Patent Description:
Due to age, high cholesterol and other contributing factors, a large percentage of the population has arterial atherosclerosis that totally occludes portions of the patient's vasculature and presents significant risk to the patient's health. For example, in the case of a chronic total occlusion (CTO) of a coronary artery, the result may be painful angina, loss of functional cardiac tissue or death. In another example, complete occlusion of the femoral or popliteal arteries in the leg may result in limb threatening ischemia and limb amputation.

Commonly known endovascular devices and techniques for the treatment of chronic total occlusions (CTOs) are either inefficient (resulting in a time consuming procedure), have a high risk of perforating a vessel (resulting in an unsafe procedure), or fail to cross the occlusion (resulting in poor efficacy). Physicians currently have difficulty visualizing the native vessel lumen, cannot accurately direct endovascular devices toward the visualized lumen, or fail to advance devices through the occlusion. Bypass surgery is often the preferred treatment for patients with chronic total occlusions, but surgical procedures are undesirably invasive. <CIT> discloses a vascular occlusion-crossing assembly. It includes an elongate delivery system and a flexible elongate member which passes along the body of the delivery assembly. A laterally-extending, vascular tunica-separation guide helps guide the distal end of the delivery assembly between tunica layers to a position distal of an occlusion. The distal' portion of a distally moving elongate member, typically a flexible hollow needle, is deflected into this distal lumen on the far side of an occlusion. A guidewire may be passed along the elongate member thereby crossing the occlusion. The invention is defined by the features of claim <NUM>. Embodiments not falling within the scope of the claims are no embodiments of the invention.

To address this and other unmet needs, the present disclosure provides, in exemplary non-limiting embodiments, devices for exploiting intramural (e.g., subintimal) space of a vascular wall to facilitate the treatment of vascular disease. For example, the devices disclosed herein may be used to (i) visually define the vessel wall boundary; (ii) protect the vessel wall boundary from perforation; (iii) bypass an occlusion; and/or (iv) remove an occlusion. Embodiments are described herein which perform these functions individually as well as collectively. These embodiments may be used in the treatment of a variety of vascular diseases such as chronic total occlusions in the coronary and peripheral arteries, but are not necessarily limited in terms of vascular site or disease state.

The embodiments presented herein are generally described in terms of use in the subintimal space between the intima and media for purposes of illustration, not necessarily limitation. It is contemplated that these embodiments may be used anywhere in the vascular wall (i.e., intrarnural) or between the vascular wall and an adjacent occlusion. It is also contemplated that these embodiments may operate at one or more intramural locations, and may operate within the outer limits of the vascular wall to avoid perforation out of the wall and into the pericardial space.

In one embodiment, devices and methods are disclosed herein which visually define the vessel wall boundary across an occlusion by placement of a circumferential radiopaque element in the subintimal space. In another embodiment, devices and methods are disclosed herein which protect the vessel wall boundary from perforation by a device passing through an occlusion by placement of a circumferential guard element in the subintimal space. In yet another embodiment, devices and methods are disclosed herein which bypass an occlusion by entering the subintimal space proximal of the occlusion, safely passing through the subintimal space past the occlusion, and re-entering the native lumen distal of the occlusion. Other embodiments exploiting the subintimal space are also disclosed.

It is to be understood that both the foregoing summary and the following detailed description are exemplary. Together with the following detailed description, the drawings illustrate exemplary embodiments and serve to explain certain principles. In the drawings:.

Generally, the various embodiments described herein exploit the subintimal space in a vascular wall for purposes of facilitating treatment of vascular disease. In the following detailed description, the embodiments have been organized in terms of their particular function: (i) visually defining the vessel wall boundary; (ii) guarding the vessel wall boundary from perforation; (iii) bypassing an occlusion; and (iv) alternative functions. This organizational approach is used for purposes of illustration and explanation, not for purposes of limitation, as some aspects of some embodiments may be utilized for more than one of the stated functions, and many embodiments have alternative functions not specifically stated or reflected by the organizational titles.

In order to understand the methods by which the embodiments described herein advantageously exploit the subintimal path, it is helpful to first understand the anatomical structures at hand.

With reference to <FIG>, a diseased heart <NUM> is shown schematically. Heart <NUM> includes a plurality of coronary arteries <NUM>, all of which are susceptible to occlusion. Under certain physiological circumstances and given sufficient time, some occlusions may become total or complete, such as total occlusion <NUM>.

As used herein, the terms total occlusion and complete occlusion are intended to refer to the same or similar degree-of occlusion with some possible variation in the age of the occlusion. Generally, a total occlusion refers to a vascular lumen that is <NUM>% or more functionally occluded in cross-sectional area, rendering it with little to no blood flow therethrough and making it difficult or impossible to pass a conventional guide wire therethrough. Also generally, the older the total occlusion the more organized the occlusive material will be and the more fibrous and calcified it will become. According to one accepted clinical definition, a total occlusion is considered chronic if it is greater than two (<NUM>) weeks old from symptom onset.

With reference to <FIG>, a magnified view of total occlusion <NUM> within coronary artery <NUM> is shown schematically. Generally, the proximal portion <NUM> of artery <NUM> (i.e., the portion of artery <NUM> proximal of total occlusion <NUM>) may be easily accessed using endovascular devices and has adequate blood flow to supply the surrounding cardiac muscle. The distal portion <NUM> of artery <NUM> (i.e., the portion of artery <NUM> distal of total occlusion <NUM>) is not easily accessed with interventional devices and has significantly reduced blood flow as compared to proximal portion <NUM>.

A commonly performed diagnostic procedure called an angiogram involves the infusion of a radiopaque fluid into the arterial bloodstream through a percutaneously placed angiography catheter. Using an x-ray fluoroscope, two-dimensional images of the arterial pathways may be obtained and recorded. <FIG> shows a schematic example of an angiographic image of a chronic total occlusion <NUM>. It is common that the angiogram allows a physician to visualize the proximal segment <NUM> but does not allow visualization of the occlusion <NUM> or the distal segment <NUM>.

With reference to <FIG>, a cut-away segment of coronary artery <NUM> is shown schematically. Coronary artery <NUM> includes a true or native lumen <NUM> defined by arterial wall <NUM>. The innermost layer of arterial wall <NUM> is called the intima or intimal layer <NUM> (for sake of clarity, the multi layer intima is shown as a single homogenous layer). Concentrically outward of the intima is the media or medial layer <NUM> (which also is comprised of more than one layer but is shown as a single homogenous layer). The outermost layer of the artery is the adventitia <NUM>. The transition between the outermost portion of the intima and the innermost portion of the media is referred to as the subintimal space, which may be delaminated to increase the space therebetween. The subintimal space is sometimes referred to as a false lumen, in contrast to true lumen <NUM>.

As may be appreciated from <FIG>, a total occlusion <NUM> prevents the occlusion and distal arterial segment <NUM> from being visualized using radiopaque contrast media injection fluoroscopy. In some instances, sufficient contrast media may pass through collaterals around the total occlusion <NUM> to achieve visualization of the distal segment <NUM>, but visualization of the distal segment <NUM> is often unclear and visualization of the occluded segment <NUM> is still not achieved. In some rare instances, sufficient radiopaque contrast may be injected retrograde through the venous system to achieve a fluoroscopic image of the distal segment <NUM>, but such images are often hazy and still do not illuminate the occluded segment <NUM>.

To achieve visualization of the occluded segment <NUM> and the distal segment <NUM>, a radiopaque subintimal device <NUM> may be introduced into the subintimal space as shown in <FIG>. In this illustration, subintimal device <NUM> is intended to be relatively generic, as a variety of subintimal devices may be employed as will be described in more detail hereinafter. The subintimal device <NUM> exits the true lumen <NUM> and enters the subintimal space <NUM> at entry point <NUM> proximal of the total occlusion <NUM> somewhere in the proximal segment <NUM>. Within the subintimal space <NUM>, the subintimal device <NUM> may extend across and beyond the total occlusion <NUM> and into the distal segment <NUM>. With the subintimal device positioned as shown in <FIG>, and due to the radiopaque nature of the subintimal device <NUM>, the occluded segment <NUM> and distal segment <NUM> may be fluoroscopically visualized as shown in <FIG>.

Thus, subintimal device <NUM> may be used to enhance arterial visualization by placement within the subintimal space <NUM> concentrically around the total occlusion <NUM>. The subintimal device <NUM> defines the approximate inside diameter of the artery <NUM> and also defines axial bends or tortuosity in the vessel <NUM> across the occluded segment <NUM> and distal segment <NUM>, thereby defining the circumferential boundary of the artery <NUM> across the occluded segment <NUM> and distal segment <NUM>. Also, by placement within the subintimal space <NUM> concentrically around the total occlusion <NUM>, the subintimal device <NUM> may be used to protect or guard the wall <NUM> of the artery <NUM> from perforation of devices that attempt to penetrate the total occlusion <NUM> via the true lumen <NUM>.

As shown in <FIG>, the subintimal device <NUM> is deployed in a helical pattern within the subintimal space <NUM>. The helical pattern is shown for purposes of illustration, not limitation, as other patterns may be employed as well. Various other deployment patterns are described in more detail hereinafter, but the helical pattern is used herein to further illustrate the concept.

With reference to <FIG>, a deployment device <NUM> is shown schematically. Deployment device <NUM> may be used to direct the subintimal device <NUM> into the subintimal space <NUM> at entry point <NUM> and deploy the subintimal device <NUM> in a helical pattern therein as shown in <FIG>. The deployment device <NUM> may take the form of a balloon catheter including catheter shaft <NUM> and distal balloon <NUM>. Catheter shaft <NUM> includes an outer tube <NUM> and an inner tube <NUM> defining an inflation lumen <NUM> therebetween for inflation of balloon <NUM>. The inner wire tube <NUM> defines a guide wire lumen <NUM> therein for advancement of the device <NUM> over a guide wire (not shown). A delivery tube <NUM> extends along the outer tube <NUM> and around the balloon <NUM> in a helical (or other) pattern. The delivery tube <NUM> defines a delivery lumen <NUM> therein for advancement of the subintimal device therethrough. In this particular embodiment, the subintimal device <NUM> may have a straight configuration in its relaxed state and rely on the helical delivery tube <NUM> to achieve the desired helical pattern.

With reference to <FIG>, the delivery device <NUM> is shown in position just proximal of the total occlusion <NUM>. In this position, the balloon <NUM> may be inflated within the vessel lumen <NUM> to direct the delivery tube <NUM> toward the vessel wall <NUM> at an orientation for the subintimal device <NUM> to penetrate through the intima <NUM> at an entry point and into the subintimal space. By virtue of the helical delivery tube <NUM>, the subintimal device <NUM> is sent on a helical trajectory as it is advanced through delivery tube <NUM> resulting in deployment of the subintimal device <NUM> in a helical pattern. As shown, the subintimal device <NUM> has been advanced through the delivery tube <NUM> and positioned concentrically outside the total occlusion <NUM>, outside the intimal layer <NUM>, and inside the medial layer <NUM> in the subintimal space.

With reference to <FIG>, an alternative approach to achieving a helical pattern in the subintimal space is shown. Whereas the delivery device <NUM> described previously provided a helical delivery tube to deliver a subintimal device <NUM> that had a straight configuration in its relaxed state, <FIG> schematically illustrates an alternative subintimal device <NUM> that may assume a helical shape itself. Subintimal device <NUM> includes an elongate tubular shaft <NUM>, at least a distal portion of which includes a helical interlocking gear <NUM> and a helical wire coil <NUM> disposed thereon. A helically shaped inner mandrel or tube <NUM> may be disposed in the tubular shaft <NUM> such that the shaft <NUM> rotates freely thereon. The shaft <NUM> may have a linear or straight configuration in a relaxed state and a helical configuration (shown) when the helically shaped inner member <NUM> is disposed therein. The device <NUM> may be disposed in a constraining sheath (not shown) and navigated to the intravascular site, such as the site of a total occlusion. When the device <NUM> is advanced distally out the end of the constraining sheath or when the sheath is pulled proximally relative thereto, the distal portion of the device <NUM> assumes a helical shape as shown. The shaft <NUM> may be rotated relative to the inner member <NUM> to cause rotation of the helical wire threads <NUM>, which may be used to engage the vessel wall and advance around the total occlusion in the subintimal path. A bearing (not shown) may be disposed on the inner member <NUM> to engage the proximal or distal end of the shaft <NUM> to enable the shaft <NUM> and the inner member <NUM> to be advanced in unison. Subintimal device <NUM> may include any of the variants described hereinafter, such as various gear shaft configurations, distal atraumatic tip configurations, fluidic dissection mechanisms, etc..

Generally, the subintimal devices described herein are designed for intravascular navigation and atraumatic subintimal passage. The subintimal devices <NUM> may be constructed similar to a guide wire and may include elements to atraumatically pass through the subintimal space. Such atraumatic elements may be employed to minimize damage to arterial wall and to minimize the likelihood of perforation therethrough. Examples of such atraumatic elements <NUM> are schematically illustrated in <FIG>. The subintimal device may include a ball-shaped tip 310A as shown In <FIG>, a hook-shaped or loop-shaped tip 310B as shown in <FIG>, and/or a bent tip 310C as shown in <FIG>. These atraumatic elements distribute axial forces over larger areas of tissue and thereby reduce the chance of vessel perforation. An additional aspect of the bent tip 310C is ability to torsionally direct the tip and control the path of the device through the subintimal space. The ball tip 310A may be formed from a suitable metallic material including but not limited to stainless steel, silver solder, or braze. The ball tip 310A may also be formed from suitable polymeric materials or adhesives including but not limited to polycarbonate, polyethylene or epoxy. Note that the ball tip 310A may be bulbous and larger than the shaft proximal thereto. The loop tip 310B and bent tip 310C may be created during the manufacturing process (for example by heat setting or mechanical deformation) or the tip may be shaped (for example by mechanical deformation) by the physician.

As an alternative or in addition to the atraumatic tip elements <NUM> as described above, the subintimal device <NUM> may use a guide wire <NUM> to facilitate atraumatic passage as shown in <FIG>. In this embodiment, the subintimal device <NUM> may include a lumen extending therethrough such that the device <NUM> may be advanced over the guide wire <NUM>. In this embodiment, the body of the subintimal device <NUM> has a hollow internal diameter defining a guide wire lumen therein. The guide wire lumen extends from a proximal opening to a distal opening and is sized to accept a guide wire <NUM> therethrough. The guide wire <NUM> provides an atraumatic element at its distal end and also provides a mechanism for rotationally steering the subintimal device <NUM> through the subintimal space. The guide wire <NUM> may be pushed forward by the subintimal device through a bearing element (not shown) at the proximal or distal end of the subintimal device. The bearing element may provide interference in the axial direction while allowing for relative rotation between the subintimal device and guide wire. An example of a bearing element may be a collar crimped to the distal end of the guide wire with an outside diameter larger in dimension than the guide wire lumen within the subintimal device.

Other techniques may be employed to facilitate atraumatic passage through the subintimal space. For example, pressurized fluid may be used to facilitate atraumatic passage and even promote atraumatic dissection of the layers defining the subintimal space. <FIG> schematically illustrate a system <NUM> that utilizes fluid to achieve atraumatic passage and promote dissection. System <NUM> includes a subintimal device <NUM> and associated pumping system <NUM>. The fluidic system <NUM> is similar in certain aspects to the arrangements described elsewhere herein, the various aspects of which may be combined or used in the alternative as will be appreciated by those skilled in the art. System <NUM> includes a subintimal device <NUM> which may comprise any of the tubular subintimal devices described herein. Generally, subintimal device <NUM> includes a tubular shaft <NUM> having a proximal end connected to a pumping mechanism <NUM>. A plunger rod <NUM> is slidably disposed in the tubular shaft <NUM> as shown in <FIG> and its proximal end is connected to a linear actuator <NUM> of the pumping mechanism as shown in <FIG>. The rod <NUM> extends through the tubular shaft <NUM> to a point proximal of the distal end thereof to define a pumping chamber <NUM>. A source of liquid <NUM> (e.g., saline bag) is connected to the proximal end of the subintimal device <NUM> via a fluid line <NUM> and optional valve <NUM> to supply liquid to the annular lumen between the rod <NUM> and the inner wall of the tubular shaft <NUM>. As the linear actuator moves the rod <NUM> back and forth in the tubular shaft <NUM>, liquid is caused to be expelled out of the chamber <NUM> in a pulsatile fashion, which may be used to hydraulically dissect tissues to define a subintimal path as described previously, for example. Optionally, a balloon may be disposed on the distal end of the device such that it is cyclically inflated and deflated with the pulsatile flow to cause controlled dissection. The stroke length, stroke rate and stroke volume may be adjusted to achieve the desired effect. For example, the stroke volume of the chamber <NUM> may be relatively small (<NUM><NUM> - <NUM><NUM> (<NUM> cc - <NUM> cc), for example), such that liquid exits the chamber <NUM> with high energy that dissipates quickly to minimize trauma to tissues as they are dissected. One example is a stroke volume of <NUM><NUM> (<NUM>. 25cc) and a a stroke rate of <NUM> which has been found to facilitate atraumatic passage and even promote atraumatic dissection in a bench-top model using animal tissues.

Another technique to facilitate or supplement atraumatic passage of the subintimal device is to reduce friction between the device and the surrounding tissues. The fluidic embodiment described above benefits from this technique in that saline acts to reduce friction. Friction may also be reduced by using coatings (e.g., PTFE, hydrophilic materials, etc.) which may be applied to the external surface of the subintimal device. Friction may also be reduced by taking advantage of the fact that the kinetic coefficient of friction is usually less than the static coefficient of friction for a given frictional interface. As applied to the subintimal devices described herein, the lower kinetic coefficient of friction may be utilized by rotating the device back and forth between tissues in the subintimal space. Such reciprocal rotational motion may be applied manually by rolling the proximal end of the device between the user's thumb and forefinger, or may be applied using automatically using a reciprocal motor drive, for example.

Whether it is to reduce friction, to facilitate steering, or to facilitate advancement, it may be desirable to incorporate enhanced torsional characteristics in the body <NUM> of the subintimal device <NUM> as schematically shown in <FIG>. Generally, it is desirable to maintain flexibility of at least a distal portion of the body <NUM> to avoid compromising intravascular navigation in tortuous pathways. <FIG> schematically shows a generic subintimal device <NUM> with a distal body portion <NUM> and a proximal body portion <NUM>. Relative to the proximal body portion <NUM>, the distal body portion may be more flexible since it will frequently encounter a tortuous pathway. The proximal body portion may only encounter minimal bends in a guide catheter or the like, and therefore may be made more stiff yet torsionally rigid as with a metal tube (e.g., stainless steel hypotube).

One example of a flexible yet torsionally rigid distal body <NUM> design is shown in <FIG>. In this embodiment, distal body portion <NUM> is made of a multitude of independent coils <NUM>, <NUM>, <NUM> concentrically wound in opposing directions. These coils can diametrically interact (for example internal coil diametrically expands while the-external coil diametrically contracts) with an applied torque. This interaction can provide torsional strength while maintaining axial flexibility. The core of the distal body <NUM> may be hollow or may contain a fixed wire <NUM> within its internal lumen. The fixed wire <NUM> may provide an increase in axial and/or torsional stiffness, and may also have a tapering cross-section to increase flexibility in the distal direction. A hollow core may be used for insertion of a guide wire. Coils <NUM>, <NUM>, <NUM> and core wire <NUM> may be made of suitable metallic or polymeric materials including but not limited to stainless steel, nickel titanium, platinum or ultra high molecular weight polyethylene.

Another example of a flexible yet torsionally rigid distal body <NUM> design is shown in <FIG> wherein a single coil <NUM> is wound over an internal core <NUM> surrounded by a thin polymeric sheath <NUM>. Yet another example of a flexible yet torsionally rigid distal body <NUM> design is shown in <FIG> and <FIG> wherein the body simply comprises a single open wound coil <NUM>.

A further example of a flexible yet torsionally rigid distal body <NUM> design is shown in <FIG>. The distal body <NUM> may be constructed in part or in to total of a single layer coil with geometric features along the coil length that allow adjacent coils to engage (for example mechanical engagement similar to the teeth of a gear). <FIG> shows coil <NUM> closely wound with a multitude of teeth <NUM> along the coil edges in contact such that the peaks of one coil falls within the valleys of the adjacent coil. A conventional coil (without teeth) reacts to an applied torsional load by diametrically expanding or contracting, thus forcing the wire surfaces within a turn of the coil to translate with respect to its neighboring turn. The construction of coil <NUM> resists the translation of wire surfaces within the coil thus resisting the diametric expansion or contraction (coil deformation). An increased resistance to coil deformation increases the torsional resistance of the device body while the coiled construction provides axial flexibility.

This design may be implemented in manner shown in <FIG>. The subintimal device <NUM> includes a proximal body portion <NUM> that is formed of a continuous solid metallic tube <NUM> and a distal body portion <NUM> that is formed of the same tube with a laser cut coil segment <NUM>, wherein the pattern of the laser cut defines the teeth <NUM>. Suitable materials for the metallic tube include but are not limited to stainless steel and nickel titanium. Alternatively, the coil <NUM> may be wound from a continuous wire. The wire may have a cross section that for example has been mechanically deformed (stamped) to form the teeth <NUM> and allow coil engagement.

<FIG> shows one example of a laser cut pattern from the circumference of a tube that has been shown in a flat configuration for purposes of illustration. In the pattern shown in <FIG>, the teeth <NUM> are generally trapezoidal and extend orthogonal to the coil turns <NUM>. <FIG> shows an alternative pattern wherein the teeth are generally rectangular (with a clipped corner) with a major (longer) length extending parallel to the axis of the body. The parallel orientation and longer length of the teeth <NUM> shown in <FIG> promote engagement and reduce slippage of adjacent coil turns <NUM>.

As mentioned previously, another application of a flexible yet torsionally rigid subintimal device is to facilitate advancement through the subintimal space using threads that rotationally engage vascular tissues similar to a threaded screw. <FIG> shows a subintimal device <NUM> wherein at least the distal body portion <NUM> includes threads <NUM> on the exterior surface thereof. The threads <NUM> act like an external corkscrew that has the ability to rotationally engage the arterial tissues and help drive the subintimal device <NUM> through the subintimal space. <FIG> are cross-sectional views taken along line A-A in <FIG> and show various alternative embodiments for the threads <NUM>. <FIG> shows one or more round corkscrew members <NUM> that are concentrically wound on the outside of the distal body <NUM>. <FIG> shows a multi-layer coil construction with coil layers <NUM>, <NUM>, <NUM> where corkscrew member <NUM> comprises a wire element of larger cross sectional area wound within the external concentric coil <NUM>. The corkscrew members may have a rounded shape as shown in <FIG>, or other shape such as triangular, square, or other cross-sectional shape that may aid in tissue engagement and subintimal device advancement. <FIG> shows a polymer tube with a corkscrew profile <NUM> formed therein and concentrically positioned around distal body portion <NUM>. In each of these embodiments, withdrawal of the subintimal device <NUM> may be achieved by rotating the device in the opposite direction thus driving the device back out of the subintimal space.

In some instances, it may be desirable to utilize an over-the-wire type subintimal device to facilitate advancement into and through the subintimal space. In addition to the embodiments described previously, <FIG> illustrate additional over-the-wire type embodiments of subintimal devices. These embodiments may also be used to facilitate guide wire advancement through a total occlusion, such as when it is desirable to stay in the true lumen.

<FIG> shows an over-the-wire type subintimal device <NUM> (or wire support device) having a coiled gear design <NUM> as described with reference to <FIG> and a thread design <NUM> as described with reference to <FIG>. The device <NUM> has a hollow core and may be advanced over a guide wire <NUM>. The geared coils <NUM> provide axial flexibility and torsional rigidity and the external helical threads provide mechanical engagement with the lesion or arterial wall. <FIG> shows an over-the-wire type subintimal device <NUM> (or wire support device) in longitudinal section, with an inner tube <NUM> having a coiled gear design <NUM>, and an outer tube <NUM> having a thread design <NUM>. The inner tube <NUM> contains a guide wire lumen capable of accepting a conventional guide wire <NUM>. <FIG> shows a partial enlarged view of an alternative inner tube <NUM> where a gaps <NUM> between adjacent coils allow articulation of the inner tube <NUM> upon proximal withdrawal of actuation wire <NUM>. Outer tube <NUM> may freely rotate with respect to inner tube <NUM> when the inner tube <NUM> is in both the straight and actuated positions.

In the foregoing embodiments, the subintimal device enters the subintimal space via an entry point. In other words, the subintimal device extends from the true lumen and into the subintimal space through the entry point. This may be accomplished by directing a subintimal device toward the intimal layer and penetrating therethrough. Alternatively, a guide wire may be used to penetrate the intimal layer and enter the subintimal space. This latter approach may be more commonly employed since physicians often find themselves unintentionally entering the subintimal space with a guide wire. However, to facilitate definitive exploitation of the subintimal space, the embodiments described herein intentionally facilitate penetration of the intimal layer and entry into the subintimal space, which is contrary to conventional current practice.

It is contemplated that a bare guide wire (i.e., a guide wire without a directing catheter) using a bent tip at a length and angle sufficient to engage the intima away from the true lumen, may be used to intentionally penetrate the intima and enter the subintimal space. However, a directing catheter may be employed to consistently and predictably facilitate entry into the subintimal space. As illustrated in <FIG>, various directing devices may be used to direct the subintimal device (or guide wire over which the subintimal device is advanced) to engage and penetrate the intimal layer and enter the subintimal space.

<FIG> schematically illustrates a directing catheter <NUM> substantially similar to an over-the-wire balloon catheter including a distal balloon <NUM> with the addition of a delivery and directing tube <NUM>. As shown, the directing catheter <NUM> has been advanced over a conventional guide wire <NUM> and inflated proximal to the total occlusion <NUM>. For the sake of clarity, <FIG> shows a subintimal device path that is substantially parallel to the vessel lumen, but other orientations (e.g., helical) may also be employed. The delivery and directing tube <NUM> may be positioned adjacent to and pointed slightly outward and toward the intimal layer <NUM> such that the subintimal device <NUM> may be advanced to perforate the subintimal layer <NUM>. A fluid source (e.g., syringe) <NUM> may be connected to be in fluid communication with the delivery and directing tube <NUM> via an infusion tube <NUM>. Fluid may flow from the fluid source <NUM> through the delivery and directing tube <NUM> under a controlled pressure or a controlled volume. The infused fluid may enter the subintimal space <NUM> directly from the delivery and directing tube <NUM> or from the true lumen <NUM> space defined between the distal end of the balloon <NUM> and the proximal edge of the occlusion <NUM>. The fluid may be radiopaque contrast media to facilitate fluoroscopic visualization of the subintimal space, and/or may be used to delaminate the intimal layer <NUM> and medial layer <NUM> defining the subintimal space <NUM>. <FIG> schematically illustrates an alternative embodiment of directing catheter <NUM> wherein the fluid source <NUM> is in fluid communication with a lumen within the subintimal device <NUM> thereby directly infusing fluid into the subintimal space <NUM> via subintimal device <NUM>. <FIG> schematically illustrates another embodiment wherein the directing catheter <NUM> is similar to a sub-selective guide catheter wherein the distal end <NUM> has a predefined shape or an actuating element that allows manipulation by the physician intra-operatively to direct the subintimal device <NUM> toward the intimal layer for penetration therethrough.

Once the subintimal device is in the subintimal space, the intima may be delaminated from the media to open the subintimal space by blunt dissection as the subintimal device is being advanced. Alternatively, the intima may be delaminated from the media using pressurized fluid as described previously. As a further alternative, the layers may be delaminated by actuation as illustrated in <FIG>. Subintimal device <NUM> may be actuated or self-expanded between a collapsed configuration shown in <FIG> and an expanded configuration shown in <FIG>. The device <NUM> may be advanced in a collapsed state until resistance is felt, and then expanded to delaminate layers in the expanded state in order to propagate the subintimal dissection. The subintimal device <NUM> may comprise a shaft <NUM> having a plurality of resilient expandable elements <NUM> (e.g., heat set NiTi) and an atraumatic tip <NUM> (shown bent). A sheath <NUM> may be disposed about the proximal shaft <NUM> and the expandable elements <NUM> to retain the expandable elements <NUM> in a collapsed configuration as shown in <FIG>. Upon proximal retraction of the sheath <NUM> (or distal advancement of the shaft <NUM>) the expandable elements <NUM> elastically expand as shown in <FIG> to cause propagation of the dissection. The sheath <NUM> may be advanced to collapse the expandable elements <NUM> and the device <NUM> may be advanced further into the subintimal space. Alternatively, the actuation mechanism may comprise an inflatable balloon that dissects when inflated and is advanceable when deflated.

<FIG> schematically illustrate an alternative subintimal crossing device <NUM>. Subintimal device <NUM> may be actuated or self-expanded between a collapsed configuration shown in <FIG> and an expanded configuration shown in <FIG> to delaminate the layers of the vascular wall. Alternatively, the subintimal device <NUM> may be nominally in the expanded configuration and collapsible upon retraction. The device <NUM> may be advanced in a collapsed state until resistance is felt, and then expanded to delaminate layers in the expanded state in order to propagate the subintimal dissection. The subintimal device <NUM> may comprise a flexible shaft <NUM> and an expandable element <NUM>. The shaft may comprise a flexible superelastic metal tube (e.g., NiTi) or a composite polymeric shaft (e.g., braid reinforced polyether block amide). The expandable element <NUM> may be connected to the distal end of the shaft <NUM> using an adhesive or weld joint, for example. The expandable element <NUM> may comprise a plurality of braided filaments formed of a resilient material such as NiTi, and may be heat set in the expanded state or the collapsed state. The distal end of the expandable element <NUM> may comprise an atraumatic tip comprising, for example, a weld ball <NUM> securing the individual braided filaments. The expandable element <NUM> may be expanded by pushing on the shaft <NUM> when resistance to advancement is encountered, thus delaminating adjacent tissue layers. Alternatively, the expandable element <NUM> may be expanded by pushing on the shaft <NUM> and pulling on a pull wire (not shown) attached to the distal end of the expandable element <NUM> and extending proximally through the lumen of the shaft <NUM>. A flexible polymeric sheath <NUM> may be used to facilitate delivery of the crossing device <NUM>, provide and maintain a crossing path within the vascular wall, and/or to facilitate removal of the crossing device <NUM> as shown in <FIG>. The polymeric sheath <NUM> may alternatively comprise an orienting device as described herein or another intravascular device (e.g., balloon catheter) configured to be advanced over a guide wire or the like.

<FIG> schematically illustrate an alternative subintimal crossing device <NUM>. Subintimal device <NUM> includes an elongate flexible and torqueable shaft <NUM> and a distal elastic loop <NUM> formed of a superelastic metal alloy such as NiTi, for example. The loop <NUM> may be self-expanded between a collapsed configuration shown in <FIG> and an expanded configuration shown in <FIG>. The device <NUM> may be advanced distally through sheath <NUM> for delivery and pulled proximally into sheath <NUM> for removal. When expanded, the loop <NUM> may be substantially planar, and with rotation of the shaft <NUM>, the loop <NUM> rotates in the subintimal space forcing delamination of tissue layers.

The foregoing embodiments generally involve penetrating the intimal layer, placing a subintimal device in the subintimal space, and traversing across the occluded segment for purposes of defining the vascular boundary and/or for purposes of guarding against perforation. The following bypass embodiments also involve the initial steps of penetrating the intimal layer, placing a subintimal device in the subintimal space, and traversing across the occluded segment. To this end, the devices and methods described with reference to boundary definition and perforation guard embodiments have application to the following bypass embodiments.

In addition to penetrating the intimal layer, entering the subintimal space, and traversing the occluded segment, the following bypass embodiments generally involve orientation and re-entry into the true lumen. A general approach to the foregoing bypass embodiments is schematically illustrated in <FIG>. A guide wire <NUM> may be advanced through the proximal segment <NUM> of the true lumen <NUM> of the occluded artery to the proximal edge of the total occlusion <NUM> adjacent the vessel wall <NUM> as shown in <FIG>. By manipulating and directing the guide wire <NUM> to the proximal edge of the total occlusion <NUM> toward the wall <NUM>, the guide wire <NUM> may penetrate the intimal layer <NUM> and enter the subintimal space <NUM> between the intima <NUM> and the media/adventitia <NUM>/<NUM> as shown in <FIG>. The manipulating and directing of the guide wire <NUM> as described above may be performed by using the guide wire alone or by using any of the directing devices described herein. With the guide wire <NUM> in the subintimal space <NUM>, a subintimal device <NUM> may be advanced over the guide wire <NUM> as shown in <FIG>. In the illustrated embodiment, the subintimal device <NUM> includes a hollow elongate shaft <NUM> and an atraumatic bulbous tip <NUM>. However, any of the subintimal devices described herein may be employed, particularly the over-the-wire type subintimal devices. As shown in <FIG>, the subintimal device <NUM> may be further advanced over the guide wire <NUM> such that the tip <NUM> resides in the subintimal space <NUM>. At this procedural stage, the guide wire <NUM> may be withdrawn, completely removing it from the subintimal device <NUM>. Further manipulation of the subintimal device <NUM> (both axial advancement and radial rotation) allows blunt dissection of the layers defining the subintimal space <NUM> and advancement of the device <NUM> to the distal portion of the total occlusion <NUM> as shown in <FIG>. Penetration of the intimal layer <NUM> and re-entry into the distal segment <NUM> of the true lumen <NUM> distal to the occlusion <NUM> may be achieved by various means described later in detail, which generally include the steps of orientation toward the center of the true lumen <NUM> and penetration of the intimal layer <NUM>. For purposes of illustration, not limitation, <FIG> shows a shaped re-entry device <NUM> having a curled and sharpened tip exiting the lumen of the subintimal device <NUM> distal of occlusion <NUM> and entering the distal segment <NUM> of the true lumen <NUM> through the intimal layer <NUM>. With re-entry device <NUM> in the distal segment <NUM> of the true lumen <NUM>, the subintimal device <NUM> may be advanced into the true lumen <NUM> over the re-entry device <NUM> as shown in <FIG>. The re-entry device <NUM> may be withdrawn from the subintimal device <NUM> and the guide wire <NUM> may be advanced in its place as shown in <FIG>, after which the subintimal device <NUM> may be withdrawn leaving the guide wire <NUM> in place. As such, the guide wire <NUM> extends from the proximal segment <NUM> of the true lumen <NUM> proximal of the occlusion <NUM>, traverses the occluded segment via the subintimal space <NUM>, and reenters the distal segment <NUM> of the true lumen <NUM> distal of the occlusion <NUM>, thus bypassing the total occlusion <NUM> without exiting the artery. With the guide wire <NUM> so placed, the subintimal space <NUM> may be dilated (e.g., by balloon angioplasty or atherectomy) and stented, for example, or otherwise treated using known techniques.

As mentioned above, re-entry into the true lumen from the subintimal space generally involves orientation toward the center of the true lumen and penetration of the intimal layer. Although fluoroscopy is a commonly available visualization tool used during interventional procedures, it only provides two-dimensional images which are typically insufficient, taken alone, to determine the proper direction for penetration from the subintimal space toward the center of the true lumen. As such, those skilled in the art may use visualization tools with greater accuracy or with the ability to show three dimensional data. For example, intravascular ultrasound (IVUS) or magnetic resonance imaging (MRI) may be used to determine the position and direction of true lumen re-entry from the subintimal space. However, such techniques are time consuming, expensive and often impractical, and therefore it would be desirable to facilitate orientation (i.e., direct a re-entry device from the subintimal space toward the true lumen distal of a total occlusion) without the need for such burdensome visualization techniques.

Various orientation and re-entry embodiments are described herein that take advantage of the position and geometry of the subintimal space relative to the true lumen to facilitate effective orientation of a re-entry device from the subintimal space toward the true lumen. This may be accomplished by recognizing that the subintimal space is generally annular with its radial center at the center of the true lumen. Thus, a curved device deployed in the subintimal space defines at least an arc and at most a full circle (in radial cross-section), the radial center of which must reside at the center of the true lumen. In other words, if a curved device that is deployed in the subintimal space such that the curvature of the device is aligned with the curvature of the subintimal space, then the true lumen is by necessity oriented toward the concave side of the curved subintimal device. A re-entry device may then be keyed or otherwise oriented to the concave side of the subintimal device, and is thus automatically oriented toward the true lumen without visualization.

One such embodiment that operates under this premise is shown schematically in <FIG>. In this embodiment, a helical subintimal device <NUM> is shown generically, the features of which may be incorporated into other subintimal device embodiments described herein. Subintimal device <NUM> generally includes an elongate tubular shaft <NUM> having a lumen <NUM> extending therethrough and a re-entry port <NUM> disposed distally in the region of the helical shape. In this embodiment, the distal portion of the shaft <NUM> may have a helical shape in its relaxed state such that the re-entry port <NUM> is always oriented toward the concave side or center of the helix as shown in <FIG>. The helical portion may be deployed in the subintimal space around the total occlusion as described elsewhere herein, resulting in the concave portion of the helix and the port <NUM> being oriented toward the true lumen. With this arrangement, a re-entry device such as a guide wire <NUM> or flexible stylet with a tissue penetrating tip may be advanced through the lumen <NUM> of the shaft <NUM> to exit the re-entry port <NUM> as shown in <FIG>. This arrangement may be used to establish re-entry into the true lumen after the subintimal device <NUM> has been deployed across an occlusion in the subintimal space.

Other orientation and re-entry embodiments are described herein that take advantage of the different properties of the layers of the artery wall to facilitate effective orientation of a re-entry device from the subintimal space toward the true lumen. In some instances, the intima <NUM> is more pliable than the composite of the media <NUM> and adventitia <NUM>. Thus, expansion of an element in the subintimal space <NUM> will result in more deflection of the intima <NUM> than the media <NUM> and adventitia <NUM>.

One such embodiment that operates under this premise is shown schematically in <FIG>. In this embodiment, a subintimal device (not shown) as described elsewhere herein may be used to pass the total occlusion and place a guide wire <NUM> as shown in <FIG>. The guide wire <NUM> extends across the occlusion <NUM> and is disposed in the subintimal space <NUM> between intima <NUM> and the media/adventitia <NUM>/<NUM> where re-entry into the true lumen <NUM> distal of the occlusion <NUM> is desired. A balloon catheter <NUM> is then advanced over the guide wire <NUM> until the balloon portion <NUM> is disposed adjacent the distal end of the occlusion <NUM> as shown in <FIG>. The guide wire <NUM> is pulled proximally and the balloon <NUM> is then inflated causing radial displacement of the distal end of the balloon catheter <NUM> as shown in <FIG>. Inflating the balloon <NUM> of the balloon catheter <NUM> orients the tip of the catheter <NUM> toward the intima <NUM>. The guide wire <NUM> may be removed from the balloon catheter <NUM> and a sharpened stylet <NUM> or the like may be advanced through the guide wire lumen of the catheter <NUM> until the distal end of the stylet <NUM> penetrates the intima <NUM> as shown in <FIG>, thus establishing re-entry from the subintimal path <NUM> and into the true lumen <NUM>.

In the following embodiments, detailed examples of devices are described which facilitate one or more of the steps involved in visualizing, perforation guarding, and/or bypassing a total occlusion as generally described previously. These devices may, for example: (i) facilitate subintimal device tracking by transmitting sufficient axial force and radial torque (sometimes referred to as push and twist respectively) to enter the subintimal space, delaminate the intima from surrounding tissue layers, and traverse the total occlusion via the subintimal space; (ii) facilitate alignment of the subintimal device within the subintimal space with a favorable orientation for true lumen re-entry distal of the total occlusion; (iii) facilitate advancement of a re-entry element that takes advantage of the subintimal device alignment and orientation to direct itself toward the true lumen; (iv) facilitate penetration of the intimal layer to regain access to the true lumen distal of the total occlusion; and/or (v) facilitate confirmation that true lumen re-entry has been achieved.

The embodiments described with reference to <FIG> and <FIG> illustrate features of subintimal devices that facilitate the transmission of push and twist to enter the subintimal space and advance therein. <FIG> shows an embodiment of a subintimal device <NUM> where the properties of push and twist may be provided by an internal stylet <NUM> slideably disposed within the central lumen <NUM> of a tubular shaft <NUM>. With stylet <NUM> removed, the central lumen may also accept a guide wire (not shown).

The tubular shaft <NUM> may be made from suitable polymeric materials such as polyethylene, nylon, or polyether-block-amide (e.g., Pebax™). The tubular shaft <NUM> may also have composite structure where the inside layer may have a lubricious polymer such as polyethylene or a fluoropolymer such as PTFE (e.g., Teflon™), the middle layer may have a metallic or polymeric braided structure such as polyester or stainless steel, while the outside layer may also be made of a similar polymeric material. The outside of the subintimal device <NUM> may also have a lubricious exterior coating. For example, coatings may include liquid silicone or a hydrophilic coating such as hyaluronic acid. The stylet <NUM> may be made of suitable metallic materials including but not limited to stainless steel or nickel titanium alloys. The atraumatic tip <NUM> may be made of suitable metallic or polymeric materials including, for example, stainless steel, titanium, polycarbonate, or polyether-block-amide (e.g., Pebax™).

As seen in <FIG>, which are cross sectional views taken along lines A-A and B-B, respectively, in <FIG>, all or a portion (e.g., distal portion) of the stylet <NUM> may interface with a feature <NUM> within the tubular shaft <NUM> and/or within the atraumatic tip <NUM>. For example, the tubular shaft <NUM> and/or the atraumatic tip <NUM> may contain a lumen with a geometric feature <NUM> intended to mate or key with distal tip of the stylet <NUM> as shown in <FIG>. This keying or mating feature <NUM> allows torque to be transmitted from the operators hand to the distal tip of the subintimal device through twist of the subintimal device and stylet. For the purpose of illustration, the geometric feature <NUM> is shown as a square in cross-section, but it is intended that any geometry other than round may be used to create engagement of the perimeter of the stylet <NUM> with the internal lumen of the tubular shaft <NUM> and/or atraumatic tip <NUM>.

<FIG> shows an embodiment of a subintimal device <NUM> having a proximal tubular shaft <NUM>, a distal tubular shaft <NUM>, and an atraumatic bulbous tip <NUM>. In this embodiment, the desired properties of push and twist may be provided by constructing the proximal shaft <NUM> of a rigid material (e.g., metallic hypotube) and constructing the distal shaft <NUM> in a similar manner, for example, to the gear shaft previously described with reference to <FIG> et seq. Distal gear shaft <NUM> may be flexible yet torsionally and longitudinally rigid. The distal shaft <NUM> may be disposed within an outer sheath <NUM> and may have an internal sheath <NUM> as well. The outer and inner sheaths may be made of suitable polymeric materials such as polyethylene, nylon, polyether-block-amide (e.g., Pebax™), or a fluoropolymer such as Teflon™,.

The embodiments described with reference to <FIG>, <FIG>, <FIG>, and <FIG> illustrate features of subintimal devices that facilitate orientation toward the true lumen. Generally, by deploying a subintimal device around at least a portion of the circumference (sometimes referred to as radial bend or curve), the direction of the true lumen is toward the center (concave side) of the curve. To achieve a radial bend from a longitudinally positioned subintimal device, it may be necessary or desirable to initially impart an axial bend or curve in the subintimal device to act as a transitional geometry. Hence, some subintimal device embodiments described herein have both an axial bend (e.g., <FIG>) and a radial bend (e.g., <FIG>) when deployed in the subintimal space. Since the concave side of the radial bend is consistently toward the true lumen, a re-entry device may be predictably directed toward the true lumen (without employing complex visualization techniques) by aligning itself with respect to the radial curve of the subintimal device. Thus, in the following embodiments, various subintimal device designs are illustrated that accommodate radial bends (and axial bends) to establish the direction of the true lumen toward the concave side of the radial bend.

<FIG> show subintimal device <NUM> that is capable of aiming a re-entry device (not shown) toward the true lumen <NUM> distal of a total occlusion with the aid of standard fluoroscopy. Subintimal device <NUM> with atraumatic tip <NUM> may be positioned within the subintimal space <NUM> between the intima <NUM> and media <NUM> layers. The subintimal device <NUM> may be advanced using similar techniques previously described with reference to <FIG>. Once the subintimal device <NUM> is in the proper position within the subintimal space <NUM>, a distal portion of the subintimal device <NUM> is configured to achieve a geometry having a bend in the longitudinal direction as shown in <FIG> and a bend in the radial direction as shown in <FIG>. This three-dimensional geometry may be referred to as a compound bend. As will be described in more detail herein, the compound bend may be used to facilitate alignment of a re-entry device toward the true lumen <NUM> of the artery <NUM>.

<FIG> illustrates a subintimal device <NUM>, similar to the subintimal device <NUM> described with reference to <FIG>, that may be capable of achieving a compound bend. The subintimal device <NUM> includes an elongate tubular shaft <NUM> defining an internal lumen, an actuation (e.g., push or pull) member <NUM> residing in the lumen of the shaft <NUM> and having a distal end attached to the distal end of the shaft <NUM>, and an atraumatic tip <NUM> attached to the distal end of the shaft <NUM>. The flexible yet torsionally rigid distal shaft <NUM> has one or more open areas <NUM> oriented along the actuation member <NUM>. An external sheath <NUM> may be disposed about the length of the shaft <NUM> and actuation member <NUM>, with its distal end attached to the atraumatic tip <NUM>. For purpose of illustration only, <FIG> shows a single actuation member <NUM> in the proximity of a single row of open areas <NUM> in the shaft <NUM>. The subintimal device may have one or more actuation members and may have one or more rows of open areas. For example, the shaft <NUM> may have a laser cut geometry as shown in <FIG> with two rows of open areas <NUM>.

With continued reference to <FIG>, a bend may be achieved by pulling the longitudinal actuation member <NUM>. Pulling the actuation member <NUM> partially or completely closes the open spaces <NUM> thus shortening the length of the shaft <NUM> in proximity of the open areas <NUM> and creating a bend in the device <NUM>. A compound bend may be achieved through the use of multiple rows of open areas and/or multiple longitudinal members <NUM>. Alternatively, a compound bend may also be achieved using a single row of open areas and a single longitudinal member by relying on device interaction with the adventitial layer. In this alternative, pulling the actuation member <NUM> creates the axial curvature (see <FIG>) and interaction with the adventitia may force the subintimal device to accommodate a radial curvature (see <FIG>).

<FIG> shows an alternative embodiment of a subintimal device <NUM> that may also achieve a compound bend. The subintimal device <NUM> generally includes an elongate tubular shaft <NUM> defining an internal lumen <NUM>, an actuation (e.g., push or pull) member <NUM> having a distal end attached to the distal end of the shaft <NUM>, and an atraumatic tip <NUM> attached to the distal end of the shaft <NUM>. The shaft <NUM> may be constructed from a multitude of alternating wedge-shaped polymeric segments where segment <NUM> may have a lower durometer and greater flexibility as compared to the adjacent segment <NUM>. For example, segment <NUM> may be made of <NUM> Pebax while segment <NUM> may be <NUM> Pebax. These multiple segments may be assembled together to make a continuous shaft. For example, the edges of adjacent segments may be fused together using a process that heats the segments above their melt temperature. The application of heat to segments that is held in proximity may allow said segments to fuse together. <FIG> shows a series of wedged-shaped segments wherein the relatively stiff segment <NUM> defines a larger percentage of one side along a line of the shaft <NUM> while the relatively flexible segment <NUM> defines a larger percentage of the opposing side of the same shaft.

As shown in <FIG>, the side of the shaft <NUM> with a greater percentage of relatively flexible segments <NUM> allows more relative compression upon actuation of member <NUM>, such that the shaft <NUM> may have a predisposition to flex to the side with more flexible segment material <NUM> and may have greater resistance to flex to the side with more stiff segment material <NUM>. The longitudinal actuation member <NUM> may be slideably disposed in a lumen within the wall of the shaft <NUM> and may be attached to the atraumatic tip <NUM>, extending the length of the shaft <NUM> and out the proximal end. For purpose of illustration, <FIG> and <FIG> show a single longitudinal member <NUM> in the proximity of a line of relatively flexible segments <NUM>. The subintimal device <NUM> may have one or more longitudinal members and may have one or more lines of flexible segments <NUM>.

With reference to <FIG> a compound bend may be achieved by pulling the actuation member <NUM> relative to shaft <NUM>. Pulling the actuation member <NUM> may compress segments <NUM> thus shortening the subintimal device length along the side of the of the shaft <NUM> with more flexible segment material <NUM>. A compound bend may be achieved by arranging the flexible segment material <NUM> in the desired pattern and/or by using multiple longitudinal members <NUM>. Alternatively, a compound bend may also be achieved using a single side of flexible segment material <NUM> and a single longitudinal member by relying on device interaction with the adventitial layer as described previously.

With reference to <FIG>, another embodiment of a subintimal device <NUM> capable of achieving a compound bend is shown schematically. <FIG> only shows the distal portion of the subintimal device <NUM> for purposes of illustration and clarity. In this embodiment, the tubular shaft of the subintimal device <NUM> comprises an inner tube <NUM> and an outer tube <NUM> (shown cut away), between which is disposed a series of circumferential rings <NUM> interconnected by longitudinal members <NUM>. An atraumatic tip <NUM> is connected to the distal end of the shaft, and a central lumen <NUM> runs through the device <NUM> for the acceptance of a guide wire and/or a re-entry device. Suitable materials for the circumferential rings <NUM> and longitudinal members <NUM> include but are not limited to nickel titanium, stainless steel, or MP35N. The inner tube <NUM> and the outer tube <NUM> may be made of suitable polymeric materials such as polyethylene, polyether-block-amide (e.g., Pebax™), or nylon. The distal portion of the subintimal device may have a pre-formed curved shape (e.g., compound bend) in its relaxed state as shown in <FIG>.

The subintimal device <NUM> may be slideably disposed within an external delivery sheath <NUM> as shown in <FIG>. The sheath <NUM> may be slightly stiffer then the subintimal device <NUM> such that the subintimal device <NUM> assumes a straight shape when the sheath <NUM> covers the distal portion of the device as shown in <FIG>, and assumes a curved shape when the sheath <NUM> is retracted as shown in <FIG>. Upon proximal retraction of the sheath <NUM>, the subintimal device <NUM> may assume a compound bend by virtue of its preformed shape, or it may assume axial curvature by virtue of its preformed shape and radial curvature by virtue of interaction with the adventitia as described previously.

As described above, the concave side of a subintimal device with a radial bend is consistently toward the true lumen. A re-entry device may thus be predictably directed toward the true lumen (without employing complex visualization techniques) by aligning itself with respect to the concave side of the radial curve of the subintimal device. Therefore, in the following embodiments, various re-entry devices are illustrated that align themselves relative to the concave side of a radial bend in a subintimal device to establish predictable re-entry into the true lumen (without employing complex visualization techniques).

<FIG> show embodiments of re-entry devices that may be advanced through a lumen within a subintimal device <NUM>. The subintimal device <NUM> may be similar to the devices described previously to facilitate formation of a radial bend with a concave side oriented toward the true lumen <NUM> distal of a total occlusion. With reference to <FIG>, subintimal device <NUM> may be positioned within the subintimal space <NUM> between the intimal <NUM> and medial <NUM> layers. A radial curve may be formed in the subintimal device <NUM> using any of the methods described previously, and the radial curve may be less than the radial curvature of the artery. A radial curvature with a diameter less than the inside diameter of the artery causes the tip of the subintimal device <NUM> to be pointed toward the true lumen <NUM>. The re-entry device <NUM> may comprise a guide wire, a sharpened stylet or the like to facilitate penetration through the intimal layer. Advancement of the re-entry device <NUM> though the central lumen within the subintimal device <NUM> and out the distal end results in penetration through the intimal layer <NUM> and into the true lumen <NUM>.

An alternative re-entry embodiment is shown in <FIG> wherein the subintimal device <NUM> has a radial curvature approximating the inside curvature of the artery. The subintimal device may be placed within the arterial wall between intimal <NUM> and medial <NUM> layers as described previously. In this embodiment, the re-entry device <NUM> may have a preformed bend that is less than the curvature of the subintimal device <NUM> and less than the inside curvature of the artery. The re-entry device is longitudinally and rotationally movable with respect to the subintimal device <NUM>, thus allowing the curvature of the re-entry device <NUM> to self-align with the curvature of the subintimal device <NUM>. Thus, with the concave side of the curved subintimal device oriented toward the true lumen, the concave side of the curved re-entry device <NUM> will also be oriented toward the true lumen. Advancement of the re-entry device <NUM> through the subintimal device <NUM> and out the distal end thereof results in penetration through the intimal layer <NUM> and into the true lumen <NUM>. Because the curvature of the re-entry device is less than the inside curvature of the artery, the tip of the re-entry device remains in the true lumen and does not engage the opposite wall of the artery.

Another alternative re-entry device embodiment is shown in <FIG> wherein the re-entry device <NUM> exits out a distal side port <NUM> in the subintimal device <NUM>. The side port <NUM> may be located on the concave side of the curvature of the subintimal device <NUM> thus orienting the tip of the re-entry device <NUM> toward the true lumen <NUM>. In this embodiment, the re-entry device <NUM> may have a slight bend at its distal end to bias the tip toward the port <NUM> such that it exits the port upon advancement.

Another alternative re-entry device embodiment is shown in <FIG> is a cross sectional view taken along line A-A in <FIG>. In this embodiment, the subintimal device <NUM> and the re-entry device may be provided with radial curvature for orientation toward the true lumen <NUM> as described previously. In addition, a portion of the subintimal device <NUM> such as the tip <NUM> and a distal portion of the re-entry device <NUM> may be provided with a mating or keying geometry to facilitate relative alignment. Various non-circular mating geometries may be used, including a rectangular cross section as shown in <FIG>.

<FIG> show various embodiments of penetrating tips for use on a re-entry device. As mentioned previously, the re-entry device <NUM> may comprise a guide wire or the like to facilitate penetration through the intimal layer <NUM> from the subintimal space <NUM> to the true lumen <NUM>. Alternatively, the tip of the re-entry device <NUM> may be designed to enhance penetration through the intimal layer <NUM>, particularly in the case where the intimal layer is diseased. If the intimal layer <NUM> is diseased, it will likely be tougher than healthy tissue because it may contain soft plaque, fibrous plaque and/or hard calcified plaque. The presence or absence of disease at the intended re-entry site and the nature of the disease may require a re-entry device capable of penetrating the various plaques within a nonhomogenous diseased arterial wall. In the event the re-entry site is free from disease or contains relatively soft plaque, a conventional guide wire may be used as a re-entry device. Alternatively, if disease is encountered, the tip configurations illustrated in <FIG> may be employed.

As shown in <FIG>, the re-entry device may have a rotational cutting or piercing element <NUM> capable of penetrating the arterial wall. The rotational element <NUM> may, for example, be similar to a fluted drill bit. Rotation of the re-entry device with rotational cutting element <NUM> may be achieved through manual manipulation by the physician or through a powered mechanism such as an electric motor.

As shown in <FIG>, the re-entry device may have a rotational abrasive element <NUM>. The abrasive element <NUM> may include an abrasive coating such as <NUM> grit diamond abrasive. The abrasive coating may be applied to the tip of the re-entry device through an electroplating process. Rotation of the re-entry device with rotational abrasive element <NUM> may be achieved through manual manipulation by the physician or through a powered mechanism such as an electric motor.

As shown in <FIG>, the re-entry device may have a tapered or sharpened tip <NUM>. The sharpened tip <NUM> may penetrate the intimal layer <NUM> through axial advancement or axial reciprocation. The end of the re-entry device, for example, may taper to a sharp point. Axial movement or reciprocation of the tapered or sharpened tip <NUM> may be achieved through manual manipulation by the physician or through a powered mechanism such as an electric motor or a solenoid.

Confirmation of a re-entry device entering the true arterial lumen distal of the occlusion may be difficult through the sole use of two-dimensional images obtained via fluoroscopy. These two-dimensional images may allow a physician to determine if a re-entry device is in close proximity to the artery, but may not offer adequate resolution to determine precise position (i.e. within the artery wall vs. within the true arterial lumen). Confirmation of true lumen re-entry may be achieved by understanding when the re-entry and/or the subintimal device penetrate the intimal layer <NUM> and come in contact with the blood in the true lumen <NUM> distal to the total occlusion.

One method of determining if the true arterial lumen has been accessed is by drawing intra-arterial blood from the distal entry point proximally through a lumen within the re-entry device or a lumen within the subintimal device to the proximal end of the device where the presence of blood may be detected. This method takes advantage of the fact that there is typically blood in the true lumen distal of the occlusion but there is little to no blood in the subintimal space. Thus, the absence of blood indicates the device is subintimal and the presence of blood indicates the device is in the true lumen. This technique may also be used to indicate perforation of the device out of the artery and into the pericardial space by the presence of pericardial fluid.

<FIG> illustrates a re-entry device <NUM> that facilitates confirmation of true lumen re-entry. The re-entry device <NUM> may be passed through a subintimal device <NUM>, oriented toward the true lumen <NUM>, and penetrate the intimal layer <NUM> from the subintimal space <NUM> to the true lumen <NUM> as described previously. In this embodiment, the re-entry device <NUM> is provided with an internal lumen extending from its proximal end to a distal opening <NUM>. The proximal end of the re-entry device <NUM> is connected to an indicator <NUM> which is in turn connected to a vacuum source. The indicator <NUM> may be a flow indicator such as a collection vessel where the presence and type of fluid may be visually observed. With the vacuum source generating a negative pressure, entry of the re-entry device <NUM> into the true lumen <NUM> allows blood to flow into the distal opening <NUM> and through the internal lumen to the indicator <NUM>. Alternatively, the vacuum source and indicator may be fluidly attached to the subintimal device where entry of the device into the true lumen results in similar blood flow into the indicator. Alternative indicators <NUM> may be employed such as impedance sensors, oxygen sensors, optical sensors, etc..

Various devices have been previously described herein that are deployable in the subintimal space for a variety of purposes. The following embodiments are additional examples of such deployable devices that may be used in the same or similar manner. For example, the following embodiments provide a deployable element that when released within the subintimal space along the length and around the circumference of the total occlusion may serve as: (i) a visualization aid that may help define the arterial wall during fluoroscopy; (ii) a protective element that may guard the exterior vessel layer or layers from devices passing through the total occlusion within the true arterial lumen; and/or (iii) a protective element that may provide an indication of close proximity or contact between a device passed through the total occlusion within the true arterial lumen and the protective element. The deployable element may be readily released from and re-captured into an exterior containment sheath. The deployable element may also be released and remain deployed within a patient as a permanent implant. This permanent implant may serve as a stent and/or may also elute a drug.

An example of a deployable element <NUM> is schematically illustrated in <FIG>. The deployable element <NUM> may be disposed about a subintimal device <NUM> and contained thereon by a retractable containment sheath <NUM>. In <FIG>, the deployable element <NUM> is shown in the process of release from its constrained position the proximal retraction of the containment sheath <NUM>. The deployable element <NUM> may comprise, for example, a collapsible lattice structure that is capable of expanding from a first collapsed configuration within the containment sheath <NUM> to a second deployed configuration upon retraction of the sheath <NUM> that allows it to expand within the arterial wall. In this embodiment, the deployable element <NUM> is shown in the submedial space between the media <NUM> and adventitia <NUM>. <FIG> shows the deployable element <NUM> completely released from the subintimal device <NUM> by complete retraction of the exterior containment sheath <NUM>. The deployable element <NUM> may expand around the circumference and along the length of a total occlusion (not shown) thus concentrically surrounding a diseased segment. The lattice structure of the deployable element <NUM> may be made of a material capable of withstanding strain between the collapsed configuration and the deployed configuration without significant permanent deformation. Suitable materials for the deployable element <NUM> include but are not limited to nickel titanium, stainless steel, elgiloy, or MP35N.

The deployable element may be used to aid in defining the arterial wall in the area of a total occlusion. As known to those skilled in the art, a totally occluded artery may not allow sufficient radiopaque contrast solution to penetrate the diseased segment thus preventing a physician from visualizing the artery in the occluded area. Placing a deployable element of sufficient radiopacity (as seen via fluoroscopy) within the arterial wall around a total occlusion may allow a physician to visualize the occluded segment. Visualization of the artery in the area of occlusion may allow subsequent interventional devices (i.e. guide wires, balloons, stents, etc.) to be successfully passed within the confines of the deployable element.

The deployable element may alternatively provide mechanical protection for the arterial layers concentrically outward of the deployable element from crossing devices intended to penetrate the total occlusion such as guide wires, atherectomy devices, laser ablation devices, and radiofrequency ablation devices. For example, <FIG> shows a rotational abrasive device <NUM> with an abrasive cutting tip <NUM> passing through a total occlusion <NUM> with the deployable element <NUM> protecting the arterial wall from perforation. While the abrasive tip <NUM> is effective at passing through the total occlusion <NUM>, the deployable element comprises a relatively harder material (e.g., metallic) with a lattice pattern having openings smaller than the tip <NUM> to prevent perforation therethrough.

The deployable element may alternatively provide vessel wall protection by indicating when the occlusion crossing device (guide wire, atherectomy device, laser ablation device, and radiofrequency ablation device, etc.) is in close proximity to or in contact with the vessel wall. For example, either the distal end of the deployable element or the distal end of the crossing device may act as a transmitting antenna and the other of the two may act as a receiving antenna. The transmitting antenna may be electrically connected to a radiofrequency (RF) signal generator and the receiving antenna may be connected to an RF signal receiving or detection circuit via a lengthwise insulated and/or shielded lead disposed in each of the devices. As an alternative to RF proximity detection, impedance may be similarly used as an indicator of proximity.

With either an RF or impedance based approach, a relatively weak signal is indicative of the crossing device being further away from the deployable element, for example when the crossing device is in the center of the occluded artery. A relatively stronger signal is indicative of the crossing device being in close proximity to the deployable element, for example within the subintimal space. The physician may use this proximity information to safely and effectively direct the crossing device within the confines of the deployable element and across the total occlusion within the true arterial lumen.

As an alternative to a lattice structure described previously, the deployable element <NUM> may comprise one or more continuous elastic members as shown in <FIG>. The deployable element <NUM> may be released from an exterior containment sheath (not shown) as described previously to expand circumferentially within the subintimal space. As shown in <FIG>, the deployable element <NUM> may comprise a single continuous preformed elastic wire with an atraumatic tip located at the distal end of the wire form to reduce the potential for unintended vessel wall damage. The wire may be made of suitable elastic materials that include but are not limited to nickel titanium, stainless steel, elgiloy, or MP35N. This wire form may include multi-axis bends approximating a sinusoidal pattern bent around a cylinder. The diameter of the cylindrical shape may be selected to match the inside diameter of the artery. The wire form may be restrained in a relatively straight configuration when placed within an exterior containment sheath for advancement through the vasculature to the intended deployment site. Upon withdrawal of the containment sheath, the wire form may assume the aforementioned multi-axis shape.

The deployable element may also be used to orient a re-entry device toward the true lumen distal of the total occlusion. For example, a subintimal device <NUM> may have an accessory deployable element <NUM> as shown in <FIG>. <FIG> and <FIG> are cross sectional end views of <FIG> and <FIG>, respectively. With reference to <FIG>, the subintimal device <NUM> is shown positioned in the subintimal space with the accessory deployable element <NUM> having an exposed portion disposed in a recess and a proximally extending portion in a lumen of the subintimal device <NUM>. With reference to <FIG>, advancing the proximal portion of the deployable element causes the exposed portion to protrude from a side port <NUM> and advance within the subintimal space. The geometry of the deployable element may be a preformed shape such as a U-shape to allow atraumatic expansion within the subintimal space as shown. With the accessory deployable element in the subintimal space as shown, it forms a radial curvature with a concave side that faces the true lumen <NUM>. With the concave side facing the true lumen, a re-entry device may be directed to penetrate the intimal layer into the true lumen as previously described with reference to <FIG>, <FIG>, and <FIG>.

Some of the devices described herein may also be used to facilitate complete or partial removal of a total occlusion, potentially including an inner portion of the arterial wall. <FIG> illustrate an example of this application wherein a delivery device <NUM> is used to deliver a subintimal device <NUM> around a total occlusion <NUM>, similar to what is shown and described with reference to <FIG> and <FIG>. The occlusion is then removed as will be described in more detail.

With reference to <FIG>, the delivery device <NUM> is positioned just proximal of a total occlusion <NUM>. In this position, the balloon <NUM> may be inflated within the vessel lumen <NUM> to direct the delivery tube <NUM> toward the vessel wall <NUM> at an orientation for the subintimal device <NUM> to penetrate through the intima <NUM> at an entry point and into the subintimal space. By virtue of the helical delivery tube <NUM>, the subintimal device <NUM> is sent on a helical trajectory as it is advanced through delivery tube <NUM> resulting in deployment of the subintimal device <NUM> in a helical pattern. As shown, the subintimal device <NUM> has been advanced through the delivery tube <NUM> and positioned concentrically outside the total occlusion <NUM>, outside the intimal layer <NUM>, and inside the medial layer <NUM> in the subintimal space.

With reference to <FIG>, a subintimal device capture catheter <NUM> is positioned across the chronic total occlusion <NUM> over a conventional guide wire <NUM> and within the subintimal device <NUM>. The proximal <NUM> and distal <NUM> ends of the subintimal device <NUM> have been captured and rotated by capture device <NUM> so as to reduce the outside diameter and contain the lesion <NUM> and intima <NUM> within the coils of the subintimal device <NUM>.

With reference to <FIG>, a tubular cutting device <NUM> with a sharpened leading edge may be advanced over the subintimal device <NUM> and the capture device <NUM> to engage and cut the intimal layer <NUM> with the total occlusion <NUM> therein. With reference to <FIG>, further advancement of the cutting device <NUM> cuts and separates the diseased portion including the total occlusion and surrounding intima from the remainder of the artery. Proximal withdrawal of the device from the artery results in removal of the total occlusion and a patent true lumen <NUM>. The occlusion <NUM> may be removed through the percutaneous intravascular access site or a surgical cut down may be performed to facilitate removal if the occlusion is too large for removal through the percutaneous access site. Alternatively, to reduce the size of the occlusion and thus facilitate removal through the percutaneous access site, a maceration mechanism may be employed to macerate the occlusion prior to removal.

In addition or as an alternative, a corkscrew-type device <NUM> may be used to grasp and pull the total occlusion <NUM> for removal as shown in <FIG> and <FIG>. It is contemplated that corkscrew-type device <NUM> may be used in combination with the devices described with reference to <FIG> which are not shown for sake of clarity. With reference to <FIG>, the corkscrew device <NUM> is shown with an exterior sheath <NUM>. The corkscrew device <NUM> is shown engaging occlusion <NUM> after delamination of the intimal layer <NUM> has been performed by the aforementioned methods and devices. <FIG> shows removal of the occlusion <NUM> and a portion of the intimal layer <NUM> through axial withdrawal of the corkscrew device <NUM>.

<FIG> illustrate an alternative system for bypassing a total occlusion. With reference to <FIG>, a subintimal device <NUM> is shown in the deployed configuration. The subintimal device <NUM> includes an elastic wire <NUM> with a distal form similar to the elastic wire form <NUM> described with reference to <FIG>, except with fewer sinusoidal turns. The subintimal device also includes a crescent-shaped or semi-circular delivery shaft <NUM> and a retractable constraining sheath <NUM>. As seen in <FIG>, which is a cross-sectional view taken along line A-A in <FIG>, the wire <NUM> resides in the recess of the semi-circular delivery shaft <NUM> over which the constraining sheath <NUM> is disposed. As an alternative, the constraining sheath <NUM> may be disposed about the wire <NUM> only and may reside in the recess of the delivery shaft <NUM>, provided that the constraining sheath <NUM> is sufficiently stiff to at least partially straighten the formed wire <NUM>. The distal end of the wire <NUM> is connected to a blunt tip <NUM> of the shaft <NUM>. The wire <NUM> and the semi-circular shaft <NUM> may be formed of a resilient metallic material such as nickel titanium, stainless steel, elgiloy, or MP35N, and the sheath <NUM> may be formed of a flexible polymeric material such as a polyether-block-amide (e.g., Pebax) lined with PTFE (e.g., Teflon).

Pulling the wire <NUM> proximally relative to the shaft <NUM> and advancing the sheath <NUM> over the wire form constrains the wire form in the recess and renders the device <NUM> suitable for atraumatic passage through the subintimal space. Once the device <NUM> is positioned across the total occlusion within the subintimal space, the sheath <NUM> may be retracted relative to the shaft <NUM> to release the formed portion of the wire <NUM>. Releasing the wire form causes it to extend circumferentially around the occlusion in the subintimal space as shown in <FIG>. Once the wire form is fully deployed in the subintimal space, the sheath may be completely removed.

As shown in <FIG>, with the wire form <NUM> deployed in the subintimal space and with the sheath <NUM> removed from the shaft <NUM>, a dual lumen re-entry delivery catheter <NUM> may be advance over the shaft <NUM>. As seen in <FIG>, which is a cross-sectional view taken along line A-A in <FIG>, the delivery catheter <NUM> includes a crescent-shaped or semi-circular lumen <NUM> that accommodates the shaft <NUM> extending therethrough. The delivery catheter <NUM> also includes a circular lumen <NUM> that accommodates a re-entry device <NUM> extending therethrough. The delivery catheter <NUM> may comprise a dual lumen polymeric extrusion such as polyether-block-amid (e.g., Pebax) and the re-entry device <NUM> may be the same or similar to the re-entry devices described previously herein.

Alternatively, the delivery catheter <NUM> may comprise two coaxial tubes including an elongate inner tube disposed in an elongate outer tube. The inner tube is configured to accommodate a re-entry device. The annular lumen defined between the inner tube and the outer tube is configured to accommodate semicircular delivery shaft <NUM>. At the distal end of the delivery catheter <NUM>, the inner tube may be tacked to the inside of the outer tube using a heating forming process where a portion of the outside circumference of the inner tube is thermally fused to the inside circumference of the outer tube thus creating a cross section similar to that shown in <FIG> over the heat formed area. Outside the heat formed area, the inner and outer tubes may remain coaxial and un-fused.

As described previously, the concave side of the wire form faces the true lumen, and with the fixed attachment of the wire <NUM> to the tip <NUM> of the shaft <NUM>, the concave side of the semi-circular shaft <NUM> also faces the true lumen. This feature may be used to facilitate orientation of a re-entry device toward the true lumen. For example, because lumen <NUM> of the delivery catheter <NUM> has a mating or keyed geometry with the semi-circular shaft <NUM>, and because the concave side of the semi-circular shaft <NUM> is oriented toward the true lumen, the re-entry device lumen <NUM> may be oriented toward the true lumen as well. With this in mind, any of the re-entry device orientation methods described with reference to <FIG> may be employed. As shown in <FIG>, the distal end of the semi-circular shaft <NUM> has a curvature with a concave side facing the true lumen which may be used in concert with a curved re-entry device <NUM>. Once orientation is established, the re-entry device <NUM> may penetrate the intimal layer <NUM> and re-enter the true lumen as shown.

<FIG> schematically illustrate an embodiment using one or more subintimal guide catheters <NUM>/<NUM> to introduce an orienting device <NUM>. These Figures show a window cut-away in the outer layer of the vascular wall for purposes of illustration. In this embodiment, which is an alternative bypass embodiment in some aspects, a subintimal crossing device <NUM> with or without a guide wire lumen (shown) and having a bulbous tip <NUM> (e.g., <NUM> in. diameter olive shaped weld ball) is used to safely cross the subintimal space by blunt dissection as described elsewhere herein.

As shown in <FIG>, a first (inner) sheath <NUM> having an inside diameter (e.g., <NUM> (<NUM> inches)) slightly larger than the outside diameter (e.g., <NUM> - <NUM> (<NUM> - <NUM> inches)) of the shaft of the crossing device <NUM> may be advanced by pushing and back-and-forth rotation over the crossing device <NUM> and through the subintimal space up to the bulbous tip <NUM> located adjacent the distal end of the occlusion (not shown). Once in place, a second (outer) sheath <NUM> having an outside diameter of <NUM> (<NUM> inches), for example, and an inside diameter (e.g., <NUM> (<NUM> inches)) slightly largher than the outside diameter (e.g., <NUM> (<NUM> inches)) of the inner sheath <NUM> and slightly larger than the outside diameter of the tip <NUM> may be advanced by pushing and back-and-forth rotation over the inner sheath <NUM> up to the bulbous tip <NUM> as shown in <FIG>. In this Figure, a window cut-away is shown in the distal portion of the outer sheath <NUM> for purposes of illustration. Once the outer sheath <NUM> is in this position, the subintimal crossing device <NUM> and the inner sheath <NUM> may be removed proximally through the outer sheath. Although the outer sheath <NUM> may be advanced over the subintimal crossing device <NUM> without the need for inner sheath <NUM>, the inner sheath <NUM> provides step-wise increase in dissection diameter making traversal easier. The inner sheath <NUM> may be formed of a braid reinforced polymeric construction (e.g., 55D polyether block amide) with an atraumatic tip (e.g., unreinforced 40D polyether block amide). The outer sheath <NUM> may be formed of a more rigid polymer (e.g. 72D polyether block amide) and may optionally include a braid composite construction. Braid reinforced construction provides enhances push and torque, and it is believed that rotation of the sheaths <NUM>/<NUM> enhances the ability to cross and delaminate across the subintimal path.

With the outer sheath <NUM> in place and providing a protected path across the occlusion within the subintimal space, an orienting device <NUM> may be inserted into the sheath <NUM> to the distal end thereof as shown in <FIG>. In this Figure, a window cut-away is shown in the distal portion of the outer sheath <NUM> for purposes of illustration. <FIG> shows the orienting device <NUM> in the delivery configuration with the orienting element collapsed and 33D shows the orienting device <NUM> in the deployed configuration with the orienting element expanded.

The orienting device <NUM> shown in <FIG> is similar to the orienting device <NUM> shown in <FIG>. The orienting device <NUM> may include a tubular shaft <NUM> with a wire <NUM> disposed therein. The tubular shaft <NUM> may comprise a polymeric tube with a wire ribbon (e.g., SST) embedded therein to add stiffness for pushability. The tubular shaft <NUM> includes a lumen extending therethrough, and the distal end of the lumen is directed at an angle to a side facing exit port <NUM> located proximate the orienting element <NUM>. The distal end of the wire <NUM> may include an orienting element <NUM> comprising, for example, a preformed planar sinusoid, referred to as a wire form. The wire <NUM> and the wire form <NUM> may comprise a superelastic metal alloy such as NiTi, for example, and the wire form <NUM> may be formed by heat setting. To deploy the orienting element <NUM>, the outer sheath <NUM> may be pulled proximally and the shaft <NUM> may be pushed distally in an alternating fashion until the entire wire form <NUM> is within the subintimal space.

The side port <NUM> is oriented at a right angle to the plane of the orienting element <NUM>. With this arrangement, the side port <NUM> is either directed toward the vascular true lumen <NUM> or <NUM> degrees away from the vascular true lumen <NUM>. Radiographic visualization or other techniques as described elsewhere herein may be used to determine if the port <NUM> is directed toward or away from the true lumen <NUM>. If the port <NUM> is directed away from the true lumen <NUM>, the orienting device may be retracted, rotated <NUM> degrees, and re-deployed to point the port <NUM> toward the true lumen <NUM>. A re-entry device as described elsewhere herein may then be advanced through the lumen of the tubular shaft <NUM>, through the vascular wall and into the true lumen <NUM>.

As an alternative to orienting device <NUM> shown in <FIG>, orienting device <NUM> shown in <FIG> may be employed in substantially the same manner. Orienting device <NUM> includes an outer tube <NUM> and an inner tube <NUM>. The outer tube <NUM> may be formed of a superelastic metal alloy (e.g., NiTi), and a distal portion of the outer tube <NUM> may be cut (e.g., using laser cutting techniques) to form slots to define two wings <NUM> that hinge outward in a planar fashion as shown. The inner tube <NUM> extends through the lumen of the outer tube <NUM> and is attached distally to the distal end of the outer tube <NUM>. Inner tube <NUM> is similar in design and function as tubular shaft <NUM>, and includes a distal side port <NUM> to accommodate a re-entry device as described with reference thereto. Alternatively, a flap port may be used as will be described in more detail hereinafter.

<FIG> schematically illustrate an embodiment using a subintimal crossing device or guide wire to introduce an orienting device <NUM>. In this embodiment, the orienting device <NUM> is designed to accommodate a subintimal crossing device or guide wire therein, thus negating the need for the subintimal guide catheters described previously. With specific reference to <FIG>, a detailed view of a distal portion of the orienting device <NUM> is shown. Figure 34B(<NUM>) is a cross-sectional view taken along line A-A in <FIG>, and Figure 34B(<NUM>) is a cross-sectional view taken along line B-B in <FIG>. The orienting device <NUM> includes an elongate outer tubular shaft <NUM> with a distal end connected to an orienting element <NUM>. An elongate inner tubular shaft <NUM> extends through the outer shaft <NUM> and orienting element <NUM>. The distal end of the inner shaft <NUM> is connected to the distal end of the orienting element <NUM>, as is a distal atraumatic tubular tip <NUM>. A low friction liner <NUM> may extend through the lumen of the inner shaft <NUM> to facilitate smooth passage of devices therein.

The outer shaft <NUM> may comprise, for example, a polymeric tube <NUM> that may be reinforced with an embedded braid or wire ribbon. The inner shaft <NUM> may comprise a metallic tube <NUM> (e.g., NiTi) with a solid tubular proximal segment and a spiral cut <NUM> distal segment for added flexibility and torqueability. The distal portion of the inner shaft <NUM> may include an inwardly inclined flap <NUM>. As seen in Figure 34B(<NUM>), the flap <NUM> extends into the lumen of the inner shaft <NUM> and operates to (<NUM>) direct front loaded devices (e.g., re-entry device) out the side port <NUM> of the inner shaft <NUM> adjacent the orienting element <NUM>; and (<NUM>) direct back loaded devices (e.g., subintimal crossing device or guide wire) down the lumen of the proximal segment <NUM> of the inner shaft <NUM> while preventing back loaded devices from exiting the side port <NUM>. A semi-circular slot <NUM> may be formed to accommodate the end of the flap <NUM> to prevent the edge of the flap <NUM> from snagging on devices passing by. The cuts may be formed by laser cutting or the like and the flap may be biased inwardly by heat setting.

With reference to <FIG>, the inner shaft <NUM> may have an overall length of approximately <NUM> for coronary applications, with a spiral cut <NUM> distal segment length of approximately <NUM>, for example. With reference to <FIG>, which is a detailed view of a distal portion of the inner shaft <NUM>, the cut pattern is illustrated as if the tube were laid flat with dimensions given in inches unless otherwise noted. The spiral cut <NUM> may terminate proximal of the side port <NUM> and flap <NUM>. A hinge slot <NUM> may be provided to allow the flap <NUM> to hinge when devices are back loaded as described previously. A semi-circular slot <NUM> may be provided to accommodate the end of the flap as described previously. A hole <NUM> may be used to provide connection to the distal end of the orienting element (not shown) by pinning or welding, for example.

With reference to <FIG> and <FIG>, the orienting element <NUM> may comprise a metallic tube (e.g., NiTi) with cuts made to define two wings 3442A and 3442B. In <FIG>, the cut pattern of the orienting element <NUM> is shown as if the tube were laid flat with dimensions given in inches unless otherwise noted. The cuts are made to define two separate wings 3442A and 3442B, with three hinge points <NUM>, <NUM> and <NUM> per wing <NUM>. The proximal end <NUM> of the orienting element <NUM> is connected to a flared end of the outer shaft <NUM>, and the distal end <NUM> is connected to the distal end of the inner shaft <NUM> and the proximal end of the tubular tip <NUM>. By contracting the proximal end <NUM> toward the distal end <NUM>, the proximal hinge <NUM> and the distal hinge <NUM> flex outwardly to extend each wing <NUM> outwardly, with the center hinge <NUM> at the apex of each wing <NUM>.

The distal tip <NUM> may comprise a relatively soft polymeric tube segment, optionally loaded with radiopaque material. The inner liner <NUM> may comprise a tubular extrusion <NUM> or internal coating made of a low friction material such as high density polyethylene (HDPE) or polytetrafluoroethylene (PTFE).

<FIG> schematically illustrate a method of using the orienting device <NUM> described above. As mentioned previously, orienting device <NUM> is designed to be advanced over a subintimal crossing device or guide wire, but subintimal guiding catheters may be used in addition to or in place of a crossing device or guide wire. For sake of illustration, the orienting device <NUM> is shown over subintimal crossing device <NUM> having an expandable and collapsible tip <NUM> at the distal end of an elongate shaft <NUM>, but the orienting device <NUM> may also be advanced over a conventional guide wire (not shown), another subintimal device, or another similarly sized device advanced across the occlusion within the subintimal space. Using a device with a collapsible tip (e.g., subintimal crossing device <NUM>) or a device without an enlarged tip allows it to be removed through the center lumen of the orienting device <NUM> such that a re-entry device may be subsequently advanced through the same lumen, thus using a single lumen for dual purposes and conserving device profile.

With reference to <FIG>, once the subintimal crossing device <NUM> extends across the occlusion within the subintimal space such that the tip <NUM> is adjacent the distal end of the occlusion, the orienting device <NUM> may be back-loaded (direction shown in Figure 34B(<NUM>)) over the subintimal crossing device <NUM> such that the shaft <NUM> of the crossing device <NUM> deflects the flap <NUM> outwardly and extends through the center lumen of the orienting device <NUM>. The orienting device <NUM> may then be advanced over the subintimal crossing device <NUM> until the distal end of the orienting device is adjacent the distal end of the occlusion. The tip <NUM> of the subintimal crossing device <NUM> may then be collapsed and withdrawn proximally.

With reference to <FIG>, the orienting element <NUM> may be expanded to extend the wings 3442A and 3442B in a substantially planar manner as shown. To facilitate expansion and contraction of the orienting element <NUM>, an actuation mechanism <NUM> may be used to push the outer shaft <NUM> and pull the inner shaft <NUM> relative to each other to cause expansion, or pull the outer shaft <NUM> and push the inner shaft <NUM> relative to each other to cause retraction. The actuation mechanism may comprise, for example, a fixed handle <NUM> fixedly connected to the proximal end of the outer shaft <NUM>, a rotatable handle <NUM> rotatably connected to the proximal end of inner shaft <NUM>, and a threaded shaft fixedly connected to rotatable handle <NUM> that engages internal threads (not visible) in the fixed handle <NUM>. The rotatable handle <NUM> may engage a collar (not visible) on the proximal end of the inner shaft <NUM> that permits relative rotation but prevents relative axial motion and therefore causes axial displacement of the inner shaft <NUM> upon rotation of the rotatable handle <NUM>.

With continued reference to <FIG> and additional reference to <FIG>, the side port <NUM> is either directed toward the vascular true lumen <NUM> or <NUM> degrees away from the vascular true lumen <NUM>. Radiographic visualization or other techniques as described elsewhere herein may be used to determine if the port <NUM> is directed toward or away from the true lumen <NUM>. If the port <NUM> is directed away from the true lumen <NUM>, the orienting device <NUM> may be retracted, rotated <NUM> degrees, and re-deployed to direct the port <NUM> toward the true lumen <NUM>. A re-entry device <NUM> may then be front-loaded (direction shown in Figure 34B(<NUM>)) through the center lumen of the orienting device <NUM>. Although re-entry device <NUM> is shown for purposes of illustration, other re-entry devices may be used as described elsewhere herein. As the re-entry device <NUM> is advanced into the center lumen of the orienting device <NUM>, the flap <NUM> causes the distal end of the re-entry device <NUM> to be directed out the side port <NUM>. Further advancement of the re-entry device <NUM> causes it to engage the vascular wall, and by action of the tip of re-entry device <NUM> (e.g., rotational abrasion), it may penetrate the vascular wall and enter into the vascular true lumen <NUM> distal of the occlusion <NUM>.

With additional reference to <FIG> and <FIG>, an alternative re-entry device <NUM> may be employed. The design of re-entry device <NUM> is described in more detail with reference to <FIG>. With the side port <NUM> directed toward the true lumen <NUM> as described above, re-entry device <NUM> may then be front-loaded through the center lumen of the orienting device <NUM>. As the re-entry device <NUM> is advanced into the center lumen of the orienting device <NUM>, the flap <NUM> causes the distal end of the re-entry device <NUM> to be directed out the side port <NUM>. Further advancement and rotation of the re-entry device <NUM> causes the tip to engage and screw into the vascular wall. With the tip of the re-entry device <NUM> screwed into the vascular wall and extending into the true lumen <NUM>, a number of techniques may be used to further define a path into the true lumen <NUM>. For example, the re-entry device may be pulled proximally without rotation thereby removing a portion of the vascular wall to define a hole through which a guide wire or core wire may be advanced. Alternatively, additional rotation of the tip of the re-entry device <NUM> may cut a hole in the vascular wall. As a further alternative, the tip of the re-entry device <NUM> may serve to hold the vascular wall while a subsequent device such as a guide wire or core wire inserted into the lumen of the re-entry device <NUM> is advanced therethrough to pierce or otherwise penetrate through the wall into the true lumen <NUM>. By way of illustration, <FIG> shows a guide wire <NUM> (or movable core wire) extending through the re-entry device <NUM> and into the true lumen <NUM>. Regardless of the technique, a path is thus defined from the intramural space and into the true lumen <NUM> distal of the occlusion <NUM>.

Some of the orienting devices (e.g., <NUM>, <NUM>, <NUM>) described hereinbefore have substantially planar orientation elements with an associated side port for delivery of a re-entry device. The side port is generally oriented at a right angle to the plane of the orienting element. With this arrangement, the side port is either directed toward the vascular true lumen or <NUM> degrees away from the vascular true lumen. In essence, the orienting device reduces the number of directions the side port may be facing from <NUM> degrees of freedom to two degrees of freedom, <NUM> degrees apart. The following is a description of methods to determine if the port is directed toward or away from the true lumen, thus reducing two degrees of freedom to one degree of freedom. Generally, if the side port is directed away from the true lumen, the orienting device may be retracted, rotated <NUM> degrees, and re-deployed to direct the side port toward the true lumen. A re-entry device as described elsewhere herein may then be advanced through the side port, through the vascular wall and into the true lumen.

One method of directing the side port toward the true lumen involves taking advantage of the curvature of the heart <NUM>. Generally speaking, the coronary arteries including the left anterior descending artery <NUM> as shown in <FIG> will follow the outside curvature of the heart <NUM>. An orienting device (e.g., <NUM>, <NUM>, <NUM>) inserted into the coronary artery <NUM> via a guide catheter <NUM> seated in the ostium of the artery <NUM> will generally follow the outside curvature of the artery <NUM> within the subintimal space and across the occlusion <NUM>. In this scenario, as seen in <FIG>, the true lumen <NUM> will lie toward the inside of the curvature of the artery <NUM> and thus the inside curvature (i.e., concave side) of the orienting device <NUM>. Thus, the side port of the orienting device <NUM> may be directed toward the concave side of the curvature which will predictably direct the side port toward the true lumen <NUM>. Directing the side port in this fashion may be facilitated by using radiographic visualization to view one or more radiopaque markers on the orienting device associated with the side port or a radiopaque device (e.g., guide wire) inserted into the orienting device just as it exits the side port. In addition or as an alternative, the orienting device may be pre-curved such that it naturally orients or "keys" with the curvature of the artery with the side port arranged on the concave side of the pre-curve. In addition or as an alternative, a radiopaque device (e.g., guide wire <NUM>) may be substantially advanced and bunched within the subintimal space via a subintimal device (e.g., crossing device <NUM> or orienting device <NUM>) as shown in <FIG> such that the radiopaque device extends at least partially circumferentially to assume the curvature of the artery with the true lumen oriented toward the concave side thereof.

With reference to <FIG>, alternative re-entry devices are schematically illustrated. These embodiments may be used with any of the orienting devices described previously, but are particularly suited for use with orienting devices <NUM>, <NUM>, and <NUM> described hereinbefore. Generally, each of the foregoing re-entry devices may be sized like a conventional guide wire, having a <NUM> (<NUM> inch) diameter profile for coronary applications, for example. Also generally, each of the foregoing re-entry devices utilizes rotary abrasion as a mechanism to penetrate the intimal layer and enter into the true vascular lumen.

With specific reference to <FIG>, and to <FIG> which is a detailed cross-sectional view of the distal end, re-entry device <NUM> includes a distally tapered drive shaft <NUM> which may comprise a metallic alloy such as stainless steel or NiTi, for example. The re-entry device <NUM> may have a nominal profile of <NUM> (<NUM> inches) and a length of <NUM> for coronary applications. The shaft <NUM> may have a proximal diameter of <NUM> (<NUM> inches) and a distal taper from <NUM> (<NUM> inches) to <NUM> to <NUM> (<NUM> to <NUM> inches) over approximately <NUM> (<NUM> inches). An abrasive tip <NUM> may be connected to the distal end of the shaft <NUM> by brazing or welding techniques. The shaft <NUM> just proximal of the tip <NUM> is configured with sufficient flexibility to allow flexure of the tip <NUM> after it penetrates the vascular wall into the true vascular lumen, thus preventing penetration of the opposite vascular wall. The abrasive tip <NUM> may comprise a metallic alloy tube <NUM> such as stainless steel, platinum or platinum-iridium with a weld ball cap <NUM>. The tube <NUM> may have an inside diameter of approximately <NUM> (<NUM> inches) and an outside diameter of approximately <NUM> (<NUM> inches). An abrasive coating such as a <NUM> grit diamond coating <NUM> may be applied to the outer surface of the tube <NUM> with a thickness of approximately <NUM> (<NUM> inches) using conventional techniques available from Continental Diamont Tool (New Haven, Indiana).

With reference to <FIG>, and to <FIG> which is a detailed cross-sectional view of the distal end, re-entry device <NUM> further includes a distal coil <NUM> disposed over the distal tapered portion of the shaft <NUM>. The helical coil <NUM> may comprise a stainless steel, platinum or platinum-iridium wire having a diameter of approximately <NUM> to <NUM> (<NUM> to <NUM> inches). The helical coil <NUM> generally imparts enhanced torqueability without compromising flexibility of the tapered portion of the shaft <NUM>.

With reference to <FIG>, and to <FIG> which is a detailed cross-sectional view of the distal end, re-entry device <NUM> alternatively includes a cable shaft <NUM> comprising a <NUM> by <NUM> or <NUM> by <NUM> construction having an outside profile diameter of <NUM> (<NUM> inches), for example. The cable shaft <NUM> construction generally imparts enhanced torqueability in at least one direction while increasing flexibility.

With reference to <FIG>, a rotary drive unit <NUM> is shown in perspective view. Rotary drive unit <NUM> is particularly suited for use with re-entry device <NUM> shown in <FIG>, but may be used with other re-entry devices described elsewhere herein. Generally, the rotary drive unit <NUM> provides for independent rotation and advancement of a re-entry device, wherein the rotation is provided by a motor and advancement is provided by shortening or lengthening a partial loop of an advancement sleeve that is attached at only one end and may be advanced/retract without moving the motor drive.

The rotary drive unit <NUM> includes a base <NUM> with two vertical mounting plates <NUM> and <NUM> attached thereto. A motor <NUM> is mounted to plate <NUM> and is linked by offset gears <NUM> to a hollow drive shaft <NUM>. A lock mechanism <NUM> such as a hollow pin vise or collet is secured to the hollow drive shaft <NUM>. The proximal shaft <NUM> of the re-entry device <NUM> may be secured to the locking mechanism <NUM> such that activation of the motor <NUM> by a suitable power supply causes rotation of the re-entry device <NUM>. An advancement sleeve <NUM> may be fixedly attached to the back side of vertical plate <NUM> and coaxially aligned with the hollow drive shaft <NUM> to receive the re-entry device shaft <NUM> therethrough. The advancement sleeve <NUM> extends in a semi-loop around limiting block <NUM> and slidably through holes in vertical plates <NUM> and <NUM>. The advancement sleeve <NUM> does not rotate but rather supports the rotating shaft <NUM> of the re-entry device <NUM> and thus may be manually held by the treating physician. The advancement sleeve <NUM> may be advanced or retracted thus shortening or lengthening, respectively, the semi-loop thereof and thus advancing or retracting the re-entry device <NUM> as it rotates. The advancement sleeve <NUM> thereby provides tactile feel of the distal tip <NUM> of the re-entry device <NUM> as it engages tissue without being hampered by the rotary drive thereof.

With reference to <FIG>, another alternative re-entry device <NUM> is shown schematically. <FIG> is detailed view "A" in <FIG> of the tip <NUM>, laid flat to illustrate an example of a cut pattern with dimensions given in inches unless otherwise noted. The re-entry device <NUM> includes a tubular shaft <NUM> which may comprise a metallic alloy such as stainless steel or NiTi, for example. The re-entry device <NUM> may have a nominal profile of about <NUM> (<NUM> inches) and a length of <NUM> for coronary applications, and may have a lumen of approximately <NUM> (<NUM> inches), for example, to accommodate a conventional <NUM> (<NUM> inch) guide wire therein. The shaft <NUM> may have a distal spiral cut section <NUM> to impart flexibility. The spiral cut pattern may be formed by conventional laser cutting techniques followed by electropolishing or other suitable finishing techniques. The spacing or gap between respective turns may increase at the distal tip, terminating in a sharpened distal end <NUM> as shown. The progressively decreasing gap from distal end <NUM> may serve to increase flexibility as well as cut tissue as the tip <NUM> is screwed into and through the vascular wall as described previously.

Claim 1:
A system for facilitating treatment via a vascular wall defining a vascular true lumen (<NUM>) containing an occlusion (<NUM>) therein, the system comprising:
an intramural orienting device (<NUM>) including an outer shaft (<NUM>) connected to a proximal end (<NUM>) of an orienting element (<NUM>), and an inner shaft (<NUM>) extending through the outer shaft (<NUM>) and the orienting element (<NUM>), wherein a distal end of the inner shaft (<NUM>) is connected to a distal end (<NUM>) of the orienting element (<NUM>);
wherein the inner shaft (<NUM>) includes a lumen extending therethrough to a side port (<NUM>) adjacent the orienting element (<NUM>);
wherein the orienting element (<NUM>) comprises a metallic tube with cuts made to define two wings (3442A, 3442B), wherein contracting the proximal end (<NUM>) of the orienting element (<NUM>) toward the distal end (<NUM>) of the orienting element (<NUM>) extends the wings (3442A, 3442B) outwardly in a substantially planar manner.