixation struts 105 has a secured end 106 attached to the main body 101 at a point of attachment 111 and a free barb end 107 exiting the main body from a point of egress 108 and extending radially outwards past the outer perimeter. As shown in FIG. 1A, fixation struts 105 extend through and across interior 109 of main body 101 in the expanded state.

[0034] Ribs 103 and/or fixation struts 105 may be formed from any suitable elastic material, for example, nitinol or spring steel. In the case of shape memory materials such as nitinol, the device may be provided with a memorized shape and then deformed to a reduced diameter shape. The device may restore itself to its memorized shape upon being heated to a transition temperature and/or having any restraints removed therefrom.

[0035] Depending on the specific embodiments and the requirements for the intended use, ribs 103 and/or fixation struts 105 may also be made from any other suitable biocompatible material including one or more polymers, one or more metals or combinations of polymer(s) and metal(s). Examples of suitable materials include biodegradable materials that are also biocompatible. In this context, the term “biodegradable” is used to denominate a material that undergoes breakdown or decomposition into harmless compounds as part of a normal biological process. Suitable biodegradable materials include polylactic acid, polyglycolic acid (PGA), collagen or other connective proteins or natural materials, polycaprolactone, hylauric acid, adhesive proteins, copolymers of these materials as well as composites and combinations thereof and combinations of other biodegradable polymers. Other polymers that may be used include polyester and polycarbonate copolymers. Examples of suitable metals include, but are not limited to, stainless steel, titanium, tantalum, platinum, tungsten, gold and/or alloys of any of the abovementioned metals. Examples of suitable alloys may include platinum-iridium alloys, cobalt-chromium alloys (e.g., Elgiloy and Phynox, MP35N), nickel-titanium alloys and nickel-titanium-platinum alloys.

[0036] In combination or the alternative, fixation members 105 may be formed from hypotubes.

[0037] An occlusion fabric 110 secured to the proximal end of main body 101 may aid in the prevention of blood flow and/or prevent the passage of large embolic material. Occlusion fabric 110 may be a permeable or impermeable. Fabric 110 may be made form a biocompatible material and/or may be made of a blood-permeable material having fluid conductive holes or channels extending across the membrane. These materials include, for example, ePFTE (e.g., Gore-Tex®), polyester (e.g., Dacron®), PTFE (e.g., Teflon®), silicone, urethane, metal fibers, and other biocompatible polymers. The size of the holes in the blood-permeable material may be chosen to be sufficiently small so that harmful-size emboli are filtered out from the blood flow between the appendage and the atrium. Suitable hole sizes may range, for example, from about 50 to about 400 microns in diameter. In embodiments, the filter membrane may be made of polyester (e.g., Dacron®) weave or knit having a nominal hole size of about 125 microns. The open area of the filter membrane (i.e., the hole density) may be selected or tailored to provide adequate flow conductivity for emboli-free blood to pass through the atrial appendage ostium. Further, portions of filter membrane may be coated or covered with an anticoagulant, such as heparin or another compound, or otherwise treated so that the treated portions acquire antithrombogenic properties to inhibit the formation of hole-clogging blood clots.

[0038] As shown in greater detail in FIG. 2A, a point of egress 108 may be a passage or any opening extending through a rib 103 through which a free barb end 107 of at least one fixation strut 105 may pass. The passage shown in FIG. 2A may be formed by cutting, drilling or otherwise providing a hole through rib 103. In combination or the alternative, point of egress 108 may be formed by bending a rib 103 to from an eyelet or similar structure, as shown in FIG. 2B. Point of egress 108 may also be formed from space provided when at least two ribs 103 are braided, woven, latticed and/or otherwise intertwined, as shown in FIG. 2C. Point of egress 108, in combination or the alternative, may also, as shown in FIG. 2D, be an opening in a closed cell pattern. In other embodiments, as shown in FIG. 2E, an intersection of two ribs may serves as point of egress 108.

[0039] As shown in FIG. 1, the distance separating the point of attachment 111 of a fixation strut 105 and the point of egress 108 for the respective free barb 107 is greater in the constrained state, d_c, than the expanded state d_e. Accordingly, as main body 101 transitions from the expanded state to the constrained state the secured ends 106 of each fixation strut 105 are displaced proximally with respect to the respective point of egress 108. The proximal displacement draws the free barb ends 107 inwards to main body 101 thereby reducing the amount each free bard end 107 protrudes from main body 101. During transition from the expanded state to the constrained, the main body 101 thus acts like a tether pulling on the secured ends 106 of fixation struts 105, reducing the height and/or changing the angle free barb ends 107 projects from main body 101. The resulting reduction and/or change in angle may cause an easier detachment of the depicted implantable medical device from the surrounding tissue when repositioning, removing and/or recapturing via a catheter.

[0040] The main body may act like a tether when the fixation members are secured at locations other than those depicted in FIG. 1. For example, secured ends 106 of fixation struts 105 need not be attached to main body 101 at the same latitude.

[0041] Likewise, points of egress 108 for free barb ends 107 of fixation struts 105 need not be positioned at the same latitude. Additionally, a secured end 106 of a fixation member 105 may be connected to the main body at an axial location.

[0042] FIG. 3 depicts an embodiment in which at least two of the fixation struts 105 are secured to main body 101 at an axial location. In the embodiment shown, the points of attachment 111 for secured ends 106 are located at nexus 104. Free barb ends 107, directed radially outwards from nexus 104, exit main body 101 at points of egress 108 and projecting radially outwards past outer perimeter 102. Accordingly, as shown in FIG. 3, each fixation struts 105 extends through and across a portion of interior 109. When nexus 104 is displaced proximally, such as when the depicted implantable medical device is pulled into a catheter during recapture, nexus 104 pulls on secured ends 106 like a tether reducing the height and/or changing the angle free barb ends 107 project from main body 101. The resulting reduction in the amount and/or change in angle free barb ends 107 protrude from main body 101 may reduce fixation on the surrounding tissue permitting an easier and/or less traumatic detachment of the depicted implantable medical device from the surrounding tissue.

[0043] The points of attachment for the secured ends of the fixation struts, in combination or the alternative, may be located at a distal nexus as shown in FIG. 4. The embodiment depicted in FIG. 4 contains a main body 101 having a caged serpentine structure formed from a plurality of ribs 103 extending radially outwards from nexus 104 at the proximal end and combining at second nexus 401 at the distal end. Fixation struts 105 are formed from the distal terminations of ribs 103. As shown in FIG. 4, at least some of ribs 103 contain a bend 402 directing free barb ends 107 to exit main body 101 from points of egress 108 and extend radially outwards past the outer perimeter 102. Accordingly, fixation struts 105 extend across and through a portion of interior 109 of main body 101 in the expanded state. As bends 402 connect fixation struts 105 to main body 101, bends 402 represent one possible embodiment of point of attachments in which fixation struts 105 are an integrated part of at least a portion of ribs 103.

[0044] As shown in FIGS. 4A and 4B, the embodiment depicted has an expanded state 400a, FIG. 4A, and a constrained state 400b, FIG. 4B. When the embodiment depicted in FIG. 4 transitions from the expanded state 400a to the constrained state 400b, nexus 401 is displaced proximally with respect to points of egress 108 as main body 101 constricts, causing movement of the fixation struts as depicted in FIG. 4C. The constriction of main body 101 pushes fixation struts 105 to a more vertical orientation, indicated by dashed lines, in the direction of arrows 403. Movement of fixation struts 105 along arrows 403 compresses bends 402 resulting in the proximal displacement of bends 402 in the direction of arrows 404. Compression of bends 402, in turn, induces rotation of their terminal ends about nexus 401 along the paths indicated by arrows 405.

[0045] As shown in FIGS. 4A and B, the transition of fixations struts 105 to a more vertical orientation in the constrained state increases the distance (d_c in the constrained state and d_e in the expanded state) separating bend 402 of a fixation strut 105 and the point of egress 108 for the respective free barb 107. Accordingly, as main body 101 transitions from expanded state 400a to constrained state 400b the points of attachments, bends 402, for secured ends 106 of each fixation struts 105 are displaced a greater distance from the respective points of egress 108. The displacement draws free barb ends 107 inwards to main body 101, thereby reducing the amount and/or changing the angle each free barb end 107 protrudes from main body 101. The resulting reduction and/or change in angle may cause an easier and/or less traumatic detachment of the depicted implantable medical device from the surrounding tissue when repositioning, removing and/or recapturing via a catheter. In combination or the alternative, the reduction in height and/or change in the angle free barb ends 107 protrude from main body 101 may lessen damage inflicted on inner surfaces of the catheter utilized for recapture or otherwise reduce the likelihood of complications resulting from damage to the catheter.

[0046] In combination or the alternative, fixation members may be made integral to the main boy 101 and/or ribs 103. For example, the fixation members and the ribs being collectively cut into body 101. In combination or the alternative, at least a portion of the plurality of fixation members 105 may be attached to main body 101 via an intermediary structure.

[0047] A proximal displacement of the points of attachment 111 of secured ends 106 is not necessary for reducing the amount and/or changing the angle free barb ends 107 protrude from main body 101 in a constrained state. In combination or the alternative, embodiments may utilize a distal displacement. Some embodiments of the present invention, additionally or in the alternative, may contain a hub connecting all or some of the fixation struts to the main body. In the embodiment shown in FIG. 5 a distal displacement of hub 501, connecting secured ends 106 to nexus 401, reduces the amount and/or changes the angle free barb ends 107 protrude from main body 101. Hub 501 acts as a point of attachment connecting secured ends 106 of fixation members 105 to main body 101. As with the embodiment depicted in FIG. 4, fixation struts 105 extend across and through a portion of interior 109 of main body 101 in the expanded state. Free barb ends 107 exiting main body 101 at points of egress 108 are directed radially outwards and project past the outer perimeter 102.

[0048] As shown in FIG. 5C, hub 501 and fixation struts 105 may be integral components formed by laser cutting and/or other means readily recognizable to those skilled in the art.

[0049] As shown in FIGS. 5A and 5B, the embodiment depicted has an expanded state 500a, FIG. 5A, and a constrained state 500b, FIG. 5B. The distance separating the point of attachment 111 of a fixation strut 105 and the point of egress 108 for the respective free barb 107 is greater in the constrained state, d_e, than the expanded state d_e. Accordingly, when nexus 401 is displaced distally, such as when the depicted implantable medical device is pulled into a catheter during recapture, nexus 401 via hub 501 pulls on secured ends 106 like a tether reducing the height and/or changing the angle of free barb ends 107. The resulting reduction in the amount and/or angle free barb ends 107 protrude from main body 101 may cause an easier and/or less traumatic detachment of the depicted implantable medical device from the surrounding tissue.

[0050] The above disclosure is intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in this field of art. All these alternatives and variations are intended to be included within the scope of the claims where the term “comprising” means “including, but not limited to.” Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims.

[0051] Further, the particular features presented in the dependent claims can be combined with each other in other manners within the scope of the invention such that the invention should be recognized as also specifically directed to other embodiments having any other possible combination of the features of the dependent claims. For instance, for purposes of claim publication, any dependent claim which follows should be taken as alternatively written in a multiple dependent form from all prior claims which possess all antecedents referenced in such dependent claim if such multiple dependent format is an accepted format within the jurisdiction (e.g. each claim depending directly from claim 1 should be alternatively taken as depending from all previous claims).

[0052] This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto.