Patent Publication Number: US-2007118099-A1

Title: Method and apparatus for endovascular graft cutting

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      The present invention relates to, and is entitled to the benefit of the earlier filing date and priority of U.S. Application No. 60/707,943 filed Aug. 15, 2005. 
    
    
     FIELD OF THE INVENTION  
      The present invention relates generally an apparatus and method for use in surgical repair, more particularly for endovascular cutting of surgical grafts.  
     BACKGROUND  
      An aneurysm is a ballooning of the wall of an artery resulting from the weakening of the artery due to disease or other conditions. Left untreated, the aneurysm will frequently rupture, resulting in loss of blood through the rupture and death.  
      Aortic aneurysms are the most common form of arterial aneurysm and are life threatening. The aorta is the main artery which supplies blood to the circulatory system. The aorta arises from the left ventricle of the heart, passes upward and bends over behind the heart, and passes down through the thorax and abdomen. Among other arterial vessels branching off the aorta along its path, the abdominal aorta supplies two side vessels to the kidneys, the renal arteries. Below the level of the renal arteries, the abdominal aorta continues to about the level of the fourth lumbar vertebrae (or the navel), where it divides into the iliac arteries. The iliac arteries, in turn, supply blood to the lower extremities and perineal region.  
      It is common for an aortic aneurysm to occur in that portion of the abdominal aorta between the renal arteries and the iliac arteries. This portion of the abdominal aorta is particularly susceptible to weakening, resulting in an aortic aneurysm. Such an aneurysm is often located near the iliac arteries. An aortic aneurysm larger than about 5 cm in diameter in this section of the aorta is ominous. Left untreated, the aneurysm may rupture, resulting in rapid, and usually fatal, hemorrhaging. Typically, a surgical procedure is not performed on aneurysms smaller than 5 cm as no statistical benefit exists to do so.  
      Aneurysms in the abdominal aorta are associated with a particularly high mortality rate; accordingly, current medical standards call for urgent operative repair. Abdominal surgery, however, results in substantial stress to the body. Although the mortality rate for an aortic aneurysm is extremely high, there is also considerable mortality and morbidity associated with open surgical intervention to repair an aortic aneurysm. This intervention involves penetrating the abdominal wall to the location of the aneurysm to reinforce or replace the diseased section of the abdominal wall (i.e., abdominal aorta). A prosthetic device, typically a synthetic tube graft, is used for this purpose. The graft serves to exclude the aneurysm from the circulatory system, thus relieving pressure and stress on the weakened section of the aorta at the aneurysm.  
      Repair of an aortic aneurysm by surgical means is a major operative procedure. Substantial morbidity accompanies the procedure, resulting in a protracted recovery period. Further, the procedure entails a substantial risk of mortality. While surgical intervention may be indicated and the surgery carries attendant risk, certain patients may not be able to tolerate the stress of intra-abdominal surgery. It is, therefore, desirable to reduce the mortality and morbidity associated with intra-abdominal surgical intervention.  
      In recent years, methods have been developed to attempt to treat an abdominal aortic aneurysm without the attendant risks of intra-abdominal surgical intervention. Although techniques have been developed that may reduce the stress, morbidity, and risk of mortality associated with surgical intervention to repair aortic aneurysms, none of the prior art systems that have been developed effectively treat the aneurysm and exclude the affected section of aorta from the pressures and stresses associated with circulation. None of the devices disclosed in the references provide a reliable and quick means to reinforce an aneurysmal artery. In addition, all of the prior references require a sufficiently large section of healthy aorta abutting the aneurysm to ensure attachment of the graft. The proximal aortic neck (i.e., above the aneurysm) is usually sufficient to support a graft&#39;s attachment means. However, when an aneurysm is located near the iliac arteries, there may be an ill-defined neck or no neck below the aneurysm. Such an ill-defined neck would have an insufficient amount of healthy aortic tissue to which to successfully attach a graft. Furthermore, much of the abdominal aortic wall may be calcified making it extremely difficult to attach a graft thereto.  
      Additionally, there are occasions when it is advantageous to use an unsupported endograft. A new approach to the endovascular treatment of aortic aneurysms involves using only unsupported endografts where the unsupported endograft can be inserted and the tube portion attached to the aortic neck and the distal limbs attached to the iliac arteries with commercially available stents. An endovascular approach using unsupported endografts would substantially lower costs associated with the procedure because a current supported endograft typically costs about $20,000. A problem with this approach is that the unsupported endograft must be cut before it is inserted into the body because there is no currently available method to cut an unsupported endograft endovascularly. Because it is impossible to know the exact length needed for the limbs of the endograft without completing some type of preoperative imaging study, there is a need to develop a method and apparatus to cut the endografts after they have been inserted into the artery. There is a need in the industry to develop an apparatus and method to trim excess graft material from an endograft following placement of the endograft at the surgical site.  
      Additional advantages of various embodiments of the invention are set forth, in part, in the description that follows and, in part, will be apparent to those of ordinary skill in the art from the description and/or from the practice of the invention.  
     SUMMARY  
      Embodiments of the present invention are directed to a method and apparatus for cutting endografts endovascularly. One embodiment of the present invention is to develop a method and apparatus to cut an unsupported endograft after the endograft has been inserted into the artery for the repair of an aortic aneurysm, including, but not limited to, an abdominal aortic aneurysm.  
      Further embodiments of the method and apparatus of using the present invention include using the stent that is inserted into the distal limbs of the unsupported endograft to cut the unsupported endograft. In one embodiment, a current is applied to a filament imbedded in the outside portion of the distal end of the stent that will heat the filament sufficiently to burn through the material of the endograft that is in the immediate contact with the distal end of the stent.  
      One embodiment of an apparatus for endovascularly cutting a graft comprises a catheter having a first end, a second end, an inner lumen, and an outer surface, further comprising at least one opening near its first end, at least one wire further comprising a filament extending through the at least one opening and around an outer surface of the catheter, wherein the wire is movable within the catheter and can be extended to form a ring disposed a predetermined distance around the outer surface of the catheter.  
      One embodiment of an apparatus for endovascularly cutting a graft comprises a stent having a distal end, a catheter having a first end, a second end, an inner lumen, and an outer surface, a filament disposed within the circumference of the distal end of the stent, and a wire having a first end and a second end, wherein the first end is in communication with the filament and the second end extends away from the stent into the lumen of the catheter.  
      One embodiment of an apparatus for endovascularly cutting a graft comprises a flared sheath having a first flared end, a second end, an inner lumen, and an outer surface, a catheter having a first end, a second end, an inner lumen, and an outer surface, wherein a portion of the catheter is disposed within the inner lumen of the flared sheath, an inner sheath having a first end, a second end, an inner lumen, and an outer surface, wherein a portion of the inner sheath is disposed within the inner lumen of the catheter, and an optical fiber having a first end and a second end, wherein a portion of the optical fiber is disposed within the inner sheath.  
      One embodiment of of the present invention is a method for endovascularly cutting a graft comprising the steps of inserting a catheter having a first end, a second end, an inner lumen, and an outer surface, further comprising at least one opening near its first end and at least one wire further comprising a filament extending through the at least one opening and around an outer surface of the catheter, extending the wire comprising the filament to form a ring disposed a predetermined distance around the outer surface of the catheter and contacting the filament to a portion of the graft to be cut, and applying a current to the wire and the filament such that the filament cuts the graft.  
      An embodiment of the method and apparatus of the present invention includes using a catheter to cut the unsupported endograft. In one embodiment, the catheter includes an optical fiber that is circumferentially rotated to cut the unsupported endograft near the distal end of the inserted stent. In an additional embodiment, the catheter contains a ring with a heated filament that is expanded radially to cut the unsupported endograft.  
      Additional advantages of the invention will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention. Where appropriate, the same reference numerals refer to the same or similar elements.  
       FIG. 1  is a schematic view of a supported endograft for an abdominal aortic aneurysm.  
       FIG. 2-4  are schematic views of an unsupported endograft for an abdominal aortic aneurysm held by a rigid guidewire.  
       FIG. 5-6  are schematic views of an unsupported endograft for an abdominal aortic aneurysm showing the top of the endograft attached to the aorta neck wall.  
       FIGS. 7-8  are schematic views showing the insertion of a stent into an iliac artery.  
       FIG. 9  is a schematic view of a stent expanded in an iliac artery.  
       FIG. 10  is a schematic view showing the transection of the unsupported endograft limb by the distal end of the stent.  
       FIG. 11  is schematic view of the stent and the endograft limb after the transection.  
       FIGS. 12-14  are schematic views of the transection of the endograft limb using a catheter.  
       FIGS. 15-17  are schematic views of an alternate embodiment for the transection of the endograft limb using a catheter.  
       FIG. 18  is a schematic view of a catheter of an embodiment of the present invention.  
       FIG. 19  is a top view of a catheter of an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION  
       FIG. 1  shows that one method to treat a patient with an aortic aneurysm  1 , for example, an abdominal aortic aneurysm (AAA), is to insert prosthetic bifurcation endograft  2 , sometimes also referred to, but not limited to, an “endograft”, through external iliac artery  3  and into right common iliac artery  4  and/or left common iliac artery  12  and attach proximal tube portion  5  of endograft  2  to the undilated portion of aorta  6 , also referred to as the “aortic neck”, below right renal artery  7  and left renal artery  8 . One method to attach the top of tube portion  5  of endograft  2  is to place surgical fasteners  9  as described in U.S. Pat. Nos. 5,957,940; 5,997,556; 6,248,118; 6,520,974; and 6,635,066 and U.S. Patent Application Nos. 60/537,888 and 60/538,242, herein incorporated in their entirety by reference. Endograft  2  may also be attached to aorta  6  by sutures, fasteners, staples, hooks, or any other suitable attachment method. Right bifurcation limb  10  and left bifurcation limb  11  be attached distally to right common iliac artery  4  and left common iliac artery  12  with stents  13  and  14 , respectively. These limbs can be cut to their proper length, based on measurements from an imaging study such as computed tomography (CT scan), prior to endograft insertion. An embodiment of the present invention is an apparatus and method to allow the interventionalist inserting the endograft to insert a endograft whose limbs may be too long for the anatomy of the patient and then, after endograft  2  is inserted and attached to aortic neck  6 , be able to place stents  13  and  14  and then transect, cut, and/or trim right  10  and left  11  endograft limbs at distal end  15  and  16  of stents  13  and  14 , respectively. In this manner endograft  2  can be better matched to the anatomy found during actual endograft insertion without the need for precise preoperative measurements of the endograft limbs. This allows the interventionalist to customize the graft to the individual patient following the placement of the endograft at the surgical site.  
       FIG. 2  shows top  17  of endograft  2  being held in suprarenal aorta  18  by guidewire  19  attached to struts  20  which, in turn, are attached to top  17  of endograft  2 . Right  10  and left  11  limbs of endograft  2  are within aneurysm I and are attached to sutures  21  and  22  that pass through right  23  and left  24  insertion sheaths that have previously been inserted through the right and left femoral arteries (not shown).  
       FIG. 3  shows right  25  and left  26  flared sheaths that have been inserted through insertion sheaths  23  and  24  respectively. Flared sheaths  25  and  26  have a first end, second end, inner lumen and an outer surface. The first end of flared sheaths  25  and  26  are inserted into insertion sheaths  23  and  24  and are designed or biased to flair outward when unconstrained. In an embodiment they are designed to be heat resistant such that they will protect tissue contacting their outer diameter even when a hot filament is compressed against their inner diameter. Flared sheaths  25  and  26  may be composed of a metal, such as, but not limited to, stainless steel, and/or Nitinol, and/or any number of well known plastic or polymer materials, such as, but not limited to Teflon or any number of polyamide materials with the necessary heat resistant properties.  
       FIG. 4  shows insertion sheaths  23  and  24  withdrawn into external iliac arteries  3  and  27 . By withdrawing the restraining effect of insertion sheaths  23  and  24 , flared sheaths  25  and  26  have flared in common iliac arteries  4  and  12  respectively.  
       FIG. 5  shows top  17  of endograft  2  attached to aorta  6  neck wall with surgical fasteners  9 . Endograft  2  may also be attached to aorta  6  by sutures, fasteners, staples, hooks, or any other suitable attachment method. Endograft limbs  10  and  11  may be too long for the patient and require trimming. The long endograft limbs  10  and  11  have been pulled into flared sheaths  25  and  26  and positioned in right  4  and left  12  common iliac arteries. Endograft limbs  10  and  11  may be pulled into flared sheaths  25  and  26  by use of sutures  21  and  22 .  
       FIG. 6  shows catheter  40  inserted through right flared sheath  25 . Catheter  40  comprises a first end, a second end, an inner lumen, and an outer surface. In one embodiment distal end  29  of stent  13  is positioned at the point where it is desired to trim and/or transect endograft limb  10 .  
       FIG. 7  is a magnified view of right common  4  and external  3  iliac arteries with their contents: right limb  10  of endograft  2  with attached sutures  21 , insertion sheath  23 , flared sheath  25  inserted through insertion sheath  23 , and catheter  40  containing stent  13  within the first end of catheter  40 . Attached to distal end  29  of stent  13  is insulated wire  30  leading to filament  31  housed around the circumference of distal end  29  of stent  13 . Filament  31  may be comprised of, but not limited to, materials such as tungsten, chromium steel, or any other suitable material. Right common  4  and external  3  iliac arteries, endografts, and components will be used for illustrative purposes in the following figures. The same components, apparatus, and methods may or may not be employed in the left common  12  and external  27  iliac arteries.  
       FIG. 8  shows stent  13  unsheathed from catheter  40  and expanded such that it compresses endograft limb  10  to common iliac artery  4  from the proximal end of stent  13  ( proximal to the heart) to first end  32  (distal to the interventionalist, proximal to the heart) of flared sheath  25 . It also compresses endograft limb  10  to the portion of the flared sheath  25  from first end  32  to the end of distal end  29  of stent  13 . These relationships are also diagramed in  FIG. 9  to further demonstrate the relationships when the various layers are drawn immediately adjacent to one another as they would be when stent  13  is in its sufficiently dilated configuration.  
       FIG. 10  depicts a trimming or transection of endograft limb  10  at position  43  thus detaching excess endograft material  34  of endograft limb  10  distal to distal end  29  of stent  13 . In an embodiment of the present invention this is achieved by applying a current to insulated wire  30  that is attached to filament  31  imbedded on the outside portion of distal end  29  of stent  13 . This will heat filament  31  sufficiently to burn through the material of endograft  2  that is in immediate contact with filament  31  disposed in stent  13 . Flared sheath  25  serves to protect common iliac artery wall  4  at the level of heated filament  31  disposed in distal end  29  of stent  13 .  
       FIG. 11  shows the shortened endograft limb  10  cut at the distal end  29  of stent  13 . Excess endograft material  34 , insulated wire  30  and flared sheath  25  have been removed. Insulated wire  30  may be detached from filament  31  by any suitable means, including, but not limited to, cutting, or filament  31  may be withdrawn from stent  13  along with insulated wire  30 .  
      In an embodiment of the present invention, stent  13  could be equipped with alternative means of transecting endograft limb  10 . In addition to heat, endograft limb  10  could be transected using any mechanical, electrical, or optical force, including but not limited to, lasers, mechanical cutting, or any other suitable method that can be adapted for use in stent  13 .  
       FIGS. 12-14  show one embodiment of the apparatus and method of transecting a endograft limb. In  FIG. 12 , catheter  40  comprising outer sheath  35 , inner sheath  36  and optical fiber  37  is inserted through flared sheath  25 . Inner sheath  36  and outer sheath  35  both comprise a first end, a second end, an inner lumen, and an outer surface. Optical fiber  37  comprises a first end and a second end. Expandable housing  38  may be disposed on a proximal portion, or first end, of outer sheath  35 . Expandable housing  38  may comprise a balloon, expandable and retractable struts, or any other similar expandable or stabilizing mechanism.  
       FIG. 13  shows housing  38  expanded to compress endograft limb  10  against flared sheath  25 , which, in turn, is compressed against the inner portion of common iliac artery  4  wall. Outer sheath  35  is tip deflected and inner sheath  36  and optical fiber  37  are advanced within outer sheath  35  until they are close to or touching endograft limb  10 .  
      The laser and optical fiber  37  are activated and outer sheath  35  is rotated circumferentially until endograft limb  10  is transected as depicted in  FIG. 14 . After endograft limb  10  is transected, outer sheath  35  is straightened, housing  38  is retracted and catheter  40  components  35 ,  36 ,  37 , flared sheath  25 , insertion sheath  23  and transected excess material  34  of endograft limb  10  and attached sutures  21  are removed.  
      An embodiment for transecting endograft limb  10  is depicted in  FIGS. 15-17 . In  FIG. 15  catheter  40  comprises wire  41  with a first end, a second end, and a mid portion disposed between the first end and the second end. The mid portion of wire  41  extends, for example, from at least one opening  44  disposed in catheter  40  near its leading edge, or first end, and extends around the outer surface of catheter  40 . The first end of catheter  40  comprising wire  41  is inserted through flared sheath  25 . Wire  41  may comprise an insulated portion on all or part of wire  41  within catheter  40 , or only on one surface of wire  41 . Insulating material may comprise, but is not limited to, polyurethane, and/or any other suitable insulating material. Wire  41  may incorporate filament  31  on the portion of wire  41  that will be extended from catheter  40  during the surgical procedure. Filament  31  may be insulated such that the outer circumference of filament  31  insulated, or such that the inner circumference of filament  31  is insulated. Catheter  40  also may have an inner lumen so it can be passed over a guidewire (not shown). The first end of catheter  40  is inserted through flared sheath  25  and advanced into position within endograft limb  10 .  
       FIG. 16  depicts wire  41  having been advanced through catheter  40  such that wire ring  42  is advanced to compress endograft limb  10  at a position, for example, position  43  of desired transection. Ring  42  comprises filament  31  on its outer surface, or outer circumference, such that, when a current is passed through wire  41  and filament  31 , filament  31  will heat sufficiently to transect endograft limb  10  by contact burning. Filament  31  may be insulated on its inner surface, or inner circumference. Flared sheath  25  is in position to prevent any burn damage to the adjacent common iliac artery  4  wall. The entire length of wire  41  may comprise filament  31 , or only portions of wire  41  that will be exposed to transect endograft  2  may comprise filament  31 . In an alternative embodiment of the present invention, ring  42  is disposed between flared sheath  25  and endograft limb  10 . In this embodiment limb  10  is transected by the action of filament  31  on the outer surface of limb  10  as ring  42  is drawn into contact with limb  10  by reducing the diameter of ring  42 . In this embodiment, the outer surface or outer circumference of filament  31  may be insulated, with the inner surface or inner circumference capable of cutting limb  10 .  
       FIG. 17  shows endograft limb  10  transected at position  43  near distal end  29  of stent  13 . After endograft limb  10  is transected, wire  41  comprising filament  31  are retracted into catheter  40 . Catheter  40 , flared sheath  25 , insertion sheath  23  and transected excess material  34  portion of endograft  2  and attached sutures  21  are removed.  
      In an embodiment it may be advantageous to have at least two sets of wire  41  comprising filament  31  disposed within catheter  40 .  FIG. 18  depicts catheter  40  with two sets of wire  41  comprising filament  31  and four exit ports  44  near the leading edge, or first end, of catheter  40 . As shown, a first pair of ports  44  are slightly nearer the first end of catheter  40  than a second pair of ports  44 . When wires  41  comprising filament  31  are advanced through catheter  40 , two rings  42  are formed as shown in  FIG. 19 .  FIG. 19  shows rings  42  as they would appear from above when both sets of wires  41  are advanced at the same time thus forming a circle which, when looked at laterally, would show a first set of wires  41  slightly above a second set of wires  41 . Filament  31  is exposed along the portion of wires  41  that contact the graft material to be cut.  
      Alternatively, in an embodiment of the present invention, the catheter could be equipped with alternative means of transecting the endograft limb. In addition to heat and lasers, the endograft could be transected using any mechanical, electrical, or optical force, including but not limited to mechanical cutting, or any other suitable method that can be adapted for the catheter.  
      Numerous characteristics and advantages have been set forth in the foregoing description, together with details of structure and function. The novel features are pointed out in the appended claims. The disclosure, however, is illustrative only, and changes, may be made in detail, especially in matters of shape, size, and arrangement of parts, within the principle of the invention, to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.