Abstract:
A method and apparatus that facilitates the prevention of type II endoleaks in stent-graft treated arterial aneurysmal sacs comprising a catheter having an elongate tubular body with a balloon or wire mesh basket attached to the body adjacent its distal end. The balloon preferably comprising a plurality of energy conducting elements attached thereto for transmitting RF energy to tissue to be treated. In operation, the catheter is inserted into the femoral artery of a patient and then advanced through the femoral artery into the aorta until the balloon or basket is positioned within an aneurysmal sac. Once in place, the balloon or basket is expanded to compress the clot material within the aneurysmal sack under a pressure in the range of about 2-5 atmospheres. While compressed, the clot material is then heated by transmitting RF energy to the wire basket or the conducting elements on the balloon until the clot material is cauterized and collateral blood flow channels in the clot material are occluded. The balloon or basket is then returned to an unexpanded state and the catheter is removed from the aorta. Once the catheter is removed, a stent-graft may be placed within the aorta in accordance with conventional procedures.

Description:
FIELD OF THE INVENTION 
     The present invention relates to endoluminal surgical procedures and devices and, more particularly, to an endoluminal method and apparatus that facilitates the prevention of type II endoleaks associated with post stent-graft treated arterial aneurysms. 
     BACKGROUND OF THE INVENTION 
     For a significant portion of the general public, abdominal aortic aneurysms (AAA) represent a major medical problem. Aneurysms are a form of atherosclerosis characterized by degeneration of the arterial wall in which the wall weakens and balloons outward by thinning. The conventional approach to repairing aneurysms involves a very invasive operation entailing the dissection of the aorta and replacement of the aneurysm with an artificial artery known as a prosthetic graft. In order to expose the aorta and perform this procedure, a significant abdominal incision extending from the breast bone to the pubic bone is required. 
     Over recent years, however, physicians have made widespread use of a significantly less invasive approach to aneurysmal repair involving the transluminal placement of an endoluminal graft within the aorta. With the use of expandable stents, the graft is attached to the internal surface of the arterial wall, above and below the aneurysm, without sewing. Once in place, the blood flows through the graft by-passing the aneurysm. 
     It has been reported, however, that about thirty percent of all aneurysms repaired with endoluminal stent-grafts fail to adequately exclude the associated aneurysmal sac from systematic aortic pressures. Eighty percent or more of these failures are said to be due to type II endoleaks. Type II endoleaks occur when blood flow takes a circuitous route traveling through branches from the non-stented portion of the aorta through anastomotic connections into collateral vessels with a direct communication with the aneurysmal sac. Blood then travels in a retrograde direction in these collateral vessels, eventually emptying into the sac behind the stent-graft. These collateral vessels, prior to aortic exclusion via the stent-graft, carried blood from the aorta to nutrient beds of lower pressure. When the aorta from which they originate is excluded, the pressure gradient favors flow in the opposite direction. In conventional surgical repairs of aneurysms, these collateral vessels are typically ligated. This is not possible with current endoluminal graft technology. 
     Moreover, current endoluminal graft technology does not enable a physician to stop such endoleaks once the stent-graft has been placed and the leak has formed. Although embolization has been demonstrated to occlude flow to the aneurysmal sac from embolized vessels, this approach tends to be largely ineffective. Because the aneurysmal sac provides so many paths through which blood can flow, like the “nidas” of an arterial-venous-malformation (AVM) (see FIG.  5 ), it is difficult to stop the flow entirely without destroying the “nidas.” 
     Thus, it is desirable to provide a method and apparatus that facilitates the prevention or elimination of type II endoleaks in stent-graft treated aneurysmal sacs and other arterial aneurysms. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a method and apparatus that facilitates the prevention or elimination of type II endoleaks in stent-graft treated arterial aneurysms, such as aneurysms occurring in the abdominal aorta, the iliac, the thoracic aorta, and the like. In a preferred embodiment, an apparatus of the present invention comprises a perfusion balloon catheter having an elongate tubular body with a balloon mounted on the body adjacent its distal end. The balloon preferably comprises a plurality of energy conducting elements attached thereto for transmitting RF energy to tissue to be treated. Alternatively, the apparatus of the present invention may comprise a catheter having an elongate tubular body with a wire mesh basket extending from its distal end. An articulating wire attaches to the distal end of the wire basket and extends through the catheter body. When pulled, the articulating wire applies a force to the distal end of the basket to compress the basket longitudinally and expand the basket radially. 
     In operation, e.g., for treatment of an abdominal aorta aneurysm (AAA), the catheter is inserted into a femoral artery of a patient and then advanced through the femoral artery into the aorta until the balloon or basket is positioned within the aneurysmal sac. Once in place, the balloon or basket is expanded to compress a clot material within the aneurysmal sac and close collateral blood flow pathways through the clot material. The compression is preferably conducted under a pressure in the range of about 2-5 atmospheres. While compressed, the clot material is heated by transmitting RF energy to the wire basket or the conducting elements on the balloon until the clot material is cauterized or coagulated and collateral blood flow pathways through the clot material are occluded. Other means of heating may include inductive or direct current (DC) heating. The balloon or basket is then returned to an unexpanded state and the catheter is removed from the aorta. Once the catheter is removed, a stent-graft may be placed within the aorta in accordance with conventional endoluminal graft methodology. 
     Further, objects and advantages of the invention will become apparent from the following detailed description and accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a diagrammatic view of an abdominal aorta artery with an aneurysm sac and collateral vessels. 
     FIG. 2 is a cross-section view through an abdominal aorta aneurysm sac showing blood flow through the abdominal aorta aneurysm sac and out to the internal mammary (IMA) and lumbar arteries prior to treatment. 
     FIG. 3 is a cross-section view through an abdominal aorta aneurysm sac post stent-graft placement showing blood flow through a typical IMA to lumbar type II endoleak. 
     FIG. 4 is a cross-section view through an abdominal aorta aneurysm sac post stent-graft placement showing blood flow through a typical IMA to lumbar type II endoleak after IMA embolization. 
     FIG. 5 is a diagrammatic view of an arterial venous malformation. 
     FIG. 6 is a diagrammatic view of the thermal ablation balloon catheter of the present invention. 
     FIG. 6A is a diagrammatic end view of an alternative embodiment for a balloon catheter of the present invention. 
     FIG. 7 is a detailed partial view of a distal tip of the thermal ablation balloon catheter shown in FIG.  9 . 
     FIG. 7A is a diagrammatic view of a balloon attached to the distal tip shown in FIG.  7 . 
     FIG. 8 is a cross-sectional view of the distal tip of the thermal ablation balloon catheter taken along line  8 — 8  of FIG.  7 . 
     FIG. 9 is a cut-away diagrammatic view of an abdominal aorta artery with an aneurysm sac and collateral vessels. 
     FIG. 10 is a cut-away diagrammatic view of the abdominal aorta artery and aneurysm sac of FIG. 9 with a thermal ablation balloon catheter of the present invention positioned within the aneurysm sac and expanded to treat the aneurysm sac to prevent the formation of a type II endoleak post stent-graft placement. 
     FIG. 11 is a cross-sectional view through the abdominal aorta aneurysm sac post treatment with the thermal ablation balloon catheter of the present invention. 
     FIG. 12 is a cut-away diagrammatic view of the abdominal aorta artery and aneurysm sac of FIG. 9 with a thermal ablation catheter of the present invention having a wire-mesh basket positioned within the aneurysm sac and expanded to treat the aneurysm sac to prevent the formation of a type II endoleak post stent-graft placement. 
     FIG. 13 is a diagrammatic view of the thermal ablation catheter with its wire-mesh basket in an unexpanded state. 
     FIG. 14 is a diagrammatic view of the thermal ablation catheter with its wire-mesh basket in an expanded state. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring in detail to the drawings, an improved method and apparatus for preventing or eliminating type II endoleaks in arterial aneurysms is described and illustrated herein. For exemplary purposes only, the following discussion focuses on the treatment of type II endoleaks in abdominal aorta aneurysms. However, one skilled in the art will understand that the method and apparatus discussed herein may be used to treat type II endoleak of other arterial aneurysms in such arteries as the iliac, the thoracic aorta and the like. 
     Turning to FIG. 1, a diagrammatic view of an abdominal aorta  10  is provided. As depicted, the abdominal aorta  10  includes a section in which its walls are ballooned out forming an abdominal aortic aneurysm (AAA). As is typical, numerous collateral vessels  14  are shown to be interconnected with the aneurysmal sac  12  and/or the non-aneurysm portion of the aorta  10 . 
     Referring to FIG. 2, the aneurysmal sac  12  typically includes a gelatinous clot material  18  filling the space bounded by the expanded arterial wall  15 . The main blood flow from the aorta  10  to the femoral arteries  11  and  13  passes through the aneurysmal sac  12  through a channel  16  formed in the gelatinous clot material  18 . As depicted, blood also flows through collateral pathways  21 ,  23  and  25  formed in the gelatinous clot material  18  to an internal mammary artery (IMA)  20  and a pair of lumbar arteries  22  and  24 . 
     Turning to FIGS. 3 and 4, a stent-graft  30  is shown centrally placed within the aneurysmal sac  12 . A typical IMA  20  to lumbar  22  and  24  type II endoleak  26  is depicted in FIG. 3 wherein blood enters from the IMA  20 , fills the endoleak  26  and then exits through the lumbar vessels  22  and  24 . In such leaks, the blood tends to channel in circuitous routes through the gelatinous clot material  18  passing through collateral pathways  21 ,  23  and  25  between the IMA  10  and the lumbar arteries  22  and  24 . In FIG. 4, embolization of the IMA  20 , with a coil, embolics or the like  28 , is shown to be ineffective in stopping such leaks. For instance, once the IMA  20  is blocked, blood simply flows into the sac  12  from one of the lumbar arteries  22  instead of the IMA  20 , fills the endoleak  26 , and then exits through the other lumbar artery  24 . Because the aneurysmal sac  12  tends to act like a nidas of an arterial venous malformation (AVM)  40  having multiple entering  42 ,  44 ,  46  and  48  and exiting  43 ,  45  and  47  pathways (see FIG.  5 ), it is difficult to stop the flow entirely without destroying the “nidas.” 
     Once the stent-graft  30  has been endoluminally placed so that blood flow by-passes the aneurysmal sac  12 , and an endoleak  26  has formed, current endoluminal graft technology can not enable a physician to endoluminally treat or eliminate the endoleak  26 . Accordingly, the present invention is directed to a method and apparatus that tends to prevent the formation of such leaks by treating the aneurysmal sac  12  prior to endoluminal placement of the stent-graft  30 . 
     Referring to FIG. 6, an illustrated embodiment of a perfusion-type balloon catheter  50  of the present invention is shown to include an elongate tubular body  52  having proximal and distal ends and a balloon  54  attached to the body  52  adjacent its distal end. The balloon  54  is shown in an operative or expanded state. However, one of skill in the art would understand that the balloon  54  may be rolled or folded about the catheter body  52  to create a low profile for insertion of the catheter  50  into a patient. 
     The catheter body  52  is preferably formed from a semi-compliant material to enable the catheter  50  to easily pass through a vessel or artery, such as the femoral artery, and make its way into the interior regions of a patient&#39;s aorta  10 . The body  52 , which is open at its distal end, includes at least three lumens—a main or perfusion lumen  53 , a guidewire lumen  57  and a fill/evacuate lumen  59 . A hole (not shown) in the wall of the catheter body  52  enables the fill/evacuate lumen  59  to communicate with the interior of the balloon  54 . The guidewire lumen  57  generally extends the length of the body  52 . The perfusion lumen  53  extends from the axial opening at the distal end of the body  52  to a radial perfusion opening  55  extending longitudinally in the wall of the body  52  just beyond where a proximal end of the balloon  54  attaches to the body  52 . The perfusion catheter  50  may also be in the form shown in U.S. Pat. Nos. 5,458,579, 5,087,247, or 4,581,017, the disclosures of which are incorporated herein by reference. 
     The perfusion catheter  150  may include a multi-lobular balloon  156  as shown in FIG.  6 A. Individual balloon lobes  154  are attached to the catheter body  152  and, when inflated, form gaps  155  therebetween. Instead of passing through a catheter lumen, blood passes through the gaps  155  between the balloon lobes  154 . 
     The balloon  54  is generally cylindrical in shape and is preferably formed from compliant or semi-compliant material to minimize risk of rupture and to enable conformability within the aneurysmal sac  12 . RF conductive elements  56 , such as metallic wire or circuit traces, are attached to the outer surface of the balloon  54  and are used to transmit energy to tissue such as the gelatinous clot material  18  in a monopolar or bipolar manner. A wire (not shown) for providing power to the wire traces  56  on the balloon  54  may extend as a trace along the body  52  or may be encapsulated in the body  52  of the body. The wire preferably connects to an electrical cable  61  that extends from the proximal end of the body  52  of the catheter  50 . The cable  61  ends with a plug  62  that connects with an energy source and appropriate conventional catheter control equipment (not shown). Preferably, the energy source is capable of supplying power in a range of about 20-200 watts. 
     As shown in FIGS. 6,  7  and  8 , the body  52  also includes a fill/evacuate lumen  59  and a fill/evacuate port  60  extending from catheter body  52  toward its proximal end. Multiple wire lumens  51  may also be provided as shown. In addition, the distal end of the catheter body  52  may include a conically shaped slit  63  forming a radially directed and longitudinally extending opening into the perfusion lumen  53  to improve blood flow into the perfusion lumen  53 . With the slit  63 , the distal tip  64  of the catheter body tends to have a semi-annular or horse-shoe like shape. As shown in FIG. 7A, the balloon  54  may be attached to the distal tip  64  and have an inflated shape that directs blood flow toward the slit  63  and into the lumen  53 . 
     As noted above, the catheter  50  of the present invention is preferably used to treat the gelatinous clot material  18  of the aneurysmal sac  12  prior to placement of the stent-graft  30 . In operation, as shown in FIGS. 9 and 10, the catheter  50 , with the balloon  54  in an uninflated state, is inserted into one of the femoral arteries  11  in the groin region of the patient. The catheter  50  is then guided through the femoral artery  11  into the abdominal aortic artery  10  along a guidewire  58 . The catheter  50  is positioned within the aorta  10  such that the balloon  54  of the catheter is positioned within the aneurysmal sac  12  using well known visualization techniques such as x-ray, ultrasound, and the like. 
     Once in position, the balloon  54  is inflated with about 2-5 atmospheres of pressure, such that the gelatinous clot material  18  is compressed. With the balloon  54  inflated, blood flow through the aorta  10  is occluded and must flow through the perfusion lumen  53  of the catheter  50 . Blood flow enters the perfusion lumen  53  through the opening in the distal end of the catheter body  52  and the conically shaped slit  63 . After passing through the perfusion lumen  53 , blood flows out of the perfusion opening  55  toward the proximal end of the catheter body  52  into the lower aorta  10  and femoral arteries  11  and  13 . If the balloon catheter  150  shown in FIG. 6A is used, the blood would flow through the gaps  155  between the balloon lobes  156 . 
     With the clot material  18  compressed or condensed, flow through the collateral pathways  19  is blocked. RF energy is then transmitted to the conductive elements  56  on the exterior of the balloon  54 . As shown, the energy E is directed from the elements  56  on the balloon  54  into the clot material  18  in the aneurysmal sac  12 . Alternatively, heating may be accomplished inductively or with DC. Depending on the size of the lesion and the heat transfer parameters of the gelatinous clot material  18 , energy may be applied in a power range of about 20-200 watts. The heat tends to cauterize or coagulate the clot material  18 . Optionally, the clot material  18  may be cauterized by rapidly pulsing the RF energy E into the clot material  18  to a depth of about 1-2 mm. The heating of blood is preferably minimized to the point of coagulation of the blood or other non-target tissue to avoid creating distal embolisms and/or other unnecessary vessel injury responses. 
     The cauterized tissue tends to form an inner egg shell layer  17 , occluding or blocking collateral pathways  19  formed in the clot material  18  that had connected the collateral arteries  14 . As shown in FIG. 11, the collateral pathways  21 ,  23  and  25  through the clot material  18  are blocked, thus preventing the channeling of blood through the clot material  18  between the IMA  20  and lumbar arteries  22  and  24 . The cauterized tissue tends to scar over time and form a permanent occlusion such that no new collateral pathways may form within the clot  18 . 
     After deflation of the balloon  54  and removal of the catheter  50  from the aneurysmal sac  12 , the stent-graft  30  may be installed in a routine manner in accordance with conventional procedures. 
     Turning to FIGS. 12-14, an alternate embodiment of the present invention is shown to comprise a catheter  150  having an elongate tubular body  152  with distal and proximal ends. An expandable wire mesh basket  154  extends from the distal end of the catheter body  152  and a cable (not shown) extends from the proximal end of the catheter body  152 . The cable includes a plug (not shown) that connects with an energy source and conventional catheter control equipment (not shown). 
     The wire basket  154 , as shown in FIG. 13, includes a mesh of criss-crossing wires that are uninsulated at a mid-section  156  of the basket  154  and insulated at proximal and distal end portions  155  and  157  of the basket  154 . The basket  154  may include a membrane such as a braided fabric to prevent the basket  154  from slicing or cutting into the gelatinous clot material  18  too deeply such that the basket becomes lodged or creates emboli upon removal. 
     An articulating wire  151  extends through the interior of the catheter body  152  and basket  154  to a ring attached to the distal end of the basket  154 . When the articulating wire  151  is withdrawn from or pulled out of the catheter body  152 , the corresponding force applied to the distal end of the basket  154  causes the basket  154  to longitudinally compress and radially expand. (See FIG.  13 ). When the articulating wire  151  is released, the basket  154  returns in spring-like fashion to its unexpanded, low profile state. 
     In operation, the catheter  150 , with the basket  154  in an unexpanded state, is inserted into one of the femoral arteries  11  in the groin region of the patient. The catheter  150  is then guided through the femoral artery  11  into the abdominal aorta  10  along a guidewire (not shown). The catheter  150  is positioned within the aortic artery  10  such that the basket  154  of the catheter  150  is positioned within the aneurysmal sac  12 . Once in position, as shown in FIG. 12, the basket  154  is expanded by drawing or pulling on the articulating wire  151  such that the gelatinous clot material  18  is compressed. With the basket  154  expanded, blood flow through the aorta  10  flows through the basket  154  into the lower aorta  10  and femoral arteries  11  and  13 . 
     With the clot material  18  compressed or condensed, flow through the collateral pathways  19  is blocked. RF energy is then transmitted to the basket  154 . As shown, the energy E is directed from the basket  154  into the clot material  18  in the aneurysmal sac  12 . Depending on the size of the lesion and the heat transfer parameters of the gelatinous clot material  18 , energy may be applied in a range of about 20-200 watts. The heat tends to cauterize the clot material  18 . As with the previous embodiment, the heating of blood is preferably minimized to the point of coagulation of the blood or other non-target tissue to avoid creating distal embolisms and/or other unnecessary vessel injury responses. 
     After the basket  154  is returned to its unexpanded state and the catheter  150  is removed from the aneurysmal sac  12 , the stent-graft  30  may be installed in a routine manner in accordance with conventional procedures. 
     While various preferred embodiments of the invention have been shown for purposes of illustration, it will be understood that those skilled in the art may make modifications thereof without departing from the true scope of the invention as set forth in the appended claims including equivalents thereof.