Patent Description:
An interventional guide wire or other interventional device is often used in medical procedures that attempt to establish a pathway through a heavily stenosed or chronically occluded vessel. A chronically occluded vessel is referred to as containing a chronic total occlusion or CTO. During these procedures, the guide wire or device can only be of clinical benefit to establish vessel patency if it is advanced distally into the vessel true lumen.

One technique for restoring patency across a CTO involves advancing a guide wire through the intimal layer of the vessel wall and into the subintimal plane or space, where it can be further advanced distally beyond the CTO. Once in this sub-intimal plane beyond the CTO, it becomes difficult to navigate the guide wire or device back through the subintimal tissue layer to re-gain access into the vessel true lumen, sometimes referred to as a "reentry" into the vessel lumen from the sub-intimal space distally of the CTO. The layer of tissue that separates the vessel true lumen from the subintimal plane is typically in the range from <NUM> to <NUM> micrometers thick for vessels in the diameter range from <NUM> to <NUM>, and from <NUM> to <NUM> microns thick, in the largest vessels of the body.

A variety of catheters have been proposed for reentry around a CTO. One is described and shown in <CIT>. In this system, the re-entry catheter requires the operator to rotate a catheter shaft while observing a radiopaque marker on the catheter shaft to ensure that a side or lateral port is aimed at the true lumen of the blood vessel. Once the marker indicates the correct orientation of the lateral port, a cannula is extended through the lateral port in order to penetrate through the intimal layer of the blood vessel. It is believed that one drawback of this system is the requirement to rotate the catheter to the correct position while under fluoroscopic imaging otherwise an incorrect orientation of the cannula could cause failure to reenter the parent lumen and potentially cause damage to the vessel.

Another system is described and illustrated in <CIT>. In this publication, a balloon is used to orient the cannula into the proper orientation for re-entry into the true vessel lumen. To achieve this, the catheter utilizes an asymmetrical catheter lumen for the cannula. It is believed that this system also suffers from a similar drawback in that the lateral port of the cannula must be oriented in the correct direction towards the true lumen while under fluoroscopy. This is to ensure that the cannula does not penetrate away from the true lumen, which could lead to internal hemorrhaging.

Other intravascular catheter and cannula systems are disclosed for example in <CIT>and <CIT>.

Despite the foregoing and other efforts in the prior art, there remains a need for an improved reentry catheter and method for traversing total chronic occlusions.

The invention is defined in the independent claims <NUM> and <NUM>. Preferred embodiments are matter of the appended dependent claims. Subject-matter referred to as embodiments and/or disclosures which are not covered by the claims are not part of the invention.

Referring to <FIG>, there is disclosed a catheter <NUM> in accordance with one aspect of the present disclosure. Although primarily described in the context of a reentry catheter with a single central lumen, catheters of the present disclosure can readily be modified to incorporate additional structures, such as permanent or removable column strength enhancing mandrels, two or more lumen such as to permit drug or irrigant infusion or to supply inflation media to an inflatable balloon, or combinations of these features, as will be readily apparent to one of skill in the art in view of the disclosure herein.

The catheters disclosed herein may readily be adapted for use throughout the body wherever it may be desirable to create an extravascular access or a neo lumen, such as to traverse a CTO or otherwise exit and reenter the lumen. For example, catheter shafts in accordance with the present disclosure may be dimensioned for use throughout the coronary and peripheral vasculature, the gastrointestinal tract, the urethra, ureters, Fallopian tubes and other lumens and potential lumens, as well.

The catheter <NUM> generally comprises an elongate tubular body <NUM> extending between a proximal end <NUM> and a distal functional end <NUM>. The length of the tubular body <NUM> depends upon the desired application. For example, lengths in the area of from about <NUM> to about <NUM> or more are typical for use in femoral access percutaneous transluminal coronary applications. Intracranial or other applications may call for a different catheter shaft length depending upon the vascular access site, as will be understood in the art.

The proximal end <NUM> of catheter <NUM> is additionally provided with a manifold <NUM> having one or more access ports as is known in the art. Generally, manifold <NUM> is provided with a guidewire port <NUM> in an over-the-wire construction, and an optional side port <NUM> depending upon the desired functionality. Additional access ports may be provided as needed, depending upon the functional capabilities of the catheter. Manifold <NUM> may be injection molded from any of a variety of medical grade plastics, or formed in accordance with other techniques known in the art.

The tubular body <NUM> is provided with a reentry zone <NUM>, extending between a proximal exit port <NUM> and a distal exit port <NUM>, configured to permit exit of a guidewire therethrough. Preferably at least three or five or seven or more exit ports or port pairs are provided, arranged circumferentially offset from each other so that regardless of the rotational orientation of the catheter in the vessel, at least one exit port will be facing the direction of the true vessel lumen. The exit ports may be arranged in a spiral, with axially adjacent ports rotated from each other about the longitudinal axis of the catheter within the range of from about <NUM> degrees and <NUM> degrees, preferably between about <NUM> degrees and <NUM> degrees, and in some embodiments between about <NUM> degrees and <NUM> degrees.

In an axial direction, adjacent ports may be spaced apart by a distance within the range of from about <NUM> to about <NUM> or about <NUM> and about <NUM>. Side ports define a reentry zone <NUM> having an axial length from the proximal most port <NUM> to the distal most port <NUM> of at least about <NUM> and generally less than about <NUM>; in many implementations between about <NUM> and <NUM>. The side ports define a spiral that extends at least about <NUM> or <NUM> degrees around the catheter side wall but typically no more than about <NUM> degrees and in certain embodiments within the range of from about <NUM> degrees and <NUM> degrees.

Referring to <FIG> the coronary artery walls are made up of three main layers. The intima is the innermost layer consisting of a single layer of endothelial cells. The fibromuscualar media includes nonstriated myocytes. The adventitia is the outermost layer composed of collagen and elastin.

The intima layer can thicken considerably over time, occluding the blood flow through the artery. A chronic total occlusion (CTO) is a complete blockage of the artery. The present disclosure relates to a method (not claimed) to treat a CTO by creating a new lumen in the subintimal space (between the adventitia and intima) in order to allow blood flow in the artery around the occlusion.

Referring to <FIG>, a guidewire <NUM> is advanced through the arterial lumen <NUM> to the proximal side of an obstruction to be treated such as a CTO <NUM>. Progress of the wire <NUM> may be impeded or deflected due to the CTO. If the guidewire cannot cross the lesion, the guidewire may be passed distally beyond the lesion by way of an intentional dissection, and is advanced in a created subintimal channel between the intimal and medial layers of the arterial wall. This allows the guidewire <NUM> to cross the CTO <NUM> via the subintimal space. A reentry catheter <NUM> is then advanced over the guide wire <NUM>, following the guidewire from the native arterial lumen, through the dissection and into the subintimal space. The guidewire <NUM> may thereafter be retracted into the guide catheter.

As seen in more detail in <FIG>, the reentry catheter <NUM> exits the native lumen at a subintimal entry point <NUM>, and travels distally within the subintimal space. The guide wire <NUM> may thereafter be advanced distally within the reentry catheter <NUM> and rotated to find the exit port having the desired axial and rotational orientation to direct the guidewire <NUM> towards the native vascular lumen <NUM>. The guidewire may thereafter be distally advanced to exit through the selected exit port <NUM>, distal of the lesion <NUM>, for reentry into the native vascular lumen <NUM> at guidewire reentry point <NUM>.

Once the guidewire <NUM> has correctly reentered the lumen distally of the CTO, the reentry catheter <NUM> can be proximally retracted from the subintimal space leaving the guidewire in position via the neo lumen across the CTO. The reentry catheter can thereafter be withdrawn from the artery.

Any of a variety of procedures can be accomplished with the guidewire in position across the CTO. For example, referring to <FIG>, a balloon catheter <NUM> can be advanced over the guide wire <NUM> to position an inflatable balloon <NUM> in the subintimal space. Dilitation of the balloon can open a flow channel to cross the CTO via the subintimal space. The balloon may carry a balloon expandable stent <NUM> which can be expanded spanning the CTO to support the neo lumen against collapse following removal of the balloon as is understood in the art. Alternatively a self-expanding stent may be deployed across the CTO, preferably following a mechanical dilatation (e.g., balloon dilatation step).

Additional details of the catheter design may be seen with reference to <FIG>. A plurality of successive axially spaced exit ports <NUM> are arranged in a spiral such as a helix about the longitudinal axis of the catheter. The guide wire <NUM> may have a pre- bent tip so that it is biased laterally against the inside diameter of the reentry catheter sidewall. The guide wire may be distally advanced and rotated to align, for example, with distal most exit port <NUM> and advanced through that port.

Alternatively, if the native arterial lumen is in a different orientation relative to the reentry catheter <NUM>, the guide wire can be axially repositioned and rotated to align and exit via a second different exit port to reenter the arterial lumen at a different orientation as seen in <FIG>.

Referring to <FIG> and <FIG>, the proximal most port <NUM> and distal most port <NUM> define reentry zone <NUM> along which a plurality of ports <NUM> will generally encompass at least about <NUM> and preferably about <NUM> degrees around the circumference of the reentry catheter <NUM>. Generally between about <NUM> and <NUM> ports are provided with one embodiment between about six and ten ports. A reentry zone <NUM> having eight ports aligned along a <NUM> degree spiral results in <NUM> degrees of rotation between adjacent ports. Preferably, ports are arranged in sets of opposing pairs, as is discussed further below.

Referring to <FIG>, the ports will generally have a major axis <NUM> extending longitudinally along the catheter and a minor, transverse axis extending circumferentially around the tubular body. The major axis will typically be within about <NUM> degrees or <NUM> degrees or less from parallel with the catheter longitudinal axis and may be about parallel to the longitudinal axis as shown in <FIG>, or aligned with the spiral on which the ports reside.

The major axis <NUM> is generally longer than the minor axis <NUM>, and may be at least about <NUM>%, or <NUM>% or <NUM>% or more than the length of the minor axis <NUM>. In the present disclosure, all values expressed in inches are to be considered in the knowledge that <NUM> inch corresponds to <NUM> millimeters. In some implementations of a reentry catheter, the minor axis <NUM> is within the range of from about <NUM> inches to about <NUM> inches; or about <NUM> inches to about <NUM> inches. The major axis <NUM> is within the range of from about <NUM> inches to about <NUM> inches, or about <NUM> inches to about <NUM> inches. In one example, the port is about <NUM> by about <NUM> inches in a catheter having an OD of about <NUM> inches. The minor axis of the port may be less than about half of the tubular body OD and over about half of the catheter body ID.

Preferably, the ID of the tubular catheter body is at least about <NUM>% or <NUM>% or <NUM> % or <NUM>% or more of the OD of the GW intended to be used with the catheter. In one implementation, a catheter having an ID of about <NUM> inches is intended for use with a <NUM> inch guide wire. The difference between the diameter of the guide wire and the ID of the catheter is generally at least about <NUM> or about <NUM> or more, to facilitate manipulation of the guidewire and directing the guidewire towards a desired exit port.

In addition, the relatively large space between the guidewire and the ID of the catheter facilitates application of vacuum (e.g., up to about <NUM>" Hg, or <NUM> Hg) while the guide wire is in position extending through the tubular body, which allows negative pressure applied to the central lumen to produce suction at the exit ports for anchoring the catheter to the adjacent tissue. Anchoring the reentry zone to adjacent tissue may be desirable to stabilize the catheter and facilitate penetration during the step of puncturing tissue with the guidewire to reenter the vessel lumen distally of the obstruction.

The exit ports <NUM> may be spaced apart axially by a distance within the range of from about <NUM> inches to about <NUM> inches or in some embodiments from about <NUM> inches to about <NUM> inches. Multi-sized ports can be provided, with a first set of guidewire exit ports and a second set of smaller aspiration ports arrayed among the guidewire ports. Multiple sizes of ports may also be utilized for infusion of therapeutic agents.

A variety of port geometries and ramp geometries may be utilized to optimize control over port selection and guidewire exit. Referring to <FIG>, the edge of the catheter wall at the distal end of a port <NUM> may be provided with a ramped surface <NUM> configured to facilitate exit of the guidewire. Alternatively, a ramp surface <NUM> may be provided by forming a tab <NUM> that inclines radially inwardly in a proximal direction into the lumen. A guidewire with a laterally biased tip can be rotated and advanced until the tip enters the port assisted by the ramp <NUM> on the sidewall or on a tab.

Deflection of the guidewire may also be facilitated by an intermediate deflection element such a deflection guide <NUM>. The deflection guide <NUM> may comprise a shape memory (e.g., Nitinol) tube <NUM> that is preset to an angle upon proximal retraction of or distal advance from of a restraint.

Referring to <FIG>, there is illustrated a reentry catheter <NUM> including a reentry zone support <NUM> extending throughout the reentry zone <NUM>. The support <NUM> includes a tubular body <NUM> extending between a proximal end <NUM> and a distal end <NUM> and which carries a plurality of exit ports <NUM> spaced apart by a plurality of intervening flexible links <NUM>. Additional detail is described in connection with <FIG>.

Extending proximally from the support <NUM> is a kink resistance and torque transmission feature such as a braided tubular sidewall component <NUM>. Braid <NUM> may be a stainless steel braid having between about <NUM> and <NUM> filaments, and in one implementation <NUM> rectangular filaments having a width that is at least about 3x or 4x the thickness. The braid may overlay a coil layer <NUM>, which in one implementation is a four filar coil of <NUM>" tungsten wire at about <NUM>" pitch. The braid <NUM> overlaps the proximal end of the support <NUM>, but in the illustrated implementation the distal end of the coil <NUM> is spaced proximally apart from the proximal end of the support <NUM>.

At least a first eyelet frame <NUM> comprising an annular strut <NUM> encircles a guidewire exit port or aperture <NUM> on a first side of the tubular body <NUM>. In the illustrated embodiment, the first eyelet frame <NUM> is spaced apart from the proximal end <NUM> by a first flexible link <NUM> in the form of an elongated helical strut <NUM>. Proximal end <NUM> is additionally provided with a plurality of anchors such as at least about four or six or eight or more proximally extending ribs <NUM>, for facilitating attachment to the outer surface of an underlying catheter body component such as a woven or braided reinforcement layer as shown in <FIG>.

A second eyelet frame <NUM> in the form of a second annular strut <NUM> defines a second aperture <NUM>. Second eyelet frame <NUM> is space distally apart from the first eyelet frame <NUM> by a second flexible link <NUM> in the form of a second helical strut <NUM>. The total number of apertures in a reentry zone on a particular reentry catheter can be varied depending upon the desired clinical performance, as has been discussed elsewhere here in.

Referring to <FIG>, the distal end of the reentry support <NUM> is provided with at least about four or six or eight or more tip anchors such as axially extending ribs <NUM>. Ribs <NUM> may be provided with a circumferential segment <NUM> to create an interference fit when embedded in the polymer of the tip <NUM>, which may comprise 35D PEBAX. As shown in <FIG>, selected portions of the reentry support may be provided with a radiopaque marker such as a radiopaque coating layer. In the illustrated embodiment, the annular struts or eyelets that define the ports are provided with a layer of radiopaque material such as a Pt / Ir alloy, allowing an opposing port pair to appear as an oval aperture when aligned with the viewing axis.

As seen in <FIG>, a six port implementation is shown in which each aperture on a first side of the tubular body is paired with a second opposing aperture on the opposite side of the tubular body to form first, second and third aperture pairs <NUM>, <NUM> and <NUM>. A support <NUM> viewed from the perspective of <FIG> along an axis that extends at a perpendicular through each of the first and second windows 104A and 104B of the first aperture pair <NUM> appears under fluoroscopic visualization as a dark ring surrounding an opening, or an "O" or other indicium of a first rotational orientation.

The support <NUM> as shown in <FIG> has been rotated about its longitudinal axis by <NUM>° compared to <FIG>. Viewed from the same viewing angle, the first aperture pair <NUM> is no longer aligned with the viewing axis so the window 104A has visually disappeared. Instead a sidewall of the tubular body becomes opaque such as in the form of an "X" or other indicium of a second rotational orientation. The first and third aperture pairs <NUM>, <NUM> appear as an X or other indicium of non alignment. A further rotation of the support through an additional <NUM> degrees produces the view shown in <FIG>, in which the visualized "O" has moved to the third aperture pair <NUM>.

Thus, the white "O" will progress along the length of the support from exit port pair to next adjacent exit port pair, as a function of rotational orientation. In this manner, the clinician can determine the rotational orientation of the distal end of the catheter under fluoroscopic visualization by tracking the location of the O and the X's relative to catheter rotation. This facilitates rotational alignment of the catheter relative to the true lumen, and selection of the appropriate exit port for launching the guidewire through the selected port and in the direction of the true lumen.

Referring to <FIG>, there is illustrated an exploded view of the different functional components of the support. The components may be separately formed and connected such as by welding, or the entire assembly may be cut from a single piece of tubestock such as by laser cutting, EDM or other techniques known in the art.

Trackability and pushability are catheter characteristics that rely on the ability for the distal end of the catheter to push through the tortuous anatomy of the cardiac arteries. The consistency of the bending moments throughout the catheter shaft have significant impact on these use characteristics. The illustrated support insert comprises <NUM> discrete regions, labelled <NUM>-<NUM> in <FIG>.

Any of the pitch and width dimensions provided above can be varied by +/- <NUM>%, <NUM>% <NUM>%, or <NUM>% depending upon the desired performance.

Reinforcement of the apertures can be accomplished with multiple components that can articulate. Reinforcement may have spring like components for inter-connection. Material may be polymeric or metallic. Material may be radiopaque. Reinforcement will be layered within polymeric tubing to create a laminate structure. Ports may be cut through the braided regions before or after lamination. Multiple materials of construction may be used. Components may be welded together for robustness. Ports can be singulated (discrete components) and positioned in multiple orientations to optimize selection by the guidewire. Material may be polymeric or metallic. Ports can be single sided. Ports can be dual sided as illustrated.

One aspect of the disclosure involves aspiration via the side ports to secure adjacent tissue. Aspiration can be accomplished via the guidewire exit ports and / or separate aspiration ports.

For example, referring to <FIG>, there is illustrated a perspective cross section through a catheter body segment <NUM>, showing a guidewire lumen <NUM> in communication with at least one exit port <NUM>, and a separate aspiration lumen <NUM> in communication with at least one aspiration port <NUM>. In any of the embodiments disclosed herein, the aspiration lumen or guidewire lumen may also be used to infuse fluids which may include one or more drugs.

<FIG> illustrates a reentry catheter segment having relatively larger guidewire exit ports, and a plurality of smaller aspiration ports. Aspiration can be accomplished either via guidewire exit ports or dedicated aspiration ports. In either case, aspiration can reduce the blood volume in the neo lumen and or stabilize the wall of the neo lumen (intima) to facilitate puncture by the guidewire to facilitate reentry into the native lumen.

Blood aspiration flow rates, pressure may be controlled via an external vacuum source. Vacuum regulators may be provided to control flow rates, and absolute pressures. Guidwire Re-entry port design may also be used to aspirate blood during access into subintimal space. The vacuum source will be able to measure pressure differentials within the device. The vacuum source may be design as a stand-alone system or connected to a lab's vacuum source. Additionally, a pressure pump may be used as a vacuum source. Vacuum can be applied in a multitude of modes that are controlled by surgeon or automated. Pulsatile for effective aspiration of hematoma, pulsatile to allow axial advancement while removing hematoma, high pressure or low pressure pulsatile vacuum can be controlled by an automatic valve that pulses at a discrete or variable frequency.

<FIG> shows different visualization schemes that may be employed. Preferably, the distal tip has high radiopacity to facilitate visualization. First and second marker bands are preferably positioned at the proximal and distal ends of the reentry zone. In one implementation, the reentry zone may be substantially radiolucent, and the frame surrounding each exit port is radiopaque.

The catheter shaft may be steerable bi-directionally or unidirectionality. The catheter shaft may have the ability to accumulate torque between the handle and the tip. The catheter may have the ability to advance in a way that 'taps' to facilitate tracking - axial extension and compression. All of these characteristics are to facilitate tracking through tortuous anatomy and facilitate traversing the subintimal plane.

Referring to <FIG>, there is illustrated a bidirectionally steerable catheter <NUM>. A proximal control <NUM> such as a rotatable wheel or axial slider is in communication with a distal steering zone <NUM> by at least one and, as illustrated, two pull wires <NUM>, <NUM>. Manipulation of the control <NUM> to proximally retract the pull wire <NUM> will deflect the steering zone <NUM> in a first direction as illustrated. Proximal retraction of the second pull wire <NUM> will cause deflection of the steering zone <NUM> in a second, opposite direction.

Referring to <FIG>, the design may optionally incorporate an internal steerable guide sheath <NUM> between the guidewire and the catheter shaft. Guide sheath includes a guidewire lumen <NUM> which terminates distally in a ramped surface to direct a guidewire through a lateral guide wire port <NUM>. To prevent a physician from spinning a GW (trial and error) to get to a desired exit port, the sheath <NUM> will cover all holes except the desired re-entry port which is aligned with sheath port <NUM>. The user may easily select the desired ports by localizing the ports under fluoroscopy and axially and rotationally adjusting the guide sheath to aim at the desired exit port.

Referring to <FIG>, a dual-lumen catheter shaft may be provided to allow for a Rapid Exchange catheter design. A first, reentry guidewire may be advanced through the lumen accessed vial the proximal luer, and a second, navigational guidewire may be advanced through the second, rapid exchange lumen. In this configuration, the proximal exit port for the second, rapid exchange lumen will be located on a side of the catheter distally of the proximal luer, such as within about <NUM> or <NUM> or <NUM> of the distal end of the catheter.

The first lumen may also be used for aspiration while the second lumen may only be available for a guidewire. It may be desirable to isolate one or more lumens for aspiration, such as shown in <FIG>. For example a one-way valve may permit passing of a guidewire but also close when the guidewire is removed to facilitate aspiration via the other lumen.

Referring to <FIG>, the integrated handle may be connected to a power source (<NUM>) for therapeutic delivery while accessing the subintimal space. Power sources may include, for example, radio frequency generators for RF ablation or cryoablation generators, and a RF or cryo delivery element may be carried by the distal end of the catheter or by a removable catheter insert depending upon the desired functionality.

The integrated handle may also be connected to a vacuum source (<NUM>) for blood aspiration to prevent hematoma as well as assisting with device fixation within the subintimal space. The integrated device may include a vacuum accumulator within the handle that could interact with operator controls.

The integrated handle and one or two or more lumen extending throughout the catheter may also be configured to be compatible with a variety of commonly used tools for CTO crossing procedures, including guidewires, guide liners to increase stiffness for increase pushability, drilling microcatheters to gain access to the subintimal space; dilation balloon catheters; or infusion pumps for delivering therapeutic agents.

Referring to <FIG>, the catheter <NUM> provides the ability to access the subintimal space and achieve a variety of additional advantages such as the ability to deliver drugs such as therapeutic agents to help heal dissections, anticoagulants, or contrast, or monitor ECG signals. In addition, the catheter enables delivery of a variety of devices <NUM>, such as customized implants or sensors.

It may be desirable to coat the outside surface of the guidewire and/or the inside surface of the wall defining the guidewire lumen with a lubricous coating to minimize friction as the catheter <NUM> is axially moved with respect to the guidewire. A variety of coatings may be utilized, such as Paralene, Teflon, silicone rubber, polyimide-polytetrafluoroethylene composite materials or others known in the art and suitable depending upon the material of the guidewire or inner surface of the tubular wall.

In prior art intravascular catheters, the intended guidewire is normally configured to substantially occupy the guidewire lumen, with a minimal tolerance necessary to avoid excessive friction. For example, a catheter having a <NUM>" ID guidewire lumen might be used with a <NUM>" guidewire. The reentry guidewire of the present disclosure is preferably substantially smaller than the ID of the complementary lumen. For example, a <NUM>" guidewire may be used with a catheter <NUM> having a <NUM>" lumen. In general, the guidewire will have a diameter that is no more than about <NUM>%, and preferably no more than about <NUM>% or <NUM>% of the ID of the corresponding lumen. This provides an aspiration flow path in the space between the guidewire and the lumen wall to enable aspiration of blood from the intraluminal space and anchoring of the catheter against adjacent tissue while the guidewire remains in place. For example, with a <NUM>" guidewire present and a maximum vacuum pressure of 20mmHg, at least about <NUM>/Min, and preferably at least about <NUM>/MIN or at least about <NUM>/min of saline or water or more is aspirated.

The catheters of the present disclosure may comprise any of a variety of biologically compatible polymeric resins having suitable characteristics when formed into the tubular catheter body segments. Exemplary materials include polyvinyl chloride, polyethers, polyamides, polyethylenes, polyurethanes, copolymers thereof, and the like. Optionally, the tubular body may further comprise other components, such as radiopaque fillers; colorants; reinforcing materials; reinforcement layers, such as braids and helical reinforcement elements; or the like. In particular, the tubular body may be reinforced such as with an embedded coil or one or two or more braided tubular layers in order to enhance its column strength and torqueability while preferably limiting its wall thickness and outside diameter. The tubular body <NUM> may be produced in accordance with any of a variety of known techniques for manufacturing interventional catheter bodies, such as by extrusion of appropriate biocompatible polymeric materials.

Radiopaque markers may be provided at least at the distal end <NUM> and the proximal end of the reentry zone <NUM>. One suitable radiopaque marker comprises a metal band which is fully embedded within the catheter wall. Suitable marker bands can be produced from a variety of materials, including platinum, gold, and tungsten/rhenium alloy.

In many applications, the tubular body <NUM> is provided with an approximately circular cross-sectional configuration having an external diameter within the range of from about <NUM> inches to about <NUM> inches. In accordance with one embodiment of the invention, the proximal section of tubular body <NUM> has an external diameter of about <NUM> inches (<NUM> f) throughout most of its length. Alternatively, a generally oval or flattened cross-sectional configuration can be provided in a distal zone, as well as other noncircular configurations, depending upon the desired performance.

In a catheter intended for peripheral vascular applications, at least the proximal section of body <NUM> will typically have an outside diameter within the range of from about <NUM> inches to about <NUM> inches. In coronary vascular applications, the proximal section of body <NUM> will typically have an outside diameter within the range of from about <NUM> inches to about <NUM> inches. The OD of the catheter may taper or step to a smaller diameter or dimension in a distal zone.

Diameters outside of the preferred ranges may also be used, provided that the functional consequences of the diameter are acceptable for the intended purpose of the catheter. For example, the lower limit of the diameter for any portion of tubular body <NUM> in a given application will be a function of the number of fluid or other functional lumen contained in the catheter, together with the acceptable minimum performance characteristics.

For example, referring to <FIG>, a strain relief <NUM> may extend within the range of from about <NUM> to about <NUM>, or about <NUM> to about <NUM> from the proximal hub. The OD steps down from about <NUM>" to about <NUM>" (less than about <NUM>% or <NUM>% or less than about <NUM>% of the OD of the strain relief <NUM> section of the catheter body) distally of transition <NUM>. The catheter body distally of transition <NUM> may include at least two or three zones of distinct flexibility. In a modified <NUM> point bend test, a) a distal most zone will preferably exert between about <NUM>-<NUM>. 098067N (<NUM>-10gf) when deflected <NUM> but less than <NUM>. 1471N (15gf). An intermediate or mid shaft zone will preferably exert between about <NUM>-<NUM>. 196133N (<NUM>-20gf) when deflected <NUM> but less than <NUM>. 2942N (30gf), and a proximal zone will preferably exert between about <NUM>-<NUM>. 588399N (<NUM>-60gf) when deflected <NUM> but less than <NUM>. 980665N (100gf). Preferably, the catheter shaft will exert at least about <NUM> N-mm (<NUM> ozf-in) at the metallic insert junction when rotated <NUM> but less than <NUM> N-mm (<NUM> ozf-in).

The proximal zone may have a length within the range of from about <NUM> - <NUM>, and in some implementations from about <NUM> to about <NUM>. The intermediate zone may have a length within the range of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or about <NUM> to about <NUM>. The distal zone may have a length within the range of from about <NUM> to about <NUM>, from about <NUM> to about <NUM>, or about <NUM> to about <NUM>.

Claim 1:
An intravascular catheter (<NUM>) with fluoroscopically visible indicium of rotational orientation, comprising:
an elongate flexible tubular body (<NUM>), having a proximal end (<NUM>), a distal end (<NUM>) and a tubular side wall defining at least one lumen extending there through;
first, second, and third opposing pairs of radiopaque rings in the side wall, spaced axially apart from each other, each ring surrounding an exit aperture (<NUM>, <NUM>, <NUM>) formed within an eyelet in the side wall;
wherein a first transverse axis extending through the first pair of rings is rotationally offset within the range of from about <NUM>° to about <NUM>° from a second transverse axis extending through the second pair of rings, and the second transverse axis is rotationally offset within the range of from about <NUM>° to about <NUM>° from a third transverse axis extending through the third pair of rings.