Self-cinching surgical clips and delivery system

[0001] The present application claims priority under 35 U.S.C. §119 to U.S. Provisional Application Ser. No. 61/568,048, filed Dec. 7, 2011.

[0002] The present invention relates generally to the field of medical devices. More particularly, this application relates to self-cinching clips and clip delivery systems for use in surgical procedures.

[0003] Prosthetic heart valves are used to replace damaged or diseased heart valves. The natural heart valves are the aortic, mitral (or bicuspid), tricuspid and pulmonary valves. Prosthetic heart valves can be used to replace any of these naturally occurring valves. Repair or replacement of the aortic or mitral valves is most common because they reside in the left side of the heart where pressures are the greatest.

[0004] Where replacement of a heart valve is indicated, the dysfunctional valve is typically cut out and replaced with either a mechanical valve or a tissue valve. Typically, an artificial valve has flexible (e.g., bioprosthetic) leaflets attached to a wireform structure with arcuate cusps and upstanding commissures supporting the leaflets within the valve. The artificial valve also has an annular stent and a soft sewing ring for better attachment to and sealing against the native valve annulus. The alternating cusps and commissures mimic the natural contour of leaflet attachment. Importantly, the wireform provides continuous support for each leaflet along the cusp region so as to better simulate the natural support structure.

[0005] In a typical prosthetic heart valve implantation, approximately 12-18 sutures are placed through the patient's native valve annulus. These sutures are subsequently passed through the sewing ring of the prosthetic valve outside of the surgical cavity. The valve is then “parachuted” down these sutures to the point where it meets the target annulus. At that point, the sutures are tied to secure the prosthesis to the heart. The process of placing the sutures through the annulus and subsequently tying 3-10 knots per suture is very time consuming and greatly adds to the time the patient is on heart-lung bypass, anesthesia, etc. There is a direct correlation between time spent on heart-lung bypass and poor outcomes. Additionally, for mitral valves, there is the possibility of “suture looping” to occur during knot tying in which the suture is looped over a valve commissure and partially constrains a pair of valve leaflets, thus preventing normal function of the prosthesis.

[0006] Various methods of attaching a prosthetic heart valve to a heart with few or no sutures have been developed in the past. Attempted attachment methods include the utilization of hooks or barbs integrated into the prosthesis that bite into the native tissue to anchor the device. These devices have bulky delivery systems and it can be difficult to position the prosthesis accurately.

[0007] Another possible solution is to implant a valve in much the same way as traditionally done with sutures, but to replace most or all of the sutures with rapidly deploying clips to attach the sewing ring to the annulus. Past designs have disclosed instrumentation that would deploy a clip with sharpened edges necessary to puncture the tissues or materials that are to be secured together. Such designs with sharp-ended clips have created local tissue irritation due to the exposed ends.

[0008] Most of the current devices, such as those disclosed in U.S. Pat. Nos. 5,480,406; 6,913,607; 7,407,505; and 7,862,572 all require access to both sides of the tissue/structures which are being sewn/clipped together. This is of particular disadvantage in attaching a prosthetic heart valve to an annulus because the prosthetic valve impedes access to the inflow side of the annulus.

[0009] It would therefore be desirable to develop a method of attaching a prosthetic heart valve to a valve annulus with few or no sutures, using a smaller device to deliver the clips which requires access to only one side of the target. It would also be advantageous to have a deployment mechanism with a clip with no sharp edges or tips so as to reduce tissue irritation.

[0010] The present invention provides an instrument for use in intricate, minimally-invasive procedures. More specifically, the present disclosure discusses a device for securing a surgical clip to secure at least two layers of tissue and/or synthetic materials together, for example, to secure a sewing ring of a prosthetic heart valve to a native valve annulus.

[0011] In some embodiments the delivery device comprises a housing, a pusher assembly, and a substantially straight tube assembly. A self-cinching clip made of a super-elastic material is disposed within the tube assembly, said clip having a relaxed configuration and a constrained configuration. The tube assembly comprises an outer tube and inner tube slidably disposed within the outer tube, the inner tube having a sharpened end configured to puncture at least two layers of tissue or material. In some embodiments, the outer tube comprises a sharpened end configured to puncture the at least two layers of tissue or material. The outer tube can include a stop flange. The device can further include a revolving cylinder holding at least one clip, where each clip is in a separate chamber and each chamber is arranged around the perimeter of the revolving cylinder.

[0012] The self-cinching clip preferably is made of Nitinol (highly flexible Ni—Ti alloy). In its relaxed state the ends of the clip are brought into close approximation. For instance, the clip can have a spiral shape having two open ends terminating at different but closely-spaced locations, or a circular shape with two ends terminating at approximately the same location, or a semicircle shape with two ends of the clip overlapping.

[0013] The present invention also provides for a method for securing at least two layers of tissue or material together comprising the steps of: advancing a securing device toward at least two layers of tissue or material, the securing device containing a clip and a tube assembly, wherein the tube assembly has a sharpened end and wherein the clip is made of a super-elastic material and is constrained in a substantially straight position within the tube assembly; puncturing from only one side of the at least two layers of tissue or material through the at least two layers of tissue or material using the sharpened end of the tube assembly; and deploying said clip into the at least two layers of tissue or material, wherein the clip returns to its relaxed shape as it exits the tube assembly such that the ends of the clip are brought into close approximation, thereby securing the at least two layers together.

[0014] A further understanding of the nature and advantages of the present invention are set forth in the following description and claims, particularly when considered in conjunction with the accompanying drawings in which like parts bear like reference numerals.

[0032] The following description refers to the accompanying drawings, which illustrate specific embodiments of the invention. Other embodiments having different structures and operation do not depart from the scope of the present invention.

[0033] Described herein is a surgical clip delivery device, which includes a self-closing surgical clip made of a superelastic or shape-memory material such as Nitinol, and methods for delivering the clip to a surgical site. While the device will be described in connection with a heart valve replacement procedure, it is to be understood that the device can be used in general surgery or in any procedure where two or more materials or layers are joined together. Its use is thus not limited to the surgical replacement of cardiac valves.

[0034] The self-closing surgical clip is designed such that when it is deformed into a configuration for delivery, the strains in the clip are below the yield point of the superelastic material. The clip is held within the delivery device in a constrained state and returns to its relaxed state once it is deployed from the delivery device. Specifically, when the clip is released from its constrained state, it returns or transitions toward its relaxed shape where the ends of the clip are brought into close approximation, thereby securing multiple layers of tissue or material together. It should be understood that intervening tissue or material may impede the clip from entirely resuming its relaxed shape, though the clips are designed to revert as near as possible to their relaxed states and thereby fasten the layers of tissue or material together.

[0035] FIGS. 1 and 2 illustrate an exemplary embodiment of a surgical clip delivery device 10. The device 10 comprises a housing 18 having a proximal end (to the right) and a distal end (to the left). A pusher assembly 16 includes a pusher handle 20 and a pusher shaft 26. The distal end of the device 10 contains a distal wall 12 through which an outer tube 24 and a hollow inner needle 28 extend distally from a graspable hub 22. The outer tube 24 is mounted for longitudinal movement through a bore in the distal wall 12 in the distal end of the housing 18, and the inner needle 28 slides within the lumen of the outer tube 24, as shown in cross-section in FIG. 2. Furthermore, the graspable hub 22 has a nipple 23 that removably couples with a short bore 25 in the proximal end of the outer tube 24 so that the two elements may be temporarily coupled together and slide together back and forth along a channel 13 of the housing between the distal wall 12 and a proximal wall 14.

[0036] The pusher assembly 16 functions to deploy a self-cinching surgical clip 30 out of the inner needle 28 of the device and prevent the clip from backing out of the tissue or material. In this regard, a clip 30 is first loaded into the lumen of the inner needle 28 and the shaft 26 of the pusher assembly 16 advanced to locate the clip near the distal end of the needle 28, as seen in FIG. 3A. In this position, the coupled outer tube 24, inner needle 28 and graspable hub 22 are located to the left (or distally) within the channel 13. While the clip 30 is within the inner needle 28, it is constrained in a substantially straight position (or takes the shape of the inner needle 28 if that is not straight).

[0037] Both the inner needle 28 and outer tube 24 guide the clip 30 from the housing 18 into the tissue or material during deployment. FIG. 3B shows the delivery step where the user displaces the inner needle 28 and graspable hub 22 to the right a distance A along the channel 13, which is about the clip length, while the pusher assembly 16 remains in place relative to the housing 18. The pusher shaft 16 has a length L sufficient to urge the clip 30 from the end of the inner needle 28. The outer tube 24 also remains in place, preferably with a stop flange 32 staying in contact with the tissue or material layer, as will be explained.

[0038] FIGS. 4-5 present a detailed view of alternative embodiments of the outer tube 24 and the inner needle 28 of the delivery device 10. Outer tube 24 is an elongate tube having the stop flange 32 positioned at its distal end and, in the illustrated embodiment, axial slot 34 that extends from the stop flange a short distance proximally. The stop flange 32 prevents the outer tube 24 from penetrating the tissue or material too deeply. Slot 34 may be present to allow the clip 30 to assume a curved shape once the clip 30 has reached a certain point of deployment within the inner needle 28, as will be explained in more detail below.

[0039] As shown best in FIG. 4, in one particular embodiment the distal end of the inner needle 28 has a sharpened end 39 which assists in the insertion of the inner needle 28 into the tissue or material. The term, “sharpened end” will be used herein to represent sharpened tips, whether beveled, tapered, or some other configuration. The sharpened end 39 of the inner needle 28 of the delivery system 10 is used to puncture the tissue and/or prosthetic device. This obviates the need for the end of the clip 30, which remains inside of the inner needle 28 of the delivery device 10, to be sharp, and it is thus desirably blunt. Therefore, no sharp ends remain in the patient's body once the clips 30 are deployed. This is important in reducing irritation of the surrounding tissue and increases the safety of the clips 30 after implantation. It is well known that leaving clips or other devices in the body that have exposed sharp ends can cause irritation and necrosis of the surrounding tissue. Additionally, sharp tips have the potential to pierce other adjacent organs and therefore present a risk. In a preferred embodiment the free ends of each clip have been ground so as to be rounded and not even have right angle corners.

[0040] As shown in FIG. 6, the inner needle 28 of the delivery device 10 has a clip channel 42 to allow for passage and deployment of clip 30. In some embodiments, the clip channel 42 extends from a point between the proximal and distal ends of the inner needle 28 to the distal end of the inner needle 28. A single clip or multiple clips end-to-end in series can be pre-loaded within the inner needle 28 of the device prior to use. The combination of the outer tube 24 and inner needle 28 of FIGS. 4-6 permit the clip 30 to exit laterally from within the inner needle 28, through the aligned axial slot 34 and clip channel 42, as will be explained, in contrast to being ejected from a distal end as in FIGS. 1-3.

[0041] FIGS. 7A and 7B are additional detailed illustrations of the clip 30 as it is deployed from the outer tube 24 and inner needle 28 of FIGS. 4-6. In this embodiment, as the clip 30 exits the inner needle 28, it is no longer constrained in a straight position by the inner needle 28 and it therefore relaxes into its “no-stress” state shown in FIGS. 8-10, depending on the clip embodiment utilized. Due to its ability to return to its pre-shaped unconstrained closed-end shape, the clip 30 can be referred to as self-closing. The interaction of the outer tube 24 and inner needle 28 is such that relative rotation of one with respect to the other can alternately align and misalign the axial slot 34 and clip channel 42, so as to control the timing of the clip ejection. That is, first the clip 30 is urged to the end of the inner needle 28, and then the axial slot 34 and clip channel 42 are aligned to permit the clip 30 to curl and enter the target tissue or material layers.

[0042] As shown in FIGS. 8-10, the clips can have a variety of shapes in their unstressed or unconstrained condition. Such shapes include semicircle-shaped (FIG. 8), modified spiral (FIG. 9), and circular (FIG. 10). The clip 30 is preferably made of a superelastic shape-memory material such as Nitinol so that when unconstrained, the clips 30 are self-closing toward their no-stress configurations. In each of the possible configurations, the clip 30 is designed such that when it is deformed into a delivery configuration the strains in the clip 30 are below the yield point of the superelastic material. In all configurations, the clip 30 does not have any sharp ends or edges.

[0043] In some of the variations presented here, such as the semicircle-shaped clip type shown in FIG. 8, the two ends of the clip overlap when deployed. This serves to reduce tissue irritation and increase the anchoring force to the tissue. In other embodiments, such as the circular clip shown in FIG. 10, the clip ends come together after deployment, thereby eliminating any exposed ends and reducing the potential for tissue irritation. The overlap of the two ends of the circular clip of FIG. 10 may further reduce tissue irritation as well as increase the holding force that can be generated by the clip. In other embodiments, such as the spiral configuration shown in FIG. 9, the clip has two open ends both terminating near the center of the clip.

[0044] The wire of the clips may have a round cross section, however, the cross section could be other shapes including, but not limited to, rectangular, triangular, etc. The cross section shape and dimension of the clip wire could also vary along its length to create variable amounts of stiffness in different portions of the clip. For example, with respect to the spiral clip 30 shown in FIG. 9, stiffness can be variable based upon the cross-sectional thickness, and the number and pitch of each individual coil. The overall shape of the clips could change as well and should not be considered limited to the three shapes disclosed herein.

[0045] The deployment sequence of a particular embodiment utilizing a circular clip 30 is shown in FIG. 11. First, the surgical clip delivery device 10 seen in FIG. 1 is advanced to the target site where the clip 30 is to be deployed. The surgeon pierces the sharp end of the inner needle 28 completely through the layers of tissue and/or synthetic materials to be fastened together. The stop flange 32 prevents the outer tube 24 from penetrating the tissue or material too deeply. Deployment of the clip 30 occurs as the pusher assembly 16 (not shown, see FIG. 1) is advanced distally toward the housing 18. In one particular embodiment, the distal end of the pusher shaft 26 is lined up end-to-end with the proximal end of the clip 30 within the inner needle 28 assembly. Distal advancement of the pusher shaft 26 therefore causing distal advancement of the clip 30. In another particular embodiment, the pusher assembly 16 remains static at the proximal end of the delivery device 10 as a stopper to prevent clip 30 from backing out of the proximal end of the inner needle 28.

[0046] In yet another embodiment, to deploy the clip 30, the pusher assembly 16 is advanced distally toward the housing 18 causing distal advancement of the clip 30 as described above. However, only a portion of the clip 30 is deployed this way, the remaining portion being deployed when the inner needle 28 is retracted proximally. The pusher assembly 16 moves distally a distance equal to only a portion of the length of the clip 30, exposing that portion of the clip 30 on the distal side of the tissue layers. The entire device 10 is then retracted exposing the proximal end of the clip 30 on the proximal side of the target. Alternatively, the clip 30 can be advanced using any other tool advancement mechanism known in the art.

[0047] Referring again to FIG. 11, the delivery sequence is as follows: the delivery device 10 is positioned over, and the distal end of the inner needle 28 pierces through, the target layers. The pusher assembly 16 that displaces the clip 30 is advanced forward until the clip 30 is completely deployed. The delivery device 10 is then removed. In some embodiments, the clip 30 is restrained within the inner needle 28 and the outer tube 24 until the tubes are rotated with respect to each other and their respective slots 34 and 40 are aligned allowing the clip 30 to be released from the tubes 28, 24.

[0048] Similarly, an example delivery sequence for the spiral clip 30 is shown in FIG. 12. In this particular embodiment, the device 10 is placed in a location proximate the target layers. The inner needle 28, having a sharpened and/or slanted end 39, pierces the target layers until the stop 32 hits the top layer. The clip 30 is deployed when the pusher assembly 16 (not shown) is advanced distally toward the housing 18. This action causes the clip 30 to begin exiting the distal end of the inner needle 28. As the clip 30 advances into the tissue, it begins to spiral around the axis of the inner needle 28 on the opposite side of the layers from the device 10. When the clip 30 is fully deployed, in one particular embodiment, portions of the clip 30 as well as the two ends of the clip are on opposite sides of the layers. In other embodiments, the ends may have varied final locations with respect to each other and varying portions of the clip may be on either side of the layers being held together by the clip 30. In some embodiments, once a sufficient portion of the clip 30 is deployed on the opposite side of the layers, the inner needle 28 is removed from the layer before the clip 30 is fully deployed to allow a portion of the clip 30 to be on the device-side of the layers.

[0049] FIG. 13 illustrates an artificial heart valve implanted within the aortic valve annulus utilizing the device 10 and clips 30 described herein. The prosthetic heart valve 50 is surgically inserted via the aorta 54 near the location of the native aortic heart valve annulus 52. The clip delivery device 10 is then inserted into the aorta 54 and the inner needle 28 first pierces the valve's securing ring and then the native valve annulus 52. The clip 30 is deployed as described above in connection with regarding FIGS. 11 and 12, securing the two layers (i.e., the valve's securing ring and the native valve annulus) together. Advantageously, the clips 30 shown in FIG. 13 were deployed entirely from the outflow side of the valve. The device disclosed herein is able to deliver the clips “blindly,” i.e. with access to only one side of the target.

[0050] To facilitate installation of a number of the clips 30, the delivery device may include a cartridge of clips that periodically increments to present a new clip to be delivered. For example, FIGS. 14A-14C are cross-sectional views through an alternative clip delivery system 60 having a cartridge 62 that holds multiple clips 30. As in the single-clip version of the surgical clip delivery device 10, the system 60 has a housing 64 with a distal wall 66, a proximal wall 68, and a channel 70 therebetween and within which the cartridge 62 linearly reciprocates. FIG. 15 is an elevational view of the cartridge 62. A cylinder 72 portion of the cartridge 62 rotates about a shaft extending from a non-rotating portion 74. The inner needle 28 is connected to and extends away from the non-rotating portion 74 of the cartridge 62 into the outer tube 24.

[0051] An assembly of a pusher handle 20′ and a pusher shaft 26′ are arranged to be held at a proximal end of the housing channel 70 such that the pusher shaft extends through one of the cartridge chambers 76 and through the inner needle 28 lumen when the cartridge 62 is in its proximal position. The pusher handle 20′ and a pusher shaft 26′ are removable from the cartridge chamber 76 to permit the movable portion 72 of the cartridge 62 to be repositioned to align a different chamber with the inner needle 28, as will be explained.

[0052] In one particular embodiment, multiple clips 30, each in their own cartridge chamber 76, are arranged around the perimeter of the revolving cylinder 72 portion of the cartridge 62, as shown in FIG. 15. The assembly of the pusher handle 20′ and pusher shaft 26′ at the proximal end of the cylinder 72 are first removed, as in FIG. 14C, and then each individual chamber 76 is also brought into alignment one at a time. The cylinder 72 revolves around the longitudinal axis of the system 60 which allows alignment of each chamber with the clip channel of the inner needle 28 for deployment. That done, the pusher handle 20′ and pusher shaft 26′ are inserted again to move each clip 30 into the clip channel of the inner needle 28. FIG. 14B shows proximal movement of the cartridge 62 such that the pusher shaft 26′ ejects the clip 30 from the inner needle 28. The inner needle 28 and cartridge 62 move a distance A approximately equal to the length of each clip 30 in its straightened shape and the clips curl toward their relaxed shapes when ejected. The outer tube 24 remains in place, preferably with its stop flange staying in contact with the target tissue or material layer. The next clip 30 is then aligned via the rotation of the cylinder 72. The chambers may be internal or external to the cylinder 72. This embodiment allows multiple clips 30 to be deployed without the user reloading the system 60.

[0053] While particular forms of the invention have been illustrated and described, it will be apparent that various modifications can be made without departing from the spirit and scope of the invention. For example, in addition to the delivery device discussed herein, the clips of the present invention could also be delivered though a catheter or a laparoscopic type instrument. The delivery system could also be modified such that the clips could be delivered through a flexible catheter. The delivery device could also be placed on the end of a long shaft for delivery in a deep surgical incision such as an aortic valve replacement through a thoracotomy. Accordingly, it is not intended that the invention be limited, except as by the appended claims.