Fabricating Equipment For Tissue Type Heart Valve

Abstract

A device for making a replacement heart valve having a plurality of cusps. The combination includes a mold means for forming a tissue, suitably an animal tissue and particularly a homologous tissue, into cusp form. A clamping means causes the mold means to form the tissue into a cusp shape, and a tissue-engaging means, such as a trim guide, holds such tissue in place, advantageously in unstretched condition, to facilitate suturing and trimming to desired, predetermined size. Such tissue-engaging means may be a plurality of pins adapted to pierce the tissue and hold it in place. The mold means, clamping means, and tissue-engaging means are all rotatable and are movable arcuately with respect to the long axis of the combination or assembly to enable easy access to the workpiece or valve. A valve stent is brought into engagement with the mold means, clamp means, and tissue-engaging means, so that the tissue can easily be sutured to the stent with ready access thereto and in a rapid operation which can be carried out by one operator.

Description

SUMMARY OF THE INVENTION

This invention relates to a device and method for rapid manufacture of a replacement heart valve while surgery is in progress; and in particular it concerns a device and method for the rapid sizing, shaping and attachment of tissue, especially of live tissue, and particularly of a plurality of tissue sections to a preformed stent, which is a metal ring having suitable struts and covered with a biocompatible fabric to which the tissue can be sutured.

The production of heart valves incorporating animal tissue has, of course, been known to the art. However, sizing, shaping, and attaching tissue, especially live tissue, such as fascia lata or other suitable tissue to the stent or valve ring is a difficult procedure, almost always requiring the cooperative effort of two people, if no mechanical aid is used. In one application of the concept of a mechanical aid to impart a cusp shape to the tissue, a mold to form the cusps has been used, but assembly required one person to hold the device together and a second person to do the sewing of the tissue to the stent. In addition, the various parts of the mold device get in the way of the individual doing the sewing and therefore obstruct or make more difficult the suturing of the tissue to the stent. The tissue itself is often slippery and difficult to hold or manipulate.

One object of this invention is to provide a device by which the tissue to be formed into cusps in a replacement heart valve can be held mechanically in place on a mold means, preferably in unstretched condition, for holding it in to the desired shape and for providing uniform size and shape and reproducibility of cusps. It is an object, therefore, to provide a means for shaping and sizing each valve cusp of a plurality of such cusps, for instance, three separate cusp pieces for a tricuspid valve. A still further object is to provide a mechanical means to hold such valve tissue in contact with a stent while suturing to the stent. An important object of the invention is to provide a means and method of accurately sizing and shaping each cusp and to provide sufficient tissue to cover all surfaces of the stent. Thus, the completed valve can be sewn into the heart tissue at the proper location with the valve's tissue in contact with the heart wall and with the blood, enabling vascularization of the valve's tissue. The shape of the cusp tissue is determined before it is affixed to the stent.

It is a particular object to provide holding and clamping means which afford ready access to the workpiece by the person doing the suturing. It is another object of the invention to provide guides for trimming tissue to size, which can be released to enable completion of the suturing of the tissue to the stent. It is an object of the invention to provide a quicker and more accurate method of making a heart valve; and another object is to provide a device to this end which will reduce the number of people required to manufacture such a valve.

The invention relates to a lathe-like device for making a replacement heart valve including a plurality of molds for forming each of a plurality of tissue pieces in assembly into valve cusp sections, each in the form of a valve cusp and each section being approximately the size and shape of the desired cusp. It includes means for holding the sections on the molds, including a clamp means for bringing the molds and sections into clamped, face-to-face arrangement, a plurality of trim guides in association with the molds, with means such as pins, to detachably engage the outer portion of the later-applied tissue, and means for clamping trim guides into a position associated with the molds. It provides means for independently releasing the trim guides from their positioned arrangement, and means to move the assembly, especially angularly to its long axis, to afford the operator easy access to the workpiece.

The invention also relates to a method of preparing a replacement heart valve, which comprises approximately sizing each of a plurality of selected strips of tissue to form valve cusp sections; imparting the desired cusp shape to the sections by draping the sections on a plurality of individual molds in open position; securing outer portions of tissue sections in unstretched condition (as by means of pins in a plurality of trim guides); closing the molds and associated trim guides into clamped position; inserting a stent and affixing a portion of each section around each associated strut of the stent; then precisely sizing or trimming to size each section; releasing the trim guides, folding the trimmed portion of the sections around the sewing flange at the base of the stent; and suturing all cusps to the sewing flange to completely cover all surfaces thereof; releasing the clamp means for the molds; and removing the finished valve. It is necessary to suture the tissue covering the sewing flange at the interior of the base of the stent to assure free action of the cusps.

These and other objects are attained by the device and method of the present invention as will become apparent from the description below and the annexed drawings. It is an advantage of this invention that the tissue is securely held in place without stretching while suturing and trimming to size. This in turn insures perfect formation and functioning of the valve because coaptation of the cusps is controlled. Another advantage is that the configuration of each cusp is reproduced exactly, and the sewing flange for attachment to the heart is completely covered with tissue.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be illustrated as to one embodiment by the following specific description and by the annexed drawings, which are given for purposes of illustration only. Modifications and variations can be made therein by those skilled in the art without departing from the spirit and scope of the appended claims.

In the drawings:

FIG. 1 is an elevational side view, partially in section, of a device according to this invention. Alternative positions of some parts are shown in broken lines.

FIG. 2 is a partial top plan view of the device of FIG. 1, partially cut away to show the arrangement of the clamping device for altering the position of the molding and tissue-engaging assembly.

FIG. 3 is an elevational end view of the device of FIG. 1, with a piece of tissue in place over one cusp mold and partially cut away.

FIG. 4 is a view taken on line 4--4 of FIG. 3, showing placement of tissue on the mold element.

FIG. 5 is a top plan view of a finished tricuspid heart valve made with the aid of the device of this invention.

DETAILED DESCRIPTION OF THE INVENTION

In the drawings, the device 10 of this invention comprises a base 11 on which rests a mounting support 12. A disc 13 is rotatably mounted to the support 12, so that the disc 13 can rotate through a predetermined angle, its travel being limited by a stop pin 14 which is affixed to the support 12 and extends through an arcuate slot 15 in the disc 13, preferably extending 90.degree. of the arc. Hence, rotary travel of the disc 13 is stopped when the pin 14 abuts either end 16, 16' of the slot 15; the disc 13 can also be stopped at any intermediate position.

Affixed permanently to or even integral with the disc 13, preferably diametrically across a flat face 20 thereof is a spindle housing 17, within a bore 21 of which are bearings 22 that rotatably support a spindle 18. The spindle 18 is preferably provided at its outer end with a hand-rotatable knob 19 abutting a flat 23 of the housing 17. Diametrically opposite the flat 23 is a flat 24, and a shoulder 25 of the spindle 18 supports a thrust washer 26 against the flat 24.

Thus, the spindle 18 is retained in place by the thrust washer 26 and the knob 19, which has an enlarged stem 19a and is threadedly attached to the spindle 18. To remove the spindle 18 and its associated elements, the knob 19 is unscrewed, and the spindle 18 can be pulled to the left (in FIG. 1) and out of the housing bore 21. The thrust-washer 26 and the bearings 22 can then be withdrawn.

Beyond the shoulder 25, the spindle 18 has a threaded portion 27, and threadedly connected to the portion 27 is an actuating sleeve 28 which extends within, is attached to and is controlled by a knob 29, affixed thereto by a suitable keying device such as a set screw 29a. The sleeve 28 has an annular flange 29b at its end distant from the knob 29, and an actuating collar 30 is disposed between the flange 29b and the knob 29 around the smooth outer periphery of the sleeve 28, so that the rotation of the sleeve 28 does not rotate the collar 30.

The actuating collar 30 has a plurality of radially extending brackets 31, preferably three of them when making a tricuspid valve. Pivotally attached to each bracket 31 of the collar 30 is an operating link 32. The links 32 are identical and are spaced equidistantly from each other around the circumference of the collar 30, and one such link 32 and its associated parts and operation thereof are described as illustrative of all links and parts associated therewith. In the manufacturing of a tricuspid heart valve, one such link 32 with its associated elements is provided for each of the three cusps, and there are two such links 32 in the case of a bicuspid valve.

A lever arm 33 is pivotally attached to each link 32 adjacent the end that is remote from the collar 30. The attachment may be by means of a fulcrum pin 34. Mounted at the forward end of each lever arm 33 is a tissue clamp or mold member 35. A collar 36 forms the innermost end of the threaded portion 27 of the spindle 18, and the collar 36 has a smooth cylindrical surface and a series of pairs of radially outwardly extending brackets 36a and 36b, with a slot 36c between them milled into the collar 36 and having an angularly extending surface. Each pair of brackets 36a and 36b supports a fulcrum pin 34a on which are pivoted one of the lever arms 33 and also a lever arm 37. Each lever arm 33 extends generally forward and its forward end lies parallel to the axis of the spindle 18, and it pivots about a fulcrum pin 34a as it is actuated by the arm 32 through the fulcrum pin 34.

Each lever arm 37 extends forwardly and diverges from the axis of the spindle 18, and it pivots only about the fulcrum pin 34a. At the forward end of the bracket 37 is disposed an arcuate flange or trim guide 38 extending inwardly toward and concentric with the central axis of the spindle 18, transverse to the bracket 37.

Each arm 37 has a countersink or depression 53 (FIG. 3), engageable by a ball 54 that lies inside a screw 55 and urged outwardly by a spring 56. The screw 55 is threaded into a cylindrical housing 57 and secures it to an arm 33. The purpose of all this is to provide the arm 37 with means normally forcing it to operate with the arm 33 while also enabling independent movement of the arm 37 relatively to the arm 33 when that is desired. Thus, movement in and out of the mold members 35, in accordance with swinging movement of the arms 37, normally results in concurrent movement in and out of the trim guides 38 and in keeping the spacing between the trim guides 38 and mold members 35 constant; however, when desired each trim guide 38 can be swung further away from its associated mold or clamp member 35 by forcing the arm 37 free of the spring-urged ball 54. The arrangement is such that once it is forced free of the ball 54, the trim guide 38 can be swung outwardly or inwardly independently of the arrangement supporting the mold 35.

The trim guide 38 bears a plurality of pins 39 arranged along an arc that is similarly concentric with the spindle 18. These pins 39 are adapted to pierce and assist in holding in place a later-applied tissue section 41. Each trim guide 38 is spaced away from its associated mold member 35, and its top surface is advantageously co-planar with the top surface of the mold member 35. The mold member or clamp piece 35 has a cylindrical outer wall 40 and a pair of tissue-forming or tissue-contacting faces 42 and 43 meeting at an edge 44 and adapted to form the tissue 41 into a desired shape; and when a tricuspid valve graft is being made, end mold member 35 is approximately triangular in transverse cross-section, with an arcuate outer side 40.

As noted above, the spindle housing 17 is mounted on and affixed to the face 20 of the disc 13, and the disc 13 is mounted on the mounting support 12. A screw 45 with a suitable control knob 46 is threadedly connected to and through the mounting support 12 to the disc 13 and its substantially integral spindle housing 17, so that the spindle housing 17 and the disc 13 can be rotated as a unit when the knob 46 is turned to loosen the screw 45. The members 12, 13, and 17 are fixed in desired position within the limits of the slot 15 by tightening the knob 46. Normally the movement is between a vertical position of the spindle 18 and a horizontal or nearly horizontal position thereof.

All of the parts may suitably be made of stainless steel, but other sterilizable materials can be used, if desired.

In operating the device of this invention to make a tricuspid valve, the knob 29 is rotated to move it along the spindle's threaded portion 27 to a position as near as possible to the thrust washer 26, so as to open the mold and trim guide assembly; then, strips of tissue 41, such as fascia lata, perio-cardial tissue or dura mater, for example, are obtained and placed on the molds 35 and the trim guides 38. Fascia lata can be excised from the patient or obtained from a donor, and dura mater would be obtained from a donor, for instance.

The spindle 18 is moved to a vertical position, and each strip of tissue 41 for one cusp section is draped over the exposed faces 42 and 43 of a mold 35, with a straight tissue edge 50 even with the edge 49 of the mold 35, and the outer portion of the tissue 41 extends over the trim guide 38 and is spindled onto the pins 39. After each mold 35 is covered in this manner, the knob 29 is rotated in a direction towards the molds 35, thereby causing the molds 35 to move together to clamp the tissues 41 together between faces 42 and 43. A valve stent 47 having struts 48 is moved into contact and to nest with the mold pieces 35 and the tissues 41, as shown in phantom in FIG. 3. The tissue of each tissue 41 covers one side of a strut 48, so that two adjacent tissues 41 act to completely cover one strut 48.

The spindle 18 is moved to a horizontal or nearly horizontal position, and the tissues 41 are sutured to the struts 48 by sewing through fabric wings disposed at each side of each strut 48, as described in the co-pending patent application of Edwards, Kahn and Goodenough, Ser. No. 93,545 filed on Nov. 30, 1970, each strut 48 extending between corresponding trim guide 38 and mold piece 35. The tissues 41 thus are formed into cusps having a pair of straight edges 50 to form the coaptation area.

Now the spindle 18 is moved back to its vertical position and each tissue section 41 is then cut along the inner edge 51 of the trim guide 38, which determines the amount of tissue needed to lap over the stent 47 and to be sewn to the fabric 52 at the interior edge of the base of the stent 47. The trim guides 38 are now swung away from the molds 35 by rotating them about the fulcrum pin 34a and releasing the spring-urged ball 54 from the socket 53. The clamped assembly of the stent 47, the tissue 41, and the molds 35 can be rotated by the knob 19 or repositioned by the knob 46 for easy access for suturing around the base of the stent 47. After completion of suturing, the molds 35 are unclamped by backing off the knob 29, and the finished replacement valve is removed from the fixture.

It will be understood that the above specific description and drawings have been given for purposes of illustration only and that variations and modifications can be made therein without departing from the spirit and scope of the appended claims.

Claims

Having now described the invention what is claimed is:

1. Apparatus for manufacturing a replacement heart valve from a prepared stent and a plurality of strips of animal tissue, each strip having a pretrimmed inner edge, an inner portion adjacent said inner edge, and an outer untrimmed portion, said apparatus including in combination:

stable stationary support means,

spindle housing means supported by said support means and rotatable with respect thereto over an arc of about 90.degree. ,

a spindle extending through said housing means and rotatable therewith between a vertical position and a horizontal position and rotatable with respect thereto about the axis of said spindle,

a plurality of complementary clamping and molding members mating with each other into a generally cylindrical shape and each having a pair of intersecting axially and radially extending inner surfaces for receiving the inner portion of a said tissue strip and a radially extending end surface across which the tissue strip can extend,

first actuating means supported by said spindle and supporting said clamping and molding means and serving to move them apart from each other for emplacing the tissue strips with their inner portions covering said inner surfaces and for moving them together for clamping the inner portions of said strips against each other and for holding a stent in place adjacent said strips,

a plurality of complementary trim guide means corresponding in number to said clamping and molding means, arranged around a circle and spaced radially away from said clamping and molding means and having a face on about the same plane as the end surfaces of said clamping and molding means, said trim guide means having means for retaining in place the outer portion of each said tissue and having a radially inner arcuate trim guiding edge,

second actuating means supported by said spindle and supporting said trim guide means and for moving them radially inwardly and outwardly, and

releasable means enabling synchronization of said second actuating means with said first actuating means during earlier stages of manufacture of each said valve, so that said trim guide means are kept at a constant spacing from said clamping and molding means, and enabling movement of said second actuating means independent of said first actuating means during later stages thereof, so that said trim guide means can be moved farther away from said clamping and molding means after trimming to afford better access to the tissue on said clamping and molding means.

2. The apparatus of claim 1 having three said clamping and molding members to form a tricuspid valve graft.

3. The apparatus of claim 2 wherein each said clamping and molding member has a tissue-contacting face of triangular transverse cross-section.

4. The apparatus of claim 2 wherein said trim guide means is a tripartite ring concentric with the axis of said clamping and molding members, spaced from said clamping and molding member and provided, as said means for retaining, with a plurality of pins adapted to pierce and engage said tissue.

5. The device of claim 4 wherein said pins are arcuately arranged.

6. The device of claim 1 wherein said first actuating means comprises a knob threadedly engaged on said spindle, a collar keyed to said knob for fore-and-aft movement therewith without rotation therewith, a first set of pivots secured to said spindle, a set of links pivoted to said collar, a second set of pivots on the outer extremities of said links, and a set of arms each pivoted to one each of both said first and second set of pivots and each supporting one of said clamping and molding members.

7. The device of claim 6 wherein said second actuating means comprises a second set of arms pivoted to said first set of pivots and said releasable means comprises detent means on each arm of the first set of arms and a detent-engaging socket on each arm of said second set of arms.

8. A device for application of a strip of tissue to a valve ring to form a replacement heart valve comprising in combination:

a base and a support thereon having a stop pin affixed thereon,

a generally circular rotatable disc rotatably connected to said support and provided with an arcuate slot through which said stop pin extends to determine the limits of travel of said rotatable disc,

a spindle housing affixed to said disc and rotatable therewith about a central axis,

a rotatable spindle within said housing and having an outer end beyond one end of said spindle housing, a threaded portion extending towards the other end, and terminating in a first collar, carrying a set of first pivots,

a hand-operable control wheel detachably affixed to said outer end,

an actuating sleeve threadedly connected to the threaded inner portion of said spindle and having a smooth cylindrical outer surface,

a second collar mounted around said smooth surface of said sleeve for fore-and-aft movement with said sleeve while not rotated by it,

a set of links pivoted to said second collar and extending radially and axially of said spindle and having a second set of pivots at their outer ends,

a first set of arms pivoted to both said first and second set of pivots and extending radially and axially of said spindle,

a plurality of tissue-molding means, one on the end of each of said first set of arms,

a second set of arms pivoted to said first set of pivots,

a plurality of arcuate trim guide members carried on said second set of arms and spaced from said tissue-molding means, concentric with said central axis, and each having an end surface co-planar with an end surface of said tissue-molding means, each said trim guide member also having an arcuate trim guiding inner edge,

a plurality of pins arcuately disposed on each said trim guide member and adapted to pierce and engage a later-applied tissue, and

quickly releasable means for joining each second arm to a first arm for simultaneous movement therewith for keying during that time-constant spacing between said tissue molding means and said trim guide members, and for disconnecting said second arm from said first arm for separate movement of each said trim guide member relative to said tissue-molding means.

9. A method of applying animal tissue to a fabric-covered stent having a ring base, a sewing flange thereon and a plurality of struts, to form a replacement heart valve, which comprises:

approximately sizing and trimming along one edge a plurality of selected strips of said tissue to form a plurality of valve cusp sections,

draping and securing each of said formed sections in unstretched state so that the portion adjacent to the trimmed edge lies along two meeting planes, all planes extending radially of the same cylindrical volume,

clamping together the tissue sections lying along said planes, so that in each instance two planar tissue portions are brought together,

inserting said stent with said struts adjacent surfaces of said clamped sections, suturing a portion of each said section partially around each said strut,

precisely trimming said sections to provide an outer edge with an outer portion adjacent thereto,

folding said outer portion around said sewing flange,

sewing said folded outer portion to said sewing flange, and

completing suturing of said sections over said ring base,

said tissue covering all surfaces of said stent to form said replacement valve.

10. The method of claim 9 wherein said valve is a tricuspid valve.

11. The method of claim 9 wherein said tissue is sewed to said flange at the interior of said sewing flange.

12. A method of applying animal tissue to a fabric-covered stent having a ring base, a sewing flange thereon, and a plurality of struts, to form a replacement heart valve, comprising:

2. approximately sizing a plurality of selected strips of said tissue to form a plurality of valve cusp sections each having a coaptation area and an outer portion,

b. placing each said section on a mold adapted to form said section into cusp shape and in assembly on said molds to nest with a later-applied stent,

c. detachably affixing each said outer portion to an associated holding means to maintain each said section in place in unstretched condition,

d. clamping together said molds and associated holding means,

e. bringing a stent having struts into nesting arrangement with said molds and sections in assembly,

f. suturing adjacent portions of each said section to the struts enclosed by them,

g. precisely trimming each said outer portion to a predetermined size,

h. withdrawing said holding means,

i. folding said outer portion around said sewing flange,

j. suturing said tissue cusps to said stent to cover all surfaces thereof, and

k. unclamping said molds and withdrawing said replacement heart valve.