Patent Publication Number: US-2009230167-A1

Title: Endostapler Biasing Mechanism

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to endostapler delivery systems employed in the treatment of vascular disease. More particularly, the present invention relates to endostapler delivery systems including a biasing mechanism for use in the fixation of grafts to the walls of vessels. 
     BACKGROUND 
     In modern medical practice, it is sometimes desirable to pass a stapling device into or through the wall of a luminal anatomical structure (e.g., a blood vessel or other anatomical conduit) for the purpose of attaching an article (e.g., an endoluminal, extraluminal or transluminal graft) or other apparatus to the wall of the anatomical structure. 
     Examples of medical procedures wherein it is desirable to anchor or attach a graft or other apparatus to the wall of a blood vessel or other luminal anatomical conduit include certain endovascular grafting procedures wherein a tubular graft is placed within the lumen of an aneurysmal blood vessel to create a neo-lumen or artificial flow conduit through an aneurysm, thereby reducing if not completely eliminating the exertion of blood pressure on the aneurysm and allowing the aneurysmal sac to subsequently become stagnant and transform to granulation tissue. These endovascular grafting procedures have heretofore been used to treat aneurysms of the abdominal aorta, as well as aneurysms of the descending thoracic aorta. Endovascular grafts used typically incorporate or are combined with one or more radially expandable stents which are radially expanded in situ to anchor the tubular graft to the wall of the blood vessel at sites upstream and downstream of the aneurysm. Thus, the grafts are typically held in place by mechanical engagement, tissue ingrowth, and friction via the self-expanding or balloon expandable stents. The grafts may also be affixed to vessels with hooks or barbs. 
     However, in the event that the force provided by these stent(s) fails to establish sound mechanical and/or frictional engagement with the blood vessel wall, the graft may undergo undesirable migration or slippage, or blood may leak into the aneurysmal sac (sometimes referred to as an “endoleak”). Thus, in view of the above-mentioned undesirable complications associated with the use of radially expandable stents to mechanically and/or frictionally anchor a graft or other apparatus to the wall of a blood vessel (or other luminal anatomical structure) there exists a need in the art for the development of new endoluminal attachment devices which may be used to attach the ends of a endoluminal tube graft (or other article) to the surrounding wall of a blood vessel or other tubular anatomical conduit, thereby ensuring sound and permanent placement of the graft or other article. 
     BRIEF SUMMARY OF THE INVENTION 
     Embodiments described herein relate to an endostapler delivery system for delivering a stapling device through a body lumen. The system includes a catheter shaft including a proximal portion and a distal portion, the catheter shaft defining a first lumen having an exit port disposed at the distal portion of the catheter shaft and a second lumen having a side exit port disposed at the distal portion of the catheter shaft. The first and second lumens extend side-by-side from the proximal portion to the distal portion of the catheter shaft, and the first lumen of the catheter shaft is of a sufficient size such that the stapling device may be advanced there through. An expandable biasing cage is disposed within the second lumen of the catheter shaft. An actuator is disposed at the proximal portion of the catheter shaft, wherein the actuator is adapted to expand the biasing cage to a dome shape extending outside of the catheter shaft via the side exit port such that the biasing cage abuts a vessel wall of the body lumen and/or a graft implanted within the body lumen. The biasing cage when expanded does not block or occlude the body lumen such that blood may flow there through. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The foregoing and other features and advantages will be apparent from the following description of embodiments as illustrated in the accompanying drawings. The accompanying drawings, which are incorporated herein and form a part of the specification, further serve to explain the principles used in the embodiments. The drawings are not to scale. 
         FIG. 1  is a schematic isometric view of an endostapler delivery system. 
         FIG. 2  is a cross-sectional view of a vessel within which the endostapler delivery system in  FIG. 1  (only the end of which can be seen) is configured to position the stapler opening of the system adjacent the vessel wall for attaching an endoluminal graft to a vessel wall. 
         FIG. 3  is a sectional side view of the endostapler delivery system of  FIG. 1 , wherein a ribbon of a biasing cage of the endostapler delivery system is in an unexpanded configuration. 
         FIG. 4  is a sectional side view of the endostapler delivery system of  FIG. 1 , wherein the ribbon of the biasing cage of the endostapler delivery system is in an expanded configuration. 
         FIG. 5A  is a cross-sectional view of the endostapler delivery system of  FIG. 1 . 
         FIG. 5B  is a cross-sectional view of another embodiment of the endostapler delivery system of  FIG. 1 . 
         FIG. 6  is a pictorial view of a distal portion of the endostapler delivery system illustrated in  FIG. 1 , wherein the biasing cage of the endostapler delivery system in an expanded configuration. 
         FIG. 7  is a schematic isometric view of another embodiment of an endostapler delivery system. 
         FIG. 8  is a cross-sectional view of a vessel within which the endostapler delivery system in  FIG. 7  (only the end view of which can be seen) is configured to position the stapler opening of the system adjacent the vessel wall. 
         FIG. 9A  is a sectional side view of the endostapler delivery system of  FIG. 7 , wherein a plurality of braided elements of a biasing cage of the endostapler delivery system are in an unexpanded configuration. 
         FIG. 9B  is a sectional side view of the endostapler delivery system of  FIG. 7 , wherein the braided elements of the biasing cage of the endostapler delivery system are in an expanded configuration. 
         FIG. 10  is a side pictorial view of a distal portion of the endostapler delivery system of  FIG. 7 , wherein the braided elements of the biasing cage of the endostapler delivery system are in an expanded configuration. 
         FIG. 11  is a schematic isometric view of another embodiment of an endostapler delivery system. 
         FIG. 12  is a cross-sectional view of a vessel within which the endostapler delivery system of  FIG. 11  (only the end view of which can be seen) is configured to position the stapler opening of the system adjacent the vessel wall. 
         FIG. 13A  is a sectional side view of the endostapler delivery system of  FIG. 11 , wherein the braided elements and ribbon of a biasing cage of the endostapler delivery system are in an unexpanded configuration. 
         FIG. 13B  is a sectional side view of the endostapler delivery system of  FIG. 11 , wherein the braided elements and ribbon of a biasing cage of the endostapler delivery system are in an expanded configuration. 
         FIG. 14  is a top pictorial view of a distal portion of the endostapler delivery system of  FIG. 11 , wherein the braided elements and ribbon of the biasing cage of the endostapler delivery system are in an expanded configuration. 
         FIG. 15  is a side view illustration of a distal portion of the endostapler delivery system of  FIG. 11 , wherein the braided elements and ribbon of the biasing cage of the endostapler delivery system are in an expanded configuration. 
         FIG. 16  is a sectional side view of an endostapler delivery system according to another embodiment, wherein a biasing cage of the endostapler delivery system is in an unexpanded configuration. 
     
    
    
     DETAILED DESCRIPTION 
     Specific embodiments are now described with reference to the figures, wherein like reference numbers indicate identical or functionally similar elements. The terms “distal” and “proximal” are used in the following description with respect to a position or direction relative to the treating clinician. “Distal” or “distally” are a position distant from or in a direction away from the clinician. “Proximal” and “proximally” are a position near or in a direction toward the clinician. 
     The following detailed description is merely exemplary in nature and is not intended to limit the number of possible variations of embodiments according to the invention. Although the description of embodiments is in the context of treatment of blood vessels such as the coronary, carotid and renal arteries, the embodiments may also be used in any other body passageways where it is deemed useful. 
     Embodiments described relate to an endostapler delivery system having a biasing mechanism to offset or counter forces generated by a stapling device. A delivery system includes a catheter having at least one lumen extending there through for receiving the stapling device. A biasing mechanism is an expandable biasing cage having a dome or semi-circular expanded shape provided at the distal portion of the catheter. When expanded, the biasing cage forces the stapling device against a receiving area of a vessel wall and/or graft where a staple is to be fired. Further, the biasing cage prevents the stapling device from moving during the firing of the staple. An expanded biasing cage does not block or occlude the vessel in order to allow blood flow to continue during the stapling procedure. Thus, the biasing cage allows blood perfusion at all times while simultaneously offsetting or countering forces generated by the stapling device. In one embodiment, the biasing cage includes a plurality of ribbons or strands that extend parallel to the blood flow when expanded in situ. In another embodiment, the biasing cage includes a mesh or braided structure. In another embodiment, the biasing cage includes a plurality of ribbons or strands that extend parallel to the blood flow when expanded in situ and a mesh or braided structure placed over the plurality of ribbons. Further details and description of these embodiments are provided below. 
     Referring to  FIGS. 1-2 , an endostapler delivery system  100  includes a catheter shaft  102  having an expandable biasing cage  110  disposed at the distal portion thereof.  FIG. 1  is an schematic isometric view of endostapler delivery system  100 , while  FIG. 2  is an end view of the endostapler delivery system  100  positioned within a vessel for attaching an endoluminal graft to a vessel wall  232 . Catheter shaft  102  includes a proximal portion  104  and a distal portion  106 , wherein distal portion  106  includes an exit port  107 . In addition, as will be explained in more detail below, catheter shaft  102  has at least one lumen extending there through for receiving a stapling device for attaching an endovascular graft  230  to a vessel wall  232  of a body lumen. A side recess or port  112  is provided at the distal portion  106  of catheter shaft  102  for exposing the expandable biasing cage  110 . An actuator  108  is provided at the proximal portion  104  of catheter shaft  102  for expanding biasing cage  110  to a dome or semi-circular shape. Biasing cage  110  is expanded to the dome or semi-circular shape in situ in order to ensure that the stapling device abuts the vessel and/or graft. During operation of the stapling device, expanded biasing cage  110  acts as an anchor to offset or counter forces generated by the stapling device. 
     Biasing cage  110  includes a plurality of ribbons or strands  114  that extend generally parallel to the blood flow when expanded. Open spaces  115  disposed between the plurality of ribbons or strands  114  when biasing cage is expanded allow blood or other fluid to flow there through during the stapling procedure such that the blood vessel is not blocked or occluded. In one example shown in  FIGS. 1-2  and  6 , biasing cage  110  includes three ribbons  114 a,  114 b, and  114 c. However, one of ordinary skill in the art will appreciate that biasing cage  110  may include any number of ribbons or strands. For example, biasing cage  110  may include between two and five ribbons or strands that extend generally parallel to the blood flow when expanded. The plurality of ribbons  114  have sufficient mechanical strength to anchor the catheter shaft  102  to offset or counter forces generated by a stapling device when the stapling device is utilized in securing endovascular graft  230  (only a cross section of which is shown) to a vessel wall  232  of a body lumen. More particularly, biasing cage  110  may be expanded prior to the firing of a staple. Expanding biasing cage  110  forces the stapling device against a receiving area of the vessel wall  232  and/or graft  230  where a staple is to be fired. Preferably, the receiving area of the vessel wall  232  and/or graft  230  is positioned on the opposite side of the vessel to the average centerline of force vectors associated with the expansion of the various components of the biasing cage  110 . In addition to placing the stapling device immediately adjacent to the receiving area of the vessel wall  232  and/or graft  230 , biasing cage  110  also assists with preventing the stapling device from moving during the firing of the staple. 
     Embodiments described may be used with any conventional stapling device capable of securing graft  230  to vessel wall  232 . Thus, it will be apparent to those of ordinary skill in the art that any features of the stapling device discussed herein are exemplary in nature. For example, the stapling device may be any stapling device known in the art, including but not limited to those shown or described in US Patent Publication 20040176786 assigned to Edrich Vascular, US Patent Publication 20070073389 assigned to Aptus Endosystems, Inc., and US Patent Publication 20070162053 assigned to Anson Medical. In another embodiment (not shown), the stapling device may be an integral part of the biasing endostapler delivery system, i.e., formed as one integral piece within a lumen of the catheter. 
     As shown in  FIG. 3 , catheter shaft  102  is a multi-lumen catheter.  FIG. 3  is a sectional side view of the endostapler delivery system  100  illustrated in  FIG. 1 . Catheter shaft  102  includes a first lumen  316  extending along the entire length thereof for receiving a stapling device. In the present embodiment, first lumen  316  is open-ended and in fluid communication with exit port  107  such that the stapling device may exit out of the exit port  107  at the distal portion  106  of catheter shaft  102 . However, as will be explained in greater detail herein, alternatively the first lumen may be closed-ended but in fluid communication with an exit port located in the side of the catheter shaft such that a side-firing stapling device may be used. Catheter shaft  102  also includes a second lumen  318  that extends from the proximal portion  104  to the distal portion  106  of catheter shaft  102  for housing the biasing mechanism, including biasing cage  110 . Second lumen  318  is parallel and adjacent to first lumen  316 . Second lumen  318  is closed-ended but in fluid communication with side recess or port  112  provided at the distal portion  106  of catheter shaft  102 . Side recess or port  112  allows biasing cage  110  to expand and abut the vessel wall  232  and/or graft  230 . 
     First lumen  316  and second lumen  318  are thus in a side-by-side arrangement through the length of the catheter, and may each have any suitable cross-section. For example,  FIG. 5A  is a cross-sectional view of endostapler delivery system  100  in accordance with one embodiment in which both first lumen  316 A and second lumen  318 A have circular or elliptical cross-sections. First lumen  316  of catheter shaft  102  is of a sufficient size to accommodate a stapling device. For example, a conventional stapling typically has a profile or an outer diameter of approximately 4 mm-5 mm (12-15 French units) and thus the diameter of first lumen  316  of catheter shaft  102  should be of a slightly larger size in order to ensure that a conventional stapling device can be advanced through catheter shaft  102 . However, second lumen  318  of catheter shaft  102  is relatively smaller than first lumen  316  because second lumen  318  must only be of a sufficient size to accommodate the biasing mechanism, including unexpanded biasing cage  110 . It is desirable to keep second lumen  318  as small as possible in order to minimize the outer diameter of catheter shaft  102 , thus minimizing the size of endostapler delivery system  100  such that endostapler delivery system  100  may fit within relatively small vessels. The outer diameter of the catheter shaft may be approximately 3 mm-8 mm. 
     Other embodiments of catheter shaft  102  may have first lumen  316  and second lumen  318  in other dual lumen arrangements, such as a kidney or arc-shaped second lumen above a circular first lumen as shown in  FIG. 5B .  FIG. 5B  is a cross-sectional view of the endostapler delivery system illustrated in  FIG. 1  in accordance with another embodiment. Another alternative dual lumen arrangement is a crescent-shaped second lumen above a circular first lumen (not illustrated). As described above, the only limitation on the cross-sectional shapes of first lumen  316  and second lumen  318  is that first lumen  316  must be a sufficient size to accommodate a stapling device and second lumen  318  must be of a sufficient size to accommodate the biasing mechanism. 
     While not shown in any of the figures, the use of an outer cover, catheter outer sheath may be employed to provide a continuous smooth and slick (e.g., lubricious hydrophilic coating coated) surface to facilitate easy introduction of the catheter into the patient. Once the end of the catheter has been positioned near the delivery location, the outer cover is drawn back, either by the closing of a gap at the handle, or by splitting the outer sheath and having at least a proximal portion of it constructed as a peel away type sheath. 
     Referring now to  FIGS. 3-4 , biasing cage  110  is movable from an unexpanded position (shown in  FIG. 3 ) to an expanded position (shown in  FIG. 4 ). In the unexpanded position, biasing cage  110  is relatively straight in order to minimize the delivery profile as endostapler delivery system  100  is advanced to a position within graft  230 . Further, in the unexpanded position, biasing cage  110  is completely housed within second lumen  318 . Biasing cage  110  is then expanded via actuator  108  to the expanded position shown in  FIG. 4 , as well as  FIGS. 1 ,  2  and  6 . In the expanded position, biasing cage  110  assumes a dome or semi-circular shape extending outside of catheter shaft  102  via side recess or port  112  such that biasing cage  110  abuts the vessel wall  232  and/or graft  230 . Thus, the height of the expanded biasing cage  110  must be sufficient to enable the biasing cage  110  to abut the vessel wall  232  and/or graft  230 . For example, a target vessel lumen may be approximately 36 mm in diameter. Accordingly, if the outer diameter of catheter shaft  102  is approximately 3 mm-8 mm, the deployment height of the expanded biasing cage (that is, the height of the dome or semi-circular shape extending outside of catheter shaft  102 ) should be approximately 12 mm-30 mm or of a slightly larger size in order to ensure that the expanded biasing cage  110  abuts the vessel wall  232  and/or graft  230 . 
     As shown in  FIGS. 3 and 4 , to expand biasing cage  110 , actuator  108  may be a turning or push-pull actuator (i.e., a knob or handle) that is attached or connected to a rod  320  which extends through second lumen  318 . Rod  320  has a proximal end  322  and a distal end  324 , the proximal end  322  being connected to actuator  108  and the distal end  324  being connected to a proximal end  326  of biasing cage  110 . A distal end  328  of biasing cage  110  is fixed via a connection  334  to catheter shaft  102 . When actuator  108  is operated (i.e., manually turned or pushed), rod  320  is advanced through second lumen  318  of catheter shaft  102 . Since distal end  328  of biasing cage  110  is fixed, biasing cage  110  expands or deploys to the expanded dome or semi-circular shape when the material of biasing cage  110  radially expands via side recess or port  112 . In another embodiment, biasing cage  110  may extend through the entire second lumen  318  of catheter  102  such that the proximal end  326  of the biasing cage  110  is connected to the actuator  108 , thus eliminating the need for rod  320 . 
     Distal end  328  of biasing cage  110  may be attached to catheter shaft  102  in any suitable manner known in the art. For example, connection  334  may be formed by welding, such as by resistance welding, friction welding, laser welding or another form of welding such that no additional materials are used to connect biasing cage  110  to catheter shaft  102 . Alternatively, biasing cage  110  and catheter shaft  102  can be connected by soldering, by the use of an adhesive, by the addition of a connecting element there between, or by another mechanical method. 
     In order to expand or deploy biasing cage  110 , endostapler delivery system  100  must be tracked to and properly positioned at implanted endoluminal graft  230 . In general, a guidewire (not shown) is introduced into the target vessel. Endostapler delivery system  100  is then tracked over the guidewire such that the exit port  107  is adjacent to the implanted endoluminal graft  230 . Once endostapler delivery system  100  is in place as desired, the guidewire may be removed and a conventional stapling device is inserted through first lumen  316  and exit port  107  of catheter shaft  102  and tracked to a position in which the stapling device is adjacent a receiving area of the vessel wall  232  and/or graft  230  where a staple is to be fired. With the guidewire removed, endostapler delivery catheter acts as a guide catheter for tracking the conventional stapling device to the site of the implanted endoluminal graft  230 . Alternatively, if the stapling device is an over the wire type device, the guidewire may be left in place within endostapler delivery system  100  and the stapling device may inserted through catheter shaft  102  and tracked over the guidewire. Alternately, the endostapler delivery catheter can be constructed with an additional lumen for a guide wire. 
     Once the stapling device is in place (that is, adjacent a receiving area of the vessel wall  232  and/or graft  230  where a staple is to be fired), biasing cage  110  may be expanded or deployed in order to maintain the desired position. Expansion of biasing cage  110  pushes the stapling portion of the stapling device against the vessel wall  232  and/or graft  230  where a staple is to be fired. When the staple is fired from the stapling device, biasing cage  110  remains expanded so that it prevents the stapling device from moving during the firing of the staple. Following each staple deployment, biasing cage  110  may be partially or fully collapsed to the unexpanded position. The stapling device is rotated to a second position in preparation for the firing of a second or subsequent staple, and the process is repeated to deploy the next staple. Prior to firing the second or subsequent staple, biasing cage  110  is expanded to place the stapling portion of the stapling device in position in preparation for firing. Once all the staples have been delivered and graft  230  is secured as desired, biasing cage  110  is fully collapsed to the unexpanded position. The stapling device and endostapler delivery system  100  are retracted and removed from the patient. Although methods of using specific embodiments are described herein for securing an endoluminal graft to a vessel wall, it will be apparent to those of ordinary skill in the art that such embodiments may also be utilized for securing extraluminal or transluminal grafts to a vessel wall. 
     Ribbons  114  of biasing cage  110  are preferably constructed of biocompatible materials having good mechanical strength. For example, non-exhaustive examples of metallic materials for ribbons  114  are stainless steel, cobalt based alloys (605L, MP35N), titanium, tantalum, tungsten based alloys, superelastic nickel-titanium alloy, other biocompatible metals, thermoplastic polymers, or combinations of any of these. 
     The catheter shaft may be an extruded multi-lumen shaft formed of any suitable flexible polymeric material. Non-exhaustive examples of material for the catheter shaft are polyethylene terephalate (PET), nylon, polyethylene, PEBAX, or combinations of any of these, either blended or co-extruded. Optionally, a portion of the catheter shaft may be formed as a composite having a reinforcement material incorporated within a polymeric body in order to enhance strength, flexibility, and/or toughness. Suitable reinforcement layers include braiding, wire mesh layers, embedded axial wires, embedded helical or circumferential wires, and the like. In an embodiment, the proximal portion of the catheter shaft may in some instances be formed from a reinforced polymeric tube, for example, as shown and described in U.S. Pat. No. 5,827,242 to Follmer et al. which is incorporated by reference herein in its entirety. The catheter shaft may have any suitable working length, for example, 550 mm-650 mm, in order to extend to a target location where a staple is to be fired. 
     As previously discussed, embodiments described relate to a biasing mechanism to ensure that the stapling portion of the stapling device is secure against a vessel wall and/or graft. Another embodiment of a biasing device which may be utilized for this purpose is shown in  FIGS. 7-10 . Referring to  FIGS. 7 and 8 , an endostapler delivery system  700  includes a catheter shaft  702  having an expandable biasing cage  710  at the distal portion thereof.  FIG. 7  is an isometric view of endostapler delivery system  700 , and  FIG. 8  is a front view of the endostapler delivery system  700  utilized within a vessel for attaching an endoluminal graft to a vessel wall. Catheter shaft  702  includes a proximal portion  704  and a distal portion  706 , wherein distal portion  706  includes an exit port  707 . A side recess or port  712  is provided at the distal portion  706  of catheter shaft  702  for exposing an expandable biasing cage  710 . An actuator  708  is provided at the proximal portion  704  of catheter shaft  702  for expanding biasing cage  710  to a dome or semi-circular shape. Biasing cage  710  is expanded to the dome or semi-circular shape in situ in order to ensure that a stapling device inserted through catheter shaft  702  abuts a vessel and/or graft. The stapling device may be any conventional stapling device capable of securing graft  230  to vessel wall  232 . 
     Biasing cage  710  includes a braided structure or mesh  736 . Open spaces  715  disposed within mesh  736  when biasing cage  710  is expanded allow blood or other fluid to flow through the vessel during the stapling procedure. The braided structure or mesh  736  has sufficient mechanical strength to offset or counter forces generated by a stapling device when the stapling device is utilized in securing endovascular graft  230  to a vessel wall  232  of a body lumen. More particularly, biasing cage  710  may be expanded prior to the firing of a staple. Expanding biasing cage  710  forces the stapling device against a receiving area of a vessel wall  232  and/or graft  230  where a staple is to be fired. Preferably, the receiving area of the vessel wall  232  and/or graft  230  is positioned on the opposite side of the vessel than biasing cage  710 . In addition to placing the stapling device immediately adjacent to the receiving area of the vessel wall  232  and/or graft  230 , biasing cage  710  also assists with preventing the stapling device from moving during the firing of the staple. 
     As shown in  FIG. 9A , catheter shaft  702  is a multi-lumen catheter.  FIG. 9A  is a sectional side view of the endostapler delivery system illustrated in  FIG. 7 . Catheter shaft  702  includes a first lumen  916  extending along the entire length thereof for receiving a stapling device. First lumen  916  is open-ended such that it is in fluid communication with exit port  707  such that stapling device may exit out of the exit port  707  of catheter shaft  702 . However, as will be explained in greater detail herein, alternatively the first lumen may be closed-ended but in fluid communication with an exit port located in the side of the catheter shaft such that a side-firing stapling device may be used. Catheter shaft  702  also includes a second lumen  918  that extends from the proximal portion  704  to the distal portion  706  of catheter shaft  702  for housing the biasing mechanism, including biasing cage  710 . Second lumen  918  is parallel and adjacent to first lumen  916 . Second lumen  918  is closed-ended but in fluid communication with side recess or port  712  provided at the distal portion  706  of catheter shaft  702 . Side recess or port  712  allows biasing cage  710  to expand and abut the vessel wall  232  and/or graft  230 . As described above with respect to previous embodiments, first lumen  916  of catheter shaft  702  is of a sufficient size to accommodate a stapling device and second lumen  918  is of a sufficient size to accommodate the biasing mechanism, including biasing cage  710 . First lumen  916  and second lumen  918  may each have any suitable cross-section such as those described with respect to previous embodiments. 
     Referring now to  FIGS. 9A-9B , biasing cage  710  is movable from an unexpanded position (shown in  FIG. 9A ) to an expanded position (shown in  FIG. 9B ). In the unexpanded position, biasing cage  710  is relatively straight in order to minimize the delivery profile as endostapler delivery system  700  is advanced to graft  230 . Further, in the unexpanded position, biasing cage  710  is completely housed with second lumen  918 . Biasing cage  710  is then expanded via actuator  708  to the expanded position shown in  FIGS. 9B and 10 . In the expanded position, biasing cage  710  assumes a dome or semi-circular shape extending outside of catheter shaft  702  via side recess or port  712  such that biasing cage  710  abuts the vessel wall  232  and/or graft  230 . Thus, the height of the expanded biasing cage  710  must be sufficient to enable the biasing cage  710  to abut the vessel wall  232  and/or graft  230 . In order to expand biasing cage  710 , actuator  708  may be a rotational (to be turned) or push-pull actuator (i.e., a knob or handle) that is attached or connected to a rod  920  which extends through second lumen  918 . Rod  920  includes a proximal end  922  and a distal end  924 , the proximal end  922  being connected to actuator  708  and the distal end  924  being connected to a proximal end  926  of biasing cage  710 . A distal end  928  of biasing cage  710  is fixed via a connection  934  to catheter shaft  702 . Distal end  928  of biasing cage  710  may be attached to catheter shaft  702  in any suitable manner known in the art as described above with respect to previous embodiments. When actuator  708  is operated (i.e., manually, turned, rotated, or pushed), rod  920  is advanced through second lumen  918  of catheter shaft  702 . Since distal end  928  of biasing cage  710  is fixed, biasing cage  710  expands or deploys to the expanded dome or semi-circular shape when the material of biasing cage  710  radially expands via side recess or port  712 . In another embodiment, biasing cage  710  may extend through the entire second lumen  918  of catheter  702  such that the proximal end  926  of the biasing cage  710  is connected to the actuator  708 , thus eliminating the need for rod  920 . 
     Mesh  736  (shown in  FIG. 10 ) of biasing cage  710  is preferably constructed of implantable polymeric or metallic materials having good mechanical strength. Non-exhaustive examples of polymeric materials for mesh  736  are polyurethane, polyethylene terephalate (PET), nylon, polyethylene, PEBAX, or combinations of any of these, either blended or co-extruded. Non-exhaustive examples of metallic materials for mesh  736  are stainless steel, cobalt based alloys (605L, MP35N), titanium, tantalum, superelastic nickel-titanium alloy, or combinations of any of these. 
     As previously discussed, the embodiments described relate to a biasing mechanism to ensure that the stapling portion of the stapling device is secure (anchored) against a vessel wall and/or graft. Another embodiment of a biasing device which may be utilized for this purpose is shown in  FIGS. 11-15 . Referring to  FIGS. 11 and 12 , an endostapler delivery system  1100  includes a catheter shaft  1102  having an expandable biasing cage  1110  at a distal portion thereof.  FIG. 11  is a schematic isometric view of endostapler delivery system  1100 , and  FIG. 12  is a front view of the endostapler delivery system  1100  utilized within a vessel for attaching an endoluminal graft  230  to a vessel wall  232 . Catheter shaft  1102  includes a proximal portion  1104  and a distal portion  1106 , wherein distal portion  1106  includes an exit port  1107 . A side recess or port  1112  is provided at the distal portion  1106  of catheter shaft  1102  for exposing an expandable biasing cage  1110 . An actuator  1108  is provided at the proximal portion  1104  of catheter shaft  1102  for expanding biasing cage  1110  to a dome or semi-circular shape. Biasing cage  1110  is expanded to the dome or semi-circular shape in situ in order to ensure that a stapling device inserted through catheter shaft  1102  abuts a vessel wall  232  and/or a graft  230 . The stapling device may be any conventional stapling device capable of securing graft  230  to vessel wall  232 . 
     Biasing cage  1110  includes a plurality of ribbons or strands  1140  that extend generally parallel to the blood flow when expanded, and includes a braided structure or mesh  1142  placed over the plurality of ribbons  1140 . Biasing cage  1110  does not block or occlude a vessel and thus allows blood or other fluid to flow there through during the stapling procedure. In one example shown in  FIGS. 11-15 , biasing cage  1110  includes three ribbons  1140   a,    1140   b,  and  1140   c.  However, one of ordinary skill in the art will appreciate that biasing cage  1110  may include any number of ribbons or strands. For example, biasing cage  1110  may include between two and five ribbons or strands that extend generally parallel to the blood flow when expanded. In this embodiment, the plurality of ribbons  1140  have sufficient mechanical strength to offset or counter forces generated by a stapling device when the stapling device is utilized in securing endovascular graft  230  to a vessel wall  232  of a body lumen while mesh  1142  provides atraumatic gentle contact with a vessel wall. More particularly, biasing cage  1110  may be expanded prior to the firing of a staple. Expanding biasing cage  1110  forces the stapling device against a receiving area of a vessel wall  232  and/or graft  230  where a staple is to be fired. Preferably, the receiving area of the vessel wall  232  and/or graft  230  is positioned on the opposite side of the vessel than biasing cage  1110 . In addition to placing the stapling device immediately adjacent to the receiving area of the vessel wall  232  and/or graft  230 , biasing cage  1110  also assists with preventing the stapling device from moving during the firing of the staple. 
     As shown in  FIG. 13A , catheter shaft  1102  is a multi-lumen catheter.  FIG. 13A  is a sectional side view of the endostapler delivery system illustrated in  FIG. 11 . Catheter shaft  1102  includes a first lumen  1316  extending along the entire length thereof for receiving a stapling device. First lumen  1316  is open-ended and in fluid communication with exit port  1107  such that the stapling device may exit out of the exit port  1107  of catheter shaft  1102 . However, as will be explained in greater detail herein, alternatively the first lumen may be closed-ended but in fluid communication with an exit port located in the side of the catheter shaft such that a side-firing stapling device may be used. Catheter shaft  1102  also includes a second lumen  1318  that extends from the proximal portion  1104  to the distal portion  1106  of catheter shaft  1102  for housing the biasing mechanism, including biasing cage  1110 . Second lumen  1318  is parallel and adjacent to first lumen  1316 . Second lumen  1318  is closed-ended but in fluid communication with side recess or port  1112  provided at the distal portion  1106  of catheter shaft  1102 . Side recess or port  1112  allows biasing cage  1110  to expand and abut the vessel wall  232  and/or graft  230 . As described above with respect to previous embodiments, first lumen  1316  of catheter shaft  1102  is of a sufficient size to accommodate a stapling device and second lumen  1318  is of a sufficient size to accommodate the biasing mechanism, including biasing cage  1110 . First lumen  1316  and second lumen  1318  may each have any suitable cross-section such as those described with respect to previous embodiments. 
     Referring now to  FIGS. 13A-13B , biasing cage  1110  is movable from an unexpanded position (shown in  FIG. 13A ) to an expanded position (shown in  FIG. 13B ). In the unexpanded position, biasing cage  1110  is relatively straight in order to minimize the delivery profile as endostapler delivery system  1100  is advanced to graft  230 . Further, in the unexpanded position, biasing cage  1110  is completely housed with second lumen  1318 . Biasing cage  1110  is then expanded via actuator  1108  to the expanded position shown in FIGS.  13 B and  14 - 15 . In the expanded position, biasing cage  1110  assumes a dome or semi-circular shape extending outside of catheter shaft  1102  via side recess or port  1112  such that biasing cage  1110  abuts the vessel wall  232  and/or graft  230 . Thus, the height of the expanded biasing cage  1110  must be sufficient to enable the biasing cage  1110  to abut the vessel wall  232  and/or graft  230 . To expand biasing cage  1110 , actuator  1108  may be a rotational (to be turned) or push-pull actuator (i.e., a knob or handle) that is attached or connected to a rod  1320  which extends through second lumen  1318 . Rod  1320  has a proximal end  1322  and a distal end  1324 , the proximal end  1322  being connected to actuator  1108  and the distal end  1324  being connected to a proximal end  1326  of biasing cage  1110 . A distal end  1328  of biasing cage  1110  is fixed via a connection  1334  to catheter shaft  1102 . Distal end  1328  of biasing cage  1110  may be attached to catheter shaft  1102  in any suitable manner known in the art as described above with respect to previous embodiments. When actuator  1108  is operated (i.e., manually, turned, rotated, or pushed), rod  1320  is advanced through second lumen  1318  of catheter shaft  1102 . Since second distal end  1328  of biasing cage  1110  is fixed, biasing cage  1110  expands or deploys to the expanded dome or semi-circular shape when the material of biasing cage  1110  radially expands via side recess or port  1112 . In another embodiment, biasing cage  1110  may extend through the entire second lumen  1318  of catheter  1102  such that the proximal end  1326  of the biasing cage  1110  is connected to the actuator  1108 , thus eliminating the need for rod  1320 . 
     Mesh  1142  is positioned or superimposed over ribbons  1140  to form biasing cage  1110 . Mesh  1142  of biasing cage  1110  provides atraumatic gentle contact with the vessel wall and thus is preferably constructed of a flexible implantable polymeric material. Non-exhaustive examples of polymeric materials for mesh  1142  are polyurethane, polyethylene terephalate (PET), nylon, polyethylene, PEBAX, or combinations of any of these, either blended or co-extruded. Ribbons  1140  have sufficient mechanical strength to offset or counter forces generated by a stapling device and thus are preferably constructed from an implantable metallic material having good mechanical strength. Non-exhaustive examples of metallic materials for ribbons  1140  are stainless steel, cobalt based alloys (605L, MP35N), titanium, tantalum, superelastic nickel-titanium alloy, or combinations of any of these. 
     Biasing cage  1110  having a combination of a plurality of ribbons or strands  1140  and a braided structure or mesh  1142  would have an advantage of a smaller delivery profile. Ribbons  1140  act as the structural element in that they provide the majority of the structural support needed to assure catheter contact with the vessel wall. Ribbons  1140  can be constructed with a narrower cross sectional configuration to minimize catheter crossing profile, as the adjacent mesh structure  1142  will distribute the force exerted over a larger area than just the surface of the ribbons and as such will provide a combined element that provides atraumatic contact with the vessel wall. The general understood means of forming such shape memory ribbons would be used to shape the ribbon to pre-set shape expanded predetermined diameter. In operation, a push pull and/or screw actuation mechanism would then be used for deployment. 
     As previously described, the first lumen of the catheter shaft that receives the stapling device may be open-ended and in fluid communication with an exit port such that the stapling device may exit out of the distal open-ended exit port. Alternatively, the first lumen of the catheter shaft may be closed-ended but in fluid communication with an exit port located in the side of the catheter shaft such that a side-firing stapling device may be utilized. For example, as shown in  FIG. 16 , catheter shaft  1602  is a multi-lumen catheter including a first lumen  1616  extending along the entire length thereof for receiving a stapling device. First lumen  316  is closed-ended but in fluid communication with side exit port  1617  of the catheter such that a side-firing stapling device may exit out of the side exit port  1617  at the distal portion  1606  of catheter shaft  102 . Similar to previously described embodiments, catheter shaft  1602  also includes a second lumen  1618  that extends from the proximal portion  1604  to the distal portion  1606  of catheter shaft  1602  for housing the biasing mechanism, including biasing cage  1610 . Second lumen  1618  is parallel and adjacent to first lumen  1616 . Second lumen  1618  is closed-ended but in fluid communication with side recess or port  1612  provided at the distal portion  1606  of catheter shaft  1602  to allow biasing cage  1610  to expand and abut the vessel wall and/or graft. Distal side exit port  1617  is located directly across from (on the opposite side of the catheter shaft) side recess or port  1612  so that a staple is fired directly opposite from the approximate centerline of an expanded portion of the biasing mechanism (biasing cage  1610 ). 
     While various embodiments according to the present invention have been described above, it should be understood that they have been presented by way of illustration and example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of that described. It will also be understood that each feature of each embodiment discussed herein, and of each reference cited herein, can be used in combination with the features of any other embodiment. All patents and publications discussed herein are incorporated by reference herein in their entirety.