US20110295181A1 - Implantable and removable customizable body conduit - Google Patents

Abstract

An apparatus and method are provided to treat a stenosis. A delivery device is provided that has an elongate tubular member coupled therewith. The elongate tubular member has an outside surface that is configured to prevent adherence of in vivo matter. The tubular member has a proximal end and a distal end and is reinforced along its length to maintain open lumen under a transverse load. The tubular member is placed in the vasculature such that the distal end of the elongate tubular member is disposed distal of a stenosis. The proximal end of the elongate tubular member is disposed inside the vessel, preferably at a location proximal of the stenosis. Thereafter, after a therapeutic period, the elongate tubular member is removed intact.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a continuation-in-part of U.S. application Ser. No. 12/397,275, filed Mar. 3, 2009, which claims the benefit of U.S. Provisional Application No. 61/034,125, filed Mar. 5, 2008, which is hereby incorporated by reference herein its entirety. Each of the following applications also is incorporated by reference herein in its entirety: U.S. application Ser. No. 11/600,589, filed Nov. 16, 2006, U.S. application Ser. No. 11/216,536 filed on Aug. 31, 2005, and U.S. application Ser. No. 10/962,200, filed on Oct. 8, 2004.
BACKGROUND OF THE INVENTIONS
• 1. Field of the Inventions
• This application relates to systems and methods for treating or bypassing stenosis in a body conduit, and connecting multiple portions of fluid carrying conduits.
• 2. Description of the Related Art
• In the United States, approximately 400,000 people have end-stage renal disease requiring chronic hemodialysis. Permanent vascular access sites for performing hemodialysis may be formed by creating an arteriovenous (AV) anastomosis whereby a vein is attached to an artery to form a high-flow shunt or fistula. A vein may be directly attached to an artery, but it may take 6 to 8 weeks before the venous section of the fistula has sufficiently matured to provide adequate blood flow for use with hemodialysis. Moreover, a direct anastomosis may not be feasible in all patients due to anatomical considerations. Other patients may require the use of artificial graft material to provide an access site between the arterial and venous vascular systems.
• Although many materials that have been used to create prosthetic grafts for arterial replacement have also been tried for dialysis access, expanded polytetrafluoroethylene (ePTFE) is the preferred material. The reasons for this include its ease of needle puncture and particularly low complication rates (pseudo-aneurysm, infection, and thrombosis). However, AV grafts still require time for the graft material to mature prior to use, so that a temporary access device, such as a Quinton catheter, must be inserted into a patient for hemodialysis access until the AV graft has matured. The use of temporary catheter access exposes the patient to additional risk of bleeding and infection, as well as discomfort. Also, patency rates of ePTFE access grafts are still not satisfactory, as the overall graft failure rate remains high. Sixty percent of these grafts fail yearly, usually due to stenosis at the venous end. (See Besarab, A & Samararpungavan D., “Measuring the Adequacy of Hemodialysis Access”.Curr Opin Nephrol Hypertens5(6) 527-531, 1996, Raju, S. “PTFE Grafts for Hemodialysis Access”.Ann Surg206(5), 666-673, November 1987, Koo Seen Lin, L C & Burnapp, L. “Contemporary Vascular Access Surgery for Chronic Hemodialysis”.J R Coll Surg41, 164-169, 1996, and Kumpe, D A & Cohen, M A H “Angioplasty/Thrombolytic Treatment of Failing and Failed Hemodialysis Access Sites: Comparison with Surgical Treatment”.Prog Cardiovasc Dis34(4), 263-278, 1992, all herein incorporated by reference in their entirety). These failure rates are further increased in higher-risk patients, such as diabetics. These access failures result in disruption in the routine dialysis schedule and create hospital costs of over $2 billion per year. See Sharafuddin, M J A, Kadir, S., et al. “Percutaneous Balloon-assisted aspiration thrombectomy of clotted Hemodialysis access Grafts”.J Vasc Interv Radiol7(2) 177-183, 1996, herein incorporated by reference in its entirety.
• Many individuals have vascular segments that are stenosed, narrowed, occluded, or otherwise compromised to inhibit flow. This is frequently a problem in dialysis patients due to placement of previous catheters for dialysis access, as described by Davis, D, Petersen, J, Feldman, R, et al.Subclavian venous stenosis. A complication of subclavian dialysis.JAMA 1984; 252:3404. The stenosis is commonly caused by dialysis catheters presence in the subclavian vein. Edema, pain and discomfort in the arm are frequently reported in these individuals. These side effects are often accelerated during dialysis sessions.
SUMMARY OF THE INVENTIONS
• In one method, a stenosis is treated to improve the patency of a vascular segment. In the method, a delivery device is provided that has an elongate tubular member coupled therewith. The elongate tubular member has an outside surface that is configured to prevent adherence of in vivo matter. For example, a very smooth and impermeable surface can be provided. As discussed below, silicone is a material that can have such properties. The tissue and vasculature response is minimal due to the biocompatibility, surface finish, lack of porosity and possibly compliance and/or surface energy of silicone. Other materials providing comparable properties in one or more of these areas may be suitable substitutes, as elaborated below. The tubular member has a proximal end and a distal end and is reinforced along its length to maintain open lumen under a transverse load. The delivery device and the tubular member are advanced into the vasculature such that the distal end of the elongate tubular member is disposed distal of a stenosis. The proximal end of the elongate tubular member is disposed inside the vessel, preferably at a location proximal of the stenosis. Thereafter, the elongate tubular member is separated from the delivery device to deploy the elongate tubular member. The deployed elongate tubular member remains in the body as the delivery device is removed. The deployed elongate tubular member provides a stenting or dilating effect and thereby displaces the stenosis radially outward and expands the vessel lumen. Thereafter, after a therapeutic period, the elongate tubular member is removed intact. The therapeutic period can be defined as one in which remodeling of the vessel occurs.
• As used herein “remodeling” is a broad term and includes the durable widening of a previously narrowed body vessel to a larger size, permitting a greater degree of flow, less flow resistance, less back pressure, and/or other flow benefits. The embodiments described herein can find application in any body conduit, such as any blood vessel. Arterial and venous vessels can be treated with these apparatuses and methods. Also, a variety of such vessels of different size and body regions can be treated. This method can be applied anywhere in the vasculature, but is has been tested with great success in the venous vasculature. Other body lumens outside the vascular system can be treated as well, including the esophagus, respiratory and nasal passages, lumens of the gastro-intestinal track, urinary tract, biliary duct.
• A delivery device can be provided that is configured to couple with the elongate tubular member to apply an axial force, e.g., an tensile axial force, to actuate the elongate tubular member from an expanded configuration capable of providing the open lumen, as discussed above, to a low crossing profile configuration. The delivery device can be advanced with the tubular member disposed thereon or therein in the low crossing profile configuration. The delivery device can be configured to release the tensile axial force to permit the tubular member to move from the low crossing profile configuration to the expanded configuration.
• In various applications, the treatment envisions removing the tubular member after a therapeutic period. In other words, the tubular member is intended to be a temporary implanted structure. The therapeutic period can be as few as 1 day. In some cases, the therapeutic period can be up to 12 months. Significant permanent benefit may take approximately 2 months.
• In another aspect, a method of bypassing a stenosis in the vasculature is provided. In this method, a first graft member is coupled with a first vessel segment upstream of the stenosis and a second graft member is coupled with a second vessel segment downstream of the stenosis. A first end of the blood flow conduit is coupled with the first graft member and a second end of the blood flow conduit with the second graft member by applying a connection force, e.g., providing relative motion between an end of the blood flow conduit and a connector disposed on an end of one of the graft members. Both the first and second ends of the blood flow conduit are disposed outside the vasculature. When the first and second grafts are connected to the blood flow conduit, a force required to disconnect the blood flow conduit from the first or second graft is significantly higher than the connection force. In some variations of this method, one or both of the first and at least a portion of the blood flow conduit are disposed beneath the skin of the patient.
• In another aspect, a method bypasses a stenosis and provides vascular access for a periodic therapeutic procedure, such as hemodialysis. A distal blood conduit and a proximal blood conduit comprising a graft and a connector are provided. The connector has a retention feature located thereon. The distal blood conduit includes a catheter comprising a braided structure embedded therein. A distal zone of the distal blood conduit is inserted into the vasculature and through a stenosis in the vasculature. In some embodiments, the distal end includes an outlet and the outlet is positioned anywhere beyond the stenosis but still within the vasculature. Downstream of the distal end, the blood exits the blood conduit and rejoins flow in the cardiovascular system.
• Though not required in all methods of bypassing a stenosis and providing vascular access, the catheter can be cut through the braided structure to size the catheter in-situ. The catheter is advanced over a distal segment of the connector until at least a portion of the braided structure is positioned proximal of the retention feature. Also, although this method has been discussed herein in the context of a multi-component blood conduit, for bypassing a stenosis and providing vascular access, not all embodiments need be multi-component.
• Furthermore, in certain variations of this method of bypassing a stenosis and providing vascular access, it is desired to also provide a treatment in which the stenosis is remodeled. A variety of techniques for configuring a conduit to provide for remodeling are discussed herein and can be used to provide remodeling in conjunction with bypassing a stenosis and providing vascular access.
• In another aspect, a system for bypassing a stenosis is provided. The system includes a catheter, a first connector, and a second connector. The catheter has a proximal portion, a distal portion, and an elongate body extending between the proximal and distal portions. The elongate body defined an inner wall having an inner perimeter defining a blood flow lumen. The catheter has a braided structure embedded in the elongate body and disposed about the lumen. The first connector is for fluidly coupling a first vascular graft with the proximal portion of the catheter. The first connector comprises a connector body and an engagement feature. The connector body has an outer surface defining a first outer perimeter and an inner surface defining a lumen. The engagement feature is disposed on the outer surface of the connector body adjacent a distal end thereof. The engagement feature defines a second outer perimeter greater than the first outer perimeter. The second connector is configured to securely engage a second vascular graft with the distal portion of the catheter. The proximal portion of the catheter has a first configuration in the free state and a second configuration when in axial compression. In the first configuration, the inner perimeter is less than the first outer perimeter. In the second configuration, the braided structure expands to permit the inner perimeter of the catheter body to expand such that the proximal end portion of the catheter can be advanced over the engagement feature of the connector body.
BRIEF DESCRIPTION OF THE DRAWINGS
• The structure and method of using the invention will be better understood with the following detailed description of embodiments of the invention, along with the accompanying illustrations, in which:
• FIG. 1 is a perspective view of a vascular access system having a proximal end adapted to couple with a first vascular segment and a distal end adapted for insertion into a second vascular segment;
• FIG. 2 is a perspective view of a catheter that has a distal portion adapted for positioning in a blood vessel and a proximal portion configured to provide an enhanced connection to another blood conduit;
• FIG. 2A is a schematic view of a distal portion of the catheter illustrating techniques for embedding a braided structure therein;
• FIG. 3 is a side view of a reinforcement member configured to be incorporated into the blood flow conduit ofFIG. 2;
• FIG. 3A is an end view of one braided member of the braided structure ofFIG. 3;
• FIG. 4 is a plan view of a connector that is adapted to couple a first blood flow conduit with a second blood flow conduit;
• FIG. 5 is a graph illustrating a retention force for various engagement mechanisms described herein;
• FIG. 6 is a graph illustrating a retention force corresponding to various techniques for connecting an engagement mechanism having two barbs;
• FIG. 7 is a graph illustrating a retention force for an engagement mechanism having a braided structure with different pic counts;
• FIG. 8 is a graph of attachment forces for various embodiments;
• FIG. 9 illustrates schematically a method of treating a stenosis in a blood vessel using an elongate tubular member;
• FIG. 9A illustrates a distal portion of one embodiment of a delivery device capable of delivering a temporary stent for a body conduit;
• FIG. 10 illustrates a method of bypassing a stenosis; and
• FIG. 11 illustrates a system for and method of bypassing a stenosis in the vasculature.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
• This application relates to new vascular access systems, new connector systems, and new fluid-carrying conduits. The fluid carrying conduits are arteriovenous (AV) shunts or catheters in various embodiments. Some of the embodiments described herein may be incorporated into a hemodialysis system. These embodiments also can be used to treat or bypass stenoses in the vasculature, as discussed below.
• Hemodialysis treatments and vascular access devices therefore are discussed in greater detail in U.S. patent applications Ser. No. 10/962,200 (US Publication No. 2005-0137614-A1), Ser. No. 11/216,536 (US Publication No. 2006-0064159 A1), and Ser. No. 11/600,589 (US Publication No. 2007-0167901 A1) and in U.S. Pat. Nos. 6,102,884 and 6,582,409. The embodiments described herein can be combined with the systems and methods of any of these applications and patents, all of which are hereby incorporated by reference in their entirety.
• As will be understood in view of the description herein provided, the new connector systems and apparatuses can improve one or more areas of performance of vascular access systems. For example, the embodiments described herein improve in-situ connection of a catheter, or other blood-carrying conduit, configured for use as an outflow component, to another component or device of a vascular access system or to a plurality of other components of a bypass system.
• In some embodiments, a reinforcement member can be incorporated into a blood conveying system (e.g., in a proximal portion of a catheter or other blood carrying conduit) to enhance the security of a connection between a catheter and another component of the system. In some cases, the reinforcement member also extends through a substantial portion of the length of a blood carrying conduit to improves kink and crush resistance of the fluid carrying conduit. The reinforcement can also provide enhanced hoop strength or outwardly directed hoop stress to displace tissue, e.g., subcutaneous tissue around blood vessels or stenotic matter creating blockages in vessels. These and other advantages of the new devices and methods described herein could be useful in a number of environments that employ a vascular access system, such as vascular access devices, ventricular assist devices, total artificial hearts, and various types of hemodialysis systems.
• Environments in which these improvements could be used include short-term applications (e.g., several days to a week) and longer-term application. For example, the improvements described herein are useful in longer-term applications of 30 days or more. The improvements described herein are useful in longer-term applications of 90 days or more. In some cases, the improvements described herein are useful in long-term applications of 1 year or more. The embodiments described herein can be incorporated into short-term and into longer-term applications for dialysis. Discussed further below in connection withFIG. 9, certain apparatuses discussed herein could be used or modified by use as temporary stents to assist in remodeling the vasculature to improve patency during and after a therapeutic period.
• As will be discussed below, a braided structure can be incorporated into a fluid-carrying conduit. In some embodiments, the braided structure can be embedded in an elongate body of the fluid-carrying conduit, providing a smooth relatively constant outer surface. The braided structure can improve the security or integrity of the connection between the blood-carrying conduit and other structures to which it is attached. In various embodiments, these innovations provide greater durability and manufacturability. In addition, the implantation process can be enhanced, such as by providing better connectability and, in some cases, a tactile confirmation of the security of a connection, as discussed below. In some cases, a visual confirmation of the security of a connection can be provided.
• FIG. 1 depicts one embodiment of avascular access system10 that is configured to shunt blood from a first vascular segment to a second vascular segment. Thevascular access system10 can take any suitable form, but preferably the system is adapted to be implanted beneath the skin of the patient. In one embodiment, thevascular access system10 is implanted primarily extravascularly, though a distal portion thereof may reside in or extend through a blood vessel. Thevascular access system10 can be partly or completely implanted. Various techniques for implanting are discussed below, including placement of at least a portion of thesystem10 in a vascular segment.FIG. 10 illustrates methods of using acatheter system10A similar to the access systemFIG. 1 to provide improved blood flow through a stenotic region of a blood vessel. In this method, thesystem10A can be used solely for improving patency through the stenosis or both for improved flow and access during a dialysis or other periodic therapeutic procedure. Also, acatheter system10B similar to thevascular access system10 can be implanted in a subcutaneous tunnel, as discussed further below.FIG. 11 illustratescatheter system10B that is configured to provide bypass of a stenotic vascular segment where thesystem10B is disposed in a subcutaneous tunnel. Additional details of processes for implantation are discussed in the patents and applications listed above, which are incorporated by reference herein.
• With continued reference toFIG. 1, thevascular access system10 has aproximal end14 and adistal end18 and alumen20 that extends between the proximal and distal ends14,18. Theproximal end14 can be adapted to couple with, e.g., attached to, a first vascular segment and thedistal end18 can be adapted to be coupled with, e.g., inserted into a second vascular segment. Thelumen20 preferably extends between the proximal and distal ends14,18 and provides a pathway for blood to flow between the first and second vascular segments. Thelumen20 also can be accessed from outside the patient to facilitate dialysis or other treatment. In some applications and embodiments, thelumen20 provides blood flow from an upstream to a downstream location without any periodic access required or anticipated.
• The first and second vascular segments are arterial or venous vascular segments in various techniques. For example, theproximal end14 can be adapted to be coupled with a brachial artery or other artery that resides close to the skin. Any suitable coupling between theproximal end14 and the first vascular segment can be used. In one embodiment theproximal end14 can be attached by an end-to-side anastomosis to a brachial artery. Thedistal end18 can be adapted to couple with or extend into a vein, e.g., in the central venous system, as discussed below and in the application incorporated by reference herein.
• In one embodiment, thevascular access system10 includes a plurality of components that can be assembled to form thelumen20. In one embodiment, a firstblood carrying conduit22 extends from theproximal end14 toward thedistal end18 and a secondblood carrying conduit26 extends from the distal18 toward theproximal end14. In one embodiment a thirdblood carrying conduit30 is positioned between the first and secondblood carrying conduits22,26. As discussed below, the thirdblood carrying conduit30 is adapted to connect the first and secondblood carrying conduits22,26 together in various embodiments.
• Where provided, the thirdblood carrying conduit30 enables the first and secondblood carrying conduits22,26 to have different characteristics that are well suited for the unique ways in which these conduits interact with the vasculature. For example, the firstblood carrying conduit22 can be specifically configured to be integrated into the vessel with which it is coupled, e.g., by anastomosis connection to an artery. Also, the secondblood carrying conduit26 can be specifically configured to interact with a vascular segment to minimize the likelihood of adverse side effects, e.g., by being flexible or otherwise formed to enable a distal portion of theconduit26 to extend into the central venous system and interact in an atraumatic manner with vessel walls and other tissues in the vasculature or heart. Thus, this innovation pertains to the unique requirements of a device that perform both as a permanently implanted extravascular graft and as an intravascular catheter.
• FIG. 11 illustrates embodiments in which one or more additional blood carrying conduits may be incorporated into asystem10B to provide a bypass system. As discussed above, this can enable end portions to couple with blood vessels and a central portion to have an enhanced patency configuration.
• Thevascular access system10 and thebypass system10B can be configured with one ormore engagement mechanism32 that enhances the security of a connection between two blood carrying conduits of the system. Theengagement mechanism32 can include multiple portions with at least one portion located on the secondblood carrying conduit26 and at least one portion is located on the thirdblood carrying conduit30. In some embodiments, theengagement mechanism32 is configured such that the connection formed thereby requires a greater force to disconnect than is required to connect the second and thirdblood carrying conduits26,30. This provides greater security of and confidence in the connection at theengagement mechanism32.
• In various embodiments, theengagement mechanism32 includes anengagement feature33 located on one of the second and thirdblood carrying conduits26,30 and anenlargeable portion34 on the other of the second and thirdblood carrying conduits26,30. For example, as discussed in more detail below, the thirdblood carrying conduit30 can include at least one barb and the secondblood carrying conduit26 can be formed to apply an inward and sometimes distally directed force on the barb to resist disconnection of the conduits. In one embodiment, a distal portion of the thirdblood carrying conduit30 includes two barbs. In one embodiment, the secondblood carrying conduit26 includes a braided structure or otherexpandable reinforcement member35 that generates a compressive force on the barb or barbs to enhance the security of theengagement mechanism32.FIG. 1 only shows the braided structure partially for clarity. As discussed further below, the braided structure can extend to theproximal end14 and toward thedistal end18. Various additional examples of features of engagement mechanisms are discussed below.
• In some embodiments, thevascular access system10 also includes anengagement mechanism36 that facilitates coupling the firstblood carrying conduit22 with a distal portion of thelumen20. As discussed further below, theengagement mechanism36 can be incorporated into a proximal portion of a connector. In other embodiments, the first andthird conduits22,30 can be unitary in construction such that theengagement mechanism36 is not required.
• The firstblood carrying conduit22 can take any suitable form for providing fluid communication between a patient's vascular system and thelumen20. In one form the firstblood carrying conduit22 is a graft formed of a suitable material, e.g., ePTFE. In some applications, it is desirable to provide access to thelumen20 very soon after implantation of thesystem10. Various features for enabling access very soon after implantation, if not immediately thereafter, are discussed in the applications incorporated by reference herein above, including U.S. application Ser. No. 11/216,536 (US Publication No. 2006-0064159 A1) and Ser. No. 11/600,589 (US Publication No. 2007-0167901 A1). Other suitable biocompatible materials can be used and these will be apparent to one skilled in the art.
• Although illustrated in an AV shunt context, the engagement mechanism is also relevant to other context. Accordingly, the firstblood carrying conduit22 could be a proximal portion of a connector, or a component of another system that conveys blood, e.g., in a ventricular assist device. Also, as discussed in connection withFIGS. 10-11, the engagement mechanism can be useful for systems and methods directed to bypassing a stenosis.
• In one embodiment, the secondblood carrying conduit26 is configured as a catheter for returning blood to a patient's vasculature. In some embodiments, theconduit26 is an outflow component of thesystem10. The catheter preferably is adapted such that, in use, at least a distal end portion thereof can freely float within a vascular segment when thevascular access system10 is applied to a patient. This feature reflects research that indicates that graft failures from localized stenosis at the venous end of AV grafts are primarily due to intimal hyperplasia, compliance mismatch between the graft and the native vein anastomosis, and turbulent flow at the anastomosis site. Kanterman R. Y. et al “Dialysis access grafts: Anatomic location of venous stenosis and results of angioplasty.” Radiology 195: 135-139, 1995. We hypothesize that these causes could be circumvented by eliminating the venous anastomosis and instead, using a fluid carrying conduit to discharge the blood directly into the venous system. We have developed vascular access system that eliminates the venous anastomosis in the AV shunt, using a catheter element at the venous end and a synthetic graft element anastomosed to the artery in the standard fashion. We believe that such system should eliminate or reduce venous hyperplasia, which is the largest reason for AV shunt failure.
• Accordingly, at least a portion of the second blood carrying conduit26 (e.g., a distal portion thereof) can be configured to freely float to provide atraumatic interaction with the blood vessel. Such a configuration also can minimize the likelihood of damage to the vessel in which the distal end portion resides by minimizing trauma to the vessel. This approach is also relevant to the bypass technique ofFIG. 10, discussed below, where a first zone is configured to expand into engagement with and in fact remodel a stenosis while a second zone is configured to freely float to minimize adverse trauma at the second zone.
• In some embodiments, theconduit30 or portions thereof can be integrated into another component, e.g., into the firstblood carrying conduit22. Thus, thesystem10 can be configured with less than three, e.g., only two, separate blood carrying conduits. Additionally, the primary function of the thirdblood carrying conduit30 is to couple the first and secondblood carrying conduits22,26 and thus the third blood carrying conduit need not be exposed to blood or form a part of thelumen20 in all embodiments.
• FIG. 2 shows one embodiment of acatheter100 that can be used in thevascular access system10. As used herein “catheter” is a broad term that includes any blood carrying conduit that can be at least partially inserted into a blood vessel and advanced therein to a selected location, including into the atrium. Thecatheter100 can take any suitable form, consistent with the below description. In some embodiments, the catheter is configured as an outflow component.
• Thecatheter100 has aproximal portion104, adistal portion108, and anelongate body112 that extends therebetween. In some applications, thecatheter100 is configured such that theproximal portion104 is connectable over a barb, as discussed below, to enhance securement of thecatheter100 to a connector, which can be incorporated into theconduit30. Theproximal portion104 preferably also is trimmable such that the length of thecatheter100 can be determined in-situ. In one embodiment, thecatheter100 also has a sizingregion114 that facilitates customizing the size of thecatheter100 to the patient. In one embodiment, the sizingregion114 is located in theproximal portion104 of thecatheter100. As will be discussed further below, the sizingregion114 can be trimmed or cut through to reduce the length of thecatheter100. Preferably the sizingregion114 is configured to be cut by hand using any standard cutting implement that would be present in the operating room, such as surgical scissors.
• Theelongate body112 preferably defines aninner wall116 that surrounds ablood flow lumen120. Theinner wall116 has aninner perimeter124 that in part defines the blood flow capacity of thecatheter100. In one embodiment, theblood flow lumen120 is substantially cylindrical and theinner wall116 and theinner perimeter124 define are substantially circular in cross-section. In one embodiment, theblood flow lumen120 has an inner diameter of about 5.0 mm. Lumens of other shapes can be used as well, as will be understood by one skilled in the art. Forming thelumen120 to have a 5.0 mm diameter lumen provides a benefit of being able to handle sufficient blood flow for dialysis while permitting the outer size of thecatheter100 to be small enough to be insertable into the internal jugular vein in one technique. The outer size andinner perimeter124 of thecatheter100 can be substantially constant through the length of thelumen120 or can vary as will be understood by one skilled in the art.
• FIG. 9 below discusses using astent400 with a configuration that is similar to that of thecatheter100. Accordingly, the features of thecatheter100 are incorporated below in the discussion of thestent400. Thestent400 may have an inner perimeter, e.g., diameter, of anywhere from 1.0-15 mm depending on the applications. A variety of embodiments for vascular therapies have an expanded size in the range of about 5.0 mm to about 14.0 mm. In some embodiments particularly suited for neurological therapies, thestent400 can be configured to expand to an inner size of between about 2.0 mm and about 4.0 mm. In other embodiments particularly suited for therapies in carotid vessels, thestent400 can be configured to expand to an inner size of between about 6.0 mm and about 10.0 mm.
• Theelongate body112, particularly theinner wall116 can be configured to provide adequate hemocompatibility such that blood flowing therethrough is not damaged or adversely affected thereby. Theblood flow lumen120 preferably is configured to convey blood in a substantially atraumatic manner between theportions104,108. In one embodiment theinner wall116 is sufficiently smooth in surface finish to minimize turbulence at the wall. If thecatheter100 is integrated into the vascular access system10 (e.g., as the second blood carrying conduit26), thelumen120 can form a portion of thelumen20. Other portions of thelumen20 can be defined in one or both of the first and thirdblood carrying conduits22,30.
• Thecatheter100 preferably is configured such that in use thedistal portion108 can freely float within a vascular segment. As discussed elsewhere herein, thesystem10 can be applied such that thedistal portion108 is positioned in, extends within, or is inserted through a blood vessel, e.g., in the central venous system. Accordingly, thedistal portion108 preferably is configured to have a smaller outer size than the vessel in which it resides. This enables blood to pass around thedistal end portion108. For example, thedistal portion108 can reside in the central venous system in such a manner that blood flows between an outer surface of thedistal portion108 and an inner surface of the blood vessel. In one embodiment, thedistal portion108 of thecatheter100 has an outer perimeter that is substantially circular with an outer diameter of about 6.1 mm. In comparison, the typical vessel through which thedistal portion108 can be inserted is about 8-20 mm. In some patients, a portion of the central venous system, e.g., the internal jugular vein, can be stenosed, reducing its size significantly. In some cases, the internal jugular vein has a lumen that is as small as 0 to 1 mm in width. These patients may benefit form a method and a device capable of enlarging the lumen in the internal jugular vein or other vessel of the central venous system, as discussed below. Although larger catheters can be used for some patients and for some other applications, 6.1 mm is a size that is particularly well suited for insertion into an internal jugular vein of an adult human patient. Smaller catheters can be used for certain techniques, e.g., for more peripheral applications.
• FIG. 10 illustrates a bypass application, in which a zone of acatheter100′ between the distal portion and the proximal portion thereof is large enough to engage a stenotic lesion, e.g., having an outside diameter that is larger than non-stenotic vessel bore by a percentage appropriate to compensate for vessel recoil upon withdrawal. For example, recoil observed during angioplasty of veins and arteries with interventional techniques is typically 20-30%. The venous system is more elastic and therefore may be on the upper end of this range. It is anticipated that the invention will take up to or less than this amount due to the longer treatment period (stent implant vs. balloon intervention). Therefore, in various embodiments, the outer perimeter (e.g., diameter) is about 20-30% larger than the non-stenotic vessel bore to produce the therapeutic effect. In some treatments, e.g., with longer therapeutic period, the outer perimeter (e.g., diameter) is larger than the non-stenotic vessel bore by up to about 20% to produce the therapeutic effect. One embodiment provides for sizing the stenosis engagement zone at about 20% of the non-stenotic vessel bore where the therapeutic period is at least about 2 months to produce the therapeutic effect.
• The dimensions of thesystem10 and the components described herein that can be used in thesystem10 are not limiting. Rather the dimensions provide examples of specific embodiments. For other applications, other dimensions may be appropriate. For example, the outer diameter of thedistal portion108 of thecatheter100 need not be 6.1 mm but rather would be a function of the vessels into which it is to be inserted. In other applications currently contemplated, the outer diameter of thedistal portion108 could be about 4 mm to about 8 mm. More generally, the outer diameter can be within a range of about 2 to about 14 mm.
• Additionally, as discussed below, thedistal portion108 preferably is formed to be relatively flexible. The flexibility permits thedistal portion108 to relatively gently interact with the blood vessel in which it resides. In one application, thecatheter100 is applied through a superficial vessel and is advanced through the internal jugular vein toward the heart. In this environment, a relatively low stiffness construction is sufficient for delivery of thedistal portion108 thecatheter100.
• FIG. 2A illustrates one approach to making thecatheter100 more flexible in which a soft material is incorporated into theelongate body112. In various embodiments, all or a portion of theelongate body112 can be formed of any suitable flexible elastomer, such as polyurethane, CFlex, SIBS (styrene isoprene butadiene) or polyolephins. In one example, silicone tubing can be used in aninner portion100A of thecatheter100. More generally, theelongate body112 can be formed of an implantable thermoplastic elastomer. In one embodiment, silicone tubing has a durometer of about 50 Shore A or less is used to form theinner portion100A of thecatheter100. In some applications, thecatheter100 can be formed of a material having a durometer of 30-80 Shore A will perform adequately. In other embodiments, a higher or lower durometer material can be used. As further discussed below, there can be particular advantages to the softer durometers of 30-60 Shore A and 40-50 Shore A. As discussed further below, anouter portion100B of thecatheter100 can be formed of a similar or the same material as theinner portion100A.
• In addition, at least one of the outer andinner portions100A,100B can include hydrophilic or lubricious coatings. These coatings may provide improved performance. For example, such coatings can enhance performance such as improved lubricity for deployment and reduced thrombogenicity for improved patency. Also, for the temporary stent discussed below such coatings can help to facilitate explant procedures.
• In various embodiments, the base material preferably is flexible and base material strength is less critical. In this application, the ability for the braided tubing to expand radially over a connector barbs is preferred. As mentioned previously this is an advantage of a braided reinforcement over a single filament, coiled reinforcement, which cannot expand to slip over a barb. This is similarly an advantage of braid reinforced tube using a softer base material (such as one with a relatively low durometer, e.g., <70 Shore A) over one with a harder base material. Forcing a braided tube with a hard base material over a barb would require an unacceptably high force. Furthermore, under the forces anticipated to be applied during in use, a braided tube with a harder base material would not provide the degree of necking that is desirable in some clinical situations.
• Thecatheter100 also can include abraided structure140 or other reinforcing member between theinner portion100A and theouter portion100B. Thebraided structure140 provides a number of benefits to thecatheter100. For example, thebraided structure140 can be configured to contribute to at least in part, resistance to radial compression of theelongate body112. Also, thebraided structure140 can be configured to provide at least in part, resistance to kinking of theelongate body112.
• In one embodiment, thebraided structure140 is provided primarily to enhance the security of a connection between thecatheter100 and another component of a blood carrying system, such as thevascular access system10. For example, thebraided structure140 can enhance the security of an engagement mechanism of which the braided structure forms a part.
• In one embodiment, thebraided structure140 includes aproximal end144 and adistal end148. Thebraided structure140 can be disposed about thelumen120, e.g., substantially or completely surrounding the lumen. Thebraided structure140 also can extend along thelumen120 such that theproximal end144 is within theproximal portion104 of theelongate body112 and thedistal end148 is within thedistal portion108 of the elongate body. In one embodiment, thebraided structure140 is configured such that theproximal end144 extends to or adjacent to the proximal end of theelongate body112.
• In one embodiment, thebraided structure140 is configured such that thedistal end148 is located proximal of the distal end of theelongate body112. For example, thedistal end148 of thebraided structure140 can be located about 0.2 inches, about 0.25 inches, or from about 0.2 to about 0.25 inches proximal of the distal end of thecatheter100. This arrangement permits a device for visualization to be located distal of thedistal end148 of thebraided structure140. For example, aradiopaque marker149 can be located in thedistal portion108 of the elongate body. In one embodiment, theradiopaque marker149 is a ring formed of platinum, tantalum, tungsten, gold, palladium, iridium, barium sulfate, or another radiopaque material, and any combination thereof. Although themarker149 is configured as a solid ring, in other embodiments, these marking materials can be doped into layers of thecatheter100 or configured as a plurality of rings or one or more patches, plates, wire, or other shapes. They may be distributed in the entire device or at one or both ends of the device or anywhere in between. Any other suitable device to provide the clinician with an indication of where thedistal portion108 of thecatheter100 is located when the blood flow conduit is being advanced in the vasculature can be used instead of theradiopaque marker149 as will be understood by those skilled in the art.
• Also, the configuration of thebraided structure140 can be varied along the length of the catheter to optimize certain performance metrics of the catheter. For example, as discussed herein, thedistal portion108 preferably is relatively flexible to minimize trauma to the patient's vasculature. As discussed below, certain therapeutic methods benefit from higher hoop strength or outwardly directed force. It is thought to be advantageous to have high hoop (radial) strength while having low bending strength. This produces a device which is resistant to collapse but is flexible for accommodating various structures within the body while minimizing the force exerted by and upon the device. Where such properties are primarily derived from the braided structure, it may be desirable to enhance these properties by varying the braid pattern in a treatment zone. These variations can be achieved by varying the pic count of thebraided structure140. Additionally, a proximal portion of thebraided structure140 can be optimized to enhance the connection strength of an engagement mechanism as discussed herein.
• FIG. 2A illustrates that thebraided structure140 can be embedded in theelongate body112. In one embodiment, thebraided structure140 is embedded in theelongate body112 such that an outer surface of theelongate body112 surrounds thebraided structure140. In some cases, thebraided structure140 is disposed within theelongate body112 such that the outer surface of theelongate body112 is substantially smooth along the longitudinal axis of the catheter body. When embedded in theelongate body112, thebraided structure140 also can be disposed radially outside of theinner wall116 of theelongate body112. Thebraided structure140 also can be disposed radially between theinner wall116 of theelongate body112 and an outer surface thereof.
• Although thecatheter100 is relatively soft, thebraided structure140 provides reinforcement that prevents or substantially minimizes kinking, crushing, and other phenomenon that can cause at least partial collapse of thelumen120. Collapse of thelumen120 can occur when thecatheter100 traverses a bend of relatively small radius. For example, in some applications thecatheter100 is required to traverse a joint, such as the shoulder of a patient. Such a traverse could require a relatively small bend radius. In other applications, thecatheter100 need not traverse a small bend radius (e.g., when not crossing a joint). In some applications, a preferred routing of thecatheter100 may cause the conduit to traverse a bend with a radius of about 1.0 inch. In some applications, a preferred routing of thecatheter100 may cause the conduit to traverse a bend with a radius of 1.0 inch or more. In other applications, in a preferred routing thecatheter100 may have to traverse a bend with a radius of about 0.25 inch. In other applications, in a preferred routing thecatheter100 may have to traverse a bend with a radius of about 0.5 inch. In other applications, in a preferred routing thecatheter100 may have to traverse a bend with a radius of between about 0.25 inch and about 1.0 inch. In all of these cases, thebraided structure140 provides a reinforcement to prevent or substantially minimize collapse of thelumen120.
• Properties of thebraided structure140 and variations thereof result in desirable kink minimizing properties not achievable using a coil reinforcement. At very small bend diameters, thebraided structure140 is expected to gradually flatten, instead of suddenly inflecting to a kinked configuration. This is advantageous for several reasons. First, gradual flattening of thebraided structure140 will be detectable by a clinician (e.g., using an imaging technology such as X-Ray imaging) such that the clinician can recognize that a less than desirable bend radius is present before full narrowing of the blood conduit occurs. Secondly, a coil reinforcement undergoes higher strain levels and alternating strains than thebraided structure140. This prevents or delays undesirable fracture or failure due to repeated flexure at very small bend radii. In addition, only a fraction of the plurality of members in thebraided structure140 undergo significant stress or strain level at minimum bend radii. The braid members on the top and bottom of the fold undergo negligible stress compared to the members at the sides of the fold. This means that even if the loading conditions were severe enough to fracture braid members on the sides of the fold, the majority of braid members at the fold would not fracture and the device would remain substantially intact. In previous single filament, coil reinforced devices, any fracture was potentially catastrophic. Also, the disclosed braid configurations advantageously exhibit full narrowing or kinking at a much smaller bend radii than prior coil reinforced devices. Prior coil reinforced devices had a kink radius of approximately 0.5 inch, whereas various embodiments of thecatheter100 have a kink radius of approximately 0.2 inches.
• In some embodiments, thebraided structure140 forms a part of an engagement mechanism, similar to theengagement mechanism32.
• FIG. 3 illustrates further details of one embodiment of thebraided structure140. In one embodiment, thebraided structure140 has a plurality ofbraid members152 that overlap each other in the structure. Thebraided structure140 can comprise a shape memory material, such as a nickel titanium alloy (e.g., a nitinol alloy) in various embodiments. Other suitable materials include stainless steel (e.g., 304 or 316), titanium, glass, Kevlar and other similar fibrous materials. For example, each of the braidedmembers152 can comprise a nickel titanium alloy or other shape memory material. In some embodiments, the braidedmembers152 are woven together to form thebraided structure140. Thebraid members152 can have a cross-section with a first transverse dimension D1 being greater than a second transverse dimension D2, the first transverse dimension D1 being perpendicular to the second transverse dimension D2. In one embodiment, the second transverse dimension D2 (e.g., the shorter of the two dimensions) is generally radially extending relative to the longitudinal axis of thelumen120. These embodiments are illustrated byFIG. 3A.
• Such an arrangement can minimize the thickness of theelongate body112 between theinner wall116 and the outer surface of the elongate body. This can result in a very thin structure, e.g., with a thickness of about 2.0 mm or less. In one embodiment, the thickness of thecatheter100 between theinside wall116 and an outer surface of the catheter is about 1.1 mm. In one embodiment, the thickness of thebraided member152 is less than about 50 percent of the thickness of theelongate body112. In one embodiment, the thickness of thebraided member152 is less than about 25 percent of the thickness of theelongate body112. In one embodiment, the thickness of thebraided member152 is about 10 percent of the thickness of theelongate body112. Minimizing the thickness of the wall of the catheter is important in some embodiments because it can maximize the size of the lumen for carrying blood while still maintaining the ability to insert thecatheter100 into selected vessels.
• By reducing the dimension D2, the crossing profile of thecatheter100 can be reduced or minimized. Reducing the crossing profile provides an advantage of permitting access to the vascular system through a smaller incision. In some embodiments, by reducing the dimension D2, the size of thelumen120 can be increased for a given crossing profile. Increase in the size of thelumen120 is advantageous in that it permits greater fluid carrying capacity in the lumen. Thebraided structure140 provides considerable kink and crush resistance and relative flexibility of theelongate body112.
• One embodiment illustrated byFIG. 3A provides a plurality of braidedmembers152 that have elongate cross-sections provided by a plurality of axi-symmetric side-by-side wires. For example, a braided member could include two circular cross-section wires provided in a side-by-side arrangement. In this embodiment, the radial dimension (D2) of the braidedmembers152 is about equal to the diameter of the wires and the dimension transverse to the radial dimension (D1) is about equal to twice the diameter of the wires. One useful construct for the braidedmembers152 incorporates two 0.005 inch wires that are formed of a nickel titanium alloy. Other embodiments could incorporate 0.006 inch or larger wires. Some embodiments could incorporate 0.004 inch or smaller wires. Larger wires may be suitable for larger catheters or for catheters that can use smaller lumens. Smaller wires may be suitable for smaller catheters or for catheters subject to less crush or kink forces. In other embodiments, the braidedmembers152 can be formed with one or more flat or oval cross-section wires. A suitable alloy would include 56 weight % nickel and 44 weight % titanium. This material can be treated to provide suitable properties, such as by a straight annealing. A light oxide finish is suitable for some embodiments.
• Any suitable woven pattern can be provided for creating thebraided structure140. For example, a hopsack weave can be employed in which the braidedmembers152 cross over a first transverse braided member then cross under a second transverse braided member adjacent the first transverse braided member. This pattern can be repeated throughout thebraided structure140 to provide a suitable weave. Hopsack weave is sometimes referred to as a diamond pattern full load. In other embodiments, the weave could be a diamond pattern half-load or a herringbone weave, which will be understood by one skilled in the art. Other weave arrangements that can be used include a linen weave, for example. However, for some applications, the linen weave is not expected to perform as well as other weave patterns discussed herein.
• Further aspects of thebraided structure140 can affect its performance. For example, the density and configuration of the braidedmembers152 can affect the degree of security when thecatheter100 is engaged with another blood carrying component. For example, in one embodiment, thebraided structure140 is formed with a suitable helix angle, which is defined as the angel between any of the braidedmembers152 and a longitudinal axis of thebraided structure140. A helix angle within a range of about 40 degrees to about 65 degrees could be used in some embodiments of thebraided structure140. In other embodiments, thebraided structure140 can be formed with a helix angle in the range of about 50 degrees to about 55 degrees. In one embodiment thebraided structure140 defines a helix angle of about 51 degrees. In one embodiment thebraided structure140 defines a helix angel of about 54 degrees. A higher helix angle creates a more flexible catheter. A lower helix angle provides less flexibility but is easier to advance over a connector as discussed below. Lower helix angle also provides a less crush resistant catheter, which is less optimal in some applications.
• Another aspect of thebraided structure140 that relates to the performance of theengagement mechanism32 of which the braided structure may be a part is the pic count (crossings per unit length) of thebraided structure140. One skilled in the art will recognize that pic count and helix angle are related. More particularly, pic count can affect the connectability of thecatheter100 with a connector, which can form a part of the thirdblood carrying conduit30. Greater pic count corresponds to a higher force required for coupling theengagement mechanism32. Lesser pic count corresponds to lower connecting forces. Catheters with lower pic counts are more subject to kinking. In one embodiment, thebraided structure140 has a pic count between about 21 ppi and about 24 ppi. In another embodiment, thebraided structure140 has a pic count of between about 22-24 ppi when assembled on thecatheter100. In another embodiment, thebraided structure140 has a pic count of about 21 ppi. In another embodiment, thebraided structure140 has a pic count of about 23 ppi. In another embodiment, a pic count of 22 ppi would be suitable.
• FIGS. 7 and 8 illustrate a comparison of the retention force and attachment force respectively for various embodiments of an engagement mechanism. In this study, pic count of a braided structure in a catheter and various aspects of theengagement feature240 of theconnector200 were varied. The variables that were varied in theconnector200 are shown in the table below, with all dimensions being in inches):

• 	Length	Length	Spacing	Height	Height
  	of Barb	of Barb	Between Barbs	of barb	ofbarb
  	244	248	244 and 248	244	248

  Embodiment 1	0.065	0.065	0.240	0.012	0.012
  Embodiment 2	0.065	0.05	0.225	0.012	0.011
  Embodiment 3	0.065	0.05	0.240	0.012	0.011
  Embodiment 4	0.065	0.04	0.240	0.012	0.009

• FIG. 8 shows a general trend to lower attachment forces forEmbodiment 4 compared to other embodiments.Embodiment 4 had lower values for the height and the length of thebarb248. Also,FIG. 8 shows that a lower pic count of the braided structure of the catheter can result in a significantly lower attachment force compared to a higher pic count arrangement, where the connector has two barbs. Lowering the attachment force is desirable in some embodiments to provide faster and easier assembling of a vascular access system in-situ for the clinician.
• FIG. 7 shows that for the embodiments described in the table above, retention force (e.g., the force needed to disconnect thecatheter100 from the connector200) was not highly dependent on pic count for the embodiments of the connector studied. Although there is an increase in retention force forEmbodiment 2 compared to the other embodiments, all four embodiments had relatively high retention forces compared to an engagement mechanism including a connector with a single barb engaged with a catheter having a braided structure.
• Also, the performance of thebraided structure140 can relate to the number of wires incorporated into the weave. In some embodiments, thebraided structure140 includes about forty-eightbraided members152. Other numbers of braidedmembers152 can be provided, however. For example, in one embodiment, twenty-fourbraided members152 can be provided. Fewer wires provide less crush and kink resistance. More wires provide greater resistance in thebraided structure140 to kinking and crushing. Other numbers of wires for forming thebraided structure140 can also be used, as will be understood by one skilled in the art.
• In some embodiments, theconduit30, theconnector200, and variants thereof can be in the form of a connector and can be coupled with or integrated into another treatment device for handling blood. For example, theconduit30 can comprise a connector for connecting a pump or other component of a vascular assist device or other cardiovascular treatment device. These combinations provide very secure connections between such components and thecatheter100 and variant thereof as discussed herein.
Techniques for Forming Blood Carrying Conduits
• Various techniques are contemplated for forming thecatheter100 with inner andouter portions100A,100B. In some techniques, theouter portion100B is formed in a different process than theinner portion100A. For example, the in a first step of one embodiment, an elongate tubular section of silicone or a flexible elastomer is slid onto a solid mandrel to provide theinner portion100A. The tubular section can have a durometer of about 50 shore A or any other suitable hardness as discussed herein. The tubular section optionally is loaded with barium sulphate. In one technique, the inner diameter of the tubular section is about 5.0 mm and the outer diameter of the tubular section is about 5.5 mm.
• Thereafter, thebraided structure140 can be placed over the outer surface of theinner portion100A. Thebraided structure140 can have a diameter of about the same as that of the tubular section outer diameter. In one embodiment, thebraided structure140 has an inner diameter of about 5.5 mm. In one embodiment, thebraided structure140 has an inner diameter of slightly less than the outer diameter of the tubular section. For example, an inner diameter of about 5.4 mm for thebraided structure140 would be suitable. This arrangement causes thebraided structure140 to cinch down on the outer surface of the tubular section forming theinner portion100A. In one technique, thebraided structure140 is sized such that its length is substantially the same as or slightly less than that of the tubular section.
• Thereafter a platinum iridium marker band (or visualization device of other configuration) is positioned over theinner portion100A. This can be achieved by sliding the marker band over the distal end to a location between the distal end of the braided structure and the distal end of the tubular section. In another technique, strands of thebraided structure140, particularly strands located in the distal portion thereof, can be configured to be visible using radiography or another similar technique.
• Thereafter, the assembly formed to this point in the process can be covered with a suitable material to form theouter portion100B of thecatheter100. For example, the assembly can be coated with a suitable material to form theouter portion100B of thecatheter100. In one technique, theouter portion100B is formed by dip or spray coating silicone, polyurethane or other suitable material over the assembly. In another technique, the outer layer can placed over the assembly and bonded, shrunk, thermally fused or otherwise formed together. In another technique, the outer layer can be formed by in-line extrusion over the assembly.
• Other optional steps can thereafter be performed in various embodiments. For example, the construct can be cut to size and luer fittings (or other suitable connectors) can be formed on a proximal end thereof as needed. The forgoing steps are illustrative and need not be performed in the order recited.
Engagement Features & Mechanisms
• As discussed above, in various embodiments, thebraided structure140 extends to theproximal portion108 of thecatheter100. At least the portion of thebraided structure140 that so extends can interface with theblood carrying conduit30 forming a part of theengagement mechanism32.
• FIG. 4 illustrates one embodiment of aconnector200 that can be incorporated into theblood carrying conduit30 of thesystem10. Theconnector200 includes aconnector body202 that has aproximal portion204, adistal portion208, andlumen212 extending therebetween. Thelumen212 can take any suitable form. In one embodiment, thelumen212 includes a tapered section similar to that described in U.S. application Ser. No. 10/962,200.
• Theproximal portion204 preferably is configured to interface with, e.g., be coupled to, theblood carrying conduit22. The connection between theconnector200 and theconduit22 can be achieved in any suitable manner. For example, theproximal portion204 can have anenlarged portion214 over which theconduit22 can be advanced. Theenlarged portion214 can comprise a portion of theengagement mechanism36. Other techniques and structures for connecting theconnector200 and theconduit22 are described in the applications incorporated by reference herein above, including U.S. application Ser. Nos. 11/216,536 and 11/600,589.
• Thedistal portion208 is configured to interface with theblood carrying conduit26 or with thecatheter100. In one embodiment, thedistal portion208 includes anouter surface220 that extends between adistal end224 and aproximal end228 of theconnector200. In one embodiment, theouter surface220 extends from thedistal end224 to a proximal end of thedistal portion208, adjacent to anenlarged segment250. Theconnector200 also includes anengagement feature240 that is disposed on theouter surface220. In one embodiment, theengagement feature240 comprises a portion of an engagement mechanism.
• Theengagement feature240 can take any suitable form. For example, in one embodiment, theconnector body202 has a first outer size CB₁and theengagement feature240 has a second outer size CB₂that is greater than the first outer size CB₁. The outer sizes CB₁, CB₂can correspond to diameters in one embodiment, but could correspond to outer perimeters. In one embodiment, CB₁is a diameter of about 5.4 mm. In one embodiment, CB₂is a diameter of about 6.0 mm. As discussed above, the inner diameter of thecatheter100 is about 5.0 mm in one embodiment. This corresponds to a prestressing of about 1 mm in the diameter of thecatheter100. In some embodiments, a prestressing of about 20% of the inner diameter of a catheter being inserted over theengagement feature240 can provide suitable connectability. In some embodiments, a suitable amount of prestressing (e.g. enlargement of the inner diameter of a catheter connected over the engagement feature240) can range from 16-24%. In other embodiments, a suitable amount of prestressing (e.g. enlargement of the inner diameter of a catheter connected over the engagement feature240) can range from 8-28%.
• Prestressing, or stretching the inner size of thecatheter100 creates an enhanced security of the connection formed by theengagement mechanism32. In particular, thebraided structure140 and the proximal portion of thecatheter100 expand upon being placed in compression during the distal advancement of theconnector200 relative to the catheter. After advancement, thebraided structure140 seeks to return to its pre-formed shape, which produced an inwardly directed force on theconnector200 increasing the security of the engagement between theconnector200 and thecatheter100. Also, the configuration of thebraided structure140 is such that if a force for disconnecting theconnector200 and thecatheter100 is applied, the braided structure will increase the inwardly directed force further securing the connection. This action at the engagement mechanism is analogous to a Chinese finger trap toy, which reduces in cross-sectional size upon elongation.
• Providing one or more barbs creates an even more secure connection. In some embodiments, theengagement feature240 includes abarb244 that extends over a portion of theconnector body202. Thebarb244 can include any structure that includes a raised surface that extends to above the connector body.
• FIG. 4 illustrates that in one embodiment asecond barb248 is provided between thefirst barb244 and theproximal portion204 of theconnector200. As discussed below, thesecond barb248 of the engagement feature greatly enhances the security of the connection between thecatheter100 and theconnector200. Thesecond barb248 can take any suitable form. In some embodiments of theconnector200, thesecond barb248 is smaller than thefirst barb244. For example, thesecond barb248 can be about 5.8 mm in diameter in one embodiment. Thefirst barb244 can be about 5.99 in diameter.
• In some embodiments, the height of the engagement feature240 (e.g., thebarbs244 or248) can be important. Barb height can be measured on the distance from a location of the barb that is farthest radially from an axis of the lumen through theconnector200 to thesurface220 adjacent to thebarb244,248. In one embodiment, this distance is between about 0.005 inches and about 0.020 inches. In one embodiment, the height of the engagement feature is about 0.013 inches. In one embodiment, the height of the engagement feature is about 0.012 inches. In one embodiment, the height of the engagement feature or barb is between about 0.008 inches and about 0.009 inches. In one embodiment, the height of a first barb of theengagement feature240 is about 0.012 inches and the height of a second barb of theengagement feature240 is about 0.008 inches. The height and diameter of the engagement features240 can be increased to increase retention force. In some embodiments, increasing these dimensions may be limited by the force required to advance theconnector200 into thecatheter100, which is generally done manually.
• Another aspect of theengagement feature240 is the length thereof or of individual portions thereof. For example, one embodiment has two barbs as discussed above. In one arrangement a distal-most barb is about 0.065 inches in length, though longer barbs could be used. In one embodiment, a proximal-most barb is about 0.065 inches in length. The proximal-most barb can be shorter or longer. For example, in one embodiment, the proximal-most barb is about 0.040 inches in length. In one embodiment, the distal-most barb is 0.065 inches and the proximal most barb is 0.040 inches.
• Two additional features that contribute to the connection in some embodiments are the spacing between thebarbs244,248 and the distance that the catheter is advanced past the proximal most barb.
• FIG. 5 demonstrates performance of various barb spacings. One configuration was tested with a maximum peak to peak barb spacing of about 0.740 inches. This chart shows a general trend of increase in retention force for greater barb spacing. Some of the increase in force observed in the chart could be attributable to a greater length of catheter in contact with the connector apparatus. As the barb spacing increased, so did the total length of connected catheter.FIG. 5 can be interpreted to indicate a minimum spacing of approximately 0.100 inches in some embodiments. At lesser barb spacings than this value the retention force drops rapidly. However, at increased spacings greater that this value, the force increases more slowly. InFIG. 5, one technique computed the rates of change as about 7 lbs/0.040 inches before an inflection point and about 1.2 lbs/0.040 inches after the critical point. This analysis employed a simple linear fit. One skilled in the art will recognize that a more complex fit of the data would produce a different mathematical description of the data. However, it is expected that other such curve fits would still reveal a relatively steep slope toward 0.100 inches and a flatter slope toward the middle of the data. Similarly inFIG. 6, discussed below, a more complex curve fit might reveal a generally asymptotic profile at one or both ends of the data set.
• FIG. 5 shows that the dual barb configuration has superior connection strength to a single barb at all barb spacings and more than twice the strength once the peak to peak spacing exceeds about 0.100 inches. Also, the difference between bare silicone and braid reinforced silicone is apparent inFIG. 5. Note that in addition to the superior performance at any barb spacing, the slope of the line is greater for a braided catheter. This may be due in part to an amplified retention force generated by the combination of theretention feature240 and thebraided structure140 in thecatheter100 upon connection of the catheter to theconnector200. This highlights the superiority of the braided flexible catheter over alternative designs. More particularly, the braided structure has much greater retention strength for a given barb dimension compared to a non-braided catheter of identical material. Also, the braided structure has the ability to further increase the retention strength by the use of multiple barbs on theconnector200. Also, the use of the braided structure compared to other reinforcements facilitates the use of barbs and optimized barb geometry on theconnector200. Moreover, the use of a softelongate body112 in thecatheter100 allows the braidedstructure140 to neck down behind the barb and thereby increase the retention strength.
• Given the results illustrated inFIG. 5, the spacing can be any suitable spacing, but as discussed below preferably is at least about 0.100 inches in an arrangement with two barb, or more. In one embodiment, the spacing between the peaks ofadjacent barbs244,248 is about 0.229 inches. In one embodiment, the spacing between the peaks is about 0.240 inches.
• AlthoughFIG. 5 illustrates the vast improvements that can be achieved with the embodiments described above, in some applications an engagement mechanism having less redundancy provides adequate retention force. For example,FIG. 5 shows one embodiment where an engagement mechanism with a single barb provides about 10 pounds of retention force. This amount of force is sufficient for some applications. Also, althoughFIG. 5 shows that bare silicone generally provides a much lower retention force for various dual barb arrangements a combination of bare silicon and a connector can be sufficient in some arrangements, such as if the silicone is clamped at an outside surface thereof.
• In various embodiments, it is preferable to advance the catheter proximally past the proximal-most barb. The sensitivity to this variable is illustrated byFIG. 6. Also, a single barb example is illustrated inFIG. 6. The dual barb variable setup demonstrated little or no increase in retention force when the amount past the barb exceeded about 0.125 inches for one embodiment. This suggests that a suitable range for the catheter connection past the barb could be about 2-3 mm (0.080″-0.120″) or about 1.5-4 mm (0.060″-0.160″) for one embodiment of the catheter and connector combination.
• FIG. 6 shows that a catheter flush with the proximal side of the second barb exceeds the retention strength of a single barb where the catheter is about 0.125 inch or less beyond the proximal side of the single barb. Other embodiments provide advancement beyond theretention feature240 of between about 0.080 inches and 0.120 inches. In some embodiments, it is preferable to advance the catheter proximally past the proximal-most barb by between about 0.060 inches and 0.160 inches. In some embodiments, it is preferable to advance the catheter proximally past the proximal-most barb by about 0.010 or about 0.111 inches. In some embodiments, it is preferable to advance the catheter proximally past the proximal-most barb by between at least about 0.125 inches.
• As discussed above, theengagement mechanism32 particularly when configured to include portions of thecatheter100 and theconnector200 provides a number of clinical advantages over other arteriovenous shunt devices. Specifically, the combination of at least one of a braided structure and a barb in the engagement mechanism improves the ease of use of the device. As discussed above, thecatheter100 can be cut and connected without the need to further modify a catheter prior to connection. Also, the embodiments discussed herein have improved connectability in that a lesser force can be used to connect theengagement mechanism32 than would be sufficient to disconnect the mechanism. Also, thesystem10 is “one-size-fits-all” because it is configured to be trimmed to any desired length.
• Other advantages that are provided include improved durability. Thecatheter100 has many independent braidedmembers152 within thebraided structure140. The plurality of braidedmembers152 provides redundant support, which results in improved resistance to clamping and fatigue fracture. The plurality of braidedmembers152 also provides improvement in tensile strength. Compared to other prior approaches, less manufacturing steps are required, reducing the labor and cost of production. Also, it is expected that at least some of the embodiments of thecatheter100 withstand higher radial loads before collapsing and can be placed in a tighter radius without kinking than was possible with prior devices. In at least some applications, improved burst resistance (the ability to withstand high pressures without detaching from the connector or rupturing) can be advantageous but is not required.
• Other advantages of the embodiments discussed herein include a benefit for the physician to receive feedback indicating that the catheter has been properly connected. For example, the multiple barb system provides increase in strength even when the catheter is minimally past a second barb. Visible deformation, e.g., by expansion of thecatheter100 or thebraided structure140, serves as a visual indication of proper attachment. This allows the user to observe the visible reference to insure that the catheter is past both barbs by referencing the two visible rings as the braided catheter goes over the first and second barbs. If not visible, this expansion can create ribbed portion on the otherwise smooth outer surface of thecatheter100 to provide a tactile confirmation of proper attachment.
• Although it is recommended that the catheter be fully advanced against the centralenlarged segment250 of theconnector200, the integrity of the connection provides sufficient strength if inserted less than this amount, e.g., by only one-half of the distance from thebarb248 to thesegment250. This is expected to result in strength that is almost double when compared to a similar single barb system. When fully inserted it is expected that the strength will be almost tripled.
• As discussed above, multiple and single barb engagement features can be suitable for secure connections. A properly designed single barb and braided catheter connection system can be made very secure, e.g., with about six times the retention force as a catheter made from the same material but without the braid. The second barb is expected to add at least a 100% increase in retention strength. This makes the engagement mechanism more robust, providing the added benefit of reducing the urgency of optimal insertion of the catheter over the connector to theenlarged section250.
• These features provide the desired level of security while providing the end user with both an increase in the confidence of achieving a secure connection.
Systems and Methods Adapted for Treating Vascular Stenosis
• FIGS. 9-11 illustrate various methods and apparatuses for treating vascular stenoses. In each figure, astenosis300 is illustrated as narrowing the blood flow lumen of a vessel V compared to the un-occluded state of the vessel. The narrowing prevents blood from reaching tissue downstream, causing ischemia, insufficient blood flow for effective dialysis, and other maladies.
• FIG. 9 shows, in an upper portion, a segment of the vessel V prior to being treated and, in a lower portion, the same vessel segment during a treatment with atemporary stent400. Thestent400 is one form of a blood carrying conduit, as discussed herein and can incorporate certain structural features discussed above. In use, thestent400 is placed in a blood vessel to displace thestenosis300 to increase the blood carrying capacity of the vessel V, providing a method for opening up the vessel V. Thestent400 has a structure that causes it to move thestenosis300 radially away from the center of the vessel V so that the vessel is wider. In contrast to known stents, thestent400 is configured for temporary placement and remodeling of the vessel.
• Thestent400 includes an elongate tubular member404 having an outside surface that is configured to prevent adherence of in vivo matter. For example, it is preferred that the outside surface of thestent400 prevents growth of tissue into at least a portion of thestent400. For example, the outside surface can be formed similar to theouter portion100B of thecatheter100, e.g., being formed of silicone or other silastic material. Alternatively, polymeric materials including polyerethanes with trade names such as Pellathane, Tecothane (aliphatic polyether polyurethane), Tecoflex (aromatic thermoplastic polyurethane) may be used. This is distinct from typical stents, which are configured as an open lattice or exposed cell pattern, though which tissue can easily grow. Because there is a preference to remove the device after a therapeutic period, such ingrowth is to be avoided. In some cases, the outer surface of thestent400 also prevents cellular structures from the patient from adhering to thestent400. Adherence of smooth muscle cells to thestent400, which could impede removal of the stent, is resisted.
• The tubular member404 comprises aproximal end408 and adistal end412 and is reinforced to maintain an expanded configuration under a transverse load. Any reinforcement can be used, so long as thestent400 has sufficient strength to displace thestenosis300 and to produce a remodeling effect, as discussed herein. One reinforcement that is particularly useful is a braided structure. Thebraided structure140 and any of its variants or substitutes discussed above can be used as the reinforcement.
• The ability to displace the tissue surrounding a vessel to be treated depends on several factors, including the expanded size of thestent400. In general, the unconstrained expanded width of thestent400 should be greater than the stenosed vessel lumen width. If thestent400 is generally self-expanding, it can relax from the stressed, reduced diameter size to a larger size, e.g., toward the unconstrained size. As discussed herein, the process of returning to the expanded size can be controlled as part of the treatment. In various applications, the unconstrained width (e.g., diameter) of thestent400 can be about 4 mm to about 8 mm for certain vessels. More generally, the outer diameter can be within a range of about 2 to about 14 mm.
• The length between the proximal anddistal ends408,412 can be any suitable length. In some embodiments, the length is pre-determined. In other embodiments, the length of thestent400 can be determined during the procedure. For example, thestent400 can be formed during the procedure by cutting a portion of the tubular member404 to create a selected size. The length can also be a function of the vasculature to be treated. For example, if thestent400 is to be used to treat the neuro-vasculature, the length can be between about 2 cm and about 4 cm. If used to treat the carotid vasculature, thestent400 can be between about 2 and about 15 cm. If used to treat peripheral vessels, thestent400 could be longer.
• One class of vessels for which thestent400 may be particularly suited includes those vessels that are very mobile and subjected to high cycles, e.g., vessels traversing from one side to another of a skeletal joint. For example, the superficial femoral artery (SFA) traverses the knee joint and is cycled with every bend of the kneed. This subjects the SFA to tremendous movement and any structure in it to corresponding cycles. Thestent400 has an extremely robust design to resist failure from fatigue induced by these cycles. For this reason, thestent400 is believed to be advantageous for the SFA and similar blood vessels. Typical lengths for SFA embodiments are between 40 mm and 550 mm. In certain embodiments, thestent400 is configured to have a deployed length of between 200 and 300 mm. One embodiment is about 240 mm in length. In certain embodiments, thestent400 is sized to be at least about twice as long as a typical lesion. Lesions are typically in the range of about 70 mm to about 100 mm. Other applications for thestent400 include deployment in the biliary system and for such an application, thestent400 would be sized appropriately to at least cover the stenosis and to be sufficiently large to dilate the lumen.
• Other vessels in which thestent400 could be deployed include the subclavian artery or vein, the internal jugular artery or vein, and inominate artery or vein, the superior vena cava.
• In one method, the tubular member404 is advanced into the vasculature of a patient in a low crossing-profile configuration such that thedistal end412 is disposed distal of thestenosis300 and theproximal end408 is disposed proximal of thestenosis300. The low crossing-profile configuration can be induced by an axial load, such as a force applied to stretch or elongate the member404. The axial load on the tubular member404 is thereafter released to cause the tubular member to transition from the low crossing-profile configuration to the expanded configuration.
• FIG. 9A illustrates adelivery tool420 that is configured to stretch, and thereby to diametrically collapse, thestent400. As thestent400 is stretched, the diameter is reduced. The reduced diameter state enables thestent400 to be advanced through a smaller incision and into smaller vessels. Thedelivery tool420 includes a centralelongate body424 with aguidewire channel428 extending therethrough. Anatraumatic tip432 disposed on a distal end of theelongate body424 aids in tracking thetool420 over the guidewire. Aproximal portion436 of thetip432 has astent engagement feature440 adapted to grip at least one of a distal face of thedistal end412 of the stent or a circumferential band of the inner lumen of the stent400 (similar to theinner lumen120, discussed above).
• Asleeve452 disposed about theelongate body424 is configured to be movable relative to theelongate body424 and to provide the stretching function by such movement. For example, adistal portion456 of thesleeve452 can include astent engagement feature460 adapted to grip at least one of a proximal face of theproximal end408 of thestent400 or a circumferential band of the inner lumen of the stent400 (similar to theinner lumen120, discussed above).
• In one deployment technique, the stent engagement features440,460 are coupled with the proximal anddistal ends408,412 of thestent400 respectively. Thereafter, relative motion is provided between thesleeve452 and theelongate body424 such that the stent engagement features440,460 are moved away from each other along the longitudinal axis of thetool420. The movement causes thestent400 to stretch, which reduces its diameter. The stent is thus moved to a low crossing-profile configuration.
• After thestent400 has been delivered to a treatment site, the axial load on thestent400 is released to cause thestent400 to transition from the low crossing-profile configuration to the expanded configuration. In one technique, the axial load of thetool420 can be released by providing relative movement between thesleeve452 and theelongate body424 such that the stent engagement features440,460 are moved toward each other along the longitudinal axis of thetool420. This causes thestent400 to expand diametrically such that it separates from thetool420. Preferably the depth of the stent engagement features440,460 is sufficiently small, e.g., sized with diameters similar to the diameter of the low crossing profile diameter, such that theelongate body424 can be retracted through the lumen of thestent400 and out of the patient after the stent is deployed. A variation of thetool420 is to providefeatures440 and460 made of flexible material, e.g., silicone to provide the ability to collapse radially as theelongate body424 is retracted.
• A variation of thetool420 provides a biasing force to bias apart prior to delivery stent engagement features. The biasing force can be released by an elongate wire or rip cord that is threaded through a channel of thetool420. Releasing the biasing force releases the stretching function and allows for deployment of thestent400. Thestent400 may be attached to one end of thetool420 for transport to the treatment site as illustrated inFIG. 9A or contained within a delivery tool, such as between thetool420 and a sleeve disposed over thetool420.
• A variation on thedeployment tool420 would maintain the compressed state of thestent400 for example by providing a sheath disposed about the stent, with the stent in a collapsed state. Thestent400 can be placed in a collapsed state by folding at least a portion of the tubular member404 inwardly into the lumen of the body. For example, an arcuate segment of the tubular member404 can be involuted into the lumen and the ends of the segment can be brought together to create a smaller cross-sectional profile. A sleeve can be disposed about the inwardly folded stent. In one variation of this approach, a removable constraint is provided about the foldedstent400 to decrease the pressure applied by thestent400 to the sleeve. This structure reduces the force needed to retract the sleeve compared to where the sleeve provides the entire compressive action to hold thestent400 in the folded state.
• An alternative to the deployment tool ofFIG. 9A is a catheter device that deploys thestent400 at approximately its full size. Such a deployment technique may be combined with other techniques or devices, such as distal protection devices that address the risk of side effects such as the dislodgement of plaque or thrombus.
• Although inserting thestent400 percutaneously would be advantageous, the significant clinical benefit of thestent400 can be obtained even if the stent is placed by surgical cut down. For certain vessels that are relatively peripheral and superficial, such an approach may be preferred to a percutaneous approach.
• Various treatments involve removing thestent400 after a therapeutic period. In other words, the tubular member is intended to be a temporary implanted structure. This method can be applied anywhere in the vasculature, but is has been observed to work in the venous vasculature. The vessel was shown to have greatly improved patency compared to prior to the implantation of the device. The therapeutic period can be as few as 1 day. In some cases, the therapeutic period can be up to 12 months. Significant permanent benefit may take approximately 2 months.
• In one variation, thestent400 is configured to expand during a significant portion of the therapeutic period. This feature provides that upon deployment, thestent400 is released to a first expanded diameter. After deployment, thestent400 continues to expand to ever increasing diameters over time as the stenosis is moved and the vessel reacts to the force applied by thestent400. Thestent400 may be constructed such that the radial force it exerts on the vessel or body conduit is low enough that the stent does not immediately expand to its fully unconstrained outer diameter (e.g., pre-deployment diameter). This configuration advantageously enables imaging techniques, such as X-ray or fluoroscopy, to be used to assess diameter change of the vessel over time. This diameter change can be used to determine the amount of force the vessel is exerting on the device. In one therapy, thestent400 is monitored until an increase in size of up to about 100% of the delivery diameter is achieved. In another therapy, thestent400 is monitored until an increase in size of at least about 50% of the delivery diameter is achieved. After these percentages increases, thestent400 can be removed. This information can be used to predict the amount of vessel relaxation (vessel re-narrowing) upon removal of the stent. Accordingly, thestent400 can be deployed for a therapeutic period that can be tailored to the needs of the specific patient and treatment to provide the proper amount of time to expand/remodel the vessel to the appropriate diameter. Another approach is to determine the therapeutic period by reference to a potential for vessel recoil. For example, where some recoil is anticipated, the expansion of thestent400 can be monitored until the internal lumen in thestent400 has a width (e.g., diameter) that exceeds the desired blood vessel bore by a predetermined amount. For example, thestent400 can be monitored until its inner diameter is at least about 20% to 30% greater than the desired post-treatment bore of the vessel. In some techniques, the expansion of thestent400 is greater than the desired post-treatment bore of the vessel by up to 20%.
• One way to configure thestent400 to provide this time-expansion property is to modify, e.g., lower the pic count of thebraid140 or otherwise reduce the radial stiffness to enhance the expansion range. Alternatively a smaller diameter braid wire or material with a lower modulus of elasticity may be used to reduce the stiffness. A lower pic count braid would result in a device that is more responsive, with more diameter change in response to changes in vessel loading.
• Thestent400 preferably is configured to holds its position in the vessel V so that the treatment continues for as long as desired at thestenosis300. Under the right conditions, friction may be enough to maintain the position of thestent400 in the vessel. An additional outer material, outward flared ends or coarser surface texture may be employed to improve the friction between thestent400 and the vessel wall.
• Other techniques include using a fastener, such as a suture or clip, to affix thestent400 in position. In other embodiments, it may be acceptable to provide a cuff, short length of endothelialization promoting structure, or a radially outwardly oriented barb at one or both of the proximal anddistal ends408,412 of the elongate body404.
• FIG. 9A shows that in one embodiment aseparation zone480 is provided a between acuff484 and thestent400 to facilitate separation of the stent from thecuff484. Theseparation zone480 provides a partial, or relatively easily torn, bond between thestent400 and thecuff484. In this embodiment, ingrowth is permitted in thecuff484 to stabilize thestent400 and minimally invasive removability is provided. In the illustrated embodiment, thecuff484 is disposed on the proximal end of thestent400. This enables the leading edge of thestent400 to be anchored when thestent400 is deployed in a vessel where the blood flows through the lumen of thestent400 in a proximal-to-distal direction. In other embodiments, thecuff484 can be on the distal end of the stent, which may be beneficial for deployment in a vessel where the flow of blood is through the lumen in a distal-to-proximal direction. In other embodiments, cuffs may be provided on both the proximal and distal ends of thestent400.
• Thecuff484 could be constructed of a relatively soft, textile like construction having similar or less stiffness than the vessel wall. For example a ring of ePTFE or Dacron could be incorporated into thecuff484. Thecuff484 can be very thin, in one embodiment about 0.010″ thick, and in other embodiments between about 0.005 and about 0.015″ thick. In other embodiments, thecuff484 can be about 0.001″ to less than about 0.005″ thick. In some cases, thecuff484 can be greater than 0.015″ thick. Thecuff484 can be relatively short, for example about 0.100″. In some cases, thecuff484 can be between about 0.050″ to about 0.500″ long. In further embodiments, thecuff484 can be less than about 0.050″ long while in other embodiments, the cuff can be greater than 0.500″ long.
• Thecuff484 can be joined to thestent400 by any suitable technique, such as by having a smaller internal diameter than the stent outer diameter or by an appropriately weak adhesive. Additionally, thecuff484 could be constructed of a bioresorbable material to facilitate the return to totally native structures. The cuff(s)484 can be configured to be fully encapsulated in the intima of the vessel or absorbed or dissolved into the blood over time.
• When explant is desired, thestent400 can be grasped and separated from the cuff(s)484, which is left in place proximal and/or distal of the treatment zone. Separation from the cuff(s)484 may be accomplished by applying a force to thestent400 along the longitudinal axis of the blood vessel away from acuff484. For example, a balloon could be inserted into the lumen of thestent400 and expanded into engagement with the inner wall of thestent400. The inner wall of thestent400 can be similar to theinner wall116, discussed above in connection with theelongate body112. A distal zone of the inner wall can be configured to have enhanced frictional engagement with an outside surface of an explant tool, e.g., with an outside surface of a balloon of an explant tool.
• In various embodiments, thestent400 is configured to make explant easier. As discussed above, the outer surface is configured to prevent or minimize adherence of in-vivo matter. In addition, the outer surface preferably is configured to slide very easily during explant, e.g., proximally out of a treatment zone. In one embodiment, silicone disposed at the outer surface of thestent400 greatly reduced the proximal directed force needed to extract thestent400 from the body. This low force slideability reduces the chance of any trauma to the treatment zone, which can cause bleeding, inflammation and potentially restenosis. Other materials can be provided on thestent400 consistent with this. For example, inner layers or structures could comprise materials that would require higher force slideability than the outer layer. In some embodiments, an outer layer can comprise a hydrophilic coating, which can reduce the force needed to remove thestent400, e.g., by increasing the lubricity of thestent400. Other materials, such as those discussed above in connection with thecatheter100, with comparable low force slideability could be used to form thestent400 or be disposed on the outer surface thereof.
• As an alternative, a currently marketed intravascular snare may be utilized for retrieval.
• FIG. 10 illustrates a treatment that can involve bypassing a stenosis using a blood circuit that is at least partially extravascular in nature. The method can also involve treatment of multiple medical maladies. For example, the method provides a bypass of a stenosis and provides vascular access for a periodic therapeutic procedure, such as hemodialysis.
• Prior to the method, anocclusion300 is noted in an artery or vein. Theocclusion300 results in a narrowing of the vessel V compared to, for example, an upstream segment A. This method can be performed with acatheter system10A, as discussed above. Adistal blood conduit26A and a proximal blood conduit, which can include theconduit22 and theconduit30 are provided. As discussed above, theconduit22 can be a graft made of a convention a material such as ePTFE. Theconduit30 can be a connector, such as theconnector200 illustrated inFIG. 4.
• Theconnector30,200 preferably has one or more a retention feature located thereon, which can be similar to thebarbs244,248, discussed above. Thedistal blood conduit26A can be configured as acatheter100′ similar to thecatheter100 discussed above, e.g., having abraided structure140 embedded therein.
• A distal zone orportion500 of thedistal blood conduit26A,100′ is inserted into the vasculature and through a stenosis in the vasculature. Thedistal portion500 has at least two discrete regions in one technique. Afirst region500A extends from the site of vascular access into the vessel V near the distal end of the un-occluded up-stream segment A. Asecond region500B extends proximally from the distal end of thedistal blood conduit26A,100′. Thesecond region500B is configured for soft interactions with the vasculature, as discussed above. This prevents any adverse side effects due to the presence of thesecond region500B in the vessel.
• Thefirst region500A preferably is optimized to treat thestenosis300. In particular, thefirst region500A can be sized, as discussed above in connection with thestent400, to displace thestenosis300 out of the lumen of the blood vessel V. At least thefirst region500A preferably is reinforced as discussed above to displace thestenosis300 rather than being deformed into the vessel lumen by the stenosis. At least thefirst region500A of thedistal portion500 has a smooth outside surface. The smooth surface is configured to prevent adherence of in vivo matter. The smooth surface is also well adapted to facilitate smooth non-traumatic explant by applying a force to the proximal end of thecatheter26A,100′.
• Thecatheter26A,100′ is adapted to be cut through the braided structure, as discussed above, to size the catheter in-situ. Thecatheter26A,100′ is advanced over a distal segment of theconnector30 until at least a portion of thebraided structure140 is positioned proximal of the retention feature, e.g., the barb(s)244,248.
• Combination treatment can be provided by the method ofFIG. 10 in that flow through the occluded region is improved and thestenosis300 is treated to increase the patency of the vessel V downstream of the un-occluded zone A. The treatment of thestenosis300 can be considered a distinct treatment. Also, thesystem10A can provide access to blood that flows through theconduit22. The access can be with a needle, e.g., to facilitate hemodialysis. Flow is mostly or entirely diverted through the system, as indicated the arrow entering thesystem10A at the vessel end of theconduit22 and the arrow exiting the distal end of thesecond region500B. Upon removal of the system as applied inFIG. 10, the previously obstructed portion of the vessel V will be much more open than prior to the treatment.
• The technique ofFIG. 10 is primarily intended as a treatment for single vessel, e.g., with proximal and distal components coupled with segments of the same vessel. In some variations, adjoining venous or adjoining arterial vessels can be treated in this way.
• A variant of the method ofFIG. 10 involves connection of thesystem10A from an artery to a vein. For example, a proximal end of theconduit22 can be connected to a patient's brachial artery, e.g., by anastomosis. A distal end of theconduit22 can be inserted into a vein and advanced to a position within the central venous system. In one method, a stenosis is observed in the central venous system and the distal end of thecatheter26,100′ is advanced distally until the outlet is distal of or at least unobstructed by the stenosis. Thereafter, blood is permitted to flow through thesystem10A from the arterial vasculature to the venous vasculature beyond the stenosis. In this way, the presence of the stenosis does not interfere with dialysis treatment. As discussed herein, thecatheter26,100′ can be configured in at least that portion that interacts with the stenosis to displace the stenosis out of the lumen of the vessel. In some methods, thesystem10A is left in place for a therapeutic period, e.g., at least as long as needed to improve patency through the stenosed region, and may thereafter be removed. A variety of techniques for connecting an arterial segment to a venous segment are discussed in the documents incorporated by reference hereinabove, such as (a) U.S. Pat. No. 6,102,884, see, e.g., FIG. 8; (b) Ser. No. 11/216,536 (US Publication No. 2006-0064159 A1), see, e.g., FIGS. 23A-23F, 26, and 37A-37E; (c) Ser. No. 11/600,589 (US Publication No. 2007-0167901 A1), see, e.g., FIGS. 8A-9E; and (d).
• On advantageous way of treating a vessel using thesystem10A is to insert thecatheter26,100′ only as far as needed. For example, the insertion of thecatheter26,100′ can be limited to advancing the distal end thereof only to vascular locations beyond thestenosis300. While in certain embodiments, the method involves insertion of the distal end into a heart chamber, such as the left atrium, in other embodiments the distal end is placed outside of the heart within the vasculature. Placement outside the heart simplifies the procedure in that there is no need for thesystem10A to interact with the heart. Also, the procedure can be completed more quickly since thecatheter26,100′ need not be advanced as far. Another potential advantage is that by shortening thecatheter26,100′, the blood and body tissues are exposed to less foreign material because the catheter can be shorter than if it were required to be advanced farther, e.g., into the heart.
• FIG. 11 illustrates a class of treatments in which abypass system10B is applied to direct normal anatomical blood flow around thestenosis300.
• Thebypass system10B includes acatheter604, afirst connector608, and asecond connector612. Thecatheter604 has aproximal portion616, adistal portion620, and anelongate body624 extending between the proximal anddistal portions616,620. Thecatheter604 can be similar to thecatheter100, for example providing a flow lumen for blood and sufficient structural support to maintain the lumen open when implanted beneath the skin. As discussed below, thecatheter604 is not intended to be inserted into the vasculature. So, features of thecatheter100 that facilitate such insertion can be omitted. Such feature may include radiopaque markers, as discussed above. In one variation thebraided structure140 in incorporated into thecatheter604.
• Theelongate body624 defines an inner wall having an inner perimeter surrounding a blood flow lumen, similar to thelumen120. Thecatheter624 has a braidedstructure140 embedded in the elongate body and disposed about the lumen. Thefirst connector608 is for fluidly coupling a firstvascular graft640 with theproximal portion616 of thecatheter604. Thefirst connector608 comprises a connector body and an engagement feature. As discussed in connection withFIG. 4, the connector body of each of theconnectors608,612 has an outer surface defining a first outer perimeter (e.g., diameter) and an inner surface defining a lumen. The engagement feature can be disposed on the outer surface of the connector body adjacent an end thereof. As discussed above, the engagement feature defines a second outer perimeter greater than the first outer perimeter.
• The outer size of thecatheter604 is less critical than in other embodiments, but any of the sizes discussed above could be used. For example, thecatheter604 can an unconstrained size of anywhere form about 4 mm to about 8 mm. More generally, the outer diameter of thecatheter604 can be within a range of about 2 to about 14 mm. Larger sizes can be used as well since thecatheter604 is not required to fit inside a blood vessel in this application.
• The proximal portion of thecatheter604 has a first configuration in a free state and a second configuration when in axial compression. In the first configuration, the inner perimeter is less than the first outer perimeter of thefirst connector608. In the second configuration, the braided structure expands to permit the inner perimeter of the body of thecatheter604 to expand such that the proximal end portion of thecatheter604 can be advanced over the engagement feature of the connector body.
• Thesecond connector612 can take any suitable form, but preferably is configured to securely engage a secondvascular graft644 with the distal portion of the catheter. For example, thesecond connector612 can have a configuration similar to that ofFIG. 4.
• In one method, thefirst graft member640 is coupled with a first vessel segment upstream of thestenosis300. In this method both the proximal and distal ends of thecatheter604 are disposed outside the vasculature. The blood can flow into thegraft member640 through the proximal end of thegraft640. Thesecond graft member644 is coupled with a second vessel segment downstream of thestenosis300. The first and second vessel segments can be portions of the same vessel in some applications. In other applications, the first and second vessel segments can be arterial vessels or venous vessels, which may be adjacent vessels or spaced apart by one or more intervening vessels.
• A first end of thecatheter604 is coupled with thefirst graft member640 by applying a connection force, e.g., providing relative motion between an end of thecatheter604 theconnector608 disposed on an end of thegraft member640. The second end of thecatheter604 can thereafter be coupled with thesecond graft member644 in a similar fashion if thesecond connector612 has similar constructions. When using these connectors, thebraided structure140 is expanded by the axial relative motion to permit thecatheter604 to be received over the corresponding connector. When the first andsecond grafts640,644 are connected to thecatheter604, a force required to disconnect the blood flow conduit from the first or second graft is significantly higher than the required connection force. The force required to disconnect is also greater than the expected forces to occur in the body. In some variations of this method, one or both of the first andsecond grafts640,644 at least a portion of thecatheter604 are disposed beneath the skin of the patient.
• Thesystem10B can be applied with thefirst connector608 disposed at an upstream location relative to thesecond connector612, as illustrated inFIG. 11. In particular, the flow through thesystem10B can be from the location of the arrow labeled “flow” in the figure. Blood then flows through thefirst graft640 and into thecatheter604. The blood flows through a portion of theconnector608 to reach thecatheter604. Blood then flows from thecatheter604 into thesecond graft644 by way of theconnector612 and into the vessel at the arrow distal of thesecond graft644. In this way the vast majority of the blood flows into the vessel segment illustrated is bypassed around thestenosis300. In other embodiments, thesecond connector612 can be disposed at an upstream location relative to thefirst connector608, which is the opposite of what is illustrated inFIG. 11.
• In some variants of thesystem10B ofFIG. 11, thegrafts640,644 can be pre-attached to acorresponding connector608,712 or can be separate components therefrom.
• Although this invention has been disclosed in the context of certain preferred embodiments and examples, it will be understood by those skilled in the art that the present invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. Additionally, it is contemplated that various aspects and features of the invention described can be practiced separately, combined together, or substituted for one another, and that a variety of combination and sub-combinations of the features and aspects can be made and still fall within the scope of the invention. Thus, it is intended that the scope of the present invention herein disclosed should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims.

Claims (22)

1. A method of treating a stenosis, comprising:

providing a delivery device having an elongate tubular member coupled therewith, the elongate tubular member having an outside surface that is configured to prevent adherence of in vivo matter, the tubular member comprising a proximal end and a distal end and being reinforced to maintain an open lumen under a transverse load;

advancing the delivery device and the tubular member into the venous vasculature such that the distal end of the elongate tubular member is disposed distal of a stenosis and the proximal end of the elongate tubular member is disposed proximal of the stenosis in the venous vasculature;

separating the elongate tubular member from the delivery device to deploy the elongate tubular member, the deployed elongate tubular member displacing the stenosis radially outward to expand the vessel lumen; and

removing the elongate tubular member intact after a therapeutic period during which remodeling of the vessel occurs.

2. The method ofclaim 1, wherein the delivery device is coupled with the elongate tubular member and applies an axial force to actuate the elongate tubular member from an expanded configuration capable of providing the open lumen to a low crossing profile configuration; the method further comprising:

advancing tubular member on the delivery device in the low crossing profile configuration;

releasing the axial force on the elongate tubular member to cause the tubular member to move from the low crossing profile configuration to the expanded configuration.

3. The method ofclaim 2, wherein releasing comprises applying a tension force to a tension member that extends through a lumen of the delivery device.

4. The method ofclaim 1, wherein the tubular member includes a braided structure embedded therein.

5. The method ofclaim 4, wherein the braided structure comprises a cylinder that has a first diameter under a tensile axial load and a second diameter larger than the first when not subject to the tensile axial load, the cylinder having a third diameter when under a compressive axial load, the third diameter being larger than the second diameter.

6. The method ofclaim 1, wherein an outer surface of the tubular structure comprises a silicone material.

7. The method ofclaim 1, wherein the tubular member has an expanded size that is greater than the size of the vessel without stenosis.

8. The method ofclaim 7, wherein the tubular member has an expanded size that is about 20% greater than the size of the vessel without stenosis.

9. The method ofclaim 1, wherein the therapeutic period is less than about 60 days.

10. The method ofclaim 1, wherein removing the tubular member comprises:

advancing a low profile elongate body through the vasculature;

engaging the elongate body with the tubular member; and

applying an axial load to actuate the tubular member from an expanded configuration to a low crossing-profile configuration.

11. The method ofclaim 1, further comprising anchoring the tubular member by positioning tissue anchors proximally or distally of the stenosis.

12. The method ofclaim 1, wherein the anchors comprise one or more of a suture, a cuff configured to promote adherence of in vivo matter, and a surface treatment to enhance frictional engagement.

13. The method ofclaim 1, further comprising observing on at least two occasions the degree of enlargement of at least one of: (a) the size of tubular member, (b) the size of vessel segment being treated, (c) the flow through the tubular member, or (d) the flow through the vessel segment being treated to determine the therapeutic period.

14. The method ofclaim 1, wherein the elongate body is configured to expand continuously during a majority of the therapeutic period.

15. A method of bypassing a stenosis in the vasculature, comprising:

coupling a first graft member with a first vessel segment upstream of the stenosis and a second graft member with a second vessel segment downstream of the stenosis;

coupling a first end of a blood flow conduit with the first graft member and a second end of the blood flow conduit with the second graft member by applying a connection force; and

disposing the first and second graft members and the blood flow conduit beneath the skin of the patient, such that both the first and second ends of the blood flow conduit are outside the vasculature;

wherein a force required to disconnect the blood flow conduit from the first or second graft is significantly higher than the connection force.

16. The method ofclaim 15, wherein the blood flow conduit comprises a braided reinforcement embedded within a wall thereof along proximal and distal lengths of the conduit.

17. The method ofclaim 16, further comprising:

providing a connector to be disposed between at least one of (1) the first graft and the blood flow conduit and (2) the second graft and the blood flow conduit, the connector having at least one radial projection having an outer perimeter greater than the inner diameter of the blood flow conduit;

wherein coupling at least one of (1) the first graft with the blood flow conduit and (2) the second graft with the blood flow conduit comprising inserting at least a portion of the proximal and/or distal lengths of the blood flow conduit over the radial projection(s).

18. A method of bypassing a stenosis and providing vascular access, comprising:

providing a distal blood conduit and a proximal blood conduit comprising a graft and a connector having a retention feature located thereon, the distal blood conduit including a catheter comprising a braided structure embedded therein;

inserting a distal zone of the distal blood conduit into the vasculature and through a stenosis in the vasculature; and

advancing the catheter over a distal segment of the connector until at least a portion of the braided structure is positioned proximal of the retention feature.

19. The method ofclaim 18, further comprising cutting the catheter through the braided structure to size the catheter in-situ prior to advancing the catheter over the distal segment of the connector.

20. A system for bypassing a stenosis, comprising:

a catheter having a proximal portion, a distal portion, and an elongate body extending between the proximal and distal portions, the elongate body defining an inner wall having an inner perimeter defining a blood flow lumen, the catheter having a braided structure embedded in the elongate body and disposed about the lumen; and

a first connector for fluidly coupling a first vascular graft with the proximal portion of the catheter, the connector comprising:

a connector body having an outer surface defining a first outer perimeter and an inner surface defining a lumen; and

an engagement feature disposed on the outer surface of the connector body adjacent a distal end thereof, the engagement feature defining a second outer perimeter greater than the first outer perimeter; and

a second connector configured to securely engage a second vascular graft with the distal portion of the catheter;

wherein the proximal portion of the catheter has a first configuration in the free state wherein the inner perimeter is less than the first outer perimeter and a second configuration when in axial compression wherein the braided structure expands to permit the inner perimeter of the catheter body to expand such that the proximal end portion of the catheter can be advanced over the engagement feature of the connector body.

21. The system ofclaim 19, further comprising a first vascular graft pre-connected to the first connector and a second vascular graft pre-connected to the second connector.

22. The system ofclaim 19, wherein the second connector comprises:

a connector body having an outer surface defining a first outer perimeter and an inner surface defining a lumen; and

an engagement feature disposed on an outer surface of the connector body adjacent a distal end thereof, the engagement feature defining a second outer perimeter greater than the first outer perimeter.

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