Abstract:
Forming a proximal anastomosis on an aortic wall includes method and instrumentation and apparatus for forming an aortic puncture and inserting a fluid-impervious sealing element with a lateral flange and central stem into the vessel through the puncture. An anastomosis of a graft vessel over the puncture is partially completed with the central stem of the sealing element protruding through the partial anastomosis. A removal instrument attaches to the central stem and retrieves the sealing element that disassembles in helical disassociation of the flange and stem into a continuous strand that is withdrawn from the partial anastomosis prior to completion of the procedure.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to coronary bypass grafting surgery and more particularly to instruments and method to facilitate performing an aortotomy and proximal anastomosis, for example, associated with coronary artery bypass grafting surgery.  
         BACKGROUND OF THE INVENTION  
         [0002]    Contemporary coronary artery bypass grafting surgery is performed on a beating heart to obviate complications commonly associated with prior surgical practices of transitioning a patient onto and off of a heart-lung machine that maintained circulation while the heart was in quiescent condition during construction of a coronary arterial bypass. However, performing an aortotomy and a proximal anastomosis on the aorta that is perfused with blood under pressure contribute to substantial losses of blood in the absence of temporary measures taken to curtail blood flow through the aortic hole. Side-bite and surface-oriented clamping mechanisms have been used to diminish loss of blood during the surgical procedures of punching the aortic hole and anastomosing the graft vessel, but such temporary occlusions damage the endothelium and dislodge emboli that may migrate through the circulatory system. Alternative schemes for performing an aortotomy and limiting loss of blood during the period of anastomosing a bypass graft include introducing a plug or seal at the site of the aortotomy, but such schemes commonly inhibit convenient and rapid completion of the graft anastomosis, and present other complications to be resolved following the grafting procedure.  
         SUMMARY OF THE INVENTION  
         [0003]    In accordance with the method and instrumentation of the present invention, an aorto-coronary bypass graft is performed using an aortic punch including a corkscrew instrument and a hemostatic sheath that selectively delivers and positions a seal within the punched aortic hole for retention against the aortic wall under tension established by an external structure. The suture anastomosis is performed with the hemostatic seal in place and with a central stem of the seal residing near the location of the last placed stitch. A tubular removal instrument is positioned about the protruding stem to remove the seal as a tear-away strip that is pulled through the tubular removal instrument.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0004]    [0004]FIG. 1 is a pictorial illustration of the corkscrew aortic punch disposed for insertion into the aorta through a hemostatic sheath in accordance with one embodiment of the present invention;  
         [0005]    [0005]FIG. 2 is a pictorial illustration of the hemostatic sheath penetrated through the aortic wall;  
         [0006]    [0006]FIG. 3 is a pictorial illustration of the hemostatic sheath positioned within the aorta as the aortic punch is removed;  
         [0007]    [0007]FIGS. 4 and 5 are pictorial illustrations of a seal-positioning mechanism for insertion through the hemostatic sheath into the aorta;  
         [0008]    [0008]FIG. 6 is a pictorial illustration of the hemostatic seal mechanism deployed from the interior end of the hemostatic sheath;  
         [0009]    [0009]FIG. 7 is a pictorial illustration of the hemostatic seal mechanism manually positioned within the punched aortic hole as the hemostatic sheath and hemostatic seal-positioning mechanism are withdrawn;  
         [0010]    [0010]FIG. 8 is a pictorial illustration of the hemostatic seal retained in place at the punched aortic hole via an external tensioning mechanism;  
         [0011]    [0011]FIG. 9 is a pictorial illustration of suture anastomosis performed about the hemostatic seal;  
         [0012]    [0012]FIG. 10 is a pictorial frontal illustration of the suture anastomosis substantially completed with the stem of the hemostatic seal positioned near the last stitches;  
         [0013]    [0013]FIG. 11 is a pictorial frontal illustration of the tubular removal instrument disposed over the stem of the hemostatic seal in preparation for removal from the graft site;  
         [0014]    [0014]FIG. 12 is a pictorial frontal illustration of the hemostatic seal dissembled through the tubular removal instrument;  
         [0015]    [0015]FIG. 13 is a pictorial frontal illustration of the anastomosis completed upon removal of the tubular removal instrument and tying off of the suture ends about the segment of the anastomosis from which the tubular removal instrument is withdrawn.  
         [0016]    [0016]FIG. 14 is an exploded view of the aortic punch and hemostatic sheath in accordance with one embodiment of the present invention;  
         [0017]    [0017]FIG. 15 is a frontal view of the assembled aortic punch and hemostatic sheath prepared for performing an aortotomy according to the present invention;  
         [0018]    [0018]FIG. 16 is an exploded view of the hemostatic seal positioning mechanism that illustrates the hemostatic seal and tensioning structure in deployed condition and in confined condition;  
         [0019]    [0019]FIG. 17 is a pictorial illustration of the formation of a hemostatic seal in accordance with one embodiment of the present invention;  
         [0020]    [0020]FIG. 18 is a pictorial exploded illustration of a hemostatic seal removal instrument according to one embodiment of the present invention;  
         [0021]    [0021]FIG. 19 is a flow chart illustrating an embodiment of the surgical process according to the present invention; and  
         [0022]    [0022]FIG. 20 is a pictorial illustration of a sterile kit of the instruments for performing the surgical process according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]    Referring now to FIGS. 1, 2 and  3 , there are shown pictorial views of the aortic punch  9  configured for penetrating the aorta  17  of a patient in preparation for a proximal anastomosis of a bypass vessel to the aorta of the patient. Specifically, an outer hemostatic sheath  11  is coaxially disposed over the lower elongated segment  13  of the aortic punch which supports a corkscrew-type auger  15 , as shown in FIGS. 14 and 15. The punch and auger  15  are rotated into a wall of the aorta  17  and the plunger  19  can then be depressed to penetrate the sharpened edge of the lower elongated segment  13  through the aorta wall. The punched-out segment of aorta wall remains captivated on the cork screw  15 , and the hemostatic sheath  11  is positioned within the punched hole through the aorta wall. The plunger mechanism  19  and attached elongated lower segment is removed from the hemostatic sheath  11  that remains in position through the aorta wall, as shown in FIG. 3. A fluid-tight seal is included within the hemostatic sheath  11  to inhibit outflow of blood under pressure from the aorta  17  in which it is positioned.  
         [0024]    Referring now to the pictorial illustration of FIG. 4, there is shown a seal-insertion instrument  21  that includes a sheath  23  of outer diameter sized to slide within the hemostatic sheath  11 , and a plunger  25  that is disposed to slide axially within the sheath  23  for selectively ejecting the hemostatic seal structure  27  from its confinement within the sheath  23 . The hemostatic seal structure  27 , as later described herein with reference to FIG. 16, includes resilient members that are confined within the sheath  23  in preparation for positioning and expansion into sealing engagement with the aorta wall, as later descried herein.  
         [0025]    Referring now to the pictorial illustrations of FIGS. 5 and 6, the seal-insertion instrument  21  is inserted into the hemostatic sheath  11  through the fluid-tight seal therein, and the plunger  25  is depressed to eject a portion of the hemostatic seal structure  27 , within the aorta  17 . The plunger  25  includes an axial lumen therethrough to pass a length of line  28  that is attached to the hemostatic seal structure  27 . The proximal end of plunger  25  may also include a hemostatic seal  100  through which the length of line  28  passes.  
         [0026]    As illustrated in FIGS. 6, 7,  16  and  17 , a convex or mushroom-shaped sealing element  29  of the hemostatic seal structure  27  is deployed and manually restrained within the aorta  17  covering the punched aortic hole as the hemostatic sheath  11  and the seal-insertion instrument  21  are removed together from the aorta  17 . The hemostatic seal structure  27  is thereby liberated from confinement within the seal-insertion instrument  21  to expand into sealing engagement with the aorta wall inside the punched aortic hole.  
         [0027]    Referring now to FIG. 16, the hemostatic seal structure  27  includes the convex or mushroom-shaped sealing element  29 , and this sealing element  29  includes an integral central stem  30  that is attached via a suture tether  32  to a resilient frame  34  which tensions the suture tether  32 . The resilient frame  34  is attached to the length of line  28  that passes through an axial lumen through the plunger  25  as the entire structure is packed in confined configuration within the hollow sheath  23  of the seal-insertion instrument  21 . When ejected from the hemostatic sheath  23  upon depression of the plunger  25 , the resilient frame  34  expands to tension the suture tether  32 . Manual positioning by the surgeon&#39;s finger, as shown in FIG. 7, promotes proper sealing of the hole in the aorta as the resilient frame  34  expands to tension the suture tether  32 . As thus positioned in this configuration, the resilient frame  34  maintains tension on the suture tether  32  that, in turn, supports the sealing element  29  from outside the aorta to provide outwardly-directed resilient biasing force on the sealing element  29 . This resilient force establishes firm sealing engagement of the sealing element  29  against the inside wall of the aorta. In addition, the suture tether  32  greatly facilitates removal of the resilient frame  34 , as later described herein, upon simply cutting one or both ends of the suture tether  32  away from the resilient frame  34  for removal from the sealing element  29 . In one embodiment the suture-tether  32  may pass through the convex segment of the sealing element  29  to the concave side thereof on both sides of the central stem  30 . In another embodiment, the suture tether  32  may be tied to the central stem  30  closely adjacent the concave surface of the sealing element  29 .  
         [0028]    The sealing element  29  is formed in accordance with one embodiment of the present invention, as illustrated in FIG. 17. Specifically, a hollow tube  33  of flexible material such as polyvinyl chloride, PEBAX, or other polymer material may be extruded about a looped suture  35  or wire or other tensile member for improved tensile strength. Alternatively, a solid, flexible rod of similar material having sufficient tensile strength may be used. The hollow tube (or solid rod)  33  may be helically or spirally wound into the configuration of the mushroom-shaped sealing member  29 , with the central stem  30  integrally formed thereon. The adjacent convolutes of the spirally-wound tube  33  with suture  35  or other tensile member disposed therein (or solid rod) may be lightly adhered together through the application of heat and pressure to a thermoplastic material, or through other suitable adhesive attachments to form the substantially fluid-impervious sealing element  29  that is flexible and resilient for confined packing within the hollow sheath  23  of the seal-insertion instrument  21 . Light adhesion between adjacent convolutes of the spirally-wound tube  33  with a suture therein (or solid rod) promotes disassembly of the sealing element  29  as by tearing along the boundary between adjacent convolutes under tension applied to the central stem  30 , as later described herein. It should be noted that the central stem  30  is an integral and continuous portion of the spiral convolutes (or other meandering pattern) that extend continuously from the central stem portion  30  to the outer perimeter of the mushroom-shaped portion of the sealing element  29 . This assures substantially uniform high tensile strength of the hollow tube  33  with suture  35  disposed therein (or solid rod) over the entire continuous length of the tube  33  to assure complete removal from the aorta in the manner as later described herein. In one embodiment, the sealing element  29  may be formed by winding the hollow tube  33  (or solid rod) around a mandrel that includes separable flanges which are axially spaced apart by about the diameter dimension of the tube  33  (or solid rod), and that includes a central hollow support to house the portion that forms the central stem  30 . Heat and pressure applied between such flanges causes thermoplastic flow and adhesion between adjacent convolutes in the mushroom-shaped portion and to the stem  30  in the central portion of the fluid-impervious sealing element  29  thus formed. Alternatively, bioinert adhesive may be applied to the convolutes and central stem  30  to retain the shape of the fluid-impervious sealing element  29  thus formed.  
         [0029]    Referring now to the pictorial illustration of FIG. 8, the sealing element  29  is shown disposed in sealing position inside the punched aortic hole with the integral stem  30  protruding through the hole, and with suture loop  35  protruding from the proximal end of the stem  30 . It should be noted that the resilient frame  34  and the suture tether  32  are positioned on the outer wall of the aorta to exert an outwardly-directed force on the sealing element  29  to retain it in sealing engagement with the inner aortic wall, and to prevent inadvertent expulsion of the sealing element  29  from the hole or loss of the sealing element  29  into the aorta. The sealing element  29  is thus maintained in sealing position over the hole in the aorta during formation of the proximal anastomosis by suturing the graft vessel  37  onto the aorta  17 , as shown in FIGS.  9 - 11 . The stem  30  is flexible and can be gently pushed out of the way of sutures that are stitched about the hole in the aorta and into the proximal end of the graft vessel  37 . In this way, the stem  30  is left protruding through the anastomosis at a position thereon near the last stitch (or between any adjacent stitches).  
         [0030]    Referring now to FIGS.  10 - 12  and  18 , a seal-removal instrument  41  includes an outer tube  43  with an inner core  45  that is slidable within the outer tube  43  and that carries a hook  47  at its distal end. The assembly of inner core  45  disposed within the outer tube  43  is positioned over the stem  30  of the sealing element  29  with the hook  47  engaged in the suture loop  35 . The outer tube  43  is positioned onto the stem  30  down to the root of its attachment to the mushroom-shaped spiral-wound sealing element  29 , and the inner core  45  is then withdrawn from the outer tube  43 . These motions cause the spirally-wound convolutes of the sealing element  29  to tear and otherwise disassemble for convenient removal as a continuous strand  29 ′, as shown in FIG. 12, of the material from which the spirally-wound sealing element  29  was formed. Thereafter, the outer tube  43  may be withdrawn and the sutures tied off near where outer tube  43  was positioned to complete the proximal anastomosis, as shown in FIG. 13.  
         [0031]    Alternatively, the central stem  30  may be formed as an integral part of the mushroom-shaped portion of the sealing element  29  with sufficient length to extend through the outer tube  43  adequately to permit finger gripping of the stem  30  for manual tensioning and removal of the continuous strand  29 ′ through the outer tube  43  without the need for the hooked inner core  45  and associated suture loop  35 .  
         [0032]    Referring now to the flow chart of FIG. 19, an embodiment of the surgical procedure performed according to the present invention includes forming an aperture  51  in the aorta wall, as illustrated in FIGS. 1 and 2. The hemostatic seal structure in confined configuration within the hemostatic sheath is then introduced  53  into the aorta through the hole in the wall thereof. The sealing element resiliently expands  55  inside the aorta to form a fluid-tight seal over the hole in the wall, and is supported  57  on a tensioned tether from the outside of the aorta. A central stem portion of the sealing element is sufficiently flexible to be pushed away from the locations on the aorta at which suture stitches are inserted during substantial completion  59  of anastomosing the graft vessel to the aorta over the hole in the wall thereof. The central stem portion of the sealing element thus protrudes through the anastomosis between adjacent stitches and is accessible to facilitate removal of the sealing element disposed within the aorta beneath the anastomosis. The sealing element is removed through a tube that is positioned over the central stem portion by applying tensile force to the central stem portion relative to the tube. This disassembles or unravels the sealing element into a single strand  61  that is removed through the tube  63 , as shown in FIG. 12. The ends of the suture adjacent to the location on the anastomosis through which the strand was removed may then be tied off to complete the anastomosis  65 .  
         [0033]    Referring now to FIG. 20, there is shown a pictorial illustration of a kit of instruments and components suitable for performing the surgical procedure according to the present invention, as previously described herein. Specifically, at least the seal-insertion instrument  21  and seal removal tube  43  are packaged within a sealed enclosure  67  that preserves a sterile environment and facilitates convenient shipping and handling of these components without contamination or damage. Additionally, a hemostatic sheath  11  may be included within the enclosure  67  for use with a punch (separately available to a surgeon) in the manner as previously described herein with reference to FIGS. 1 and 2.  
         [0034]    Therefore, the surgical devices and procedures for forming a temporary aortic seal during proximal anastomosis of a graft vessel to the aorta greatly facilitates removal of the temporary seal with negligible risk of any residual debris being created thereby to circulate in blood flowing in the aorta or in the graft vessel. Additionally, the sealing element of the present invention promotes self sealing of an aortotomy during formation of the vessel graft, aided by a resilient frame that is disposed outside the aorta to support the sealing element during formation of the anastomosis. The resilient frame is easily removed at a convenient stage in the procedure. The sealing element thus positioned to seal off the aortotomy during formation of the anastomosis can be conveniently dissembled into a continuous strand that is pulled from the surgical site with minimal additional trauma or complication of the surgical procedure.