Abstract:
A temporary subvalvular check valve has a collar and an expandable seal structure connected by pivotable struts that together support flexible leaflets. The check valve can be introduced along a tool shaft and positioned in a chamber or vasculature by expanding the seal structure against an adjacent wall. Cardiac function is augmented during valve procedures, such as valve excision, valve implantation, or valve leaflet replacement, by placing the temporary check valve just upstream of the valve being treated. The temporary check valve is collapsible so that it can be inserted through a small incision or port in the apex of the heart or through the aorta, into the ventricular cavity. Such a system thus does not require arrest or pacing of the heart and will allow such valve repair or replacement procedures to be done without concern for time or compromise to the patients&#39; physiology.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority pursuant to 35 U.S.C. §119(e) of U.S. provisional application no. 61/371,911 filed 9 Aug. 2010 entitled “Temporary sub-valvular check valve,” which is hereby incorporated herein by reference in its entirety. 
     
    
     FIELD OF TECHNOLOGY 
       [0002]    The present disclosure relates generally to a system for performing procedures on native or prosthetic heart valves, and more particularly to the servicing, repair, or replacement of these devices without requiring cardiopulmonary bypass. 
       BACKGROUND 
       [0003]    The demographics of patients suffering valvular disease are broad and the treatment modalities for each are complex. Historically, patients younger than 65 years of age have been prescribed mechanical valves and those older receive bioprosthetic valves. These prosthetic valves eventually wear out and need to be replaced with a new, functional device. 
         [0004]    Replacement of native or prosthetic valves has traditionally required open-chest, open-heart surgery in which the patient is placed on cardiopulmonary bypass and the heart stopped and restarted again after the surgery is completed. Cardiopulmonary bypass, however, is associated with both short-term and long-term complications, such as cognitive impairment. This apparently results from the low-grade damage that occurs to the blood cells as they pass through the heart-lung machine. Although not completely understood, the process of subjecting blood constituents to pumps and oxygenators leads to the formation of small clots which then cause micro-strokes when introduced back into the patient. 
         [0005]    Performing off-pump, beating-heart surgery has been a great challenge and an important objective for surgeons for many decades; the most successful today is the surgical repair of atherosclerotic lesions in the coronary arteries. Off-pump Coronary Artery Bypass Surgery (OP-CABG) is now considered a huge advantage for patients that require Coronary Artery Bypass. Although the chest is opened to allow access to the surface of the heart, the heart continues to pump as the blood vessels that feed blood to the heart are repaired and bypassed. 
         [0006]    Surgery on other components of the heart, such as the valves of the heart, is more difficult. This is because the valves are inside the heart and opening the heart to expose them cannot be done with the heart pumping blood. The primary candidate technology for treating heart valves without stopping the heart and opening it up is the use of catheter-implantable valves. These valves are delivered through a catheter passed up through the aorta or the aortic arch, or through the apex of the heart into the ventricular cavity. These valves consist of tissue leaflets mounted on a frame that is expanded and anchored in the vicinity of the existing diseased native valve. 
         [0007]    Transcatheter Aortic Valve Implantation (TAVI) has become very popular because it avoids the potential complications of opening up the chest and placing the patient on cardiopulmonary bypass. This new technology is thus used on the very old or sick patients that have a high risk of dying if they were to undergo conventional open-heart surgery on cardiopulmonary bypass. 
         [0008]    The challenge in performing TAVI is the need to perform the procedure quickly. During the procedure itself, the native heart valve is crushed against the sides of the aorta, and during that process, the patient is essentially without a valve and thus without normal cardiac output flow. Moreover, many current generation transcatheter valves are expanded and seated in place by way of a balloon which occludes the aorta, essentially preventing any ejection of blood from the heart. To enable the balloon and the associated transcatheter valve from being ejected out of the heart, the physician rapidly paces the heart, dramatically reducing its contractions and preventing the pumping of blood. This is not an ideal situation for the patient, particularly if they are already ill and compromised from the underlying valvular disease. 
         [0009]    Another approach has been to augment the native valve with a temporary valve to augment the pumping of blood while the native valve is in the process of being repaired, excised, or replaced with a prosthetic valve. 
         [0010]    Prior temporary check valves have been placed in the ascending or descending aorta. This is not an ideal location, since the temporary valve is downstream from the coronary arteries and does not function in the appropriate manner during diastole to help in the filling of the coronary arties, as with the native aortic valve. 
         [0011]    There is also a situation when the native valve has already been replaced with a prosthetic device, and that device itself needs replacement. One such technology is the exchangeable valve concept (disclosed, for example, in U.S. Pat. No. 7,011,681 B2), in which the old, worn-out leaflet set may be pulled off the base of the valve and replaced with a new one. Such a procedure may also benefit from the use of an appropriate temporary check valve. 
         [0012]    The information included in this Background section of the specification, including any references cited herein and any description or discussion thereof, is included for technical reference purposes only and is not to be regarded subject matter by which the scope of the invention is to be bound. 
       SUMMARY 
       [0013]    The technology presented herein is a system for augmenting cardiac function during valve procedures, such as valve excision, valve implantation, or valve leaflet replacement, by placing a temporary check valve just upstream of the valve being treated. The temporary check valve is collapsible so that it can be inserted through a small incision or port in the apex of the heart or through the aorta, into the ventricular cavity. Such a system thus does not require arrest or pacing of the heart and will allow such valve repair or replacement procedures to be done without concern for time or compromise to the patients&#39; physiology. 
         [0014]    As suggested, a better location for the temporary check valve is upstream of the native aortic valve or essentially inside the ventricle, yet in intimate contact with the aortic outflow tract. Having the temporary check valve upstream of the coronary arteries, and upstream of the native valve, will enable procedures to take place on the native aortic valve and still facilitate the proper ejection of blood from the ventricle and the filling of the coronary arteries in a physiologically appropriate manner. 
         [0015]    A further application of the temporary check valve is in conjunction with the placement of a valve-supporting frame without the leaflets. The valve supporting frame can be incrementally dilated until it fits snugly in the patient&#39;s aortic root and the appropriately sized leaflets that fit into that frame can then be delivered. During the positioning and expansion of the frame, the patient may be without a fully functioning valve. The temporary check valve may thus help provide continuous cardiac output until the final leaflet set is delivered onto the valve frame. 
         [0016]    This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. A more extensive presentation of features, details, utilities, and advantages of the present invention as defined in the claims is provided in the following written description of various embodiments of the invention and illustrated in the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1A  is a schematic side isometric view of a temporary check valve mounted on a tool shaft passed into the interior of the heart. 
           [0018]      FIG. 1B  is a side elevation view in cross section of the temporary check valve of  FIG. 1A  as indicated by line  1 B- 1 B in  FIG. 2 . 
           [0019]      FIG. 2  is top plan view showing the outflow end of the temporary check valve of  FIG. 1A , with one segment of the mesh removed. 
           [0020]      FIG. 3  is a top isometric view of a schematic drawing of the temporary check valve shown in  FIG. 1A . 
           [0021]      FIG. 4  is an isometric view of the temporary check valve of  FIG. 1A  positioned against the underside of a bioprosthetic valve with exchangeable leaflets. 
           [0022]      FIG. 5  is a bottom isometric view of the temporary check valve of  FIG. 1A  positioned against the sewing cuff of a bioprosthetic valve as in  FIG. 4 . In this view, one segment of the mesh is removed for clarity. 
           [0023]      FIG. 6  is a bottom perspective view of the temporary check valve of  FIG. 1A  in a collapsed configuration. The mesh is removed for clarity. 
           [0024]      FIG. 7  is a bottom isometric view of the temporary check valve of  FIG. 1A  positioned at an intermediate location along the length of the tool shaft. The leaflets and mesh are removed for clarity. 
           [0025]      FIG. 8  is a bottom isometric view of the temporary check valve of  FIG. 1A  with one segment of the mesh removed to show the leaflets collapsed around the outside surface of the central tool shaft. 
           [0026]      FIG. 9A  is a top isometric view of the temporary check vale of  FIG. 1A  in an open flow configuration. In this view, one of the mesh segments is removed for clarity. 
           [0027]      FIG. 9B  is a bottom isometric view of the temporary check vale of  FIG. 1A  in an open flow configuration. In this view, one of the mesh segments is removed for clarity. 
           [0028]      FIG. 9C  is a bottom isometric view of the temporary check valve of  FIG. 1A  in a fully closed configuration. In this view, one of the mesh segments is removed for clarity. 
           [0029]      FIG. 10  is a bottom isometric view of the temporary check valve of  FIG. 1A  positioned below a valve frame of a two-part valve system. In this view, one of the mesh segments is removed for clarity. 
           [0030]      FIG. 11  is an isometric view of the temporary check valve of  FIG. 1A  shown in vivo placed in the ventricle below the aortic valve. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    A temporary check valve that can be positioned below the existing valve, e.g., below the aortic valve  220 , and augment the function of the original valve is disclosed herein in conjunction with the accompanying  FIGS. 1A-11 . 
         [0032]    According to a first implementation, and as can be seen in  FIGS. 1A-3 , and others, a temporary check valve  100  is composed of a sliding collar  110  that is positioned along the length of an insertion and guide tool  120 , e.g., a hollow tube, shaft, or catheter. The sliding collar can be repositioned along the shaft with a control structure, for example, sliders or pull wires  125  (as shown in  FIG. 7 ). The tool shaft  120  may facilitate the insertion or action of additional tools and may thus move along its axis further into the heart, independent of the check valve  100 . 
         [0033]    As shown in  FIGS. 1A-3  and  7 - 8 , and others, one or more (preferably three) struts  130  that support three leaflets  140  at their side edges project from the sliding collar  110  from one end of each. The struts  130  may be made of a harder material than the leaflets  140 , and are hinged at their attachment to the sliding collar  110  so that they can pivot radially outward. At the distal end of each of the struts  130  is an annular seal structure  150  that can expand and contract and seal against the interior walls of the vessels or chambers into which the tool shaft  120  and the temporary check valve  100  are inserted. As the seal structure  150  is expanded, the struts  130  pivot outward and the valve leaflets  140  are thereby expanded into position. The sliding collar  110  is held in a fixed position at a fixed distance proximal to the seal structure  150  by the fixed length struts  130 . The tool shaft  120  is free to move distally and proximally through the temporary check valve  100  within the sliding collar  110 . The side edges of the leaflets  140  are connected to the struts  130  and the narrow proximal base of each of the leaflets  140  is connected to the sliding collar  110 . The leaflets  140  thus are free to move at their distal unsupported edges  145 . 
         [0034]    The annular seal structure  150 , which is attached to the struts  130  at their distal ends, is generally circular in shape and can be activated to increase or decrease its circumference as necessary. A toroidal balloon is one possible embodiment of such an annular seal structure  150 . The balloon can be inflated with saline, as is done in other balloon applications. A tube for inflating the balloon is not shown in the figures, but can run through the inside of one of the struts  130 , or can be positioned along side one of the struts  130 , and can run along the outside or inside the tool shaft  120 , or can be incorporated into the wall material of the tool shaft  120 . As is customary in the field, these components may be made of molded or extruded plastic. 
         [0035]    In one implementation, the seal structure  150  may be designed to mate with the underside of an existing bioprosthetic valve  170 , e.g., as shown in  FIGS. 4 and 5 , as well as against the inner surface of a blood vessel or areas of the heart  200  such as in or near the aortic root to displace the native aortic valve leaflets  220 .  FIG. 10  shows a two-part bioprosthetic valve in which the valve frame  180  can be inserted first, dilated until it fits snugly in the valve position, and the appropriately sized leaflet set may then be snapped in place. This view shows the valve frame  180  without the leaflets in place and with the temporary check valve  100  in position firmly underneath the valve frame  180 . 
         [0036]    An appropriate number of segments of a collapsible mesh  160  are also attached to the struts  130 . The mesh  160  becomes substantially tight as the leaflets  140  are expanded and the struts  130  articulate outward by the expansion of the seal structure  150  which may be dilated in conjunction with or independently of valve frame  180 . When the temporary check valve  100  is closed, the leaflets  140  lean against this mesh  160  and are supported by it to form a seal against back pressure. Both the leaflets  140  and the supporting mesh  160  may be generally conical when fully expanded, as shown in the figures, but are not limited to this configuration. A generally conical shape is assumed for the following further description. When the temporary check valve  100  is closed, the leaflets  140  are pushed against the mesh  160  and mesh  160  holds the leaflets  140  in their conical shape. The free edge  145  of the leaflets  140  projects upwards past the mesh  160 , so that the leaflets  140  overlap with the inside surface  155  of the annular seal structure  150 . The free edge  145  of the leaflets  140  thus seals against the inner surface  155  of the annular seal structure  150  so that there is no leakage of fluid back through the temporary check valve  100  into the chamber  210  of the heart  200  during ventricular diastole. 
         [0037]    The presence of the mesh is desirable in that it allows the leaflets to be made very thin and collapsible, such as thin sheets of plastic that can easily fold up, as shown in  FIG. 6 . Without the mesh  160 , the leaflets  140  would need to be stiffer and stronger in order to bear the force of the fluid pressure, which is possible with materials such as thin, highly flexible metal such as Nitinol. The mesh  160  can be made from any appropriate material, such as plastic, fabric, string or could also be made of highly flexible metal, such as Nitinol. It is attached to the struts by way of sutures or pins, or can be overmolded as part of the other plastic components. 
         [0038]    One method of introducing the temporary check valve  100  into the ventricular cavity  210  is through a puncture in the ventricle  210  near the apex  230  of the heart  200  as depicted in  FIG. 11 . The temporary check valve  100  is held collapsed when the annular seal structure  150  is deflated or otherwise collapsed (as shown in  FIG. 6 ). That minimizes the diameter of the seal structure  150  and brings the struts  130  against the surface of the tool shaft. When the struts  130  are collapsed against the body of the tool shaft  120  and the leaflets  140  are appropriately wrinkled up and folded. 
         [0039]    The collapsed temporary check valve  100  may be positioned at the end of the tool shaft  120  for insertion or, alternatively, the tool shaft  120  may be initially inserted and the temporary check valve  100  may be placed about the outer diameter of the tool shaft  120  and slid along the tool shaft  120  until it is in an appropriate location for deployment. A pull wire  125  or rod or additional concentric shaft may be connected to the bottom edge of the sliding collar  110  to control and slide the temporary check valve  100  along the length of the tool shaft  120 . 
         [0040]    The temporary check valve  100  is then positioned just below the existing valve  220  inside the heart  200 , and the seal structure  150  is dilated or inflated (e.g., using a toroidal balloon) until it seals against the walls of the ventricular chamber, or the inner or under-surface of an existing prosthetic valve, as shown in  FIGS. 4 ,  5  and  10 . If the seal structure  150  of the temporary check valve  100  is made of an elastically-expanding, toroidal balloon, its collapsed shape is similar to that shown in FIG.  6 —a similar toroidal balloon with a smaller inside and outside diameter. If the seal is made from a less-elastic, non-inflatable material, then the seal structure  150  may be folded up and wrinkled as its diameter is reduced, much like the leaflets  140  of the temporary check valve  140  wrinkle up as the struts  130  are folded. If the seal is made from helically wound up material such as thin metal, it may be unwound in position expanding its diameter to the desired dimension. 
         [0041]    In normal function, all three leaflets  140  are either all open or all closed. During systole, the ventricle contracts and forces blood toward the temporary check valve  100 . The leaflets  140  collapse against the tool shaft  120  and blood flows through the mesh  160 , past the leaflets  140 , and between the tool shaft  120  and the seal structure  150 . During diastole, the leaflets  140  are forced proximally against the mesh  160  and seal against the inner surface  155  of the seal structure  150 , thus preventing backflow of blood into the ventricle  210  (or other vessel or anatomic area in which the temporary check valve  100  may be positioned).  FIGS. 9A and 9B  are schematic views showing how blood passes through the temporary check valve  100  when the leaflets  140  are open (i.e., collapsed). In these views, one of the mesh segments is removed for clarity. The arrows show the direction of blood flow.  FIG. 9C  depicts the leaflets  140  in the closed position with the leaflets  140  pressed against the mesh segments  160  to prevent backflow. 
         [0042]    Once the temporary check valve  100  is in place, additional tools can be passed through the central lumen of the tool shaft  120  over which the temporary check valve  100  is positioned, to perform the necessary procedures on the native valve  220  or prosthetic valve  170  without compromising the cardiac output function of the heart  200  or interfering with the normal filling of the coronary arteries. Provisions may be made so that any tool inserted through this hollow tool shaft  120  is appropriately sealed to prevent blood from leaking out of the heart  200  through the hollow tool shaft  120 . 
         [0043]    In a second implementation, the hollow tool shaft  120  on which the temporary check valve  100  is mounted may be a catheter that is passed through the aorta  240  from downstream of the native valve  220 , through the native valve  220 , and positioned below the native valve  220  as oppose to being delivered and positioned through the apex  230  of the heart  200 . 
         [0044]    In accordance with a third implementation, the annular seal structure  150  may be fabricated from a solid structure, for example, an elastic hoop of wire that is self expanding once it is positioned on the interior of a chamber or vessel wall. In one embodiment, the wire hoop may be formed of a shape memory material, e.g., Nitinol. The solid structure may have sufficient elasticity to push against the inner surface of the wall and make the necessary seal, similar to the inflated balloon. The solid structure may also contain an appropriately compliant covering material to properly deform and make contact with the wall of the ventricle chamber or vessel within which it is inserted. A helically wound configuration, unwound to expand and push against the inner surface of the wall can also be used as previously described. 
         [0045]    In a fourth implementation, the seal structure may be manually compressed and folded by the action of the struts  130 . If the struts  130  are forcibly collapsed against the tool shaft  120 , the seal structure may be also collapsed and fold down to a smaller size. 
         [0046]    All directional references (e.g., proximal, distal, upper, lower, upward, downward, left, right, lateral, longitudinal, front, back, top, bottom, above, below, vertical, horizontal, radial, axial, clockwise, and counterclockwise) are only used for identification purposes to aid the reader&#39;s understanding of the present invention, and do not create limitations, particularly as to the position, orientation, or use of the invention. Connection references (e.g., attached, coupled, connected, and joined) are to be construed broadly and may include intermediate members between a collection of elements and relative movement between elements unless otherwise indicated. As such, connection references do not necessarily infer that two elements are directly connected and in fixed relation to each other. The exemplary drawings are for purposes of illustration only and the dimensions, positions, order and relative sizes reflected in the drawings attached hereto may vary. 
         [0047]    The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments of the invention as defined in the claims. Although various embodiments of the claimed invention have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of the claimed invention. Other embodiments are therefore contemplated. It is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative only of particular embodiments and not limiting. Changes in detail or structure may be made without departing from the basic elements of the invention as defined in the following claims.