Abstract:
A medical device implant for the left atrial appendage of a patient&#39;s heart, to prevent strokes. The device includes a cap that overlies the opening of the LAA connected to a bulb in the LAA. Dis-continuous segmented sails attached to the cap promote tissue growth over the device.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    It is widely understood that the occlusion of the left atrial appendage of the human heart will prevent strokes. The mechanism of action is that clots present within the left atrial appendage can become entrained into the general circulation and be transported to the brain where the clots can occlude arterial vessels causing an ischemic stroke. 
         [0002]    Devices that have received significant clinical study include the “Plaato” device described in U.S. Pat. No. 6,152,144 among others, and the “Watchman” device described in U.S. Pat. No. 6,689,150 among others. Each of these clinically tested devices lies wholly within the left atrial appendage and includes a membrane that spans the opening or ostium of the left atrial appendage. The Watchman device is typically porous and in the Plaato device the membrane is impervious to the passage of blood. Additionally, the Watchman device uses a series of barbs or prongs which enter the tissue surrounding the ostium of the left atrial appendage to help secure the device during the acute phase of implant. 
         [0003]    Although both of these devices appear to be successful, they each have shortcomings and drawbacks, which suggest that additional development is required for a widely acceptable and successful left atrial appendage device. 
       SUMMARY OF THE INVENTION 
       [0004]    In contrast to the prior art clinical devices, the present invention provides a compliant cap that lies outside of the ostium of the LAA over the opening and is tethered or connected to an anchoring bulb positioned within the left atrial appendage. The overall device is highly compliant and conformable, and can accommodate a wide variety of sizes, shapes and volumes of left atrial appendage, which is desirable. The external cover cap is sufficiently pliant and conformable that is can flex to accommodate different contours of heart chamber near the left atrial appendage ostium. The cap includes multiple sail segments. These so-called “sails” are attached to the cap framework and they form a discontinuous but overlapping leaky structure. For example no individual sail structure spans the dimension of the ostium of the LAA. However, the multiple sails prevent clots from migrating but no attempt at blood filtration is made. 
         [0005]    Overall the LAA device is made up from several wire loops that connect to independent posts. The cap framework includes single wire loops that overlap to form “petals”. The bulb framework includes several wire loops that are gathered together and attached to each other at specified locations. 
         [0006]    In general, each wire loop passes through two posts. The wire loops are loosely retained in the posts and the device exhibits many degrees of freedom and is highly flexible and compliant. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Throughout the several figures like reference numerals indicate identical structure, and for this reason many reference numbers appear more than once, wherein: 
           [0008]      FIG. 1  is view of the LAA device in its un-deformed shape; 
           [0009]      FIG. 2  is a view of the LAA device deformed into conformity with an LAA; 
           [0010]      FIG. 3  is a perspective view of the device seen from the distal end; 
           [0011]      FIG. 4  is a perspective view of a portion of the device seen from the proximal end; 
           [0012]      FIG. 5  is a view of the device partially deployed out of a delivery catheter; 
           [0013]      FIG. 6  is a schematic diagram in exaggerated scale to show the topology of the device. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]      FIG. 1  shows the LAA device  10  seen from the side in its unstressed or un-deformed shape. The device includes a cap framework  12  and a bulb framework  14 . As is common in medical devices the frameworks are manufactured primarily from Nitinol with a “shape memory” shape heat set during manufacture. The device assumes this shape in the un-deformed or unstressed condition. The interconnecting posts are made from titanium or any other compatible material. 
         [0015]    The cap framework is made up of a collection or set of wire loops, typified by the wire loop  22 . Each wire loop for the cap framework is formed by a single Nitinol wire that passes though a hole in the proximal post  16  and a hole in the intermediate post  18 . A crimp connector collars typified in the figure by crimp connector collar  26  or crimp connector collar  28  is used to collect the two ends of a single wire to form a wire loop indicated in the figure as wire loop  22 . The holes in the posts are large enough to typically carry a single wire with some clearance. See for example the hole near reference numeral  32 . All holes carry at least one wire. The wire fit in the holes is “loose” and the wire are free to move with respect to each other and importantly the wires do not transfer or share much force, through the posts, with each other in use. However in manufacturing the hole shape is slightly altered by pressing, such that the wires may rotate but are restaringed against translational motion through the hole. In essence the slight crushing of the posts preserves the overall shape of the device but compliance is preserved and enhanced. The wire loops are largely independent and decouple the cap framework  12  from the bulb framework  14 . Typically each wire loop is heat set to form a loop that has a petal section in the Y-Z plane defined at reference numeral  30  and a linkage in the Y-X plane. That is each wire of the cap framework forms one of a number of independent petals that collectively make up the cap framework. Present but not well seen in this figure is a “sail” system  42  attached to elements of the cap framework  12 . Also well seen in this figure is the connection feature  17  here shown as a ball shaped protuberance that can be captured by a delivery tool. The delivery tool seen at  19  in  FIG. 5  can grasp the proximal post and thereby manipulate the device  10  in the delivery catheter  21  or in the heart chamber. 
         [0016]    The bulb framework  14  is made up from a collection of wire loops as well. For example a wire loop  24  is made from a single wire that passes through the intermediate post  18  and the distal post  20 , with the ends collected in a crimp connector collars seen at  34 . In contrast to the cap framework, a companion coupler  38  connects loops such as  24  and its neighboring companion wire loop  36 . Short barbs indicated by barb  40  are also placed at the couplers. The couplers connect two wire loops and permit forces to be shared by the two loops, for example loop  24  and loop  36  each influence each other while not influencing other wire loops. 
         [0017]      FIG. 2  shows the LAA device  10  in use in the left atrial appendage  48  of a patient. The petals of the cap framework  12  over-lie the generally annular opening ostium  50  of the LAA  48 . In general the dimension “c” of the cap framework  12  is larger than the nominal diameter of the ostium  50 . The bulb  14  is in the stressed state in this figure and the nominal diameter “d” of the bulb framework is reduced from the value of the corresponding dimension as seen in  FIG. 1 . The nominal length “l” of the device  10  in the stressed state is elongated from the unstressed state of  FIG. 1 . The LAA  48  supplies the forces required to impose these deformations and the reaction forces from the device will embed barbs such as barb  52  into the tissue proximate to the bulb  14 . The figure also demonstrates that there is essentially no force applied to the cap framework by the deformation of the bulb  14 . This independence results in substantial performance improvements and in general the heart chamber outside the ostium  50  dictates the shape or curvature of the cap framework and this tends to reduce the anchoring force required to retain the device  10  in the heart. 
         [0018]    In  FIG. 2  an axis is defined for each of the posts. Axis  54  for proximal post  16  is depicted in the figure. Axis  56  is defined for intermediate post  18  while axis  58  is defined for the distal post  20 . Each axis is concentric and coaxial in the unstressed state of  FIG. 1  but may align to any other direction under the deformation forces supplied by the native anatomy. The misalignment seen in  FIG. 2  of the posts demonstrates the supple conformation of the device taken as a whole. 
         [0019]      FIG. 3  is a perspective view of the device  10  seen from the distal end and serves to show aspects and features better seen from this viewpoint. Here it is easier to discern the overlap of wire loop  70  and wire loop  72  as they form petals in the Y-Z plane. In this version of the device a single sail  66  is attached by fold over such as fold-over  68  to wire loop petals. The sail material is both flexible and “stretchy” when wet and little force is exerted on complimentary petals. For this reason it is possible for the cap framework to adopt non-circular forms and out of place curvatures in response to the native anatomy of the heart. The deep scallop cut  64  seen in the sail  66  prevents complete occlusion of the LAA. In general the sail material will be a polymer fabric of the type well known and used in implantable medical devices. Dacron and PVA fabrics are representative and not limiting examples of sail fabric. 
         [0020]    The viewpoint of  FIG. 3  also shows bulb framework wire loop  24  near coupler  38  and again across the device near coupler  60 . The same is true for wire loop  36 . By connecting these companion loops a force  74  is reacted to by forces at  76  and not elsewhere. That is the bulb does not deform regularly or evenly but rather opposing side are strongly coupled to each other but not to other wire loops. This unusual property results in a non-uniform but highly compliment device. 
         [0021]      FIG. 4  shows a perspective view of the cap framework with an alternate sail configuration. Two separate sails  80  and  78  are seen in the figure with individually connected panel surfaces labeled  78   a    78   b  and  78   c  for sail  78 , while the panels of sail  80  are labeled  80   a,    80   b  and  80   c  in the figure. These overlapping structures serve to promote tissue growth and permit independent motion of the petals such as those formed by wire loops  70  and  72 . Blood flow but not clots will leak out and into the LAA b passing around the edges of the panels. 
         [0022]      FIG. 5  shows a deployment catheter in a somewhat schematic form. LAA devices are delivered to the LAA though a long delivery catheter  21  that enters the patient in the groin and passes though the septum into the left heart from the right heart. This pathway is well known and need not be described in detail. In the figure the distal bulb has been deployed out to the delivery catheter with the intermediate post  18  and proximal post  16  still partially in the catheter. The deployed shape and unconstrained shape of the bulb  14  reveals the independence of the shapes and decoupled nature of the device. The delivery tool  19  grasps the connection feature  19  to manipulate the device. The delivery tool  19  can push or pull the device  10  into or out of the delivery catheter  21 . The compliance of the design facilitates deployment and recapture of the device  10 . 
         [0023]      FIG. 6  is a schematic diagram that is intended to display the topology of the device and as a consequence the scale of the post and wires have been exaggerated to more clearly display the interconnections between elements. For example a single wire  22  is passed though post  16  and heat formed to make two petals in the Y-Z plane, it then traverses the in the x direction to pass though the intermediate post  18 . A crimp connector collars or weld seen at reference  26  connects the two ends of the wire. Two wire loops are seen in the bulb area. Wire  24  and  36  each pass though both the intermediate and distal posts. Crimp connections or the like are seen in the figure to close the loops. Exaggerated connections between the two wires are seen at  38  and  60 . These couplers allow these two bulb wires to share or exchange force independently of the other bulb wires not shown in the figure to simplify the drawing.