Abstract:
Described is a medical device and method for allowing fenestration of the aortic wall while maintaining distal perfusion and preventing external bleeding. The device isolates a segment of the aortic wall from the flowing column of blood using a balloon mounted on a metal alloy strut assembly. The strut assembly expands radially from a collapsed, low-profile configuration when uncovered by a constraining outer sheath. Aortic blood flow is allowed through the flow passage thus contained by the strut assembly within the center of the balloon. The balloon is inflated to contact the aortic wall. The balloon contains a pocket shaped to allow aortic fenestration. The balloon contains radiopaque markers to facilitate orientation and positioning of the pocket within the aorta. Other embodiments using spaced balloons are also disclosed.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/910,838, filed on Apr. 10, 2007, the advantages and disclosure of which are hereby incorporated by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to a medical device used in vascular surgery and methods of use thereof. More specifically, the medical device is configured for endolumenal placement within a blood vessel, such as the thoracic or abdominal aorta, via remote arterial access. The medical device provides a working space in the blood vessel that is free of blood flow while still maintaining significant blood flow through the blood vessel. This is particularly useful in performing an aortic anastomosis. 
     BACKGROUND OF THE INVENTION 
     Various methods have been developed to revascularize diseased or occluded branches of the aorta. Direct reconstruction via bypass originating from the aorta proximally and anastomosed distally to the artery of interest currently necessitates clamping and partial or total occlusion of the aorta. This interruption of aortic blood flow increases stress on the heart, potentially causing cardiac morbidity. Such occlusion of blood flow inevitably leads to ischemia of downstream organs and extremities, which potentially leads to other complications. Because the aorta itself is often diseased, with varying degrees of calcification within its wall, the act of placing occlusive clamps across the aorta risks injuring the aorta. In addition, plaque within the wall is potentially liberated to embolize distally, which is undesirable. 
     Numerous devices have been developed to avoid the use of clamps. These devices include various configurations of balloons, cannulae, and perfusion lumens that facilitate anastomosis of a bypass artery to an aorta without aortic clamping. Such devices are disclosed in U.S. Pat. No. 6,695,810 to Peacock et al.; U.S. Pat. No. 6,135,981 to Dyke; U.S. Pat. No. 6,143,015 to Nobles; and U.S. Pat. No. 6,045,531 to Davis. Some of these devices also facilitate “beating heart” bypass procedures in which some blood flow is maintained through the aorta to reduce the risks of complete blood flow occlusion. However, these devices are designed to facilitate coronary artery bypass, and are not suited to other non-coronary applications. 
     Maintenance of blood flow through the aorta during bypass procedures is important for several reasons. For instance, the avoidance of aortic clamping might allow more laparoscopic aortic procedures. Conventional operations to revascularize branch aortic vessels involve opening the chest or abdomen to allow direct exposure of the vasculature. These large incisions potentially lead to numerous complications, morbidity, or significant loss of body heat. Laparoscopic surgery via very small incisions avoids many of the disadvantages of conventional surgical exposures. It is used commonly in gastrointestinal, gynecologic, thoracic and urologic procedures, yet is not currently applied often to vascular operations. One reason for its sparse use is the current necessity for lengthy aortic occlusion times caused by conventional devices. 
     Therefore, there is a need in the art for a device and associated methods that facilitate the selective occlusion of blood flow in a working space, while maintaining blood flow through the aorta to allow less morbid arterial revascularizations. 
     SUMMARY OF THE INVENTION AND ADVANTAGES 
     The present invention provides a device for selectively occluding blood flow at a target site in a blood vessel while maintaining blood flow through the blood vessel. The device comprises an elongated member and an occlusion structure carried by the elongated member. The occlusion structure includes an occluding member operable between an occluding configuration and a non-occluding configuration. The occluding member defines a working space adapted to be free of blood flow when in the occluding configuration at the target site. The occlusion structure also includes a strut assembly operable between a collapsed and an expanded configuration. The strut assembly carries the occluding member into position at the target site. The strut assembly also defines a flow passage for allowing blood flow therethrough in the expanded configuration at the target site. 
     In one aspect of the invention, the occluding member is an inflatable member operable between an inflated configuration (corresponds to the occluding configuration) and an un-inflated configuration (corresponds to the non-occluding configuration). 
     The present invention also provides a method of selectively occluding blood flow at a target site in the thoracic or abdominal aorta while maintaining blood flow through the aorta. The method includes delivering the occluding member and the strut assembly through a remote peripheral artery to the target site in the thoracic or abdominal aorta. Once at the target site, the strut assembly is expanded to open the flow passage. Furthermore, the occluding member contacts the inner wall of the aorta and occludes blood flow in a working space at the target site while maintaining blood flow through the flow passage of the strut assembly. 
     The present invention provides many advantages over the prior art. For instance, utilizing the strut assembly to support the occluding member provides the required occlusion of blood flow in the working space, while providing a large flow passage therethrough to allow blood flow to continue in the aorta during an anastomosis. More specifically, the strut assembly provides an open-framed support structure that invites blood flow therethrough while supporting the occluding member against the wall of the aorta. 
     The present invention allows more blood to flow beyond the target site, e.g., the anastomotic region, placing less “afterload” resistance on cardiac output, which will translate into greater utility in fragile patients. The volume of blood flow allowed through the flow passage defined by the expanded strut assembly is significantly greater than that allowed by prior designs. 
     Additionally, the methods of the present invention provide placement of the device through a remote femoral or brachial access, using percutaneous techniques or small incisions. The device replaces two occlusion clamps, allowing and facilitating minimally-invasive techniques. In addition, by avoiding the ischemia of aortic clamping, anastomoses of longer duration will be tolerable by patients. These longer durations will be necessary with laparoscopic suturing, or with the training of new surgeons. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: 
         FIG. 1  is a perspective, partially schematic, and partially cross-sectional view of a device adapted for isolating a segment of an aortic wall from circulation, while allowing blood flow through its center; 
         FIG. 2  is a perspective view of distal end of the device illustrating an inflated balloon mounted to the strut assembly; 
         FIG. 3  is a cross sectional view taken along line  3 - 3  in  FIG. 1 ; 
         FIG. 4  is a cross sectional view taken along line  4 - 4  in  FIG. 1 ; 
         FIG. 5  is a cross sectional view taken along line  5 - 5  in  FIG. 1 ; 
         FIG. 6  is a cross sectional view taken along line  6 - 6  in  FIG. 1 ; 
         FIG. 7  is a cross sectional view taken along line  7 - 7  in  FIG. 1 ; 
         FIG. 8  is a perspective, partially schematic, and partially cross-sectional view of the device in a constrained, balloon-un-inflated configuration with the strut assembly collapsed; 
         FIG. 9  is a perspective, partially schematic, and partially cross-sectional view of the device in the unconstrained, balloon-un-inflated configuration with the strut assembly expanded; 
         FIG. 10  is a perspective, partially schematic, and partially cross-sectional view of an alternative embodiment of the device adapted for isolating a segment of an aortic wall from circulation, while allowing blood flow through its center; 
         FIG. 11  is a perspective view of an alternative helical strut assembly; 
         FIG. 12  is a perspective, partially schematic, and partially cross-sectional view of yet another embodiment of the device adapted for isolating a segment of an aortic wall from circulation, while allowing blood flow through its center; 
         FIG. 12A  is an elevational and partially cross-sectional view of a tubular support member illustrating threads on the tubular member and corresponding threads on a distal connector or ring; 
         FIG. 13  is a perspective, partially schematic, and partially cross-sectional view of the alternative device of  FIG. 12  in the constrained, balloon-un-inflated configuration with the strut assembly collapsed; and 
         FIG. 14  is a perspective, partially schematic, and partially cross-sectional view of the alternative device of  FIG. 12  in the unconstrained, balloon-un-inflated configuration with the strut assembly expanded. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, a device adapted for selectively occluding blood flow at a target site in a blood vessel while still maintaining blood flow through the blood vessel is generally shown at  10 . The device  10  is particularly adapted for providing a working space in an aorta that is free of blood flow to perform an anastomosis, while still maintaining a significant amount of blood flow through the aorta. Arrows in  FIG. 1  generally indicate blood flow. In  FIG. 1 , the device  10  is shown occluding blood flow from a target site X in a blood vessel, such as a thoracic or abdominal aorta A, to facilitate an end-to-side anastomosis of another blood vessel B to the aorta A. It should be appreciated that other uses of the device may be contemplated. 
     Referring to  FIGS. 1-9 , the device  10  comprises an occluding member  12 , a catheter assembly  14  for endolumenal deployment of the occluding member  12 , an inflation/deflation apparatus  16  for inflating and deflating the occluding member  12 , a strut assembly  18  for supporting and carrying the occluding member  12 , and a constraining sheath  20  for guiding deployment of the occluding member  12 . 
     The occluding member  12  is movable between an occluding configuration, shown in  FIG. 1 , and a non-occluding configuration, shown in  FIGS. 8 and 9 . The occluding member  12  is preferably an inflatable member, particularly a balloon  12  operable between inflated and un-inflated configurations. The inflated configuration corresponds to the occluding configuration and the un-inflated configuration corresponds to the non-occluding configuration. One embodiment of the balloon  12  is shown in cross-section in  FIG. 1  and in perspective in  FIG. 2 . When inflated, the balloon  12  contacts an inner surface of the aorta A and seals against the aorta A to prevent blood flow between the balloon  12  and the inner surface of the aorta A. The balloon  12  is generally annular in shape to contact the entire inner surface of the aorta A with the exception of a pocket  22  provided in the balloon  12 . The pocket  22  will be variously sized and shaped to accommodate a particular target site X, such as to allow for the standard size and shapes of typical “end-to-side” aortic anastomoses. 
     In one embodiment, the balloon  12  is formed completely of compliant materials. Preferably, however, the balloon  12  comprises a combination of compliant and non-compliant materials. More specifically, the balloon  12  includes an outer wall  24  comprising an expandable, compliant material that inflates to contact the inner surface of the aorta A and an inner wall  26  comprising a non-compliant material. The pocket  22  is preferably lined on all sides with a non-compliant material so that the sides surrounding the pocket  22  do not expand into the pocket  22 . Examples of suitable non-compliant materials include polyethylene terephthalate (PET), nylon, polyetheretherketone (PEEK), and the like. Examples of suitable compliant materials include polyurethane, nylon elastomers, and other thermoplastic elastomers. 
     Referring to  FIG. 2 , the balloon  12  is symmetric along its longitudinal axis when cut through the pocket  22 . Radiopaque markers  23  are fixed to the balloon  12  at the edges of the pocket  20 . These markers  23  allow positioning the balloon  12  within the aorta under fluoroscopy to align the pocket  22  with the optimal position for the anastomosis. The surgeon marks the target site X of the aorta A with metal clips on the aorta&#39;s adventitia, or external surface. Under fluoroscopy, the balloon  12  would then be rotated radially and advanced or withdrawn longitudinally to align the pocket  22  with the metal clips. When inflated, the balloon  12  contacts the inner surface of the aorta A and forms lateral seal zones to define the working space for the anastomoses. 
     Referring back to  FIG. 1 , the catheter assembly  14  carries the balloon  12  to the target site X for deployment. The catheter assembly  14  includes an elongated member  30  defining a pair of outer lumens  32 ,  34  and a central guidewire lumen  35 . A pair of side ports  36 ,  38  extends from the elongated member  30 . The side ports  36 ,  38  fluidly communicate with the outer lumens  32 ,  34  to convey inflation fluid to the balloon  12 . The catheter assembly  14  is flexible, yet provides longitudinal stability in the aorta A. A variety of biocompatible polymers, e.g., PVC, polyurethanes, and the like, with or without internal braided metal support, are suitable for forming the catheter assembly  14 . The elongated member  30  has a proximal end outfitted with a syringe connector  42 , such as a luer-lock connector, to allow preparatory flushing of the guidewire lumen  35 . 
     The catheter assembly  14  further includes a support member in the form of an elongated tube  44  extending distally past a distal end of the elongated member  30 . The tube  44  is fixed to the distal end of the elongated member  30 . The tube  44  may be fixed to the elongated member  30  by adhesive, ultrasonic welding, press-fit, any combination thereof, or any other suitable manner known to those skilled in the art. The tube  44  is sized such that the guidewire lumen  35  continues beyond the elongated member  30  inside the tube  44  with equal inner diameter such that the guidewire lumen  35  maintains a constant diameter through the elongated member  30  and the tube  44 . The tube  44  may comprise the same material as the catheter assembly  14  or may comprise a metal alloy, similar or the same as that used to form the strut assembly  18 . In one embodiment, a length of the tube  44  extending beyond the elongated member  30  equals a length of the strut assembly  18  and guides the device  10  over a separate guidewire (not shown). 
     The catheter assembly  14  further includes a pair of inflation conduits  48 ,  50  interconnecting the elongated member  30  and the balloon  12 . The conduits  48 ,  50  are preferably cylindrical in shape with a first end fixed to the elongated member  30  at the outer lumens  32 ,  34  to receive fluid from the outer lumens  32 ,  34 . The conduits  48 ,  50  extend from the first end to a second end fixed to the balloon  12 , e.g., integrally formed with the balloon  12 , as shown. The conduits  48 ,  50  may be fixed to the elongated member  30  and/or balloon  12  by adhesive, ultrasonic welding, press-fit, any combination thereof, or any other suitable manner known to those skilled in the art. The conduits  48 ,  50  may be seated in counterbores (not shown) in distal end of the elongated member  30  to form an inner diameter matching the diameter of the outer lumens  32 ,  34 . In the embodiment shown, the conduits  48 ,  50  have a smaller flow diameter than the outer lumens  32 ,  34 . 
     Two conduits  48 ,  50  are preferably used for even distribution of inflation fluid during use. In one embodiment, the balloon  12  may be equally divided by a pair of partitions (not shown) into first and second sections, with the second section including the pocket  22 . With separate conduits  48 ,  50 , the second section could be inflated first to form the pocket  22  and the first section could then be inflated to ensure a seal against the wall of the aorta A about the target site X. It should be appreciated that in other embodiments a single conduit  48  could be used. In this instance, only one outer lumen  32 , and one side port  36  would be necessary to convey fluid to the balloon  12 . 
     The inflation/deflation apparatus  16  comprises a pump P, manual or motorized, that moves inflation fluid through the side ports  36 ,  38 , outer lumens  32 ,  34 , and conduits  48 ,  50  into the balloon  12 . The pump P could be a hand-operated syringe similar to those used in angioplasty procedures, which measure pressure and/or volume of fluid discharged, or a similar motorized pump. The pump P conveys the sterile inflation fluid from an external fluid source F to the balloon  12 . The external fluid source F may be a reservoir in the pump P. Each of the side ports  36 ,  38  includes a three-way stopcock  52  to select between: (1) closing off the side ports  36 ,  38 ; (2) opening a fluid path between the fluid source F and the outer lumens  32 ,  34  to inflate the balloon  12 ; or (3) opening a fluid path between the outer lumens  32 ,  34  and atmosphere or a suction source (not shown) to deflate the balloon  12 . 
     Alternative embodiments of the device  10  may include a single external sideport  36  which leads to a single outer lumen  32  that divides within the elongated member  30  to form the two outer lumens  32 ,  34  (see provisional application incorporated herein by reference). Other embodiments may comprise a single sideport  36  leading to a single outer lumen  34  and a single conduit  48  to the balloon  12 . In each of these embodiments, the inflation fluid is pumped from the fluid source F under pressure to inflate the balloon  12 . 
     The strut assembly  18  comprises a plurality of struts  60 . In the embodiment shown in  FIG. 1 , proximal ends of the struts  60  are fixed to the tube  44  at the point where the tube  44  meets the distal end of the elongated member  30 . Thus, the tube  44  supports the struts  60 . The struts  60  extend to a distal end of the tube  44  and are fixed to the distal end of the tube  44 . The struts  60  concentrically support the balloon  12 . In one embodiment, six struts  60  equally spaced circumferentially about the tube  44  and radially from the tube  44  are utilized. In other embodiments more or fewer struts  60  may be utilized. The struts  60  may be fixed to the tube  44  by a biocompatible adhesive, ultrasonic welding, metal welding, or other suitable method. 
     Each of the struts  60  may comprise two angled segments  62 ,  64  interconnected by a middle segment  66 . The angled segments  62 ,  64  are disposed at an acute angle with respect to a longitudinal axis of the catheter assembly  14 . The middle segments  66  are generally parallel to the longitudinal axis of the catheter assembly  14 . The proximal angled segments  62  of the struts  60  slope away from the tube  44  for a predetermined distance until the middle segments  66  achieve a suitable diameter for blood flow. The distal angled segments  64  of the struts  60  slope toward the tube  44  until they are fixed to the distal end of the tube  44 . The limits of the middle segments  66  are marked by radiopaque markers  23  to allow for positioning of the balloon  12  under fluoroscopy. Cross struts (not shown) could also be used at certain axial positions along the strut assembly  18  to interconnect segments of adjacent struts  60 . 
     Referring to  FIG. 5 , the conduits  48 ,  50  are fixed to a pair of opposing struts  60  to support the conduits  48 ,  50  during endolumenal passage through the aorta A. The conduits  48 ,  50  may be fixed to these struts  60  by a biocompatible adhesive, ultrasonic welding, or tied by wire or other biocompatible tying material.  FIG. 6  illustrates a cross-section of the balloon  12  in its inflated configuration through the pocket  22 .  FIG. 7  illustrates a cross-sectional view of the inflated balloon  12  in the seal zone formed proximally and distally of the pocket  22 . Here, the balloon  12  contacts the inner surface of the aorta A circumferentially, and prevents blood flow into the working space protected by the pocket  22 . The shape of the balloon may be designed to minimize the length of this seal zone. The length of the seal zone can be minimized to allow for positioning of the balloon  12  in as many locations as possible without occluding branch blood vessels. 
     The inner wall  26  of the balloon  12  is attached to the middle segments  66  of the struts  60 . The inner wall  26  may be fixed to the middle segments  66  by a suitable adhesive, ultrasonic welding, wire ties, or other biocompatible tying material. In this manner, the strut assembly  18  supports the balloon  12  at the target site X and carries the balloon  12  to the target site X. 
     The strut assembly  18  is configured to expand from a collapsed configuration to an expanded configuration. In the expanded configuration, the struts  60  provide an open support framework for the balloon  12 . This open framework provides suitable support for the balloon  12  during inflation, while allowing significant blood flow therethrough. When the strut assembly  18  is opened to its expanded configuration, a flow passage is opened through the balloon  12  and between the struts  60  to allow blood flow therethrough. At the same time, the pocket  22  provides a working space free of blood flow to allow the anastomosis to be performed. Thus, the balloon  12  and strut assembly  18  together form an occlusion structure that selectively occludes blood flow in the aorta A, without completely stopping blood flow. 
     The struts  60  are preferably formed from a temperature sensitive shape memory alloy, e.g., nitinol. The struts  60  are preferably formed such that the expanded configuration is their normal configuration. Hence, when the strut assembly  18  is collapsed, a spring bias urges the struts  60  back to their expanded configuration. 
     In one embodiment shown in  FIG. 2 , the struts  60  are fixed to proximal  70  and distal  72  connectors, e.g., rings  70 ,  72 , that are mounted about the tube  44 . Here, the rings  70 ,  72  form part of strut assembly  118 . The struts  60  can be fixed to the rings  70 ,  72  by welding. The proximal ring  70  is fixed to the tube  44 , e.g., by adhesive, welding, etc., so that the proximal ring  70  cannot move along the tube  44 , while the distal ring  72  is slidable along the tube  44 . The distal ring  72  is positioned near the distal end of the tube  44  when the strut assembly  118  is in the collapsed configuration, but slides proximally along the tube  44  when the sheath  20  is removed and the struts  60  seek their normally expanded configuration. In this instance, the temperature sensitive shape memory alloy urges the struts  60  into the expanded configuration when the sheath  20  is removed. In other embodiments both rings  70 ,  72  could be fixed on the tube  44 . When both rings  70 ,  72  are fixed, or when the struts  60  are fixed to the tube  44 , the struts  60  can be slightly rotated about the tube  44  to force the struts  60  into the collapsed configuration. 
     Referring specifically to  FIGS. 8 and 9 , the sheath  20  is used to constrain the strut assembly  18  and balloon  12  during passage to the target site X and during removal from the target site X after the procedure is complete. An inner diameter of the sheath  20  is selected such that the sheath  20  is easily withdrawn over the un-inflated balloon  12  and the strut assembly  18  to deploy the device  10 . The sheath  20  has a distal end shaped to smoothly reconstrain the strut assembly  18  and the deflated balloon  12  upon advancement back over the balloon  12  and the strut assembly  18  when the procedure is completed. To this end, the sheath  20  may include a rounded end, a funnel-shaped end, or the like. The sheath  20  has a proximal end that comprises a hemostatic valve V and aspiration/flush port  80 . The hemostatic valve V prevents blood egress around the catheter assembly  14  while in the patient&#39;s bloodstream. The flush port  80  allows removal of all air from the sheath  20  prior to its insertion. 
     Referring to  FIG. 10 , an alternative device  210  is shown. The features of the device  210  are similar to those described above for device  10  so the same reference numerals are used, except that an alternative occluding member  212 , e.g., inflatable member  212 , is shown. In this alternative, the inflatable member  212  comprises two separate balloons  200 ,  202  interconnected by a tubular sleeve  204 . The sleeve  204  is preferably formed from non-compliant material. The sleeve  204  is fixed to the strut assembly  118  about the middle segments  66 , similar to the inner wall  26  of the prior balloon  12 . Here, the inner wall  206 ,  208  of each balloon  200 ,  202  is fixed to the tubular member  204 . As shown, the balloons  200 ,  202  and sleeve  204  may be integrally formed. The balloons  200 ,  202  have generally donut shapes. Each of the conduits  248 ,  250  extends to only one of the balloons  200 ,  202  to inflate the balloons  200 ,  202  separately. 
     Instead of using the pocket  22  to create the working space, which is free of blood flow, the working space is defined between the balloons  200 ,  202  outside the sleeve  204 . The sleeve  204  and strut assembly  118  define the flow passage for blood flow through the aorta A. Radiopaque markers  23  located on the inside surfaces of the balloons  200 ,  202  again define the limit of the working space. One advantage of this design is avoiding the need for radial orientation of the balloon  200 ,  202  under fluoroscopy. The conduits  248 ,  250  would still be fixed to the angled segments  62  of the struts  60 , but the distal most conduit  250  would be fixed to an inside portion of the struts  60  to reach the distal balloon  202 . In other words, the distal-most conduit  250  would be fixed to a strut  60  of the strut assembly  18  within the flow passage. The balloons  200 ,  202  are similarly designed to contact the inner surface of the aorta A circumferentially and form the proximal and distal “seal zones” for the working space. 
     Referring to  FIG. 11 , another alternative device  310  is shown. In this alternative device  310 , an alternative strut assembly  318  is employed. The strut assembly  318  comprises angled strut segments  362 ,  364 , similar to those described above, which expand and collapse to open and close the flow passage for blood flow. The alternative strut assembly  318  can be used with the alternative inflatable member  212  shown in  FIG. 10 . In this embodiment, the angled segments  362 ,  364  are interconnected by a plurality of metal wires  300  which expand to define and support the aortic flow channel. The wires  300  are helical in shape to form an expandable stent-like structure, preferably formed of nitinol, which extends between the angled strut segments  362 ,  364 . For instance, if six proximal angled segments  362  and six distal strut segments  364  are used, 6 wires, wound in a helical pattern, interconnect the angled segments  362 ,  364 . The helix structure supports the flow passage in the same manner as illustrated by the longitudinally oriented struts  60  described above. This configuration allows for more flexibility in tortuous vessels. 
     Referring to  FIGS. 12-14 , yet another alternative device  110  is shown in which the support member, e.g., tube  144 , passes entirely through the guidewire lumen  35  to extend both proximally and distally beyond the elongated member  30 . Thus, the tube  144  defines a second guidewire lumen  135  of the device  110 . In this embodiment, the tube  144 , which may be formed of metal or plastic materials, or combinations thereof, is free to rotate relative to the elongated member  30 . The internal surface of the distal ring  172  is threaded to match threads T on an external surface of a portion of the tube  144 . The portion of the tube  144  with threads T (e.g., the portion distal to the elongated member  30 ) may be formed of a more rigid material than the remainder of the tube  144 , for flexibility during insertion. The proximal ring  170  is fixed to the elongated member  30  by adhesive or the like, and not the tube  144 , so that the tube  144  can rotate within the proximal ring  170 . The rings  170 ,  172  and struts  60  form strut assembly  218 . The struts  60  are fixed to the rings  170 ,  172 . 
     A handle  199  is fixed to the proximal end of the tube  144 , by adhesive, press-fit, integrally molded therewith, or the like. The handle is rotatable relative to the elongated member  30  and abuts the proximal end of the elongated member  30 . The handle  199  has a throughbore (not shown) in communication with the second guidewire lumen  135  for receiving a guidewire (not shown). An operator rotates the tube  144  via the handle  199  to thread the tube  144  in the distal ring  172  (distal ring  172  acts as a nut). At the same time, the operator holds the elongated member  30  from movement. The distal ring  172  is prevented from rotation by the struts  60  (via fixed proximal ring  170 ), and since the handle  199  abuts the elongated member  30 , the tube  144  is restrained at its proximal end from longitudinal movement toward the strut assembly  218 . Thus, when the handle  199  and tube  144  rotate relative to the elongated member  30  and the strut assembly  218 , the distal ring  172  moves either proximally or distally to expand or collapse the strut assembly  218 . In this manner, the struts  60  may be formed of materials other than shape memory alloys. Rotations of the handle  199  can be counted to determine the diameter of the flow passage created. 
     In other embodiments, the operator could simply pull the handle  199  with the proximal end of the tube  144  fixed thereto to expand the strut assembly  218  and push the handle  199  to collapse the strut assembly  218 . In one embodiment (not shown), the external portion of the tube  144  that extends proximally from the elongated member  30  is calibrated and labeled to designate the diameter of the flow passage created. An external lock (not shown), such as a clamp placed on the tube  144  in abutment with the proximal end of the elongated member  30 , holds the strut assembly  218  in its expanded position for balloon inflation. 
     During use, the device  10 ,  110 ,  210 ,  310  is introduced into the body with the strut assembly  18 ,  118 ,  218 ,  318  in its collapsed configuration and the balloon  12 ,  200 ,  202  in its un-inflated configuration. In this configuration, the diameter of the device  10 ,  110 ,  210 ,  310  is minimized and allows introduction via the patient&#39;s peripheral arteries to the aorta A. The sheath  20  is first inserted through the peripheral artery to the target site X in the aorta A using techniques well known to those skilled in the art. 
     The catheter assembly  14 , carrying the strut assembly  18 ,  118 ,  218 ,  318  and the balloon  12 ,  200 ,  202 , is then inserted through the sheath  20  to the target site X.  FIGS. 8 and 13  show the catheter assembly  14  inside the sheath  20  prior to deployment of the strut assembly  18 ,  218  and the balloon  12 . Once at the target site X, the sheath  20  is withdrawn along the catheter assembly  14  to expose the balloon  12 ,  200 ,  202  and the strut assembly  18 ,  118 ,  218 ,  318 . As a result, the strut assembly  18 ,  118 ,  318  returns to its normally expanded configuration under the spring bias of the struts  60 . Alternatively, the strut assembly  218  is placed in its expanded configuration by rotating the handle  199  in the appropriate direction. See, e.g.,  FIGS. 9 and 14 . 
     The balloon  12 ,  200 ,  202  is then inflated such that the outer wall  24  contacts the inner surface of the aorta A to occlude blood flow in the working space. Blood flow then continues through the flow passage located centrally through the balloon  12 ,  200 ,  202  and provided by the open framework of the strut assembly  18 ,  118 ,  218 ,  318 . Once the procedure is completed, the balloon  12 ,  200 ,  202  is deflated and the strut assembly  18 ,  118 ,  218 ,  318  and balloon  12 ,  200 ,  202  are re-constrained by the sheath  20  either by pulling the catheter assembly  14  relative to the sheath  20  or by pushing the sheath  20  onto the balloon  12 ,  200 ,  202  and strut assembly  18 ,  118 ,  218 ,  318 . In the embodiment of  FIGS. 12-14 , the strut assembly  218  is collapsed by rotating the handle  199  prior to re-constraining the sheath  20  and strut assembly  218 . 
     With the devices  10 ,  110 ,  210 ,  310  of the present invention, blood flow through the vessel (e.g., aorta A) can be maintained while providing the working space at the target site X that is free of blood flow. Preferably, the devices  10 ,  110 ,  210 ,  310  are designed to maximize the area of the flow passage created through the occluding member  12 ,  212  and strut assembly  18 ,  118 ,  218 ,  318 . Preferably, the flow passage has an area (defined in cross-section perpendicular to the vessel) that is at least 20 percent of the original blood flow area of the vessel defined prior to placement of the device  10 ,  110 ,  210 ,  310 . More preferably, the flow passage has an area that is at least 35 percent of the original blood flow area of the vessel. Most preferably, the flow passage has an area that is at least 50 percent of the original blood flow area of the vessel. 
     The invention has been described in an illustrative manner, and it is to be understood that the terminology used is intended to be in the nature of words of description rather than of limitation. As is now apparent to those skilled in the art, many modifications and variations of the present invention are possible in light of the above teachings. For instance, the device  10 ,  110 ,  210 ,  310  could be used for performing angioplasty of the aorta. In this instance, the steps described above are still utilized, except that now the target site X is a stenotic segment formed from build up of cholesterol-laden plaques such as those common to atherosclerosis. The balloon  12 ,  200 ,  202  is inflated to expand the stenotic segments and further open blood vessels to the flow of blood.