Abstract:
A connector for joining a first hollow structure to the side wall of a second hollow structure, the connector comprising a first component comprising an inner collar; a hollow body; and a graft mounted to the inner collar and forming a conduit through the hollow body and the inner collar; and a second component comprising an outer collar and a hollow body, the hollow body of the second component being sized for coaxial disposition over the hollow body of the first component so that the outer collar of the second component can be adjustably positioned relative to the inner collar of the first component and so that the conduit of the graft provides fluid communication between (i) the region beyond the inner collar, and (ii) the region beyond the hollow body of the first component.

Description:
REFERENCE TO PENDING PRIOR PATENT APPLICATION 
       [0001]    This patent application claims benefit of pending prior U.S. Provisional Patent Application Ser. No. 61/234,075, filed Aug. 14, 2009 by Richard M. Beane et al. for MINIMALLY INVASIVE DISTAL ANASTOMOSIS FOR AORTIC VALVE BYPASS (Attorney&#39;s Docket No. CORREX-47 PROV), which patent application is hereby incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to surgical methods and apparatus in general, and more particularly to surgical methods and apparatus for effecting an aortic valve bypass. 
       BACKGROUND OF THE INVENTION 
       [0003]    Aortic valve bypass is a proven procedure for relieving critical aortic valve stenosis. This procedure comprises the deployment of a bypass conduit, having a prosthetic valve disposed therein, between the left ventricle and the descending aorta. This approach allows blood to be pumped from the left ventricle into the descending aorta without requiring removal of the dysfunctional native aortic valve. See  FIG. 1 . 
         [0004]    In an aortic valve bypass procedure, the connection of the bypass conduit to the descending aorta is commonly referred to as the “distal anastomosis”, and is currently one of the more difficult and time-consuming elements of an aortic valve bypass procedure. 
         [0005]    Currently, in order to effect the distal anastomosis, it is necessary to perform an anterior lateral thoracotomy of approximately six inch length in order to gain sufficient access to the descending aorta. The descending aorta is side-clamped so as to engage, but not occlude, the artery. Then a longitudinal slit is made in the clamped portion of the artery wall, and a graft (e.g., the distal end of the bypass conduit, or an element which is to be secured to the distal end of the bypass conduit), typically 14-20 mm in diameter, is sutured in place, substantially perpendicular to the side wall of the descending aorta, so as to establish the desired fluid connection. Once the perimeter of the graft has been secured to the slit aortic wall, the side clamp can be released and the distal anastomosis is complete. 
         [0006]    With respect to the foregoing, it should be appreciated that the thickness of the side wall of the descending aorta can vary considerably from patient to patient. Factors influencing the thickness of the side wall of the descending aorta can include, but are not limited to, the presence of exterior fat and connective tissue, interior calcium deposits, and interior ulcerations. In practice, the thickness of the side wall of the descending aorta can vary from about 1 mm to about 4 mm in thickness. This variation in the thickness of the side wall of the descending aorta is a factor which may need to be taken into account when forming the distal anastomosis. 
         [0007]    Aortic valve bypass is not currently a common procedure, at least in part due to the relatively difficult and time-consuming nature of the distal anastomosis. Furthermore, aortic valve bypass cannot currently be considered to be a minimally invasive procedure, due to the need to provide an anterior lateral thoracotomy of approximately 6 inch length. However, reducing the size of the thoracotomy with the current procedure is problematic at best, since reduced access to the descending aorta makes cross-clamping and suturing all the more difficult and time-consuming. Also, when the ribs are spread to create access to the thoracic cavity, the ribs can sometimes fracture, thereby causing additional trauma to the patient. 
         [0008]    Consequently, there is a need for an improved method and apparatus for effecting the distal anastomosis in an aortic valve bypass procedure. 
       SUMMARY OF THE INVENTION 
       [0009]    These and other objects of the present invention are addressed by the provision and use of a novel method and apparatus for effecting the distal anastomosis in an aortic valve bypass procedure. 
         [0010]    In one form of the invention, there is provided a connector for joining a first hollow structure to the side wall of a second hollow structure, the connector comprising: 
         [0011]    a first component comprising:
       an inner collar for disposition within the interior of the second hollow structure, the inner collar having a toroidal configuration characterized by an outer perimeter and an inner perimeter, with the inner collar being flexible;   a hollow body connected to the inner collar and upstanding therefrom, the hollow body of the inner collar being aligned with the inner perimeter of the inner collar; and   a graft element mounted to the inner collar and forming a conduit extending through the hollow body and the inner perimeter of the inner collar, the graft being formed out of a fluid-retaining material; and       
 
         [0015]    a second component for disposition outside the second hollow structure, the second component comprising an outer collar and a hollow body connected to the outer collar, the outer collar having a toroidal configuration characterized by an outer perimeter and an inner perimeter, with the hollow body of the outer collar being aligned with the inner perimeter of the outer collar; 
         [0016]    the hollow body of the second component being sized for coaxial disposition over the hollow body of the first component so that the outer collar of the second component can be adjustably positioned relative to the inner collar of the first component and so that the conduit of the graft element provides fluid communication between (i) the region beyond the inner collar, and (ii) the region beyond the hollow body of the first component. 
         [0017]    In another form of the invention, there is provided a delivery instrument for delivering a connector for joining a first hollow structure to the side wall of a second hollow structure, the delivery instrument comprising: 
         [0018]    a hollow column; 
         [0019]    at least one traction arm pivotally mounted to the hollow column so as to selectively radially project a toe of the traction arm; 
         [0020]    a rod movably mounted to the hollow column and having a clamp at the distal end thereof, the rod being adapted to selectively engage the at least one traction arm so as to cause the at least one traction arm to radially project the toe of the at least one traction arm; and 
         [0021]    at least one collar actuator slidably mounted to the hollow column. 
         [0022]    In another form of the invention, there is provided a system for joining a first hollow structure to the side wall of a second hollow structure, the system comprising: 
         [0023]    a connector comprising:
       a first component comprising:
           an inner collar for disposition within the interior of the second hollow structure, the inner collar having a toroidal configuration characterized by an outer perimeter and an inner perimeter, with the inner collar being flexible;   a hollow body connected to the inner collar and upstanding therefrom, the hollow body of the inner collar being aligned with the inner perimeter of the inner collar; and   a graft element mounted to the inner collar and forming a conduit extending through the hollow body and the inner perimeter of the inner collar, the graft being formed out of a fluid-retaining material;   
           a second component for disposition outside the second hollow structure, the second component comprising an outer collar and a hollow body connected to the outer collar, the outer collar having a toroidal configuration characterized by an outer perimeter and an inner perimeter, with the hollow body of the outer collar being aligned with the inner perimeter of the outer collar;   the hollow body of the second component being sized for coaxial disposition over the hollow body of the first component so that the outer collar of the second component can be adjustably positioned relative to the inner collar of the first component and so that the conduit of the graft element provides fluid communication between (i) the region beyond the inner collar, and (ii) the region beyond the hollow body of the first component; and       
 
         [0030]    a delivery instrument for delivering the connector to the second hollow structure, the delivery instrument comprising:
       a hollow column;   at least one traction arm pivotally mounted to the distal end of the hollow column so as to selectively radially project a toe of the traction arm;   a rod movably mounted to the hollow column and having a clamp at the distal end thereof, the rod being adapted to selectively engage the at least one traction arm so as to cause the at least one traction arm to radially project the toe of the at least one traction arm; and
           at least one collar actuator slidably mounted to the hollow column;   
               
 
         [0035]    the connector being mounted to the delivery tool such that the hollow body of the first component is mounted coaxially on the hollow column of the delivery instrument, and the at least one collar actuator is aligned with the hollow body of the second component. 
         [0036]    In another form of the invention, there is provided a method for joining a first hollow structure to the side wall of a second hollow structure, the method comprising: 
         [0037]    providing a connector having (i) a first component comprising an inner collar and a hollow graft element mounted to the inner collar and extending therefrom, and (ii) a second component comprising an outer collar; 
         [0038]    forming an opening in the side wall of the second hollow structure; 
         [0039]    positioning the inner collar of the first component within the interior of the second hollow structure, with the graft element extending through the side wall of the second hollow structure; and 
         [0040]    advancing the outer collar of the second component toward the inner collar of the first component so as to clamp the side wall of the second hollow structure therebetween. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0041]    These and other objects and features of the present invention will be more fully disclosed or rendered obvious by the following detailed description of the preferred embodiments of the invention, which is to be considered together with the accompanying drawings wherein like numbers refer to like parts, and further wherein: 
           [0042]      FIG. 1  is a schematic view showing an aortic valve bypass; 
           [0043]      FIG. 2  is a schematic view showing a novel locking collar connector formed in accordance with the present invention and being used to form a distal anastomosis; 
           [0044]      FIGS. 3-7  are schematic views showing various components of the locking collar connector of  FIG. 2 ; 
           [0045]      FIG. 8  is a schematic view showing the locking collar connector of  FIG. 2  mounted to a novel delivery instrument also formed in accordance with the present invention; 
           [0046]      FIGS. 9-12  are schematic views showing various aspects of the delivery instrument and locking collar connector shown in  FIG. 8 , with  FIG. 9  being a sectional view taken through line  9 - 9  of  FIG. 8 ; with  FIG. 10  being an enlarged end view of the distal end of the delivery instrument and locking collar connector of  FIG. 8 ; with  FIG. 11  being an end view like that of  FIG. 10 , but with the graft material removed for clarity of illustration; with  FIG. 12  being an enlarged side view of the distal end of the delivery instrument and locking collar connector, but with the graft material removed for clarity of illustration; 
           [0047]      FIGS. 13-15  are schematic views showing a distal anastomosis being formed with the locking collar connector and delivery instrument of  FIG. 8 ; and 
           [0048]      FIG. 16  is a schematic view showing an alternative form of locking collar connector formed in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0049]    The present invention comprises a novel method and apparatus for effecting the distal anastomosis in an aortic valve bypass procedure. More particularly, the present invention comprises the provision and use of a novel locking collar connector to effect the distal anastomosis in an aortic valve bypass procedure. This novel locking collar connector allows the distal anastomosis to be effected quickly and safely, while requiring significantly less access to the anastomosis site and without requiring suturing to the descending aorta. Significantly, hemostasis is effectively maintained at substantially all times, so that the distal anastomosis can be carried out while the heart is beating. 
       Locking Collar Connector 
       [0050]    Looking now at  FIGS. 2-7 , there is shown a novel locking collar connector  5  which comprises one preferred form of the present invention. Locking collar connector  5  generally comprises a ratchet bracket  10  ( FIGS. 2 ,  3 ,  5  and  6 ), an inner collar  15  ( FIGS. 2 ,  4 ,  5  and  6 ), a graft conduit  20  ( FIGS. 2 and 6 ), and an outer collar  25  ( FIGS. 2 and 7 ). In one preferred form of the present invention, and as will hereinafter be discussed in further detail, ratchet bracket  10 , inner collar  15 , and graft conduit  20  are assembled into a single integral assembly  27  ( FIG. 6 ) during manufacture, and outer collar  25  ( FIG. 7 ) is joined to this single integral assembly  27  during use ( FIG. 2 ). 
         [0051]    Ratchet bracket  10  is shown in greater detail in  FIG. 3 . More particularly, ratchet bracket  10  generally comprises a hollow ovoid body  30  having a distal end  35 , a proximal end  40 , and a lumen  45  extending therebetween. A pair of L-shaped support arms  50  extend distally, and radially outwardly, from distal end  35  of hollow ovoid body  30 . Ratchet teeth  55  are provided on the exterior surface of hollow ovoid body  30 . Preferably two sets of ratchet teeth  55  are provided on the exterior surface of hollow ovoid body  30 , with the two sets of ratchet teeth being disposed in diametrically-opposed disposition, in the manner shown in  FIG. 3 . As will hereinafter be discussed, graft conduit  20  extends through lumen  45  of hollow ovoid body  30  ( FIG. 6 ), L-shaped support arms  50  are configured to support inner collar  15  adjacent to the distal end of hollow ovoid body  30  ( FIGS. 5 and 6 ), and the two sets of ratchet teeth  55  are configured to be engaged by corresponding elements of outer collar  25  ( FIG. 2 ). 
         [0052]    Inner collar  15  (FIGS.  2  and  4 - 6 ) comprises a generally ovoid body  60  having an ovoid outer perimeter  65  and an ovoid central hole  70 . Inner collar  15  is preferably constructed from a flat sheet of 0.009″ thick Nitinol, which is heat-treated while constrained onto the outer diameter of a suitable heat-treat mandrel (about 1.5 inches in diameter) so as to form a resilient saddle-like structure. Alternatively, inner collar  15  can be formed out of other suitable materials. As noted above, and as will hereinafter be discussed, inner collar  15  is intended to be mounted to L-shaped support arms  50  of hollow ovoid body  30  ( FIGS. 5 and 6 ). Furthermore, and as will hereinafter be discussed, inner collar  15  is provided with a spring configuration (e.g., because of its Nitinol construction) which, when inner collar  15  is deployed within the interior of the descending aorta, can exert a substantial sealing force against the inner wall of the descending aorta. 
         [0053]    Graft conduit  20  ( FIGS. 2 and 6 ) comprises a generally tubular structure which is preferably constructed out of woven polyester graft (e.g., Vascutek GelWeave™). Other graft materials, including Gore-Tex® fabric or Vascutek Triplex™ material, can also be utilized to form graft conduit  20 . As noted above, and as will hereinafter be discussed, graft conduit  20  is configured to extend through lumen  45  of hollow ovoid body  30  ( FIG. 6 ). 
         [0054]    As noted above, ratchet bracket  10 , inner collar  15  and graft conduit  20  are intended to be assembled into a single integral assembly  27  ( FIG. 6 ) during manufacture, and outer collar  25  is intended to be joined to this integral assembly during use ( FIG. 2 ). More particularly, inner collar  15  is preferably attached to L-shaped support arms  50  of ratchet bracket  10  by molding the ratchet bracket about inner collar  15  so that the inner collar resides on the L-shaped support arms of the ratchet bracket ( FIG. 5 ). Woven graft (e.g., Vascutek GelWeave™)  75  ( FIG. 6 ) is then sewn onto inner collar  15  so as to envelop both sides of the inner collar  15  (i.e., so as to envelop both of the oval faces  76 ,  77 ), preferably by stitching the woven graft on both the inner and outer diameters of inner collar  15 . Finally, the distal end of graft conduit  20  is sewn (e.g., at a fluid-tight seam  80 ) to the woven graft  75  covering inner collar  15  ( FIG. 6 ). Fluid-tight seam  80  is preferably on the inner edge of the Nitinol oval, as shown in  FIG. 6 . Thus, the distal end of the lumen of graft conduit  20  opens on the ovoid central hole  70  of inner collar  15 , with inner collar  15  providing a resilient ovoid flange at the distal end of graft conduit  20  (see  FIG. 6 ). 
         [0055]    Significantly, with this construction, ratchet bracket  10  remains primarily outside of graft conduit  20  and is not covered with graft material; only the two L-shaped support arms  50  (molded onto the Nitinol oval of inner collar  15 ) are enclosed in graft material. The two resulting penetrations through the graft layer (i.e., at the locations where the distal end of graft conduit engages the two L-shaped support arms  50 ) are sutured tightly in order to eliminate potential leak paths. 
         [0056]    Outer collar  25  ( FIGS. 2 and 7 ) comprises a hollow ovoid body  85  having a distal end  90 , a proximal end  95 , and lumen  100  extending therebetween. A flange  105  is mounted to distal end  90  of hollow ovoid body  85 . A pair of ratchet arms  110 , including ratchet teeth  115  thereon, are spring mounted to hollow ovoid body  85 . As will hereinafter be discussed, hollow ovoid body  85  of outer collar  25  is intended to be slid over hollow ovoid body  30  of ratchet bracket  10  so that flange  105  of outer collar  25  opposes inner collar  15 , with ratchet teeth  115  of outer collar  25  engaging ratchet teeth  55  of ratchet bracket  10 . Outer collar  25  is preferably molded out of a medical grade acetal. Other materials suitable for permanent implant, such as silicone or polypropylene, can also be used. 
         [0057]    In use, and as will hereinafter be discussed, an opening is made in the side wall of the descending aorta; the single integral assembly  27  ( FIG. 6 ) of ratchet bracket  10 , inner collar  15  and graft conduit  20  is maneuvered so that inner collar  15  is positioned within the interior of the descending aorta while hollow ovoid body  30  and graft conduit  20  extend out the side wall of the descending aorta; and then hollow ovoid body  85  of outer collar  25  is slid down over graft conduit  20  and hollow ovoid body  30  of ratchet bracket  10  until flange  105  of outer collar  25  engages the outer wall of the descending aorta and ratchet teeth  115  of outer collar  25  engage ratchet teeth  55  of ratchet bracket  10 , with the side wall of the descending aorta being securely clamped between inner collar  15  and flange  105  of outer collar  25 , and with graft conduit  20  in fluid communication with the interior of the descending aorta. In this way, the distal anastomosis can be provided for an aortic valve bypass procedure. Thereafter, graft conduit  20  can be connected, in ways well known in the art, to the left ventricle of the heart as part of an aortic valve bypass procedure. 
         [0058]    It will be appreciated that, with this construction, ratchet bracket  10  is instrumental in locking outer collar  25  down onto the outer surface of the descending aorta while simultaneously sandwiching the aortic wall between inner collar  15  and flange  105  of outer collar  25  ( FIG. 2 ). In this respect it will also be appreciated that outer collar  25  has two diametrically-opposed ratchet teeth  115  ( FIG. 7 ), while ratchet bracket  10  has two corresponding diametrically-opposed sets of ratchet teeth  55 , with the two diametrically-opposed sets of ratchet teeth  55  being aligned with each end of the inner collar oval&#39;s major axis ( FIG. 5 ). With this arrangement, each end of outer collar  25  can be locked into a number of positions relative to ratchet bracket  10  (and hence relative to inner collar  15 ), thereby accommodating for variable aortic wall thicknesses. In this respect it will also be appreciated that the general oval shape of hollow ovoid body  85  of outer collar  25  and hollow ovoid body  30  of ratchet bracket  10  serves to automatically establish and maintain alignment between the mating ratchet teeth  55 ,  115  of the ratchet bracket and the outer collar. In other words, relative rotation between the outer collar and ratchet bracket is effectively prevented. 
         [0059]    It will also be appreciated that, on account of the foregoing construction, locked collar connector  5  presents only graft material to the lumen of the anastomosis site. 
       Delivery Instrument 
       [0060]    A novel delivery instrument  200  ( FIGS. 8-12 ) is provided to enable the physician to easily install and deploy locked collar connector  5  through a small thoracotomy into a slit in the descending aorta, whereby to form the desired distal anastomosis for the aortic valve bypass. 
         [0061]    Looking now at  FIGS. 8-12 , delivery instrument  200  generally comprises a hollow ovoid column  205  ( FIG. 9 ) having a pair of traction arms  210  movably mounted to the distal end thereof. More particularly, each of the traction arms  210  is pivotally mounted to hollow ovoid column  205  via a pivot pin  220 , whereby a toe  225  thereof may be moved radially inwardly or outwardly relative to the longitudinal axis  230  of hollow ovoid column  205 . A garter spring  235  is provided so as to urge toes  225  of traction arms  210  radially inwardly. A pair of handles  240  ( FIG. 8 ) are attached to hollow ovoid column  205 . 
         [0062]    Still looking at  FIGS. 8-12 , a clothespin rod  245 , having a bifurcated clothespin clamp  250  at its distal end, is movably mounted within hollow ovoid column  205 . As will hereinafter be discussed, clothespin clamp  250  may be used to keep inner collar  15  of locking collar connector  5  folded along its long axis. When clothespin rod  245  is in its extended position ( FIG. 9 ), clothespin rod  245  forces traction arms  210  apart, whereby to radially project toes  225 , in the manner shown in  FIG. 9 . In this way, and as will hereinafter be discussed, toes  225  can be used to support the undersides of L-shaped support arms  50  of inner collar  15 , whereby to grasp inner collar  15  to delivery instrument  200 . When clothespin rod  245  is in its retracted position ( FIG. 15 ), garter spring  235  urges toes  225  radially inwardly, in the manner shown in  FIG. 15 . In this way, and as will hereinafter be discussed, toes  225  can be withdrawn from the undersides of L-shaped support arms  50  of inner collar  15 , whereby to release inner collar  15  from delivery instrument  200 . 
         [0063]    Still looking at  FIGS. 8-12 , a pair of collar actuators  255  are movably disposed about the exterior of hollow column  205 . More particularly, collar actuators  255  include a pair of slots  260  through which handles  240  project. By gripping handles  240  and pressing on the proximal ends of collar actuators  255 , the distal ends of collar actuators  255  can be moved distally, whereby to force outer collar  25  distally, as will hereinafter be discussed. Collar actuators  255  together have an ovoid configuration. 
         [0064]    To install locking collar connector  5  onto delivery instrument  200 , collar actuators  255  are moved proximally on hollow ovoid column  205 , and clothespin rod  245  is moved proximally within hollow ovoid column  205  so that toes  225  are retracted inboard. Next, outer collar  25  of locking collar connector  5  is slid onto the distal end of hollow ovoid column  25 . Then the single integral assembly  27  of ratchet bracket  10 , inner collar  15  and graft conduit  20  is slid onto the distal end of hollow ovoid column  205 . Next, inner collar  15  is folded along the major axis of the oval. Then clothespin rod  245  is moved distally so that toes  225  project radially outward so as to support the underside of ratchet bracket  10  and so that clothespin clamp  250  holds portions of the Nitinol oval of the inner collar  15  in close proximity across the oval&#39;s minor axis. See  FIGS. 8-12 . Thus, the single integral assembly  27  of ratchet bracket  10 , inner collar  15  and graft conduit  20  is securely held in place on the distal end of delivery instrument  200 , with graft conduit  20  trapped in the annular gap between hollow ovoid column  205  and collar actuators  255 , and with outer collar  25  of locking collar connector  5  disposed on hollow ovoid column  205  proximal to the aforementioned single integral assembly  27  (of ratchet bracket  10 , inner collar  15  and graft conduit  20 ) and distal to collar actuators  255 . 
         [0065]    Note that a portion of graft conduit  20  is folded under, and is also held by, clothespin clamp  250 . See  FIGS. 10 and 13 . 
         [0066]    When locking collar connector  5  is to be deployed off the distal end of delivery instrument  200 , collar actuators  255  are advanced distally while hollow ovoid column  205  is held stationary (e.g., via handles  240 ). This causes outer collar  25  of locking collar connector  5  to move distally, with flange  205  of outer collar  205  moving toward inner collar  15  so as to clamp vascular tissue therebetween, and with ratchet teeth  115  of outer collar  25  engaging ratchet teeth  55  of ratchet bracket  10  so as to lock the two members in position relative to one another, and with graft conduit  20  in fluid communication with the desired blood flow. With locking collar connector  5  in position, clothespin rod  245  is retracted proximally, releasing inner collar  15  from clothespin clamp  250  (whereupon inner collar  15  springs back to its unfolded condition) and allowing toes  225  to retract inwardly, whereby to free delivery instrument  200  from locking collar connector  5 . Delivery instrument  200  may thereupon be withdrawn from the surgical site, leaving locking collar connector  5  in position. In this way, the distal anastomosis can be provided for an aortic valve bypass procedure. Thereafter, graft conduit  20  can be connected, in ways well known in the art, to the left ventricle of the heart as part of an aortic valve bypass procedure. 
       Installation Method 
       [0067]    The preferred method for installing locking collar connector  5  into the descending aorta using delivery instrument  200  is detailed in the steps below. 
         [0068]    1. Access to the descending aorta is created through a small thoracotomy, a thoracoscopy, or other minimally invasive opening in the thoracic cavity. 
         [0069]    2. Two balloon catheters (Cook Coda® G36042, for example) are fed up from the groin through one or both femoral arteries. A first balloon (“the proximal balloon”) is inflated above the anastomosis site (proximal to the heart), and the second balloon is inflated distal to the anastomosis site (“the distal balloon”). See  FIG. 13 . Blood flow through the aorta is effectively blocked by the two inflated balloons. 
         [0070]    3. The physician cuts a longitudinal slit at the anastomosis site ( FIG. 13 ). 
         [0071]    4. Delivery instrument  200 , with locking collar connector  5  carried thereon, is advanced through the thoracotomy to the anastomosis site. The delivery instrument is rotated so that the major axis of inner collar  15  of locking collar connector  5  is aligned with the aortic slit ( FIG. 13 ). Then inner collar  15  is inserted into the interior of the descending aorta via the aortic slit. In this respect it will be appreciated that insertion of the inner collar through the aortic slit and into the lumen of the descending aorta can be aided by “picking up” the descending aorta adjacent to the slit with a suitable pair of forceps ( FIG. 13 ), and the folded inner collar presents a narrow profile that can be fed one end at a time into the aortic slit. The process is repeated at the other end of the aortic slit until inner collar  15  is fully positioned within the lumen of the descending aorta. 
         [0072]    5. Once inner collar  15  of locking collar connector  5  is within the lumen of the descending aorta and substantially centered on the aortic slit, the physician applies traction to the inner collar via handles  240  ( FIG. 8 ). As noted above, the handles are rigidly connected to hollow ovoid column  205 , which contains the pivot axes for traction arms  210 . The traction arms are in contact with the ratchet bracket&#39;s L-shaped support arms  50  through a layer of graft. With traction applied to inner collar  15  using the handles as described above, the physician advances outer collar  25  down onto ratchet bracket  10  ( FIG. 14 ). To this end, delivery instrument  200  has a pair of collar actuators  255  ( FIG. 9 ) that may be moved independently of one another. The physician is able to push on either, or both, collar actuators as required so as to set outer collar  25 . This provides tactile feedback to the physician and enables him to properly compress each end of the outer collar onto the ratchet bracket. The aortic wall is thus securely clamped between outer collar  25  and the portion of the inner collar  15  near the major axis of the Nitinol oval of the inner collar. As this occurs, ratchet teeth  115  of outer collar  25  and ratchet teeth  55  of ratchet bracket  10  engage with each other so as to prevent the inner collar and the outer collar from separating. See  FIG. 14 . 
         [0073]    6. The physician retracts clothespin rod  245 , pulling clothespin clamp  250  off the folded inner collar  15 . As a result, the inner collar springs outward until the inner wall of the descending aorta is encountered. There is sufficient spring force in the inner collar to create at least line-to-line contact along the entire inner circumference of the aortic slit, thereby establishing hemostasis. As clothespin rod  245  is further retracted, the two traction arms  210  pivot towards each other, moving toes  225  inboard and thereby releasing support arms  50  from the delivery instrument. This action is preferably aided by the provision of garter spring  235 . See  FIG. 15 . 
         [0074]    7. Collar actuators  255  and hollow ovoid column  205  are withdrawn. The graft conduit slips out from the annular gap between the hollow ovoid column and the collar actuators. 
         [0075]    8. Means to block the neck of graft conduit  20 , and maintain hemostasis, are provided. By way of example but not limitation, a cross-clamp on the graft conduit is one such simple approach. After the graft conduit has been blocked and hemostasis is ensured, the distal balloon is deflated and withdrawn. Then the proximal balloon is deflated and withdrawn, leaving locking collar connector  5  deployed within the descending aorta. 
         [0076]    9. At this point, the distal anastomosis for the aortic valve bypass procedure is complete. Graft conduit  20  can thereafter be connected, in ways well known in the art, to the left ventricle of the heart as part of an aortic valve bypass procedure. 
       Alternative Constructions for the Locking Collar Connector 
       [0077]    An alternative embodiment of the locking collar connector is shown schematically in  FIG. 16 , and includes: 
         [0078]    1. A prosthetic valve  300  is pre-installed in the proximal end of graft conduit  20 . 
         [0079]    2. A side branch  305  is provided on graft conduit  20 . This construction is useful when a valve is pre-installed in the graft conduit. In this form of the invention, side branch  305  is installed on the delivery instrument (see below), and graft conduit  20  hangs off to the side of the delivery instrument. Side branch  305  is preferably sized to fit in the annular gap between the hollow ovoid column and the collar actuators. 
         [0080]    3. A connector  310  is provided for attaching the proximal end of graft conduit  20  to another conduit. This connector may be (i) a male-female slip connector such as is taught in  FIG. 15  of U.S. Pat. No. 7,510,561, issued Mar. 31, 2009 to Richard M. Beane et al. for APPARATUS AND METHOD FOR CONNECTING A CONDUIT TO A HOLLOW ORGAN (Attorney&#39;s Docket No. CORREX-033058-000005), which patent is hereby incorporated herein by reference, and/or (ii) a snap-together coupling of the sort known in the fluid-coupling art, with self-sealing capability on at least one side of the coupling. 
         [0081]    Inner collar  15  may also be constructed out of a stacked set of thin oval steel washers, rather than out of a single Nitinol sheet 0.009″ thick. By way of example but not limitation, a set of (4) 0.002″ thick stainless steel ovals can be stacked and joined together when the ratchet bracket is over-molded. Acting in tandem, this stack of stainless steel oval sheets can provide suitable flexibility and spring force with a low attendant stress level. Consequently, the risk of a fatigue failure can be significantly reduced. 
       Variation to the Foregoing Installation Method 
       [0082]    Where a side branch  305  is present on graft conduit  20 , the side branch can be held within the delivery instrument instead of the graft conduit. Installation then proceeds as outlined above. One advantage of this alternative configuration and approach is that a prosthetic valve  300  can be pre-installed within the graft conduit where a side branch is provided. The graft conduit, with valve, then remains undisturbed throughout the distal anastomosis. 
       Use of the Present Invention for Other Applications 
       [0083]    As disclosed above, the present invention may be used for effecting a distal anastomosis for an aortic valve bypass. However, it should be appreciated that the present invention can also be used for a distal anastomosis for any bypass procedure, or for substantially any joinder of one vessel to another vessel. 
       Further Modifications 
       [0084]    It will be understood that many additional changes in the details, materials, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art while remaining within the principles and scope of the present invention.