Patent ID: 12251128

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention.

Introduction

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.

Relevant Anatomy

With reference toFIG.1, a diseased heart100is shown schematically. Heart100includes a plurality of coronary arteries110, 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 occlusion120.

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 90% or more functionally occluded in cross-sectional area, rendering it with little to no blood flow there-through 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 (2) weeks old from symptom onset.

With reference toFIG.1A, a magnified view of total occlusion120within coronary artery110is shown schematically. Generally, the proximal portion112of artery110(i.e., the portion of artery110proximal of total occlusion120) may be easily accessed using endovascular devices and has adequate blood flow to supply the surrounding cardiac muscle. The distal portion114of artery110(i.e., the portion of artery110distal of total occlusion120) is not easily accessed with interventional devices and has significantly reduced blood flow as compared to proximal portion112.

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.1Bshows a schematic example of an angiographic image of a chronic total occlusion120. It is common that the angiogram allows a physician to visualize the proximal segment112but does not allow visualization of the occlusion120or the distal segment114.

With reference toFIG.2, a cut-away segment of coronary artery110is shown schematically. Coronary artery110includes a true or native lumen116defined by arterial wall118. The innermost layer of arterial wall118is called the intima or intimal layer113(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 layer115(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 adventitia117. 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 lumen116.

Visualization & Perforation Guard Embodiments

As may be appreciated fromFIG.1B, a total occlusion120prevents the occlusion and distal arterial segment114from being visualized using radiopaque contrast media injection fluoroscopy. In some instances, sufficient contrast media may pass through collaterals around the total occlusion120to achieve visualization of the distal segment114, but visualization of the distal segment114is often unclear and visualization of the occluded segment120is 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 segment114, but such images are often hazy and still do not illuminate the occluded segment120.

To achieve visualization of the occluded segment120and the distal segment114, a radiopaque subintimal device300may be introduced into the subintimal space as shown inFIG.3A. In this illustration, subintimal device300is intended to be relatively generic, as a variety of subintimal devices may be employed as will be described in more detail hereinafter. The subintimal device300exits the true lumen116and enters the subintimal space130at entry point132proximal of the total occlusion120somewhere in the proximal segment112. Within the subintimal space130, the sub-intimal device300may extend across and beyond the total occlusion120and into the distal segment114. With the subintimal device positioned as shown inFIG.3A, and due to the radiopaque nature of the subintimal device300, the occluded segment120and distal segment114may be fluoroscopically visualized as shown inFIG.3B.

Thus, subintimal device300may be used to enhance arterial visualization by placement within the subintimal space130concentrically around the total occlusion120. The subintimal device300defines the approximate inside diameter of the artery110and also defines axial bends or tortuosity in the vessel110across the occluded segment120and distal segment114, thereby defining the circumferential boundary of the artery110across the occluded segment120and distal segment114. Also, by placement within the subintimal space130concentrically around the total occlusion120, the subintimal device300may be used to protect or guard the wall118of the artery110from perforation of devices that attempt to penetrate the total occlusion120via the true lumen116.

As shown inFIGS.3A and3B, the subintimal device300is deployed in a helical pattern within the subintimal space130. 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 toFIGS.4,4A and4B, a deployment device400is shown schematically. Deployment device400may be used to direct the subintimal device300into the subintimal space130at entry point132and deploy the subintimal device300in a helical pattern therein as shown inFIG.5. The deployment device400may take the form of a balloon catheter including catheter shaft402and distal balloon404. Catheter shaft402includes an outer tube406and an inner tube408defining an inflation lumen410therebetween for inflation of balloon404. The inner wire tube408defines a guide wire lumen412therein for advancement of the device400over a guide wire (not shown). A delivery tube414extends along the outer tube406and around the balloon404in a helical (or other) pattern. The delivery tube414defines a delivery lumen416therein for advancement of the subintimal device therethrough. In this particular embodiment, the subintimal device300may have a straight configuration in its relaxed state and rely on the helical delivery tube414to achieve the desired helical pattern.

With reference toFIG.5, the delivery device400is shown in position just proximal of the total occlusion120. In this position, the balloon404may be inflated within the vessel lumen116to direct the delivery tube414toward the vessel wall118at an orientation for the subintimal device300to penetrate through the intima113at an entry point and into the subintimal space. By virtue of the helical delivery tube414, the subintimal device300is sent on a helical trajectory as it is advanced through delivery tube414resulting in deployment of the subintimal device300in a helical pattern. As shown, the subintimal device300has been advanced through the delivery tube414and positioned concentrically outside the total occlusion120, outside the intimal layer113, and inside the medial layer115in the subintimal space.

With reference toFIG.6, an alternative approach to achieving a helical pattern in the subintimal space is shown. Whereas the delivery device400described previously provided a helical delivery tube to deliver a subintimal device300that had a straight configuration in its relaxed state,FIG.6schematically illustrates an alternative subintimal device600that may assume a helical shape itself. Subintimal device600includes an elongate tubular shaft604, at least a distal portion of which includes a helical interlocking gear606and a helical wire coil608disposed thereon. A helically shaped inner mandrel or tube610may be disposed in the tubular shaft604such that the shaft604rotates freely thereon. The shaft604may have a linear or straight configuration in a relaxed state and a helical configuration (shown) when the helically shaped inner member610is disposed therein. The device600may be disposed in a constraining sheath (not shown) and navigated to the intravascular site, such as the site of a total occlusion. When the device600is advanced distally out the end of the constraining sheath or when the sheath is pulled proximally relative thereto, the distal portion of the device600assumes a helical shape as shown. The shaft604may be rotated relative to the inner member610to cause rotation of the helical wire threads608, 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 member610to engage the proximal or distal end of the shaft604to enable the shaft604and the inner member610to be advanced in unison. Subintimal device600may 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 devices300may 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 elements310are schematically illustrated inFIGS.7A-7C. The subintimal device may include a ball-shaped tip310A as shown InFIG.7A, a hook-shaped or loop-shaped tip310B as shown inFIG.7B, and/or a bent tip310C as shown inFIG.7C. 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 tip310C is ability to torsionally direct the tip and control the path of the device through the subintimal space. The ball tip310A may be formed from a suitable metallic material including but not limited to stainless steel, silver solder, or braze. The ball tip310A may also be formed from suitable polymeric materials or adhesives including but not limited to polycarbonate, polyethylene or epoxy. Note that the ball tip310A may be bulbous and larger than the shaft proximal thereto. The loop tip310B and bent tip310C 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 elements310as described above, the subintimal device300may use a guide wire700to facilitate atraumatic passage as shown inFIG.7D. In this embodiment, the subintimal device300may include a lumen extending therethrough such that the device300may be advanced over the guide wire700. In this embodiment, the body of the subintimal device300has 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 wire700therethrough. The guide wire700provides an atraumatic element at its distal end and also provides a mechanism for rotationally steering the subintimal device300through the subintimal space. The guide wire700may 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.FIGS.8A and8Bschematically illustrate a system800that utilizes fluid to achieve atraumatic passage and promote dissection. System800includes a subintimal device810and associated pumping system820. The fluidic system800is 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. System800includes a subintimal device810which may comprise any of the tubular subintimal devices described herein. Generally, subintimal device810includes a tubular shaft812having a proximal end connected to a pumping mechanism820. A plunger rod814is slidably disposed in the tubular shaft812as shown inFIG.8Band its proximal end is connected to a linear actuator822of the pumping mechanism as shown inFIG.8A. The rod814extends through the tubular shaft812to a point proximal of the distal end thereof to define a pumping chamber816. A source of liquid830(e.g., saline bag) is connected to the proximal end of the subintimal device810via a fluid line832and optional valve834to supply liquid to the annular lumen between the rod814and the inner wall of the tubular shaft812. As the linear actuator moves the rod814back and forth in the tubular shaft812, liquid is caused to be expelled out of the chamber816in 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 chamber816may be relatively small (0.01 cc-1.0 cc, for example) such that liquid exits the chamber816with high energy that dissipates quickly to minimize trauma to tissues as they are dissected. One example is a stroke volume of 0.25 cc and a stroke rate of 10 Hz 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 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 body302of the subintimal device300as schematically shown inFIGS.9A-9F. Generally, it is desirable to maintain flexibility of at least a distal portion of the body302to avoid compromising intravascular navigation in tortuous pathways.FIG.9Aschematically shows a generic subintimal device300with a distal body portion302and a proximal body portion304. Relative to the proximal body portion304, 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 body302design is shown inFIGS.9B and9C. In this embodiment, distal body portion302is made of a multitude of independent coils902,904,906concentrically 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 body302may be hollow or may contain a fixed wire910within its internal lumen. The fixed wire910may 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. Coils902,904,906and core wire910may 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 body302design is shown inFIG.9Dwherein a single coil908is wound over an internal core910surrounded by a thin polymeric sheath920. Yet another example of a flexible yet torsionally rigid distal body302design is shown inFIGS.9E and9Fwherein the body simply comprises a single open wound coil912.

A further example of a flexible yet torsionally rigid distal body302design is shown inFIG.9G. The distal body302may 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.9Gshows coil930closely wound with a multitude of teeth932along 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 coil930resists 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 inFIG.9H. The subintimal device300includes a proximal body portion304that is formed of a continuous solid metallic tube940and a distal body portion302that is formed of the same tube with a laser cut coil segment930, wherein the pattern of the laser cut defines the teeth932. Suitable materials for the metallic tube include but are not limited to stainless steel and nickel titanium. Alternatively, the coil930may be wound from a continuous wire. The wire may have a cross section that for example has been mechanically deformed (stamped) to form the teeth932and allow coil engagement.

FIG.9Ishows 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 inFIG.9I, the teeth932are generally trapezoidal and extend orthogonal to the coil turns930.FIG.9Jshows 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 teeth932shown inFIG.9Jpromote engagement and reduce slippage of adjacent coil turns930.

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.10Ashows a subintimal device300wherein at least the distal body portion302includes threads1000on the exterior surface thereof. The threads1000act like an external corkscrew that has the ability to rotationally engage the arterial tissues and help drive the subintimal device300through the subintimal space.FIGS.10B-10Dare cross-sectional views taken along line A-A inFIG.10Aand show various alternative embodiments for the threads1000.FIG.10Bshows one or more round corkscrew members1010that are concentrically wound on the outside of the distal body302.FIG.10Cshows a multi-layer coil construction with coil layers902,904,906where corkscrew member1020comprises a wire element of larger cross-sectional area wound within the external concentric coil906. The corkscrew members may have a rounded shape as shown inFIGS.10B and10C, or other shape such as triangular, square, or other cross-sectional shape that may aid in tissue engagement and subintimal device advancement.FIG.10Dshows a polymer tube with a corkscrew profile1030formed therein and concentrically positioned around distal body portion302. In each of these embodiments, withdrawal of the subintimal device300may 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,FIGS.11A-11Cillustrate 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.11Ashows an over-the-wire type subintimal device1100(or wire support device) having a coiled gear design930as described with reference toFIGS.9G-9Jand a thread design1000as described with reference toFIGS.10A-10D. The device1100has a hollow core and may be advanced over a guide wire700. The geared coils930provide axial flexibility and torsional rigidity and the external helical threads provide mechanical engagement with the lesion or arterial wall.FIG.11Bshows an over-the-wire type subintimal device1110(or wire support device) in longitudinal section, with an inner tube1112having a coiled gear design930, and an outer tube1114having a thread design1000. The inner tube1112contains a guide wire lumen capable of accepting a conventional guide wire700.FIG.11Cshows a partial enlarged view of an alternative inner tube1112where gaps934between adjacent coils allow articulation of the inner tube1112upon proximal withdrawal of actuation wire1118. Outer tube1114may freely rotate with respect to inner tube1112when the inner tube1112is 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 inFIGS.12A-12C, 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.12Aschematically illustrates a directing catheter1200substantially similar to an over-the-wire balloon catheter including a distal balloon1220with the addition of a delivery and directing tube1210. As shown, the directing catheter1200has been advanced over a conventional guide wire700and inflated proximal to the total occlusion120. For the sake of clarity,FIG.12Ashows 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 tube1210may be positioned adjacent to and pointed slightly outward and toward the intimal layer113such that the subintimal device300may be advanced to perforate the subintimal layer113. A fluid source (e.g., syringe)1230may be connected to be in fluid communication with the delivery and directing tube1210via an infusion tube1232. Fluid may flow from the fluid source1230through the delivery and directing tube1210under a controlled pressure or a controlled volume. The infused fluid may enter the subintimal space130directly from the delivery and directing tube1210or from the true lumen116space defined between the distal end of the balloon1220and the proximal edge of the occlusion120. The fluid may be radiopaque contrast media to facilitate fluoroscopic visualization of the subintimal space, and/or may be used to delaminate the intimal layer113and medial layer115defining the subintimal space130.FIG.12Bschematically illustrates an alternative embodiment of directing catheter1200wherein the fluid source1230is in fluid communication with a lumen within the subintimal device300thereby directly infusing fluid into the subintimal space130via subintimal device300.FIG.12Cschematically illustrates another embodiment wherein the directing catheter1250is similar to a sub-selective guide catheter wherein the distal end1252has a predefined shape or an actuating element that allows manipulation by the physician intra-operatively to direct the subintimal device300toward 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 inFIGS.13A and13B. Subintimal device1300may be actuated or self-expanded between a collapsed configuration shown inFIG.13Aand an expanded configuration shown inFIG.13B. The device1300may 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 device1300may comprise a shaft1310having a plurality of resilient expandable elements1312(e.g., heat set NiTi) and an atraumatic tip1314(shown bent). A sheath1320may be disposed about the proximal shaft1310and the expandable elements1312to retain the expandable elements1312in a collapsed configuration as shown inFIG.13A. Upon proximal retraction of the sheath1320(or distal advancement of the shaft1310) the expandable elements1312elastically expand as shown inFIG.13Bto cause propagation of the dissection. The sheath1320may be advanced to collapse the expandable elements1312and the device1300may 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.

FIGS.13C and13Dschematically illustrate an alternative subintimal crossing device1330. Subintimal device1330may be actuated or self-expanded between a collapsed configuration shown inFIG.13Dand an expanded configuration shown inFIG.13Cto delaminate the layers of the vascular wall. Alternatively, the subintimal device1330may be nominally in the expanded configuration and collapsible upon retraction. The device1330may 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 device1330may comprise a flexible shaft1332and an expandable element1334. 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 element1334may be connected to the distal end of the shaft1332using an adhesive or weld joint, for example. The expandable element1334may 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 element1334may comprise an atraumatic tip comprising, for example, a weld ball1336securing the individual braided filaments. The expandable element1334may be expanded by pushing on the shaft1332when resistance to advancement is encountered, thus delaminating adjacent tissue layers. Alternatively, the expandable element1334may be expanded by pushing on the shaft1332and pulling on a pull wire (not shown) attached to the distal end of the expandable element1334and extending proximally through the lumen of the shaft1332. A flexible polymeric sheath1340may be used to facilitate delivery of the crossing device1330, provide and maintain a crossing path within the vascular wall, and/or to facilitate removal of the crossing device1330as shown inFIG.13D. The polymeric sheath1340may 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.

FIGS.13E and13Fschematically illustrate an alternative subintimal crossing device1350. Subintimal device1350includes an elongate flexible and torqueable shaft1352and a distal elastic loop1354formed of a superelastic metal alloy such as NiTi, for example. The loop1354may be self-expanded between a collapsed configuration shown inFIG.13Fand an expanded configuration shown inFIG.13E. The device1350may be advanced distally through sheath1340for delivery and pulled proximally into sheath1340for removal. When expanded, the loop1354may be substantially planar, and with rotation of the shaft1352, the loop1354rotates in the subintimal space forcing delamination of tissue layers.

Bypass Embodiments

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 inFIGS.14A-14H. A guide wire700may be advanced through the proximal segment112of the true lumen116of the occluded artery to the proximal edge of the total occlusion120adjacent the vessel wall118as shown inFIG.14A. By manipulating and directing the guide wire700to the proximal edge of the total occlusion120toward the wall118, the guide wire700may penetrate the intimal layer113and enter the subintimal space130between the intima113and the media/adventitia115/117as shown inFIG.14B. The manipulating and directing of the guide wire700as described above may be performed by using the guide wire alone or by using any of the directing devices described herein. With the guide wire700in the subintimal space130, a subintimal device1400may be advanced over the guide wire700as shown toFIG.14C. In the illustrated embodiment, the subintimal device1400includes a hollow elongate shaft1402and an atraumatic bulbous tip1404. However, any of the subintimal devices described herein may be employed, particularly the over-the-wire type subintimal devices. As shown inFIG.14D, the subintimal device1400may be further advanced over the guide wire700such that the tip1404resides in the subintimal space130. At this procedural stage, the guide wire700may be withdrawn, completely removing it from the subintimal device1400. Further manipulation of the subintimal device1400(both axial advancement and radial rotation) allows blunt dissection of the layers defining the subintimal space130and advancement of the device1400to the distal portion of the total occlusion120as shown inFIG.14E. Penetration of the intimal layer113and re-entry into the distal segment114of the true lumen116distal to the occlusion120may be achieved by various means described later in detail, which generally include the steps of orientation toward the center of the true lumen116and penetration of the intimal layer113. For purposes of illustration, not limitation,FIG.14Fshows a shaped re-entry device1420having a curled and sharpened tip exiting the lumen of the subintimal device1400distal of occlusion120and entering the distal segment114of the true lumen116through the intimal layer113. With re-entry device1420in the distal segment114of the true lumen116, the subintimal device1400may be advanced into the true lumen116over the re-entry device1420as shown inFIG.14G. The re-entry device1420may be withdrawn from the subintimal device1400and the guide wire700may be advanced in its place as shown inFIG.14H, after which the subintimal device1400may be withdrawn leaving the guide wire700in place. As such, the guide wire700extends from the proximal segment112of the true lumen116proximal of the occlusion120, traverses the occluded segment via the subintimal space130, and reenters the distal segment114of the true lumen116distal of the occlusion120, thus bypassing the total occlusion120without exiting the artery. With the guide wire700so placed, the subintimal space130may 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 inFIGS.15A and15B. In this embodiment, a helical subintimal device1500is shown generically, the features of which may be incorporated into other subintimal device embodiments described herein. Subintimal device1500generally includes an elongate tubular shaft1502having a lumen1504extending therethrough and a re-entry port1506disposed distally in the region of the helical shape. In this embodiment, the distal portion of the shaft1502may have a helical shape in its relaxed state such that the re-entry port1506is always oriented toward the concave side or center of the helix as shown inFIG.15A. 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 port1506being oriented toward the true lumen. With this arrangement, a re-entry device such as a guide wire700or flexible stylet with a tissue penetrating tip may be advanced through the lumen1504of the shaft1502to exit the re-entry port1506as shown inFIG.15B. This arrangement may be used to establish re-entry into the true lumen after the subintimal device1500has 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 intima113is more pliable than the composite of the media115and adventitia117. Thus, expansion of an element in the subintimal space130will result in more deflection of the intima113than the media115and adventitia117.

One such embodiment that operates under this premise is shown schematically inFIGS.16A-16D. In this embodiment, a subintimal device (not shown) as described elsewhere herein may be used to pass the total occlusion and place a guide wire700as shown inFIG.16A. The guide wire700extends across the occlusion120and is disposed in the subintimal space130between intima113and the media/adventitia115/117where re-entry into the true lumen116distal of the occlusion120is desired. A balloon catheter1620is then advanced over the guide wire700until the balloon portion1622is disposed adjacent the distal end of the occlusion120as shown inFIGS.16B and16C. The guide wire700is pulled proximally and the balloon1622is then inflated causing radial displacement of the distal end of the balloon catheter1620as shown inFIG.16C. Inflating the balloon1622of the balloon catheter1620orients the tip of the catheter1620toward the intima113. The guide wire700may be removed from the balloon catheter1620and a sharpened stylet1630or the like may be advanced through the guide wire lumen of the catheter1620until the distal end of the stylet1630penetrates the intima113as shown inFIG.16D, thus establishing re-entry from the subintimal path130and into the true lumen116.

Detailed Examples of Bypass Embodiments

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.

Detailed Examples of Axial Push Force and Radial Torque Embodiments

The embodiments described with reference toFIGS.17and18illustrate features of subintimal devices that facilitate the transmission of push and twist to enter the subintimal space and advance therein.FIG.17shows an embodiment of a subintimal device1700where the properties of push and twist may be provided by an internal stylet1703slideably disposed within the central lumen1701of a tubular shaft1702. With stylet1703removed, the central lumen may also accept a guide wire (not shown).

The tubular shaft1702may be made from suitable polymeric materials such as polyethylene, nylon, or polyether-block-amide (e.g., Pebax™). The tubular shaft1702may 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 device1700may also have a lubricious exterior coating. For example, coatings may include liquid silicone or hydrophilic coating such as hyaluronic acid. The stylet1703may be made of suitable metallic materials including but not limited to stainless steel or nickel titanium alloys. The atraumatic tip1704may be made of suitable metallic or polymeric materials including, for example, stainless steel, titanium, polycarbonate, or polyether-block-amide (e.g., Pebax™)

As seen inFIGS.17A and17B, which are cross sectional views taken along lines A-A and B-B, respectively, inFIG.17, all or a portion (e.g., distal portion) of the stylet1703may interface with a feature1706within the tubular shaft1702and/or within the atraumatic tip1704. For example, the tubular shaft1702and/or the atraumatic tip1704may contain a lumen with a geometric feature1706intended to mate or key with distal tip of the stylet1707as shown inFIG.17B. This keying or mating feature1706allows 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 feature1706is 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 stylet1703with the internal lumen of the tubular shaft1702and/or atraumatic tip1704.

FIG.18shows an embodiment of a subintimal device1800having a proximal tubular shaft1804, a distal tubular shaft1802, and an atraumatic bulbous tip1805. In this embodiment, the desired properties of push and twist may be provided by constructing the proximal shaft1804of a rigid material (e.g., metallic hypotube) and constructing the distal shaft1802in a similar manner, for example, to the gear shaft previously described with reference toFIG.9et seq. Distal gear shaft1802may be flexible yet torsionally and longitudinally rigid. The distal shaft1802may be disposed within an outer sheath1801and may have an internal sheath1803as 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™.

Detailed Examples Lumen Orientation Embodiments

The embodiments described with reference toFIGS.19A-19B,20A-20B,21A-21B, and22A-22Cillustrate 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.19A) and a radial bend (e.g.,FIG.19B) 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.

FIGS.19A and19Bshow subintimal device1900that is capable of aiming a re-entry device (not shown) toward the true lumen116distal of a total occlusion with the aid of standard fluoroscopy. Subintimal device1900with atraumatic tip1902may be positioned within the subintimal space130between the intima113and media115layers. The subintimal device1900may be advanced using similar techniques previously described with reference toFIGS.14A-14E. Once the subintimal device1900is in the proper position within the subintimal space130, a distal portion of the sub-intimal device1900is configured to achieve a geometry having a bend in the longitudinal direction as shown inFIG.19Aand a bend in the radial direction as shown inFIG.19B. 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 lumen116of the artery110.

FIG.20Aillustrates a subintimal device2000, similar to the subintimal device1800described with reference toFIG.18, that may be capable of achieving a compound bend. The subintimal device2000includes an elongate tubular shaft2001defining an internal lumen, an actuation (e.g., push or pull) member2003residing in the lumen of the shaft2001and having a distal end attached to the distal end of the shaft2001, and an atraumatic tip2004attached to the distal end of the shaft2001. The flexible yet torsionally rigid distal shaft2001has one or more open areas2002oriented along the actuation member2003. An external sheath2005may be disposed about the length of the shaft2001and actuation member2003, with its distal end attached to the atraumatic tip2004. For purpose of illustration only,FIG.20Ashows a single actuation member2003in the proximity of a single row of open areas2002in the shaft2001. The subintimal device may have one or more actuation members and may have one or more rows of open areas. For example, the shaft2001may have a laser cut geometry as shown inFIG.20Bwith two rows of open areas2002.

With continued reference toFIG.20A, a bend may be achieved by pulling the longitudinal actuation member2003. Pulling the actuation member2003partially or completely closes the open spaces2002thus shortening the length of the shaft2001in proximity of the open areas2002and creating a bend in the device2000. A compound bend may be achieved through the use of multiple rows of open areas and/or multiple longitudinal members2003. 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 member2003creates the axial curvature (seeFIG.19A) and interaction with the adventitia may force the subintimal device to accommodate a radial curvature (seeFIG.19B).

FIG.21Ashows an alternative embodiment of a subintimal device2100that may also achieve a compound bend. The subintimal device2001generally includes an elongate tubular shaft2102defining an internal lumen2101, an actuation (e.g., push or pull) member2105having a distal end attached to the distal end of the shaft2102, and an atraumatic tip2106attached to the distal end of the shaft2102. The shaft2102may be constructed from a multitude of alternating wedge-shaped polymeric segments where segment2103may have a lower durometer and greater flexibility as compared to the adjacent segment2104. For example, segment2103may be made of 4033 Pebax while segment2104may be 6333 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.21Ashows a series of wedged-shaped segments wherein the relatively stiff segment2104defines a larger percentage of one side along a line of the shaft2102while the relatively flexible segment2103defines a larger percentage of the opposing side of the same shaft.

As shown inFIG.21B, the side of the shaft2102with a greater percentage of relatively flexible segments2103allows more relative compression upon actuation of member2105, such that the shaft2105may have a predisposition to flex to the side with more flexible segment material2103and may have greater resistance to flex to the side with more stiff segment material2104. The longitudinal actuation member2105may be slideably disposed in a lumen within the wall of the shaft2102and may be attached to the atraumatic tip2106, extending the length of the shaft2105and out the proximal end. For purpose of illustration,FIGS.21A and21Bshow a single longitudinal member2105in the proximity of a line of relatively flexible segments2103. The subintimal device2100may have one or more longitudinal members and may have one or more lines of flexible segments2103.

With reference toFIG.21Ba compound bend may be achieved by pulling the actuation member2105relative to shaft2102. Pulling the actuation member2105may compress segments2103thus shortening the subintimal device length along the side of the of the shaft2102with mare flexible segment material2103. A compound bend may be achieved by arranging the flexible segment material2103in the desired pattern and/or by using multiple longitudinal members2105. Alternatively, a compound bend may also be achieved using a single side of flexible segment material2103and a single longitudinal member by relying on device interaction with the adventitial layer as described previously.

With reference toFIGS.22A-22C, another embodiment of a subintimal device2200capable of achieving a compound bend is shown schematically.FIG.22Aonly shows the distal portion of the subintimal device2200for purposes of illustration and clarity. In this embodiment, the tubular shaft of the subintimal device2200comprises an inner tube2201and an outer tube2204(shown cut away), between which is disposed a series of circumferential rings2202interconnected by longitudinal members2203. An atraumatic tip2207is connected to the distal end of the shaft, and a central lumen2206runs through the device2200for the acceptance of a guide wire and/or a re-entry device. Suitable materials for the circumferential rings2202and longitudinal members2203include but are not limited to nickel titanium, stainless steel, or MP35N. The inner tube2201and the outer tube2204may 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 inFIG.22A.

The subintimal device2200may be slideably disposed within an external delivery sheath2205as shown inFIGS.22B and22C. The sheath2205may be slightly stiffer then the subintimal device2200such that the subintimal device2200assumes a straight shape when the sheath2205covers the distal portion of the device as shown inFIG.22B, and assumes a curved shape when the sheath2205is retracted as shown inFIG.22A. Upon proximal retraction of the sheath2205, the subintimal device2200may 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.

Detailed Examples of Re-entry Embodiments

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. There-fore, 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).

FIGS.23A-23Eshow embodiments of re-entry devices that may be advanced through a lumen within a subintimal device2300. The subintimal device2300may be similar to the devices described previously to facilitate formation of a radial bend with a concave side oriented toward the true lumen116distal of a total occlusion. With reference toFIG.23A, subintimal device2300may be positioned within the subintimal space130between the intimal113and medial115layers. A radial curve may be formed in the subintimal device2300using 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 device2300to be pointed toward the true lumen116. The re-entry device2310may comprise a guide wire, a sharpened stylet or the like to facilitate penetration through the intimal layer. Advancement of the re-entry device2310though the central lumen within the subintimal device2300and out the distal end results in penetration through the intimal layer113and into the true lumen116.

An alternative re-entry embodiment is shown inFIG.23Bwherein the subintimal device2300has a radial curvature approximating the inside curvature of the artery. The subintimal device may be placed within the arterial wall between intimal113and medial115layers as described previously. In this embodiment, the re-entry device2310may have a preformed bend that is less than the curvature of the subintimal device2300and less than the inside curvature of the artery. The re-entry device is longitudinally and rotationally movable with respect to the subintimal device2300, thus allowing the curvature of the re-entry device2310to self-align with the curvature of the subintimal device2300. Thus, with the concave side of the curved subintimal device oriented toward the true lumen, the concave side of the curved re-entry device2310will also be oriented toward the true lumen. Advancement of the re-entry device2310through the subintimal device2300and out the distal end thereof results in penetration through the intimal layer113and into the true lumen116. 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 inFIG.23Cwherein the re-entry device2310exits out a distal side port2302in the subintimal device2300. The side port2302may be located on the concave side of the curvature of the subintimal device2300thus orienting the tip of the re-entry device2310toward the true lumen116. In this embodiment, the re-entry device2310may have a slight bend at its distal end to bias the tip toward the port2302such that it exits the port upon advancement.

Another alternative re-entry device embodiment is shown inFIGS.23D and23E.FIG.23Eis a cross sectional view taken along line A-A inFIG.23D. In this embodiment, the subintimal device2300and the re-entry device may be provided with radial curvature for orientation toward the true lumen116as described previously. In addition, a portion of the subintimal device2300such as the tip2304and a distal portion of the re-entry device2310may 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 inFIG.23E.

FIGS.24A-24Cshow various embodiments of penetrating tips for use on a re-entry device. As mentioned previously, the re-entry device2310may comprise a guide wire or the like to facilitate penetration through the intimal layer113from the subintimal space130to the true lumen116. Alternatively, the tip of the re-entry device2310may be designed to enhance penetration through the intimal layer113, particularly in the case where the intimal layer is diseased. If the intimal layer113is 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 non-homogenous 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 inFIGS.24A-24Cmay be employed.

As shown inFIG.24A, the re-entry device may have a rotational cutting or piercing element2410capable of penetrating the arterial wall. The rotational element2410may, for example, be similar to a fluted drill bit. Rotation of the re-entry device with rotational cutting element2410may be achieved through manual manipulation by the physician or through a powered mechanism such as an electric motor.

As shown inFIG.24B, the re-entry device may have a rotational abrasive element2420. The abrasive element2420may include an abrasive coating such as220grit 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 element2420may be achieved through manual manipulation by the physician or through a powered mechanism such as an electric motor.

As shown inFIG.24C, the re-entry device may have a tapered or sharpened tip2430. The sharpened tip2430may penetrate the intimal layer113through 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 tip2430may 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 sub-intimal device penetrate the intimal layer113and come in contact with the blood in the true lumen116distal 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.25illustrates a re-entry device2500that facilitates confirmation of true lumen re-entry. The re-entry device2500may be passed through a subintimal device2300, oriented toward the true lumen116, and penetrate the intimal layer113from the subintimal space130to the true lumen116as described previously. In this embodiment, the re-entry device2500is provided with an internal lumen extending from its proximal end to a distal opening2502. The proximal end of the re-entry device2500is connected to an indicator2504which is in turn connected to a vacuum source. The indicator2504may 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 device2500into the true lumen116allows blood to flow into the distal opening2502and through the internal lumen to the indicator2504. 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 indicators2504may be employed such as impedance sensors, oxygen sensors, optical sensors etc.

Detailed Examples of Deployable Element Embodiments

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 element2600is schematically illustrated inFIG.26A. The deployable element2600may be disposed about a subintimal device2300and contained thereon by a retractable containment sheath2610. InFIG.26A, the deployable element2600is shown in the process of release from its constrained position the proximal retraction of the containment sheath2610. The deployable element2600may comprise, for example, a collapsible lattice structure that is capable of expanding from a first collapsed configuration within the containment sheath2610to a second deployed configuration upon retraction of the sheath2610that allows it to expand within the arterial wall. In this embodiment, the deployable element2600is shown in the submedial space between the media115and adventitia117.FIG.26Bshows the deployable element2600completely released from the subintimal device2300by complete retraction of the exterior containment sheath2610. The deployable element2600may 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 element2600may 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 element2600include 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.27shows a rotational abrasive device2700with an abrasive cutting tip2710passing through a total occlusion120with the deployable element2600protecting the arterial wall from perforation. While the abrasive tip2710is effective at passing through the total occlusion120, the deployable element comprises a relatively harder material (e.g., metallic) with a lattice pattern having openings smaller than the tip2710to 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 element2800may comprise one or more continuous elastic members as shown inFIG.28. The deployable element2800may be released from an exterior containment sheath (not shown) as described previously to expand circumferentially within the subintimal space. As shown inFIG.28, the deployable element2800may 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 device2900may have an accessory deployable element2910as shown inFIGS.29A-29D.FIGS.29B and29Dare cross sectional end views ofFIGS.29A and29C, respectively. With reference toFIGS.29A and29B, the subintimal device2900is shown positioned in the subintimal space with the accessory deployable element2910having an exposed portion disposed in a recess and a proximally extending portion in a lumen of the subintimal device2900. With reference toFIGS.29C and29D, advancing the proximal portion of the deployable element causes the exposed portion to protrude from a side port2904and 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 lumen116. 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 toFIGS.23A-23E,24A-24C, and25.

Occlusion Removal Embodiments

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.FIGS.30A-30Dillustrate an example of this application wherein a delivery device400is used to deliver a subintimal device300around a total occlusion120, similar to what is shown and described with reference toFIGS.4,4A,4B and5. The occlusion is then removed as will be described in more detail.

With reference toFIG.30A, the delivery device400is positioned just proximal of a total occlusion120. In this position, the balloon404may be inflated within the vessel lumen116to direct the delivery tube414toward the vessel wall118at an orientation for the subintimal device300to penetrate through the intima113at an entry point and into the subintimal space. By virtue of the helical delivery tube414, the subintimal device300is sent on a helical trajectory as it is advanced through delivery tube414resulting in deployment of the subintimal device300in a helical pattern. As shown, the subintimal device300has been advanced through the delivery tube414and positioned concentrically outside the total occlusion120, outside the intimal layer113, and inside the medial layer115in the subintimal space.

With reference toFIG.30B, a subintimal device capture catheter3010is positioned across the chronic total occlusion120over a conventional guide wire700and within the subintimal device300. The proximal301and distal303ends of the subintimal device300have been captured and rotated by capture device3010so as to reduce the outside diameter and contain the lesion120and intima113within the coils of the subintimal device300.

With reference toFIGS.30C, a tubular cutting device3020with a sharpened leading edge may be advanced over the subintimal device300and the capture device3010to engage and cut the intimal layer113with the total occlusion120therein. With reference toFIG.30D, further advancement of the cutting device3020cuts 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 lumen116. The occlusion120may 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 device3110may be used to grasp and pull the total occlusion120for removal as shown inFIGS.31A and31B. It is contemplated that corkscrew-type device3110may be used in combination with the devices described with reference toFIGS.30A-30Dwhich are not shown for sake of clarity. With reference toFIG.31A, the corkscrew device3110is shown with an exterior sheath3120. The corkscrew device3110is shown engaging occlusion120after delamination of the intimal layer113has been performed by the aforementioned methods and devices.FIG.31Bshows removal of the occlusion120and a portion of the intimal layer113through axial withdrawal of the corkscrew device3110.

Alternative Bypass Embodiment

FIGS.32A-32Eillustrate an alternative system for bypassing a total occlusion. With reference toFIG.32A, a subintimal device3200is shown in the deployed configuration. The subintimal device3200includes an elastic wire3210with a distal form similar to the elastic wire form2800described with reference toFIG.28, except with fewer sinusoidal turns. The subintimal device also includes a crescent-shaped or semi-circular delivery shaft3220and a retractable constraining sheath3230. As seen inFIG.32B, which is a cross-sectional view taken along line A-A inFIG.32A, the wire3210resides in the recess of the semi-circular delivery shaft3220over which the constraining sheath3230is disposed. As an alternative, the constraining sheath3230may be disposed about the wire3210only and may reside in the recess of the delivery shaft3220, provided that the constraining sheath3230is sufficiently stiff to at least partially straighten the formed wire3210. The distal end of the wire3210is connected to a blunt tip3222of the shaft3220. The wire3210and the semi-circular shaft3220may be formed of a resilient metallic material such as nickel titanium, stainless steel, elgiloy, or MP35N, and the sheath3230may be formed of a flexible polymeric material such as a polyether-block-amide (e.g., Pebax) lined with PTFE (e.g., Teflon).

Pulling the wire3210proximally relative to the shaft3220and advancing the sheath3230over the wire form constrains the wire form in the recess and renders the device3200suitable for atraumatic passage through the subintimal space. Once the device3200is positioned across the total occlusion within the subintimal space, the sheath3230may be retracted relative to the shaft3220to release the formed portion of the wire3210. Releasing the wire form causes it to extend circumferentially around the occlusion in the subintimal space as shown inFIG.32C. Once the wire form is fully deployed in the subintimal space, the sheath may be completely removed.

As shown inFIG.32D, with the wire form3210deployed in the subintimal space and with the sheath3230removed from the shaft3220, a dual lumen re-entry delivery catheter3250may be advance over the shaft3220. As seen inFIG.32E, which is a cross-sectional view taken along line A-A inFIG.32D), the delivery catheter3250includes a crescent-shaped or semi-circular lumen3254that accommodates the shaft3220extending therethrough. The delivery catheter3250also includes a circular lumen3252that accommodates a re-entry device3240extending therethrough. The delivery catheter3250may comprise a dual lumen polymeric extrusion such as polyether-block-amid (e.g., Pebax) and the re-entry device3240may be the same or similar to the re-entry devices described previously herein.

Alternatively, the delivery catheter3250may 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 shaft3220. At the distal end of the delivery catheter3250, 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 inFIG.32Eover 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 wire3210to the tip3222of the shaft3220, the concave side of the semi-circular shaft3220also faces the true lumen. This feature may be used to facilitate orientation of a re-entry device toward the true lumen. For example, because lumen3252of the delivery catheter3250has a mating or keyed geometry with the semi-circular shaft3220, and because the concave side of the semi-circular shaft3220is oriented toward the true lumen, the re-entry device lumen3252may be oriented toward the true lumen as well. With this in mind, any of the re-entry device orientation methods described with reference toFIGS.23A-23Emay be employed. As shown inFIG.32D, the distal end of the semi-circular shaft3220has a curvature with a concave side facing the true lumen which may be used in concert with a curved re-entry device3240. Once orientation is established, the re-entry device3240may penetrate the intimal layer113and re-enter the true lumen as shown.

Orienting Device Introduced Through Subintimal Guide Catheter Embodiment

FIGS.33A-33Eschematically illustrate an embodiment using one or more subintimal guide catheters3310/3320to introduce an orienting device3330. 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 device300with or without a guide wire lumen (shown) and having a bulbous tip310(e.g., 0.038 in. diameter olive shaped weld ball) is used to safely cross the subintimal space by blunt dissection as described elsewhere herein.

As shown inFIG.33A, a first (inner) sheath3310having an inside diameter (e.g., 0.018 inches) slightly larger than the outside diameter (e.g., 0.014-0.016 inches) of the shaft of the crossing device300may be advanced by pushing and back-and-forth rotation over the crossing device300and through the subintimal space up to the bulbous tip310located adjacent the distal end of the occlusion (not shown). Once in place, a second (outer) sheath3320having an outside diameter of 0.050 inches, for example, and an inside diameter (e.g., 0.040 inches) slightly larger than the outside diameter (e.g., 0.037 inches) of the inner sheath3310and slightly larger than the outside diameter of the tip310may be advanced by pushing and back-and-forth rotation over the inner sheath3310up to the bulbous tip310as shown inFIG.33B. In this Figure, a window cut-away is shown in the distal portion of the outer sheath3320for purposes of illustration. Once the outer sheath3320is in this position, the subintimal crossing device300and the inner sheath3310may be removed proximally through the outer sheath. Although the outer sheath3320may be advanced over the subintimal crossing device300without the need for inner sheath3310, the inner sheath3310provides step-wise increase in dissection diameter making traversal easier. The inner sheath3310may 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 sheath3320may 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 sheaths3310/3320enhances the ability to cross and delaminate across the subintimal path.

With the outer sheath3320in place and providing a protected path across the occlusion within the subintimal space, an orienting device3330may be inserted into the sheath3320to the distal end thereof as shown inFIG.33C. In this Figure, a window cut-away is shown in the distal portion of the outer sheath3320for purposes of illustration.FIG.33Cshows the orienting device3330in the delivery configuration with the orienting element collapsed andFIG.33Dshows the orienting device3330in the deployed configuration with the orienting element expanded.

The orienting device3330shown inFIG.33Dis similar to the orienting device3200shown inFIG.32A. The orienting device3330may include a tubular shaft3332with a wire3334disposed therein. The tubular shaft3332may comprise a polymeric tube with a wire ribbon (e.g., SST) embedded therein to add stiffness for pushability. The tubular shaft3332includes a lumen extending therethrough, and the distal end of the lumen is directed at an angle to a side facing exit port3338located proximate the orienting element3336. The distal end of the wire3334may include an orienting element3336comprising, for example, a preformed planar sinusoid, referred to as a wire form. The wire3334and the wire form3336may comprise a superelastic metal alloy such as NiTi, for example, and the wire form3336may be formed by heat setting. To deploy the orienting element3336, the outer sheath3320may be pulled proximally and the shaft3332may be pushed distally in an alternating fashion until the entire wire form3336is within the subintimal space.

The side port3338is oriented at a right angle to the plane of the orienting element3336. With this arrangement, the side port3338is either directed toward the vascular true lumen116or 180 degrees away from the vascular true lumen116. Radiographic visualization or other techniques as described elsewhere herein may be used to determine if the port3338is directed toward or away from the true lumen116. If the port3338is directed away from the true lumen116, the orienting device may be retracted, rotated 180 degrees, and re-deployed to point the port3338toward the true lumen116. A re-entry device as described elsewhere herein may then be advanced through the lumen of the tubular shaft3332, through the vascular wall and into the true lumen116.

As an alternative to orienting device3330shown inFIG.33D, orienting device3340shown inFIG.33Emay be employed in substantially the same manner. Orienting device3340includes an outer tube3342and an inner tube3344. The outer tube3342may be formed of a superelastic metal alloy (e.g., NiTi), and a distal portion of the outer tube3342may be cut (e.g., using laser cutting techniques) to form slots to define two wings3346that hinge outward in a planar fashion as shown. The inner tube3344extends through the lumen of the outer tube3342and is attached distally to the distal end of the outer tube3342. Inner tube3344is similar in design and function as tubular shaft3332, and includes a distal side port3348to 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.

Orienting Device Introduced Over Subintimal Crossing Device or Guide Wire Embodiment

FIGS.34A-34Hschematically illustrate an embodiment using a subintimal crossing device or guide wire to introduce an orienting device3400. In this embodiment, the orienting device3400is 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 toFIG.34A, a detailed view of a distal portion of the orienting device3400is shown.FIG.34B(1) is a cross-sectional view taken along line A-A inFIG.34A, andFIG.34B(2) is a cross-sectional view taken along line B-B inFIG.34A. The orienting device3400includes an elongate outer tubular shaft3410with a distal end connected to an orienting element3440. An elongate inner tubular shaft3420extends through the outer shaft3410and orienting element3440. The distal end of the inner shaft3420is connected to the distal end of the orienting element3440, as is a distal atraumatic tubular tip3450. A low friction liner3430may extend through the lumen of the inner shaft3420to facilitate smooth passage of devices therein.

The outer shaft3410may comprise, for example, a polymeric tube3412that may be reinforced with an embedded braid or wire ribbon. The inner shaft3420may comprise a metallic tube3422(e.g., NiTi) with a solid tubular proximal segment and a spiral cut3424distal segment for added flexibility and torqueability. The distal portion of the inner shaft3420may include an inwardly inclined flap3426. As seen inFIG.34B(1), the flap3426extends into the lumen of the inner shaft3420and operates to (1) direct front loaded devices (e.g., re-entry device) out the side port3425of the inner shaft3420adjacent the orienting element3440; and (2) direct back loaded devices (e.g., subintimal crossing device or guide wire) down the lumen of the proximal segment3422of the inner shaft3420while preventing back loaded devices from exiting the side port3425. A semi-circular slot3428may be formed to accommodate the end of the flap3426to prevent the edge of the flap3426from 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 toFIG.34C, the inner shaft3420may have an overall length of approximately 135 cm for coronary applications, with a spiral cut3424distal segment length of approximately 35 cm, for example. With reference toFIG.34D, which is a detailed view of a distal portion of the inner shaft3420, the cut pattern is illustrated as if the tube were laid flat with dimensions given in inches unless otherwise noted. The spiral cut3424may terminate proximal of the side port3425and flap3426. A hinge slot3427may be provided to allow the flap3426to hinge when devices are back loaded as described previously. A semi-circular slot3428may be provided to accommodate the end of the flap as described previously. A hole3429may be used to provide connection to the distal end of the orienting element (not shown) by pinning or welding, for example.

With reference toFIGS.34A and34E, the orienting element3440may comprise a metallic tube (e.g., NiTi) with cuts made to define two wings3442A and3442B. InFIG.34E, the cut pattern of the orienting element3440is shown as if the tube were laid flat with dimensions given in inches unless otherwise noted. The cuts are made to define two separate wings3442A and3442B, with three hinge points3443,3444and3445per wing3442. The proximal end3446of the orienting element3440is connected to a flared end of the outer shaft3410, and the distal end3448is connected to the distal end of the inner shaft3420and the proximal end of the tubular tip3450. By contracting the proximal end3446toward the distal end3448, the proximal lunge3445and the distal hinge3443flex outwardly to extend each wing3442outwardly, with the center hinge3444at the apex of each wing3442.

The distal tip3450may comprise a relatively soft polymeric tube segment, optionally loaded with radiopaque material. The inner liner3430may comprise a tubular extrusion3432or internal coating made of a low friction material such as high-density polyethylene (HDPE) or polytetrafluoroethylene (PTFE).

FIGS.34F-34Hschematically illustrate a method of using the orienting device3400described above. As mentioned previously, orienting device3400is 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 device3400is shown over subintimal crossing device1330having an expandable and collapsible tip1334at the distal end of an elongate shaft1332, but the orienting device3400may 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 device1330) or a device without an enlarged tip allows it to be removed through the center lumen of the orienting device3400such 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 toFIG.34F, once the subintimal crossing device1330extends across the occlusion within the subintimal space such that the tip1334is adjacent the distal end of the occlusion, the orienting device3400may be back-loaded (direction shown inFIG.34B(1)) over the subintimal crossing device1330such that the shaft1332of the crossing device1330deflects the flap3426outwardly and extends through the center lumen of the orienting device3400. The orienting device3400may then be advanced over the subintimal crossing device1330until the distal end of the orienting device is adjacent the distal end of the occlusion. The tip1334of the subintimal crossing device1330may then be collapsed and withdrawn proximally.

With reference toFIG.34G, the orienting element3440may be expanded to extend the wings3442A and3442B in a substantially planar manner as shown. To facilitate expansion and contraction of the orienting element3440, an actuation mechanism3460may be used to push the outer shaft3410and pull the inner shaft3420relative to each other to cause expansion, or pull the outer shaft3410and push the inner shaft3420relative to each other to cause retraction. The actuation mechanism may comprise, for example, a fixed handle3462fixedly connected to the proximal end of the outer shaft3410, a rotatable handle3464rotatably connected to the proximal end of inner shaft3420, and a threaded shaft fixedly connected to rotatable handle3464that engages internal threads (not visible) in the fixed handle3462. The rotatable handle3464may engage a collar (not visible) on the proximal end of the inner shaft3420that permits relative rotation but prevents relative axial motion and therefore causes axial displacement of the inner shaft3420upon rotation of the rotatable handle3464.

With continued reference toFIG.34Gand additional reference toFIG.34H, the side port3425is either directed toward the vascular true lumen116or 180 degrees away from the vascular true lumen116. Radiographic visualization or other techniques as described elsewhere herein may be used to determine if the port3425is directed toward or away from the true lumen116. If the port3425is directed away from the true lumen116, the orienting device3400may be retracted, rotated 180 degrees, and re-deployed to direct the port3425toward the true lumen116. A re-entry device3600may then be front-loaded (direction shown inFIG.34B(1)) through the center lumen of the orienting device3400. Although re-entry device3600is shown for purposes of illustration, other re-entry devices may be used as described elsewhere herein. As the re-entry device3600is advanced into the center lumen of the orienting device3400, the flap3426causes the distal end of the re-entry device3600to be directed out the side port3425. Further advancement of the re-entry device3600causes it to engage the vascular wall, and by action of the tip of re-entry device3600(e.g., rotational abrasion), it may penetrate the vascular wall and enter into the vascular true lumen116distal of the occlusion120.

Orienting Methods Using Planar Orienting Elements

Some of the orienting devices (e.g.,3330,3340,3400) 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 180 degrees away from the vascular true lumen. In essence, the orienting device reduces the number of directions the side port may be facing from 360 degrees of freedom to two degrees of freedom, 180 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 180 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 heart100. Generally speaking, the coronary arteries including the left anterior descending artery110as shown inFIG.35Awill follow the outside curvature of the bean100. An orienting device (e.g.,3330,3340,3400) inserted into the coronary artery110via a guide catheter200seated in the ostium of the artery110will generally follow the outside curvature of the artery110within the subintimal space and across the occlusion120. In this scenario, as seen inFIG.35B, the true lumen116will lie toward the inside of the curvature of the artery110and thus the inside curvature (i.e., concave side) of the orienting device3400. Thus, the side port of the orienting device3400may be directed toward the concave side of the curvature which will predictably direct the side port toward the true lumen116. 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 wire700) may be substantially advanced and bunched within the subintimal space via a subintimal device (e.g., crossing device300or orienting device3400) as shown inFIG.35Csuch 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.

Alternative Re-entry Devices

With reference toFIGS.36A-36G, 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 devices3330,3340, and3400described herein before. Generally, each of the foregoing re-entry devices may be sized like a conventional guide wire, having a 0.014-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 toFIG.36A, and toFIG.36Bwhich is a detailed cross-sectional view of the distal end, re-entry device3610includes a distally tapered drive shaft3612which may comprise a metallic alloy such as stainless steel or NiTi, for example. The re-entry device3610may have a nominal profile of 0.014 inches and a length of 150 cm for coronary applications. The shaft3612may have a proximal diameter of 0.014 inches and a distal taper from 0.014 inches to 0.006 to 0.008 inches over approximately 4.0 inches. An abrasive tip3620may be connected to the distal end of the shaft3612by brazing or welding techniques. The shaft3612just proximal of the tip3620is configured with sufficient flexibility to allow flexure of the tip3620after it penetrates the vascular wall into the true vascular lumen, thus preventing penetration of the opposite vascular wall. The abrasive tip3620may comprise metallic alloy tube3622such as stainless steel, platinum or platinum-iridium with a weld ball cap3624. The tube3622may have an inside diameter of approximately 0.007 inches and an outside diameter of approximately 0.0105 inches. An abrasive coating such as a 600-grit diamond coating3626may be applied to the outer surface of the tube3622with a thickness of approximately 0.0015 inches using conventional techniques available from Continental Diamond Tool (New Haven, Indiana).

With reference toFIG.36C, and toFIG.36Dwhich is a detailed cross-sectional view of the distal end, re-entry device3610further includes a distal coil3630disposed over the distal tapered portion of the shaft3612. The helical coil3630may comprise a stainless steel, platinum or platinum-iridium wire having a diameter of approximately 0.003 to 0.004 inches. The helical coil3630generally imparts enhanced torqueability without compromising flexibility of the tapered portion of the shaft3612.

With reference toFIG.36E, and toFIG.36Fwhich is a detailed cross-sectional view of the distal end, re-entry device3610alternatively includes a cable shaft3614comprising a 1 by 7 or 1 by 19 construction having an outside profile diameter of 0.014 inches, for example. The cable shaft3614construction generally imparts enhanced torqueability in at least one direction while increasing flexibility.

With reference toFIG.37, a rotary drive unit3700is shown in perspective view. Rotary drive unit3700is particularly suited for use with re-entry device3610shown inFIGS.36A-36G, but may be used with other re-entry devices described elsewhere herein, Generally, the rotary drive unit3700provides 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.

rotary drive unit3700includes a base3710with two vertical mounting plates3712and3714attached thereto. A motor3720is mounted to plate3714and is linked by offset gears3722to a hollow drive shaft3724. A lock mechanism3726such as a hollow pin vise or collet is secured to the hollow drive shaft3724. The proximal shaft3612of the re-entry device3610may be secured to the locking mechanism3726such that activation of the motor3720by a suitable power supply causes rotation of the re-entry device3610. An advancement sleeve3730may be fixedly attached to the back side of vertical plate3714and coaxially aligned with the hollow drive shaft3724to receive the re-entry device shaft3612therethrough. The advancement sleeve3720extends in a semi-loop around limiting block3716and slidably through holes in vertical plates3714and3712. The advancement sleeve3730does not rotate but rather supports the rotating shaft3612of the re-entry device3610and thus may be manually held by the treating physician. The advancement sleeve3730may be advanced or retracted thus shortening or lengthening, respectively, the semi-loop thereof and thus advancing or retracting the re-entry device3610as it rotates. The advancement sleeve3730thereby provides tactile feel of the distal tip3620of the re-entry device3610as it engages tissue without being hampered by the rotary drive thereof.

From the foregoing, it will be apparent to those skilled in the art that the present invention provides, in exemplary non-limiting embodiments, devices and methods for the treatment of chronic total occlusions. Further, those skilled in the art will recognize that the present invention may be manifested in a variety of forms other than the specific embodiments described and contemplated herein. Accordingly, departures in form and detail may be made without departing from the scope and spirit of the present invention as described in the appended claims.