Device and method for establishing an artificial arterio-venous fistula

[0001] This application claims the benefit of priority to U.S. Prov. 61/170,774 filed Apr. 20, 2009, which is incorporated herein by reference in its entirety. This application is also a continuation-in-part of U.S. patent application Ser. No. 11/696,635 filed Apr. 4, 2007, now issued U.S. Pat. No. 7,828,814, which is a continuation-in-part of U.S. patent application Ser. No. 11/356,876 filed Feb. 17, 2006, which is a continuation-in-part of U.S. patent application Ser. No. 10/927,704 filed Aug. 27, 2004, now abandoned.

[0002] The inventions described below relate to treatments for pulmonary hypertension and vascular surgery.

[0003] Chronic obstructive pulmonary disease (COPD), chronic hypoxia, hypertension, and left ventricular hypertrophy and pulmonary hypertension are diseases of the cardiopulmonary system. Chronic obstructive pulmonary disease (COPD), which includes chronic bronchitis and emphysema, is a slowly progressive lung disease caused primarily by smoking. In COPD, the lungs are damaged and the airways are partly obstructed, making it difficult to breath and leading to a gradual loss of lung function. Symptoms of COPD include chronic cough, excessive sputum production, low blood oxygen levels and severe disabling shortness of breath. COPD represents the fourth leading cause of death in the United States. Chronic hypoxia (reduction of oxygen supply to the body despite adequate blood flow through the body), hypertension, and left ventricular hypertrophy are related conditions which may be symptomatic of COPD or coincident with COPD.

[0004] These serious conditions affect many people, and the primary treatments are merely ameliorative. The primary treatments for COPD include avoidance of irritants such as tobacco smoke and breathing supplemental oxygen. In advanced cases of COPD, lung reduction surgery is sometimes performed, but it is not clear that it helps. There is no known cure for COPD.

[0005] An aortocaval fistula (ACF) is a rare clinical condition that can be either spontaneous (80% of the cases), related to abdominal aortic aneurysm, or the result of some trauma such as lumbar disk surgery. It is currently seen as a defect that should be cured with surgery and, possibly, stent-graft implantation in the aorta.

[0006] Contrary to this understanding, an intentionally formed aortocaval fistula appears to be a viable treatment for COPD. Recently, in our co-pending U.S. patent application Ser. No. 10/820,169 filed Apr. 6, 2004, entitled Implantable Arteriovenous Shunt Device and listing John L. Faul, Toshihiko Nishimura, Peter N. Kao & Ronald G. Pearl as inventors (the entirety of which is hereby incorporated by reference), we propose creation of an artificial aortocaval fistula as a treatment for COPD, and we disclose the method of creating the fistula and an implantable shunt for maintaining the aortocaval fistula.

[0007] Shunts or stents for connecting blood vessels have been proposed for the treatment of coronary artery disease. Makower, Device, System And Method For Interstitial Transvascular Intervention, U.S. Pat. No. 6,746,464 (Jun. 8, 2004) (filed Oct. 28, 1998) discloses a stent with a short tubular section spanning the thickness of a coronary artery and an adjacent parallel coronary vein. This stent includes “clovers” on either end of the stent, and these clovers fold radially outwardly to obstruct movement of the stent through the vessel walls. Two clovers on the proximal end of the stent are orthogonal (relative to the radial cross section of the stent) to two clovers on the distal end of the stent, and the interconnecting wires are parallel to the longitudinal axis of the device.

[0008] The devices and methods described below provide for treatment of COPD, hypertension (e.g., pulmonary hypertension, cardiac hypertension, etc.), and left ventricular hypertrophy, and chronic hypoxia. A vascular shunt rivet is disclosed which serves to hold contiguous points of the patient's aorta and inferior vena cava (or other arteries and there associated veins, such as the femoral artery and femoral vein, or the carotid artery and the carotid vein) together and maintain an open flow path from the aorta to the vena cava. The device functions as a rivet, holding the two vessel walls in close proximity, and as a shunt, permitting and maintaining flow from one blood vessel to the other. The device is implanted, between the aorta and inferior vena cava, as a treatment for pulmonary hypertension, COPD and chronic hypoxia.

[0009] The shunt rivet is provided in the form of an expandable wire frame structure adapted for transcutaneous delivery and deposit at the desired implantation site. The wire frame structure may be compressed into a small diameter configuration to fit within the distal tip of a delivery catheter. Upon expulsion from the catheter, the wire frame structure resiliently or pseudoelastically expands into a flow-through rivet comprising a tube with expanded heads at either end. When the rivet is released within an artificial fistula formed through the aorta and vena cava walls, it expands to trap the walls between the two expanded heads. The tubular section between the two expanded head may resiliently expand, and may also be balloon-expanded or otherwise plastically deformed to enlarge the flow-through lumen of the tubular section.

[0010] According a one aspect of the invention, the shunt rivet may comprise a coupler for implantation in a patient between a first body space, such as an artery, and a second body space, such as a vein. The coupler comprises a first member configured to stabilize the coupler in the first body space and a second member configured to stabilize the coupler in the second body space. At least a portion of the first member or the second member is configured to bioabsorb while the coupler maintains a fluid flow path between the first body space and the second body space. The bioabsorbable portion may bioabsorb through one or more processes, such as hydrolysis and/or a metabolic process. The bioabsorption process may occur in less than a day, less than a week, or in less than a month. In some embodiments, the bioabsorbable material may take up to six months or longer to bioabsorb. The coupler may include two or more bioabsorbable portions that absorb at different rates. The coupler may be placed between artery and a vein, such as an artery and vein pair distal to the renal arteries.

[0011] The bioabsorbable portion or portions may be placed in the patient's body at a location in which normal blood flow was present prior to implantation of the coupler, such as to avoid undesired alterations of previous blood flow. The bioabsorbable portion or portions may be placed in the patient's body at a location that expands after fistula creation, such as at a vessel wall that expands due to increased blood flow resulting from the fistula.

[0012] The coupler may include one or more components within the flow path between the first body space and the second body space. These one or more components may be configured to bioabsorb over time. The fluid flow path may have a constant cross-section or a variable cross section, such as a tapered cross section with a larger diameter on one end than the other. The cross section may be relatively circular or may be oval shaped.

[0013] The coupler may be self-expanding and/or be plastically deformable. The geometry of the coupler may be adjustable, such as a fluid path diameter that can be expanded with a tool. The coupler may include a ratchet design with interlocking members that maintain one or more radially expanded states. The coupler may include a mesh surface, such as a surface comprising woven material. The woven material may include a woven metal material such as woven Nitinol wire. Alternatively or additionally, the woven material may include a non-metal material such as Dacron. The woven material may be supported, such as by a wire frame along its periphery.

[0068] FIG. 1 illustrates the method of installing the shunt rivet to create and maintain an artificial aortocaval fistula. The patient 1 is shown with a delivery catheter 2 inserted into the left femoral artery/external femoral artery 3L and pushed upwardly through the left common iliac artery 4L to a point just above the aortic/iliac bifurcation in the distal abdominal aorta 5. The inferior vena cava 6 runs parallel to the aorta, and typically is contiguous with the aorta. As shown in the illustration, the left femoral artery provides a nearly straight pathway to a suitable site of the artificial aortocaval fistula 7 within the abdominal aorta (the right femoral vein 9R also provides a straight pathway to the same site on the vena cava side, and may be also be used as an access pathway). The fistula is created by forming a small hole or slit through the walls of both the aorta and the vena cava at immediately adjacent sites, and is maintained by inserting the shunt rivet 8 described below. The device may also be implanted via a route through the left femoral vein 9L, or through the right femoral artery 3R and/or right common iliac artery 4R, though these pathways are not expected to be so readily navigable. The shunt rivet may also be installed in an artificial arterio-venous fistula formed between the femoral vein and femoral artery on either side of the body, indicated as items 10R and 10L, or between the iliac artery and the femoral vein, and at locations in the aorta above the renal arteries.

[0069] FIG. 2 illustrates the aortocaval shunt rivet 8 in its restrained condition, while FIG. 3 illustrates the aortocaval shunt rivet of FIG. 2 in its resiliently expanded configuration. The shunt rivet may be formed from a single tube 11 of resilient material, such as nitinol, spring steel, glass or carbon composites or polymers, or pseudoelastic (at body temperature) material such as nitinol or comparable alloys and polymers, by laser cutting several closed-ended slots 12 along the length of the tube (leaving the extreme distal and proximal edges of the tube intact) and cutting open-ended slots 13 from the longitudinal center of the tube through the distal and proximal edges of the tube. The open-ended slots are cut between each pair of closed-end slots to form a number of loops 14 joined at the center section by waist segments 15. Though the shunt rivet illustrated in these figures can be made of several loops of wire welded together at the waist section, and many other fabrication techniques, manufacture from a single tube as illustrated has been convenient.

[0070] After the tube is cut as described above, it is formed into its eventual resiliently expanded configuration illustrated in FIG. 3. In this configuration, the loops turn radially outwardly from the center section, and evert toward the center plane of the center section, thus forming clinch members 16 in the form of arcuate, everted, petaloid frames at either end of the loop, extending from the generally tubular center section formed by the waist segments 15. For clarity, the term everted is used here to mean that the arc over which the petaloid frame runs is such that the inside surface of the device as configured in FIG. 2 faces radially outwardly from the cylinder established by the tube. FIG. 4 is a perspective view of the shunt rivet in the resiliently expanded configuration illustrated in FIG. 3, more clearly illustrating the relationship between the several petaloid frames at each end of the shunt rivet.

[0071] FIG. 5 shows a side view of the aortocaval shunt rivet of FIG. 2 in a fully expanded configuration. Even after the device has resiliently expanded to the extent possible given its impingement upon the walls of the aorta and the vena cava, the center section may be further expanded by plastic deformation. This may be accomplished by inflating a balloon within the center section, inflating the balloon, and expanding the center section beyond its elastic or superelastic deformation range. By plastically deforming the center section of the shunt rivet, the center section becomes more rigid and able to withstand the compressive force of the walls of the aorta and vena cava.

[0072] As illustrated, the construction provides several pairs of longitudinally opposed (that is, they bend to come into close proximity to each other, and perhaps but not necessarily, touch) and aligned (they are disposed along the same longitudinal line) distal and proximal petaloids. Overall, the petaloid frames of the distal section form a “corolla” (analogous to the corolla of a flower) flange or rivet clinch, which impinges on the vena cava wall and prevents expulsion into the aorta, and the petaloid frames of the proximal section form a corolla, flange or rivet clinch (this clinch would be analogous to a rivet head, but it is formed like the clinch after insertion of the rivet), which impinges on the aorta wall and prevents the expulsion of the shunt rivet into the vena cava, and the central section 17 forms a short length of rigid tubing to keep the fistula open. The resilient apposition of the two distal and proximal flanges or corollas so formed will securely hold the shunt rivet in place by resiliently clamping the walls of the aorta and vena cava (even over a considerable range of wall thickness or “grip range”).

[0073] Referring to FIGS. 2 through 5, the shunt rivet may be manufactured with an overall initial length L of about 8 to 10 mm to obtain a grip range G of about 3 mm (given a typical aortic wall thickness of 2 mm and a typical inferior vena cava wall thickness of 1 mm at the target site), a clinch allowance C of at least about 3 mm (the clinch allowance is the distally protruding portion of a rivet that is turned over, curled or flattened to form the formed head), a formed or blind head allowance A of about 10-16 mm (we use the term blind head to refer to the distal head, which is the head that is formed on the blind side of the joint), a head diameter H of 5-16 mm, an initial shank diameter D1 of 3-8 mm (in the resiliently expanded configuration, prior to plastic deformation), a final shank diameter D2 of 5-12 mm to create a flow through lumen of about 5-10 mm diameter. The grip strength of the shunt rivet should provide for a slight compressive force exerted by the opposing clinch members on the intervening blood vessel walls. Thus, the shunt rivet is formed such that, in the resiliently expanded configuration, produces a grip strength in the range of 0.1 to 1.5 oz (about 3 to 45 gram-force) per clinch member upon the intervening blood vessels of the expected thickness.

[0074] FIGS. 6 through 11 illustrate the method of releasing the shunt rivet so that the distal clinch members are released within the vena cava and the proximal clinch members are released within the aorta. Prior to insertion of the delivery catheter, the surgeon performing the implantation will image the aorta and inferior vena cava with appropriate fluoroscopic, ultrasonic, or other imaging methods, and create a pilot hole in the vessel walls with a crossing catheter. As shown in FIG. 6, the shunt rivet is housed within the distal tip of a delivery catheter 23, and is entirely restrained within the delivery catheter. The delivery catheter includes an outer sheath 24, a shaft 25 which is longitudinally slidable within the outer sheath, and a tapered or rounded tip 26 disposed on the shaft. The tapered may be mounted on a separate shaft, slidably disposed within the shaft 25, so that it may be pushed through the prepared aperture while holding the remainder of the device steady within the aorta. The distal edge of the outer sheath may also be rounded or tapered, as shown. A distally facing shoulder 27 on the shaft, just proximal to the shunt rivet, serves to keep the shunt rivet in place longitudinally as the outer sheath is withdrawn. A guide wire lumen 28 may be provided in the shaft for use with a guide wire 29, and may extend to the proximal end of the shaft for over-the-wire operation or may exit the shaft just proximal to the shunt rivet holding segment for monorail guidewire operation, and other guide wire configurations may also be used. A balloon 30 may be disposed on the shaft (and a suitable balloon inflation lumen provided in the shaft, and a suitable inflation pressure source in fluid communication with the lumen).

[0075] As shown in FIG. 7, the distal tip of the delivery catheter is pushed through a small aperture in the walls of the aorta and vena cava (items 31 and 32) (the aperture is made by the operator, using a separate or integral punch, needle or lance) to create the artificial aortocaval fistula. After the distal tip has entered the vena cava, the outer sheath is pulled proximally to release the distal petaloids, as shown in FIG. 8. After the distal petaloids have reverted to their unrestrained configuration, the entire device is pulled proximally to seat the distal petaloids against the inner wall of the vena cava. Prior to complete release of the shunt rivet, the operator should confirm that its location is acceptable (any suitable imaging technique may be used). To allow retraction in case the shunt rivet must be repositioned, a hook 33 protrudes radially from the shaft 25 and passes through a loop of the shunt rivet. This traps and secures the shunt rivet within the outer sheath 24 until the outer sheath is moved proximally to release the proximal clinch members, so that the operator may pull the shunt rivet back into the outer sheath in case its location, as visualized prior to complete release of the shunt rivet, is undesirable. Any other retaining means, such as a resilient or spring-loaded detent, a retractable pawl which engages a loop of the shunt rivet, of a retractable hook extending inwardly from the outer sheath, may be used in place of the illustrated hook.

[0076] Then the outer sheath is pulled further proximally to release the proximal petaloids, as shown in FIG. 9. With the shunt rivet securely set in the artificial fistula, the center section may then be expanded by inflating the balloon as shown in FIG. 10. Upon withdrawal of the shaft, the shunt rivet remains in place to hold the two perforations in the blood vessel wall in apposition to each other to maintain the fistula, and to maintain an open shunt pathway between the aorta and vena cava, as shown in FIG. 11.

[0077] The final form of the shunt rivet is, according to the above description, accomplished with the method that includes forming the generally tubular structure having a central section with a first diameter, a proximal clinch section defined by one or more clinch members, and a distal clinch section defined by one or more clinch members, training the proximal and distal clinch members to make them resiliently biased to bend radially outwardly from the central section; then resiliently compressing the tubular structure to maintain a generally tubular shape and restraining the compressed tubular structure in a compressed configuration suitable for percutaneous insertion into the body; inserting the structure through apposing apertures in the aorta wall and vena cava wall of a patient such that the distal clinch members protrude into the vena cava of the patient and the central section is disposed within the apertures; and then releasing the distal clinch members to permit resilient expansion of the distal clinch members followed by expanding the central section through plastic deformation to larger diameter and releasing the proximal clinch members to permit resilient expansion of the proximal clinch members (the proximal clinch members may be released before or after expansion of the central section).

[0078] The shunt rivet illustrated above may be modified as shown in FIGS. 12 and 13, which show an aortocaval shunt rivet with asymmetrically shaped distal and proximal flanges. In FIG. 12, the shunt rivet 35 is similar to the shunt rivet of FIGS. 2 through 4, and includes the central section, the distal flange comprised of multiple petaloid wire-frame members 16d, and the proximal flange comprised of multiple petaloid wire-frame members 16p. In this embodiment, the distal corolla is horn-shaped, “salverform” or “funnelform” (as those terms are used in botany), with the petaloids arcing outwardly without everting (without a substantial arc in the proximal direction), while the proximal corolla is perianth-like, arcing outwardly and everting with a substantial arc in the distal direction. Each petaloid is significantly reflexed, like the perianth of a narcissus cyclamineus. FIG. 13 illustrates another embodiment of the aortocaval shunt rivet with asymmetrically shaped distal and proximal flanges. In FIG. 13, the proximal petaloids are highly reflexed, and evert to form pigtails with an arc of over 180°, and preferably, as illustrated, an arc in excess of about 270°, such that the proximal petaloids bend radially inwardly toward the tips 36 to present a length of wire 37, rather than the tip of the petaloids, for impingement on the blood vessel wall. One or both of the distal or proximal petaloids/clinch members may be modified to form the pigtails illustrated in FIG. 13. In the embodiments shown, the petaloids are gamopetalous (with the petals united by their margins, at least at the base, as in FIG. 2 et seq.), but they may also be polypetalous as shown below FIGS. 14, 15 and 16. The embodiments shown are also actinomorphic, though they may be constructed in zygomorphic fashion with asymmetrical petaloids.

[0079] FIGS. 14, 15 and 16 illustrate an aortocaval shunt rivet 8 with diamond shaped strut members in the central section. This shunt rivet provides a central section 17 with a series of expandable loops joined by circumferentially oriented struts 38. FIG. 14 illustrates a tube 11 with numerous slots cut into it to form the shunt rivet shown in FIG. 16. Slots 12 are closed-end slots, leaving a loop 14 extending from the central section 17 to form a clinch member cell 39. Slots 40 are open or closed-end slots extending from the center of the device, leaving small circumferential struts 41 connecting adjacent cells of the device. Slots 42 are open or closed-end slots extending from the center section of the device, leaving larger waist sections 43 connecting the circumferential struts with adjacent clinch member cells of the device. Slots 44 are closed-end slots extending through the waist sections. As shown in FIG. 15, some waste area (segments intended to be removed) 46 shown in FIG. 14 are cut away and discarded, leaving expandable waist section cells 47 and clinch cells 39, interconnected by the circumferential struts 38. Though the device is illustrated with three clinch members on each end, the number of clinch members formed in the shunt rivet may be varied. The waist section cells and clinch member cells, can, as shown at 48, share struts which define contiguous cells. As shown in FIG. 16 the waist section cells, when expanded, form the diamond shaped cells of the central section. The clinch member cells comprise petaloid cells which may be described as lanceolate (narrow and tapering to an apex (though the apex is preferably blunt)), or ovate (having a broad base and narrow tip) rather than reniform or orbicular. The tip of the petaloid is preferably obtuse, rounded or blunt. As can be appreciated from FIG. 16 the clinch members may also be described as longitudinally extending wires which connect the longitudinally tips of adjacent waist section cells.

[0080] FIGS. 17 and 18 illustrate an aortocaval shunt rivet 51 formed with a single wired wrapped to form the device. In this device, a single wire has been wrapped around a specially formed mandrel to form a number of clinch members 52 on one end of the device and a number of clinch members 53 on the other end of the device. As illustrated, each clinch member is slanted relative to the radius of the device, and the wires forming the waist segment of the device are also oblique to the longitude of the device. As viewed from the top, each cinch member comprises a substantially circular arc, and the wire continues from the arc longitudinally toward the opposite end of the device, forming straight waist segment 54 where it runs substantially parallel to the long axis of the device until it arcs circumferentially away from the previous arc to form the clinch member on the opposite end, whereafter it loops around to extend retrograde relative to the circumference, forming waist segment 55 running obliquely relative to the long axis, and back toward the first end of the device until it curves again circumferentially forward to form the loop of the next clinch member circumferentially adjacent the first loop and longitudinally in line with the immediate previously formed clinch member on the opposite end of the shunt rivet, and continues in this fashion until the entire tubular structure of the device is achieved. In tracing its path, the wire may cross over one or more other portions of the wire.

[0081] FIG. 19 shows a detail of the clinch member, illustrating radiopaque markers on the shunt rivet. A radiopaque marker may be provided in the form of a radiopaque rivet 61 disposed near the tip of the clinch member 16, or it may be provided in the form of a wrapped coil of radiopaque wire or thread 62. The radiopaque markers may be comprised of platinum, iridium, tantalum, barium sulfate or other radiopaque materials. Similar markers may also be applied to the waist section. The marker material may also be selected to enhance visibility under ultrasound imaging, magnetic resonance imaging, or other suitable imaging techniques.

[0082] FIGS. 20 and 21 illustrate mandrels or dies useful for forming and training/heat setting the shunt rivets. As shown in FIG. 20, a two-part mandrel comprises a distal mandrel portion 63 and a proximal mandrel portion 64. Each mandrel is shaped to correspond to the desired final shape of the shunt rivet and its clinch members. The mandrel portions are inserted into the tube, after it has been cut, so as to deform the device. Where the device is formed from a pseudoelastic material that must be heat set or trained, the mandrels are dimensioned to deform the device to its desired open configuration. Where the device is formed of spring steel or the like, the mandrel is dimensioned to bend the clinch members beyond the desired final configuration. Thus, the mandrel of FIG. 20 and the mandrel of FIG. 21, though shaped differently, may be used to form quite similar shapes for devices made of nitinol and spring steel. The mandrel shapes may be modified as desired to achieve various clinch member shapes, such as the asymmetrical shapes shown in FIGS. 12 and 13.

[0083] The shunt rivet may be modified as shown in FIGS. 22 through 25. FIG. 22 is a perspective view of a shunt rivet 65 in which the clinch members are biased to provide pairs of clinch members 66a and 66v biased to close upon contiguous parallel portions of adjacent vessels and a pair of clinch members 67a and 67v biased to exert slight pressure, and establish slight compliance mismatch, on circumferentially spaced points on the side walls of the adjacent blood vessels. Each clinch member is slit down the center to allow radially expansion of the device through radial deformation of the clinch member.

[0084] FIG. 23 is a side view of a shunt rivet of FIG. 22 showing the substantial closure of longitudinally oriented clinch members 66a and 66v. These clinch members are formed to evert, such that the tips of opposing clinch members 66a and 66v are closely proximate each other when released (in the expanded configuration shown). A short segment at the distal tip of each clinch member is turned away from the transverse midline 68 of the device to form an atraumatic bearing surface for impingement on the blood vessels walls. As illustrated, the clinch members 66a and 66v comprise a continuously formed clip, with no intervening waist segment between the arterial portion of the clip and the venous portion of the clip. The clip resembles a tool clip, as that term is used in other arts. Preferably the clinch members making up the tool clip are joined directly together, without an intervening rectilinear base (though a rectilinear base may be incorporated if desired to accommodate the anatomy of the arterio-venous fistula in a particular site), to create a smoothly arcuate transition from the distal clinch member to the proximal clinch member. FIG. 24 is a side view of the shunt rivet 22 showing the preferred angle of the transversely oriented clinch members 67a and 67v relative to the axis 70 of the device. In this embodiment, the transversely oriented clinch members 67a and 67v (both the near and far pairs are visible in this view) are set at a small angle from axis 70. In the unrestrained configuration, the clinch members 67a on the arterial side of the device (typically the first side of the device to be released from the catheter given the preference for transvenous delivery) are inclined toward the upstream or retrograde direction. Clinch members 67v on the venous side of the device are inclined toward the upstream or retrograde direction within the vein. This configuration facilitates release of the device from the small delivery catheter used to insert it into a fistula.

[0085] FIG. 25 is a side view of the shunt rivet of FIGS. 22 through 24 showing transversely oriented clinch members 67a and 67b with substantial spacing between the tips of the clinch members (in the expanded configuration shown). Also, clinch members 67a and 67b constitute a continuously formed tension spring (shaped substantially like the tension spring used in window frames, having an arcuate or bow shape, with the ends arcing outwardly from the axial centerline 70 of the device and adapted to impinge upon or exert force on the blood vessels and the middle of the arch adapted to exert force on the remainder of the shunt rivet to which it is fixed), with no intervening waist segment between the arterial portion of the tension spring and the venous portion of the tension spring, and the tension spring formed to impinge on the sidewall of the artery or vein at a point circumferentially displaced from the center of the rivet without deforming the artery and/or vein walls to bring the opposite tips 69a and 69v into apposition such as that achieved by the tips of the tool clips. A short segment at the distal tip of each clinch member is turned away from the axial centerline 70 of the device to form an atraumatic bearing surface for impingement on the blood vessel walls.

[0086] The device may thus be described, in their open and unconstrained conditions, as comprising two parallel tool clips secured at their closed ends to two parallel tension springs, at the midpoints of the tension springs, to create an orthogonal or cruciform grouping of alternating spring clips and tension springs. Adopting the botanical language used for other embodiments, each side of the device comprises a pair of petaloids arcing outwardly from the axial centerline of the device without everting (without a substantial arc in the proximal direction), and a pair of petaloids arcing outwardly and everting with a substantial arc in the distal direction, with corresponding petaloid structures being joined at their proximal ends without an intervening waist segment. Each petaloid is formed in an open frame V-shape. Though illustrated with a pair of clips and a pair of tension springs, the device may be formed with additional tension springs or clips, as dictated by the local anatomy of a particular installation. In appropriate anatomical conditions, the device may comprise four clips in the tool clip configuration, or the comparable evening petaloid pairs (in which all clinch members evert substantially to close upon the vessel wall), arranged orthogonally, where the tool clips are arranged in a circular arrangement with the closed end of each clip being secured to the closed and of an adjacent clip, such that the open end of each tool clip is directed outwardly from the circular arrangement. The device may also include additional arcuate tension springs and/or tool clip portions, thus departing from the cruciform configuration shown while achieving the benefit of substantial spacing of the vessel contacting tips from the arterio-venous fistula.

[0087] FIG. 26 shows the shunt rivet of FIGS. 22 through 25 installed between an artery 71 and vein 72, in order to illustrate the construction of the device relative to the environment of use. The tips of the “tool clip” portion of the device (66a and 66b) close upon points in the respective vessels 73a and 73v which are longitudinally spaced (relative to the blood vessels) from the arterio-venous fistula formed in which the device is placed. The points of impingement are significantly spaced from the fistula, as illustrated. The tips of the tension spring portion (67a and 67v) of the device impinge on circumferentially spaced points 74a and 74v. As shown in FIG. 26, the circumferential points of impingement are significantly spaced from the fistula. The circumferential spacing is preferably 30° to 90°, but may be adjusted to fit local anatomy. In this manner, the shunt rivet avoids engagement of the blood vessels adjacent the fistula. As shown in FIG. 26, the ultimate shape of the installed shunt rivet may vary from the unrestrained shape due to the remaining constraint of the blood vessel walls, though the device is biased to resiliently or superelastically return to the unrestrained shapes of FIGS. 22 through 25. After installation, the shunt rivet holds the adjacent artery and vein together and maintains an open flow path through opening defined by the roughly circular arrangement of the clips and tension springs. Should the arrangement appear to be somewhat squared or angular, pentagonal, hexagonal, etc., given the particular geometries of the various parts, it is intended that such departures from perfect circular arrangement be included under the description of a circular arrangement.

[0088] Yet another variation for the shunt rivet may include varying a length of the respective clinch members. As illustrated in the perspective view of FIG. 27, shunt rivet 80 may include the longitudinally oriented clinch members 81a, 81a′ and 81v, 81v′ positioned opposite to one another and transversely oriented clinch members 82a and 82v positioned transverse relative to an axial centerline of shunt rivet 80, as described above. In this variation, clinch members 81a and 81v′ may be sized to have a length which is less than clinch members 81a′ and 81v, as described in further detail below. The respective lengths of clinch members 81a, 81v′ relative to 81a′, 81v may be variably sized to maximize or optimize the stability of shunt rivet 80 with respect to the vessels when deployed between adjacent vessels.

[0089] Moreover, varying the lengths of the respective clinch members may further provide additional advantages. For instance, the clinch members which are shortened in length may facilitate the positioning and securement of the shunt rivet between the vessels by allowing for the relatively shorter member to swing into position within the vessel lumen during deployment, as described in further detail below. Moreover, a shorter member may provide for a minimized implant size when placed against the vessel interior wall for securement as well as a mitigating any physiologic reaction to the implant, e.g., a reduction in thrombosis, etc. Additionally, clinch members which are lengthened relative to other members may provide for increased shunt stability by increase the amount of force applied against the tissue walls.

[0090] Moreover, clinch members having different lengths may additionally place the adjacent vessels in tension such that the vessel walls are drawn towards one another and the clinch members 81a, 81a′ and 81v, 81v′ contact the vessel luminal walls to stabilize not only the shunt rivet within the vessels but also the vessels with respect to one another. Additionally, having one or more clinch members 81a, 81v′ sized to have a length shorter than its respective apposed clinch member may also facilitate the deployment and/or positioning of the clinch members 81a, 81v′ within the vessel since the shorter length clinch members can more easily “swing” through an arc within the vessel lumen without contacting the interior walls. Clinch members with differing lengths may further be configured to align along different planes when deployed to facilitate vessel separation, if so desired.

[0091] As above, each of the clinch members may be formed without an intervening waist segment between the arterial portion of the shunt rivet 81a, 81a′ and the venous portion of the shunt rivet 81v, 81v′. As also previously described, the clinch members may be joined directly together, without an intervening rectilinear base (though a rectilinear base may be incorporated if desired to accommodate the anatomy of the arterio-venous fistula in a particular site), to create a smoothly arcuate transition from the distal clinch member to the proximal clinch member.

[0092] Aside from the variable length clinch members, shunt rivet 80 may further define one or more slots 83 along the length of the clinch members, such as at the terminal ends of each clinch member. The one or more slots 83 may be formed or cut, e.g., by a laser, to provide a region through which a radio-opaque marker or wire, such as tantalum wire or any other radio-opaque material as described herein, may be passed through to facilitate imaging during deployment. Shunt rivet 80 may also further include an optional radio-opaque center marking band about the center of rivet 80 to indicate the center, e.g., when viewed under fluoroscopy or any other imaging modality. Additionally, one or more of each clinch member may also optionally include a slot 84 defined along a length of the individual respective clinch member struts, as shown, to further function as a stress-relieving slot.

[0093] Although shunt rivet may be formed without an intervening waist member, it may be optionally included. As shown in the illustrative partial cross-sectional view of FIG. 28, another variation of shunt rivet 93 may be seen deployed between two respective vessels, artery 90 and vein 91. Clip connector 99 may extend between sets of clinch members 95, 96 and 97, 98 while defining lumen 94. Although the transverse clinch members have been omitted from the illustration for clarity, they may be optionally omitted from the shunt rivet entirely, if so desired. In its deployed configuration when placed through fistula 92 defined between vessels 90, 91, lumen 94 may define a flow path between the vessels, as described above. In this variation, clinch members 96, 97 are shortened in length relative to the lengths of clinch members 95, 98. The shortened clinch members 96, 97 may be configured to be deployed on opposite ends of the shunt rivet such that shortened clinch member 96 is disposed within artery 90 while shortened clinch member 97 is disposed within vein 91 and extends in a direction opposite to that of clinch member 96. Shortened clinch members 96, 97 may be similar in length and configuration or they may be varied in length relative to one another.

[0094] Likewise, clinch member 95 may be disposed in artery 90 while clinch member 98 is disposed in vein 91 such that they extend in opposing directions and are positioned opposite to their respective shortened clinch members. Like their shortened counterpart members, clinch members 95, 98 may be similar in length and configuration or they may also be varied in length relative to one another. Clinch members with differing lengths may be utilized in any of the variations described herein in combination with additional features, as described.

[0095] In addition to having clinch members of different lengths, the connector member itself may be modified such that its extends between the respective clinch members at an angle relative to a centerline of the shunt rivet, as illustrated by angled connector 100 in the top view of FIG. 29. The angled connector 100 may be configured over a number of various angles such that the blood flow between the vessels 90, 91 through angled connector 100 avoids a 90° turn.

[0096] In yet another variation, angled connector 110 may be further modified such that the cross-section of the connector is tapered along its length, as shown in the partial cross-sectional view of FIG. 30. Accordingly, in addition to having clinch members of various lengths and an angled connector, the connector 110 and/or connector lumen 94 may be tapered or it may define a non-constant cross-sectional area along its length. For instance, the connector lumen 94 may be tapered such that the cross-sectional area increases as the connector 110 extends from the arterial vessel 90 to the venous vessel 91, as shown. Alternatively, the cross-sectional area may decrease as the connector 110 extends away from the arterial vessel 90.

[0097] In yet a further variation, the shunt rivet may optionally include a hinge or flange 111 connecting one or more of the clinch members to the connector 110, as shown in FIG. 31. Such a hinge or flange may be adjustable to change an angle at which connector 110 extends between the clinch members and may utilize any number of hinging mechanisms. For instance, hinge or flange 111 may simply comprise a plastically deformable portion of the shunt rivet or it may be a mechanically hinged mechanism, e.g., which provides for frictional engagement between the clinch members and the connector 110 to maintain its position yet also allows for adjustment. The hinge or flange 111 may be adjusted prior to deploying the shunt rivet such that the clinch members extend at their predetermined angle when deployed. Alternatively, hinge or flange 111 may be adjusted during deployment or after the shunt rivet has been placed between the vessels 90, 91 by using an inflatable balloon instrument or other expandable tool. In yet another alternative, the hinge or flange 111 may be adjusted both before deployment and during or post deployment into the vessels. For example, post deployment adjustments may be accomplished anytime, e.g., within one hour of shunt deployment, or alternatively in a subsequent procedure, e.g., prior to or after thirty days of deployment within a patient.

[0098] Another variation may utilize one or more break-away or frangible segments 120 which may be integrated with the shunt rivet along a periphery of connector 99, as illustrated in the top view of FIG. 32. In this example, two break-away segments 120 may be integrated on either side of connector 99 such that when the shunt rivet has been positioned or during positioning into the vessels, connector 99 may be adjusted in size, e.g., by expanding the opening via a balloon instrument, to allow for a greater flow through the shunt rivet. The break-away segments 120 may be comprised of a number of different biocompatible materials which may be dissolved into the blood or they may be configured as opposing portions of connector 99 which are overlapped or otherwise held temporarily to one another.

[0099] Alternatively, segments 120 may be comprised of plastically deformable bands which break apart to adjust or allow for the adjustment of the cross-sectional area of the connector 99. The adjustability of the connector cross-section may allow for the shunt rivet to change from a circular cross-sectional area to an oval cross-sectional area. In the same manner, the cross-sectional area may be changed from an oval area to a round area. The adjustment of the cross-sectional area utilizing the break-away segments 120 may be performed pre-implantation, during implantation, or post implantation of the shunt rivet into the vessels.

[0100] Another variation is shown in the top view of a shunt rivet in FIG. 33 which utilizes one or more plastically deformable sections 130 which may be integrated along the periphery of connector 99. As shown, the plastically deformable sections 130 may be plastically deformed, e.g., via an inflatable balloon, either prior to, during, or post deployment to adjust the cross-sectional area of connector 99. Moreover, plastically deformable sections 130 may be integrated into connector 99 such that when connector 99 is expanded or deformed, sections 130 plastically deform and retain their deformed configuration when a deforming force is removed.

[0101] Aside from variations in adjusting the cross-sectional flow area of the shunt rivets, other optional variations may be incorporated in any of the shunt rivets described herein. For instance, FIG. 34 shows a partial cross-sectional side view of yet another variation which may utilize plastically deformable, elastically deformable, or break-away segments or portions 140 along a length of connector 110 to adjust a length of the lumen through which blood is shunted. The portions 140 may be utilized along a length of connector 110 to allow for adjustment of the distance between the vessels 90, 91 and they may be utilized with a connector length which is uniform in diameter or which is tapered or narrowed, as described above.

[0102] In utilizing a shunt rivet having different clinch member lengths, shorter length clinch members can more easily “swing” through an arc within the vessel lumen without contacting the interior walls, as mentioned above. Accordingly, such a shunt rivet may be implanted such that the clinch members are deployed in an ordered sequence. In one example, once a needle has been passed through the tissue wall to cross between vessels 90, 91, guidewire 30 may be advanced intravascularly through the needle which may then be removed leaving guidewire 30 passing through vessels 90, 91. Shaft 25 and/or outer sheath 24 may be advanced through vessel 90 over or along guidewire 30 to follow guidewire 30 into vessel 91, as shown in FIG. 35A. Shaft 25, described above, may be fabricated with a stiffened tip, such as polyimide, to facilitate crossing between vessels. Once properly positioned within vessel 91, outer sheath 24 may be pulled proximally while tracking its distal end visually via a marker band 152 until clinch member 98 is first released from the constraints of outer sheath 24 and allowed to reconfigure itself into its angled configuration, relative to a longitudinal axis of the shunt rivet. The individual clinch members of the shunt rivet may be optionally retained via anchoring pins 153 integrated with shaft 25 which may hold the clinch members in place as outer sheath 24 is retracted. These anchoring pins 153 may also serve to prevent or limit the motion of the shunt rivet itself until outer sheath 24 has been fully retracted. This particular configuration may be utilized in situations where a clinician may wish to re-sheath the shunt rivet, e.g., for abandoning a procedure or for repositioning the shunt rivet, etc.

[0103] With outer sheath 24 pulled further proximally, shortened clinch member 97 may be subsequently released. With its shortened length, relative to clinch member 98, clinch member 97 may fully deploy and arc 151 entirely within vessel 91 without interfering or contacting the distal region of the vessel wall until clinch member 97 comes into contact against the proximal region of the vessel wall. With clinch members 97, 98 fully deployed within vessel 91, outer sheath 24 may be further withdrawn relative to shaft 25 to subsequently release shortened clinch member 96, which may then arc 150 entirely within adjacent vessel 90 to contact the tissue surrounding the fistula. Subsequently, outer sheath 24 may be fully retracted to release clinch member 95 to allow it to come into contact against the tissue wall within vessel 90, thereby fully deploying the shunt rivet between vessels 90, 91. The shunt rivet may be partially deployed from shaft 25 and optionally removed and/or repositioned and re-deployed elsewhere within the body.

[0104] Another example is illustrated in FIGS. 35B and 35C, which illustrate side views of clinch members of a shunt rivet being deployed entirely within a vessel. As shown in FIG. 35B, once the assembly has been advanced intravascularly through vessel 90, e.g., an artery, and the needle and guidewire advanced from within vessel 90 and into adjacent vessel 91, e.g., a vein, shaft 25 carrying the shunt rivet may be advanced at least partially from outer sheath 24 (alternatively, outer sheath 24 may be retracted relative to shaft 25) to expose the transversely oriented clinch members 154, 156 and the clinch members 97, 98 for expansion and/or reconfiguration within vessel 91. As shown, clinch member 97 may reconfigure from a low profile configuration where clinch member 97 is positioned to extend distally along shaft 25 during delivery to a configuration where member 97 swings proximally within vessel 91, as shown, to a securement configuration.

[0105] One or more members can be deployed and by advancing the outer sheath 24 (and/or retracting shaft 25 relative to outer sheath 24), the members can be recaptured and at least partially re-sheathed to allow for removal and/or repositioning of the shunt rivet. Once desirably repositioned, the clinch members may be fully deployed into position.

[0106] As further illustrated in this example, the lengthened clinch member 98 may engage against the vessel wall within vessel 91 during deployment. If excessive pull force is applied to the shunt rivet, member 98 can deform and straighten while deflected by the walls of vessel 91, as illustrated by deformed tissue 158, so as to prevent or inhibit damage to the surrounding tissue. A clinician can visually assess, e.g., via fluoroscopy or ultrasound, the wall-to-shunt engagement by gauging the amount of deflection indicated by the lengthened clinch member 98. Along with the tactile feedback perceived by the clinician, the visual indication of the clinch member deformation may further aid in confirming suitable shunt rivet positioning.

[0107] Once the position of the shunt rivet has been confirmed within vessel 91, clinch member 98 may be fully deployed and clinch member 97 may be fully deployed to swing proximally into its securement position within vessel 91, as shown in FIG. 35C. The remaining clinch members may be subsequently released from outer sheath 24 and shaft 25 to be deployed within vessel 90.

[0108] In delivering and configuring the shunt rivets described above, additional delivery instruments may be utilized to facilitate adjustment of the shunt rivets to a desirable configuration. For instance, adjusting the cross-sectional area of the connector portion of the shunt rivet or adjusting a length of the connector lumen between the clinch members, or adjusting an angle of the shunt rivet and clinch members with respect to the vessel lumens, etc., may be accomplished with instruments as shown in FIGS. 36 to 38.

[0109] FIG. 36 illustrates one variation of an instrument 160 which may be used to adjust a length of the connector lumen. Instrument 160 may generally comprise an outer sheath 161 having an inflatable balloon or expandable member 162 disposed around a distal portion of the sheath 161. Inner sliding core 163, upon which the shunt rivet may be disposed upon or over, may be slidingly disposed within outer sheath 161 and may also have an inflatable balloon or expandable member 164 also disposed around a distal portion of core 163. As mentioned above, with the shunt rivet disposed upon sliding core 163, inflatable members 162, 164 may be expanded to temporarily engage the respective clinch members to lengthen or extend the connector length between the clinch members of the shunt rivet, e.g., to accommodate vessel separation distances, either prior to, during, or post implantation of the shunt rivet within the vessels. Alternatively, with members 162, 164 expanded, the connector length may be shortened between the clinch members.

[0110] The ability to adjust the length of the connector may allow for not only accommodating for the distance between the vessels, but also to “fine-tune” a flow rate of the blood through the shunt rivet to achieve a desired therapeutic result and/or to mitigate any side effects of the fistula. Moreover, although the adjustment to the shunt rivet may be done intra-operatively in vivo, adjustments may also be performed prior to insertion within the patient body. Moreover, an electronic or mechanical gauge or markers (such as visual markings or radio-opaque markers) may be integrated with the instrument 160 to provide feedback to the user as to the length that the shunt rivet is shortened or lengthened.

[0111] An example of another instrument which may be used to adjust an angle of the shunt rivet with respect to the vessels is shown in FIG. 37. As above, an inner sliding core 163 may be translatably positioned within outer sheath 161. A pullwire 165 may have a fixation point 166 near or at a distal end of sheath 161 and may be routed through outer sheath 161 and articulated 169 to adjust an angle of outer sheath 161 with respect to a longitudinal axis of sheath 161. Likewise, inner core 163 may also have a separate pullwire 167 with a fixation point 168 near or at a distal end of inner core 163 to adjust 169′ its angle with respect to a longitudinal axis of inner core 163. Sliding core 163 and outer sheath 161 may both be articulated independently of one another to create multiple bending configurations. In this manner, a shunt rivet disposed within outer sheath 161 and/or upon sliding core 163 may be bent or curved into various configurations by the forces imparted upon the shunt rivet to adjust its angle with respect to the clinch members and vessels.

[0112] Such an instrument may be utilized to adjust not only an angle of, e.g., connectors between the clinch members, but also the hinge or flange 111 as well as other portions of the shunt rivet variations described herein. Moreover, the instrument may be utilized to plastically deform the portions of the shunt rivet. One or more radio-opaque markers may be included on the instrument to visually indicate an angle of the instrument. An additional and/or alternative variation may further include an instrument which is used to deform the tissue neighboring the fistula site in the same manner as adjusting angles, distances, etc., of the shunt rivet. The shunt rivet may also be plastically deformed or it may be simply elastically deformed to accommodate the tissue shape changes. Additionally, the instrument may further include a mechanical or electronic gauge to indicate the degree of force imparted on the shunt rivet as well as relaying other information during or post deployment.

[0113] Yet another feature of a deployment instrument is shown in the partial cross-sectional side and end views, respectively, in FIG. 38. As shown, inflatable end effector 170 may include an inflation balloon 173 in fluid communication with an inflation lumen 172 which is disposed near or at a distal end of a delivery shaft 171. A shunt rivet may be disposed proximate to, upon, or distal to inflation balloon 173 in its deflated state for delivery into the vessels. Prior to, during, or post deployment of the shunt rivet into the vessels, inflation balloon 173 may be inflated to adjust a cross-sectional area of the shunt rivet to adjust the flow rate between the vessels, e.g., up to 5 mm or more diameter and as described above in the shunt rivet variations. Inflation balloon 173 may be configured to have a circular cross-sectional area such that expansion within the shunt rivet may adjust the shunt to have a corresponding circular cross-sectional area. Alternative variations of the inflation balloon 173 may include balloons having non-circular cross sections, e.g., such as an oval cross section with adjustable major and/or minor axes, as shown in the end view of FIG. 38, to optionally adjust a shunt rivet cross section accordingly. Other non-circular cross-sectional areas may be utilized, e.g., polygon, trapezoid, triangle, rhombus, rectangle, square, parallelogram, etc., to optimize a flow through the fistula and to vary or optimize an effective flow diameter through the shunt rivet and between the interconnected vessels.

[0114] FIG. 39 illustrates a top view of a shunt rivet having an example of an oval cross-sectional area 180, which may be optionally adjusted via the one or more instruments above. Another non-circular cross-sectional area is illustrated in FIG. 40, which shows a top view of a shunt rivet having a rectangular cross-sectional area 181. As mentioned, other non-circular cross-sectional areas (e.g., polygon, trapezoid, triangle, rhombus, rectangle, square, parallelogram, etc.) may be utilized to optimize flow conditions and/or therapeutic results for implantation between the vessels, as desired.

[0115] Referring now to FIGS. 41 through 52, various embodiments of shunt rivets of the present invention are illustrated. These shunt rivets are bioabsorbable or include one or more bioabsorbable portions or components. As used herein, the term bioabsorbable is meant to encompass materials that are broken down and gradually absorbed or eliminated by the body. The bioabsorption process or processes may involve hydrolysis, metabolic, and/or other chemical, physiologic and/or other processes.

[0116] The shunt rivet or shunt rivet portion is engineered to bioabsorb over a particular time period such as hours, days, weeks, months or even years. In specific embodiments, the shunt rivet or shunt rivet portion is designed to bioabsorb after a period such as a time during which vascular remodeling or other physiologic remodeling can occur in and/or around the fistula into which the shunt rivet is placed. In certain embodiments, the bioabsorption time is relatively short, from a few hours to a few days, such that the bioabsorbed shunt rivet, shunt rivet portion, or shunt rivet portions (collectively hereinafter “bioabsorbed portions” or “bioabsorbable portions) provide a function during the implantation procedure only and/or a scaffolding or other function that is required for only a few days or less. In different embodiments, the bioabsorbed portions are configured to bioabsorb over multiple weeks or months, such as to be present while one or more physiologic processes occur, such as endothelialization or stenosis of the fistula, vascular remodeling of the vein or artery proximate the fistula, thrombus formation, or other physiologic process which may occur during those weeks to months. In these particular embodiments, the shunt rivet function is temporary, and absence of the shunt rivet after a period of time provides one or more advantages, including but not limited to various reactions of the body in response to the presence of a foreign material. In a particular embodiment, the bioabsorbed portion is configured to bioabsorb to avoid impeding or otherwise adversely affecting expansion of the fistula and or vessel portions proximate the fistula. Due to the reduction of long term implant volume and/or surface area (absorption of one or more shunt portions over time) the bioabsorbable shunt rivets of the present invention allow placement into fistulas with small diameters and/or low flow rates. In particular embodiments, the bioabsorbable shunt rivets are configured to be placed between an artery and a vein which include a vessel of less than 3 mm or even less than 2 mm.

[0117] The bioabsorbable portion may include one or more stabilizing portions such as those described in reference to FIGS. 43 and 44a herebelow, the stabilizing portions providing a temporary support with the non-bioabsorbed portions providing a permanent or more permanent support. The bioabsorbable portion may comprise shunt segments positioned in the blood flow path with the non-bioabsorbed portions being embedded in tissue or otherwise positioned to avoid altering blood flow. In alternative embodiments, a first bioabsorbable portion is absorbed at a faster rate than a second bioabsorbable portion. In these embodiments, portions that provide a longer term function are configured to be absorbed at a slower rate than bioabsorbed portions that provide a shorter term function. In a particular embodiment, portions outside the fistula such as stabilizing portions are configured to absorb faster than portions inside the fistula such as fistula scaffolding portions, all described in reference to the various figures herebelow. In other particular embodiment, portions in the vein, fistula and/or artery are configured to bioabsorb differently than portions in a different location.

[0118] The shunt rivet may include a geometry which enhances the radial force generated at a portion of the shunt rivet such as the portion within the fistula. Radially expanding ratchet designs (see FIGS. 47a and 47b) and other radially enhanced force designs may be incorporated to enhance the force generated by the bioabsorbable materials used, such as materials which provide less mechanical force than a material such as nitinol or stainless steel. The shunt rivet may include two discrete, attachable and/or detachable clip portions, such as those described in reference to FIG. 48 below.

[0119] The shunt rivets of FIGS. 41 through 52 may include non-bioabsorbed portions such as portions constructed of nitinol. Numerous non-bioabsorbable materials can be used for these portions including but not limited to: stainless steel; one or more polymers; glass or carbon composites; one or more pseudoelastic materials such as nitinol or comparable alloys or polymers; and combinations of these. The shunt rivets of FIGS. 41 through 52 may include one or more numerous bioabsorbable materials, such as those well known to those of skill in the art. The bioabsorbable materials are chosen to be biocompatible, and/or to otherwise prevent toxic or other harmful materials from being exposed to the body. Applicable bioabsorbable materials include bioabsorbable materials used in intravascular stents, such as the stents used in the ABSORB clinical trial. The ABSORB trial used fully absorbable stents constructed of polyactic acid, a bioabsorbable polyester derived from lactic acid which breaks down to create carbon dioxide and water. This material is also used in sutures, and is metabolized by the body to be completely absorbed over time.

[0120] Numerous other bioabsorbable materials can be used, such as materials which are biocompatible and when they are bioabsorbed, cause minimal or no harmful effects on the body. Early research identified polyalactic acid, polyglycolic and polydioxanone based materials which were bioabsorbed but released acids or other toxins. These materials were applicable to implants small enough such that the toxins released caused no significant harm. Pseudo-polyamino acids are based on tyrosine, a naturally occurring amino acid. These materials have been successfully and safely used in implants such as orthopedic pins and screws. Numerous other safe, bioabsorbable materials have been developed including bioabsorbable polymer matrices and metal materials that dissolve and are slowly absorbed by the body.

[0121] Bolz et al (U.S. patent Ser. No. 09/339,927) discloses a bioabsorbable implant which includes a combination of metal materials that can be an alloy or a local galvanic element. Metal alloys consisting of at least a first component which forms a protecting passivation coat and a second component ensure sufficient corrosion of the alloy. The first component may be selected from magnesium, titanium, zirconium, niobium, tantalum, zinc and silicon and the second component is at least one metal selected from the group consisting of lithium, sodium, potassium, manganese, calcium and iron. Furst et al (U.S. patent application Ser. No. 11/368,298) discloses an implantable device at least partially formed of a bioabsorbable metal alloy that includes a majority weight percent of magnesium and at least one metal selected from calcium, a rare earth metal, yttrium, zinc and/or zirconium. Doty et al (U.S. patent application Ser. No. 11/944,977) discloses a bioabsorbable magnesium reinforce polymer stent that includes magnesium or magnesium alloys. Numerous polymers can be used such as: polylactide, poylglycolide, polysaccharides, proteins, polyesters, polyhydroxyal kanoates, polyalkelene esters, polyamides, polycaprolactone, polyvinyl esters, polyamide esters, polyvinyl alcohols, polyanhydrides and their copolymers, modified derivatives of caprolactone polymers, polytrimethylene carbonate, polyacrylates, polyethylene glycol, hydrogels, photo-curable hydrogels, terminal diols, and combinations thereof. Dunn et al (U.S. Pat. No. 563,191) discloses a medical implant including bioabsorbable fibers that reinforce a bioabsorbable polymer matrix. These and all references referred to herein are incorporated by reference in their entirety.

[0122] The shunt rivets of FIGS. 41 through 52 can be placed in a surgical procedure, such as a minimally invasive surgical procedure, on in an interventional procedure such as those described hereabove using an over a guidewire delivery catheter. The guidewire, preferably a 0.035″ guidewire, has been placed from an artery to a vein or from a vein to an artery. The delivery catheter is placed over the vessel-to-vessel guidewire, either from artery to vein or vein to artery, preferably in the same direction the guidewire was placed, and more preferably from artery to vein. The delivery catheter is constructed of materials compatible with the body for short durations, such as durations less than twenty-four hours, such as materials including but not limited to: biocompatible plastics such as Ultem and polyimide; metals such as stainless steel; and biocompatible adhesives.

[0123] The shunt rivets of the present invention may be placed during the procedure in which the fistula is created, or at a time thereafter, such as at a time more than twenty-four hours later, or more than thirty days later. In a particular embodiment, a shunt rivet with one or more bioabsorbable portions is placed one, three or six months after fistula creation, such as to increase or decrease the effective fistula diameter, or to compensate for the fistula and/or surrounding vessel(s) enlarging over time. The shunt rivet may be placed in an existing fistula, such as to improve (increase or decrease) or otherwise modify flow through the fistula. The shunt rivet may be placed before or after the placement of a second shunt rivet. The delivery catheter is placed through a percutaneous introducer such as an introducer of approximately 11 F. In a preferred embodiment, the delivery catheter is configured to recapture a partially deployed shunt rivet, as has been described hereabove. After placement, the shunt rivet may be expanded, such as via expansion with a non-compliant balloon for a period of approximately fifteen (15) seconds. The expansion device may be inserted over the same vessel-to-vessel guidewire over which the delivery catheter was deployed. In an alternative embodiment, an expanding member such as a balloon is integral to the delivery catheter. Adequate shunt deployment and resultant fistula flow is confirmed with one or more of: angiography and ultrasonic flow measurement such as Doppler flow measurement. Inadequate flow may result in subsequent dilation of the fistula and/or shunt rivet.

[0124] The shunt rivets of FIGS. 41 through 52 may be implanted to treat a patient suffering from Chronic Obstructive Pulmonary Disease (COPD). Alternatively or additionally, the patient may be treated for one or more conditions including but not limited to: congestive heart failure; systemic arterial hypertension; hypotension; respiratory failure; pulmonary arterial hypertension; lung fibrosis; and adult respiratory distress syndrome. The patient may have previously received lung volume reduction surgery or endobrachial valve implantation. The patient may be undergoing or have previously undergone treatment with one or more respiratory treatment agents such as Advair produced by Glaxo Smith Kline. In the exemplary embodiments, the therapy is performed by creating an anastomosis between an artery and a vein distal to the renal arteries and veins. A broad range of arteries and veins can be chosen for fistula locations including but not limited to: common or external iliac artery and vein, femoral artery, saphenous vein, axillary artery and vein, subclavian artery and vein, axillary artery and vein; brachial artery and vein; poplitieal artery and vein, ulner artery; radial artery; profundal artery; basilic vein, cephalic vein, medial forearm vein, medial cubital vein, the aorta, and the inferior vena cava.

[0125] Determining a location for the fistula and shunt rivet is based on numerous factors. Typical artery sizes at the fistula site range from 5-10 mm, preferably greater than 6 mm. Typical vein sizes at the fistula site range from 5-12 mm, preferably greater than 6 mm. Vessel separation distance at the fistula site is typically chosen to be less than 5 mm, preferably less than 2-3 mm. Resultant flow rate is desired to be less than 1.5 liters/min, preferably less than 1.0 liters/min, and more preferably 0.8-1.0 liters/min

[0126] In an alternative embodiment, the shunt rivets of FIGS. 41 through 52 may be implanted in the patient to create one or more of: a dialysis fistula; a cardiac bypass; or other therapeutic or diagnostic connections between two vessels such as an artery and a vein.

[0127] The shunt rivets of FIGS. 41 through 52 may be self-expanding, balloon expandable, or may include both self-expanding and balloon expandable portions. In a preferred embodiment, the shunt rivet geometry may be adjustable, such as with a tool or instrument as has been described hereabove in reference to FIGS. 36 and 37. Geometric adjustments can be performed during or subsequent to the implantation procedure. One or more portions, such as one or more bioabsorbable portions, may include a drug or other agent, coated on and/or embedded into the bioabsorbable material. Agents such as heparin and other anti-coagulants and paclitaxol, rapamycin (Sirolumis™), everolimus and other anti-stenotic compounds can be applied to the stent in polymer matrices which permit elution of these drugs over a period of time ranging from several hours to several months after implantation. The agents may be used to attract or repel platelets and/or proteins and prevent thrombus formation. Coatings may be included using a deposition processed such as ion beam or chemical vapor deposition. Coatings may be added or modified using atom transfer radical polymerization. Embedded agents may be configured to be slowly delivered over time, such as at a rate proportional to the bioabsorption rate of the shunt rivet. In an alternative embodiment, the shunt rivet includes a radioactive portion configured to prevent undesired flow path narrowing, such as narrowing due to neointimal proliferation.

[0128] Referring specifically to FIG. 41, a top sectional view of a shunt rivet of the present invention is illustrated, with typical materials and dimensions as described hereabove. Connector 200 includes bioabsorbable stabilizing arms, clinch members 295o and 296o, manufactured from one or more of the bioabsorbable materials described hereabove. Referring additionally to FIG. 42a, a side sectional view of clip 200, implanted between artery 90 and vein 91 is illustrated. Clip 200 further includes bioabsorbable stabilizing arms, clinch members 297o and 298o positioned up against the luminal wall of vein 91, with clinch member 295o and 296o positioned up against the luminal wall of artery 90. Bioabsorbable clinch member 295o, 296o, 297o and 298o provide stabilizing forces during implantation of clip 200 as well as during a post-implantation time period in which clip 200 is implanted. Clip 200 includes additional stabilizing arms, clinch members 295i and 296i, positioned along the luminal wall of vein 91, and clinch members 297i and 298i, positioned along the luminal wall of artery 90. Clinch members 295i, 296i, 297i and 298i are manufactured of non-bioabsorbable material, such as nitinol and/or other permanent materials described hereabove. In an alternative embodiment, clinch members 295i, 296i, 297i, and/or 298i are constructed of bioabsorbable materials that bioabsorb at a different rate than one or more of clinch members 295o, 296o, 297o and 298o. A mid-portion, clip connector 299, is attached to the stabilizing arms and defines lumen 94, shown as an elliptical shape, preferably with an equivalent diameter of approximately 5 mm.

[0129] Referring now to FIG. 42b, a side sectional view of clip 200′, implanted between artery 90 and vein 91 for a time period such as six months, is illustrated. Clip 200′ differs from clip 200 of FIG. 42a in that clinch members 295o, 296o, 297o and 298o of FIG. 42a are not present, having been bioabsorbed. During the bioabsorption time, clip 200′ has preferably been captured by tissue growth around clip connector 299 and/or clinch members 295i, 296i, 297i and/or 298i, the surrounding tissue growth providing a stabilizing force and obviating the need for clinch members 295o, 296o, 297o and 298o. In an alternative embodiment, one or more of clinch members 295o, 296o, 297o and 298o are not bioabsorbable, or bioabsorb at a different rate than one or more other stabilizing arms. In another alterative embodiment, one or more of mid-portion 299 and/or clinch members 295i, 296i, 297i and 298i are bioabsorbable, such as an absorption rate slower than clinch members 295o, 296o, 297o and/or 298o.

[0130] Referring specifically to FIG. 43, a perspective view of a shunt rivet of the present invention is illustrated, with typical materials and dimensions as described hereabove. Connector 380, of similar to construction to shunt rivet 80 of FIG. 27, includes bioabsorbable stabilizing arms, clinch members 381a, 381a′, 381v and 381v′, manufactured from one or more of the bioabsorbable materials described hereabove. Referring additionally to FIG. 44a, a side sectional view of clip 380, implanted between artery 90 and vein 91 is illustrated. Clinch members 381a and 381a′ are positioned up against the luminal wall of artery 90, and clinch member 381v and 381v′ are positioned up against the luminal wall of vein 91. Bioabsorbable clinch member 381a, 381a′, 381v and 381v′ provide stabilizing forces during implantation of clip 380 as well as during a post-implantation time period in which clip 380 is implanted. Clip 380 includes clinch member pair 382a and 382v, as well as clinch member pair 382a′ and 382v′, which maintain the luminal walls of artery 90 and vein 91 in proximity as well as provide long term stability for connector 380. Clinch members 382a, 382v, 382a′ and 382v′ are manufactured of non-bioabsorbable material, such as nitinol and/or other permanent materials described hereabove. Clip 380 is configured such that as the clinch members are deployed, the hoop strength of luminal portion is increased, overcoming any reduced material strength of a bioabsorbable material. In an alternative embodiment, clinch members 382a, 382a′, 382v and/or 382v′ are constructed of bioabsorbable materials that bioabsorb at a different rate than one or more of clinch members 381a, 381a′, 381v and 381v′. Within the center portion of shunt rivet 380 is lumen 94, preferably with an equivalent diameter of approximately 5 mm.

[0131] Referring now to FIG. 44b, a side sectional view of clip 380′, implanted between artery 90 and vein 91 for a time period such as six months, is illustrated. Clip 380′ differs from clip 380 of FIG. 44a in that clinch members 382a, 382a′, 382v and 382v′ of FIG. 44a are not present, having been bioabsorbed. During the bioabsorption time, clip 380 has preferably been captured by tissue growth around clip connector clinch members 381a, 381a′, 381v and/or 381v′, the surrounding tissue growth providing a stabilizing force and obviating the need for clinch members 382a, 382a′, 382v and 382v′. In an alternative embodiment, one or more of clinch members 382a, 382a′, 382v and 382v′ are not bioabsorbable, or bioabsorb at a different rate than one or more other stabilizing arms. In another alterative embodiment, one or more clinch members 381a, 381a′, 381v and/or 381v′ are bioabsorbable, such as at an absorption rate slower than clinch members 382a, 382a′, 382v and/or 382v′.

[0132] Referring specifically to FIG. 45, a top sectional view of a shunt rivet of the present invention is illustrated, with typical materials and dimensions as described hereabove. Connector 400 includes bioabsorbable stabilizing arms, clinch members 495o and 496o, manufactured from one or more of the bioabsorbable materials described hereabove. Clinch members 495o and 496o surround clinch members 495i and 496i, respectively. Clinch members 495i and 496i are constructed of non-bioabsorbable materials such as nitinol, and/or other permanent materials as have been described hereabove. Referring additionally to FIG. 46a, a side sectional view of clip 400, implanted between artery 90 and vein 91 is illustrated. Clip 200 further includes bioabsorbable stabilizing arms, clinch members 497o and 498o positioned up against the luminal wall of vein 91, with clinch member 495o and 496o positioned up against the luminal wall of artery 90. Bioabsorbable clinch member 495o, 496o, 497o and 498o provide stabilizing forces during implantation of clip 400 as well as during a post-implantation time period in which clip 400 is implanted. Clinch members 497o and 498o surround clinch members 497i and 498i, respectively. Clinch members 497i and 498i are constructed of non-bioabsorbable materials such as nitinol, and/or other permanent materials as have been described hereabove. The non-bioabsorbable portions of connector 400 may be constructed of a thin or small diameter material due to the increased support provided by the bioabsorbable portions. When the bioabsorbable portions are no longer present, tissue in-growth surrounding the permanent portions provides any additional strength necessary to adequately support long-term fistula flow. Permanent materials with thicknesses and diameters (ribbons or wires) as low as 0.003″, typically 0.005″ can be used in conjunction with the support that the bioabsorbable materials provide during the implantation procedure and early implant life. In an alternative embodiment, clinch members 495i, 496i, 497i, and/or 498i are constructed of bioabsorbable materials that bioabsorb at a different rate than one or more of clinch members 495o, 496o, 497o and 498o. A mid-portion, clip connector 499o surrounds clip connector 499i. Clip connector 499o is manufactured of bioabsorbable materials, and clip connector 499i is constructed of a permanent material or a material which bioabsorbs at a rate different than clip connector 499o. Clip connector 499o and/or 499i are attached to the stabilizing arms and define lumen 94, shown as an elliptical shape, preferably with an equivalent diameter of approximately 5 mm. In an alternative embodiment, lumen 94 may have a circular or other curvilinear shape, a polygonal cross section, or other geometry.

[0133] Referring now to FIG. 46b, a side sectional view of clip 400′, implanted between artery 90 and vein 91 for a time period such as six months, is illustrated. Clip 400′ differs from clip 400 of FIG. 46a in that clinch members 495o, 496o, 497o and 498o and clip connector 499o of FIG. 46a are not present, having been bioabsorbed. During the bioabsorption time, clip 400′ has preferably been captured by tissue growth around clip connector 499i and/or clinch members 495i, 496i, 497i and/or 498i, the surrounding tissue growth providing a stabilizing force and obviating the need for clinch members 495o, 496o, 497o and 498o and/or clip connector 499o. In an alternative embodiment, one or more of clinch members 495o, 496o, 497o and 498o, and clip connector 499o are not bioabsorbable, or bioabsorb at a different rate than one or more other stabilizing arms. In another alterative embodiment, one or more of mid-portion 499 and/or clinch members 495i, 496i, 497i and 498i are bioabsorbable, such as an absorption rate slower than clinch members 495o, 496o, 497o and/or 498o.

[0134] Referring specifically to FIGS. 47a and 47b, side and top sectional views of a shunt rivet of the present invention is illustrated, with typical materials and dimensions as described hereabove. Connector 500 is constructed of one or more of the bioabsorbable materials described hereabove. Connector 500 includes four stabilizing arms, clinch members 595, 596, 597 and 598, configured to be positioned against the luminal walls of a vein and artery pair, at a fistula site, as has been described in detail hereabove. Waist section 543 connects to clinch members 595, 596, 597 and 598 as shown. Waist section 543 comprises a flat portion of bioabsorbable material which has been rolled into a tube shape with end 545 overlapping an inner portion of waist section 543. Waist section 543 is configured similar to a rolled-stent design, such that waist section 543 can be expanded, such as with a balloon, preferably after placement within a fistula. Waist section 543 may include one or more interlocking ridges and grooves, and/or a textured surface, such that as waist section is expanded, the interlocking ridges and grooves ratchet open thereby and maintain the increased diameter when the expanding force is removed. The construction of connector 500 and waist section 543 is such that increased radial force is provided to the fistula, such as an increased radial force needed when connector 500 is constructed of one or more bioabsorbable materials.

[0135] In an alternative embodiment, waist section 543 is constructed of non-bioabsorbable material and/or materials that bioabsorb at a slower rate than clinch members 595, 596, 597 and 598. In another alternative embodiment, one or two of clinch members 595, 596, 597 and 598 are constructed of non-bioabsorbable material and/or materials that bioabsorb at a slower rate than the other of clinch members 594, 596, 597, and 598.

[0136] Referring specifically to FIGS. 48a and 48b, a first portion of a shunt rivet and a mating second portion of a shunt rivet, respectively, are illustrated, with typical materials and dimensions as described hereabove. FIG. 48a shows a top and side view of the first portion of the shunt rivet, and FIG. 48b shows a bottom and side view of the second portion of the shunt rivet. A connector comprises first portion 601 which is configured to mate with second portion 604, the mating procedure preferably occurring during the implantation procedure, such as with a single catheter that places both portions, or a first catheter in one vessel that places the first portion and a second catheter in the second vessel that mates the second portion to the first portion, catheters not shown. In a preferred embodiment, first portion 601 and second portion 604 are radiopaque or include radiopaque markers configured to provide visual feedback to assist in the mating process.

[0137] First Portion 601 includes flange 602 and cylinder 603, orthogonally attached to flange 602 and defining first lumen 94a. Second portion 604 includes flange 605 and cylinder 606, orthogonally attached to flange 605 and defining first lumen 94b. Lumens 94a and 94b are shown with a circular cross-section; however numerous mating geometries can be used, including tapered geometries.

[0138] Referring additionally to FIG. 49a, a side sectional view of clip 600, including first portion 601 and second portion 602 mated to each other and implanted between artery 90 and vein 91, is illustrated. Cylinder 603 of first portion 601 resides within and is frictionally or otherwise mechanically engaged to cylinder 606 of second portion 604. Flange 602 of first portion 601 is positioned against the luminal wall of artery 90, and flange 605 of second portion 602 is positioned against the luminal wall of vein 91.

[0139] First portion 601 and second portion 604 are constructed of bioabsorbable materials, as have been described hereabove. Referring to FIG. 49b, first portion 601 and second portion 604 have been bioabsorbed, such as during a time period of weeks or months, such that the fistula site has remodeled during the bioabsorption period. The remodeling is a physiologic change such as a change including endothelialization within the fistula lumen. In an alternative embodiment, one or more components of first portion 601 and/or second portion 604 are constructed of permanent implant materials or materials that bioabsorb at different rates than other bioabsorbable materials of first portion 601 or second portion 604.

[0140] Referring specifically to FIGS. 50a and 50b, a first portion of a shunt rivet and a mating second portion of a shunt rivet, respectively, are illustrated, with typical materials and dimensions as described hereabove. FIG. 50a shows a top and side view of the first portion of the shunt rivet, and FIG. 50b shows a bottom and side view of the second portion of the shunt rivet. A connector comprises first portion 701 which is configured to mate with second portion 704, the mating procedure preferably occurring during the implantation procedure, such as with a single catheter that places both portions, or a first catheter in one vessel that places the first portion and a second catheter in the second vessel that mates the second portion to the first portion, catheters not shown. In a preferred embodiment, first portion 701 and second portion 704 are radiopaque or include radiopaque markers configured to provide visual feedback to assist in the mating process.

[0141] First Portion 701 includes flange 702 and cylinder 703, with cylinder 703 having a tapered inside diameter defining a first lumen 94a. Second portion 704 includes flange 705 and cylinder 706, with cylinder 706 having a tapered inside diameter defining a second lumen 94b and being configured to mate with the taper of cylinder 703 of first portion 701. Lumens 94a and 94b are shown with tapered, circular cross-sections; however numerous tapered mating geometries can be used.

[0142] Referring additionally to FIG. 51a, a side sectional view of clip 700, including first portion 701 and second portion 702 mated to each other and implanted between artery 90 and vein 91, is illustrated. Cylinder 703 of first portion 701 resides within and is frictionally or otherwise mechanically engaged to cylinder 706 of second portion 704. Flange 702 of first portion 701 is positioned against the luminal wall of artery 90, and flange 705 of second portion 702 is positioned against the luminal wall of vein 91.

[0143] First portion 701 and second portion 704 are constructed of bioabsorbable materials, as have been described hereabove. Referring to FIG. 51b, first portion 701 and second portion 704 have been bioabsorbed, such as during a time period of weeks or months, such that the fistula site has remodeled during the bioabsorption period. The remodeling is a physiologic change such as a change including endothelialization within the fistula lumen. In an alternative embodiment, one or more components of first portion 701 and/or second portion 704 are constructed of permanent implant materials or materials that bioabsorb at different rates than other bioabsorbable materials of first portion 701 or second portion 704.

[0144] Referring to FIGS. 52 through 52c, a shunt rivet including a dual material mesh surface is illustrated, with typical dimensions as described hereabove. FIG. 52 shows venous end and side sectional views of shunt rivet 800. Shunt rivet 800 comprises a dual material construction. A clip connector 899 has a tubular geometry with a first end and a second end and includes wire mesh 801c which is intertwined with fabric mesh 802c. Venous portion 810 has a flared geometry configured to mate with the contour of an inner wall of a vein. Venous portion 810 is attached at the first end of the clip connector 899 and includes wire mesh 801v which is intertwined with fabric mesh 802v. Arterial portion 820 has a flared geometry configured to mate with the contour of an inner wall of an artery, adjacent the vein. Arterial portion 820 is attached to the second end of the clip connector 899 and includes wire mesh 801a which is intertwined with fabric mesh 802a. Clip connector 899 defines lumen 94, shown with a constant diameter cross-section. In alternative embodiments, clip connector 899 may have a non-constant cross-section such as a tapered cross-section. One or more portions of shunt rivet 800 may be radiopaque and/or include one or more visualization markers such as ultrasound or other markers. Wire mesh 801a, 801c and 801v are constructed of on or more resilient, biocompatible materials, such as nitinol, spring steel, glass or carbon composites or polymers, or pseudoelastic (at body temperature) materials such as nitinol or comparable alloys and polymers. Fabric mesh 802a, 802c and 802v are constructed of a biocompatible mesh material such as a biocompatible fabric material such as Dacron, PTFE, or other biocompatible, flexible material. In a preferred embodiment, wire mesh 801a, 801c and/or 801v provide structural support such as to provide radial support to lumen 94 and/or stabilizing forces to maintain the position of shunt rivet 800 in a fistula. In another preferred embodiment, fabric mesh 802a, 802c and/or 802v provide a barrier, such as a barrier which prevents bleeding or neointimal proliferation. In yet another preferred embodiment. One or more of wire mesh 801a, 801c and/or 801v, and/or fabric mesh 802a, 802c and/or 802v include one or more coatings or agents, such as anti-infective agents and/or anti-thrombotic agents. The wire mesh wires of the present invention may be round and typically have a diameter from 0.001″ to 0.005″. Alternatively, flat or ribbon wire may be used, typically with a thickness of 0.001″ to 0.005″. The fabric mesh of the present invention typically has a pore size between 0.001″ and 0.025″.

[0145] Referring to FIG. 52a, venous end and sectional side views of shunt rivet 800 placed between artery 90 and vein 91 are shown. Clip Connector 899 is placed between artery 90 and vein 91 defining lumen 94. Arterial portion 810 conforms to the inner wall of artery 90 and venous portion 820 conforms to the inner wall of vein 91. Referring to FIG. 52b, another side sectional view of shunt rivet 800 is shown. Arterial portion 810 includes wire mesh 801a and fabric mesh 802a. Channel Portion 899 includes wire mesh 801c and fabric mesh 802c. Venous portion 820 includes wire mesh 801v and fabric mesh 802v. Wire mesh 801a may be of similar or dissimilar construction or materials to wire mesh 801c or 801v. Fabric mesh 802a may be of similar or dissimilar construction or materials to fabric mesh 802c or 802v. In a particular embodiment, different thicknesses are used for one or more of the arterial portion, channel portion or venous portion for the wire or fabric meshes. In another particular embodiment, not shown, the arterial portion is connected directly to the venous portion, with the inclusion of a channel portion.

[0146] Referring now to FIG. 52c, a preferred embodiment of a clip connector 800′ is shown in which fabric mesh 802a, 802c and 802v have been bioabsorbed, such as during of time period between twenty four hours and six months. In an alternative embodiment, one or of fabric mesh 802a, 802c and 802v are not bioabsorbed. In another alternative embodiment, one or more of wire mesh 801a, 801c and/or 801v are also bioabsorbed. In another alternative embodiment, the mesh material may comprise only wire mesh or fabric mesh materials as described above. In another alternative embodiment, a wire frame, not shown, is included which surrounds one or more of wire mesh 801a, 801c and/or 801v and/or fabric mesh 802a, 802c and/or 802v, such as a wire material with a greater cross-sectional area (e.g. diameter) than the wire material of wire mesh 801a, 801c and/or 801v. The wire frame material may be a similar or dissimilar material to wire mesh 801a, 801c and/or 801v.

[0147] The devices described above are configured to be placed between two body areas that have two tissue walls separating them, such as body areas including but not limited to: ventricles of the heart, vessels such as arteries and veins, and other body spaces that include a wall that is proximate the wall of another body space. The devices described above define a lumen through which blood or other fluid may flow from a first body space to a second body space, such as the lumen of an artery to the lumen of a vein. These lumens may have one or more forms of cross-sectional geometry, such as circles, ellipses, triangles, polygons, other geometric shapes and combinations of these. Combinational shapes may include a first elliptical shape at one end of the lumen, and a circular or other elliptical shape at the other end of the lumen.

[0148] The devices described above may include one or more markers, such as radiopaque, ultrasonic, magnetic or other visualizable markers, to assist in visualizing the device during the implantation procedure. The devices described above may be provided with coatings or additional structures which serve as matrices for various therapeutic compounds. Drug eluting coatings, additional drug eluting strut members, drug eluting membranes surrounding the central section or drug eluting masses filling the cells of the device may be added to the devices. For the aortocaval application and the arterio-venous application, therapeutic agents such as heparin and other anti-coagulants and paclitaxol, rapamycin (Sirolumis™), everolimus and other anti-stenotic compounds can be applied to the stent in polymer matrices which permit elution of these drugs over a period of time ranging from several hours to several months after implantation. Polymers such as polyurethane can be used as the matrix.

[0149] While the preferred embodiments of the devices and methods have been described in reference to the environment in which they were developed, they are merely illustrative of the principles of the inventions. Modification or combinations of the above-described assemblies, other embodiments, configurations, and methods for carrying out the invention, and variations of aspects of the invention that are obvious to those of skill in the art are intended to be within the scope of the claims.