Patent Publication Number: US-11033286-B2

Title: Subintimal re-entry catheter and retrograde recanalization

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 15/195,293, filed on Jun. 28, 2016, which is a continuation of U.S. application Ser. No. 13/622,128, filed on Sep. 18, 2012, now U.S. Pat. No. 9,402,981, which claims priority under 35 U.S.C. § 119 to U.S. Provisional Application Ser. No. 61/536,229, filed on Sep. 19, 2011, the entireties of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The disclosure is directed to devices and methods for recanalization of an occluded blood vessel. More particularly, the disclosure is directed to devices and methods for re-entry into the true lumen from the extraluminal or subintimal space of a blood vessel. 
     BACKGROUND 
     Chronic total occlusion (CTO) is an arterial vessel blockage that obstructs blood flow through the vessel, and can occur in both coronary and peripheral arteries. In some instances, it may be difficult or impossible to pass through the CTO with a medical device in an antegrade direction to recanalize the vessel. Accordingly, techniques have been developed for creating a subintimal pathway (i.e., a pathway between the intimal and adventitial tissue layers of the vessel) around the occlusion and then re-entering the true lumen of the vessel distal of the occlusion in an attempt to recanalize the vessel. In some instances re-entering the true lumen from the subintimal space and/or recanalization can be difficult. Accordingly, it is desirable to provide alternative recanalization devices and/or methods of recanalizing a blood vessel in which a CTO is present. 
     SUMMARY 
     The disclosure is directed to several alternative designs, materials and methods of manufacturing medical device structures and assemblies, and uses thereof. 
     Accordingly, one illustrative embodiment is a catheter for recanalizing a blood vessel having an occlusion therein. The catheter includes a catheter shaft having a proximal end, a distal end, and a distal end portion proximate the distal end. The catheter also includes an expandable member coupled to the distal end portion of the catheter shaft. A flexible tubular member extends from the catheter shaft and along an exterior of the expandable member. Expansion of the expandable member deflects the flexible tubular member into a deflected configuration away from a longitudinal axis of the catheter shaft. 
     Another illustrative embodiment is a catheter assembly for navigating through a lumen of a blood vessel to an occlusion in an antegrade direction that is configured to redirect an atherectomy device toward the occlusion in a retrograde direction in the lumen of the blood vessel. The catheter assembly includes a catheter shaft having a proximal end, a distal end and a distal end portion proximate the distal end. The catheter assembly also includes an inflatable balloon secured to the distal end portion of the catheter shaft. A tubular member extends distally from a location on the catheter shaft proximal of the inflatable balloon. The tubular member is configured to be deflectable away from the catheter shaft into a curved configuration upon inflation of the inflatable balloon. 
     Another illustrative embodiment is a method of recanalizing a blood vessel having an occlusion therein. The method includes advancing a catheter through a lumen of a blood vessel to a location proximal of a proximal end of an occlusion. A distal end of the catheter is directed between a first tissue layer and a second tissue layer of a wall of the vessel to a location distal of a distal end of the occlusion. Thereafter, a flexible tubular member of the catheter re-enters the lumen of the blood vessel distal of the distal end of the occlusion and an occlusion crossing device is delivered through a lumen of the flexible tubular member to the distal end of the occlusion. The occlusion crossing device is then advanced into the occlusion from the distal end of the occlusion toward the proximal end of the occlusion. 
     Yet another illustrative embodiment is a method of recanalizing a blood vessel having an occlusion therein. The method includes advancing a catheter through a lumen of a blood vessel to a location proximal of a proximal end of an occlusion. The catheter includes a balloon mounted thereon and a flexible tubular member extending along an exterior of the balloon. The distal end of the catheter is directed between a first tissue layer and a second tissue layer of a wall of the vessel to a location distal of a distal end of the occlusion. The balloon is inflated between the first tissue layer and the second tissue layer distal of the distal end of the occlusion, thereby deflecting the flexible tubular member into a deflected configuration. Thereafter, the flexible tubular member of the catheter re-enters the lumen of the blood vessel distal of the distal end of the occlusion with the flexible tubular member of the catheter in the deflected configuration. 
     The above summary of some example embodiments is not intended to describe each disclosed embodiment or every implementation of the aspects of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The aspects of the disclosure may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying drawings, in which: 
         FIG. 1  is a side plan view of an exemplary catheter apparatus for recanalization of a blood vessel; 
         FIG. 2A  is an exemplary cross-sectional view of the catheter shaft of  FIG. 1  taken along line  2 - 2 ; 
         FIG. 2B  is an alternative cross-sectional view of the catheter shaft of  FIG. 1  taken along line  2 - 2 ; 
         FIG. 3  is a cross-sectional view of the catheter apparatus of  FIG. 1  taken along line  3 - 3 ; 
         FIG. 4  is a side plan view of the distal portion of the catheter apparatus of  FIG. 1  in a delivery configuration; 
         FIG. 5  is a cross-sectional view of the catheter apparatus of  FIG. 4  taken along line  5 - 5 ; 
         FIG. 6  is a side plan view of an alternative embodiment of the distal portion of the catheter apparatus of  FIG. 1  in a deflected configuration; 
         FIG. 7  illustrates possible curved or deflected configurations of the distal portion of the catheter apparatus for re-entry into a true lumen of a blood vessel; 
         FIG. 8  is a cross-sectional view of the catheter apparatus positioned in the subintimal space of a blood vessel; 
         FIGS. 9-14  illustrate aspects of an exemplary method for recanalizing an occluded blood vessel using the catheter apparatus of  FIG. 1 ; and 
         FIGS. 15-16  illustrate aspects of another exemplary method for recanalizing an occluded blood vessel using the catheter apparatus of  FIG. 1 . 
     
    
    
     While the aspects of the disclosure are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit aspects of the disclosure to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure. 
     DETAILED DESCRIPTION 
     For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification. 
     All numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the term “about” may be indicative as including numbers that are rounded to the nearest significant figure. 
     The recitation of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5). 
     Although some suitable dimensions, ranges and/or values pertaining to various components, features and/or specifications are disclosed, one of skill in the art, incited by the present disclosure, would understand desired dimensions, ranges and/or values may deviate from those expressly disclosed. 
     As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise. 
     The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The detailed description and the drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the disclosure. The illustrative embodiments depicted are intended only as exemplary. Selected features of any illustrative embodiment may be incorporated into an additional embodiment unless clearly stated to the contrary. 
     An exemplary recanalization catheter  10  is illustrated at  FIG. 1 . The recanalization catheter  10  may include a main catheter shaft  12  extending from a hub assembly  14  at a proximal end  16  of the catheter shaft  12  to an expandable member, shown as an inflatable balloon  20  mounted on a distal portion of the catheter shaft  12  proximate the distal end  18  of the catheter shaft  12 . Although the expandable member is illustrated as an inflatable balloon  20 , in some embodiments the expandable member may be an expandable framework formed of one or more, or a plurality of struts which may be automatically or manually expanded, or other manually expandable or automatically expandable structure. 
     The catheter  10  may be configured to be advanced over a guidewire  22  for delivery to a remote location in the vasculature of a patient. For example, in some instances the catheter  10  may be configured as a single-operator-exchange (SOE) catheter having a guidewire lumen  24  extending from a distal port  26  to a proximal guidewire port  28  located a short distance proximal of the balloon  20  and distal of the hub assembly  14 . In such a configuration, the guidewire  22  may extend through the guidewire lumen  24  between the distal port  26  and the proximal port  28 , and extend along an exterior of the catheter shaft  12  proximal of the proximal port  28  to the proximal end  16  of the catheter shaft  12 . In other instances, the catheter  10  may be configured as an over-the-wire (OTW) catheter having a guidewire lumen  24  extending through the entire length of the catheter  10  from a distal port  26  at a distal tip of the catheter  10  to a proximal guidewire port  30  in the hub assembly  14 .  FIG. 1  illustrates such a configuration with the proximally extending portion of the guidewire  22  in dashed lines. It is noted that in instances in which the catheter  10  is an SOE catheter, the hub assembly  14  may not include a proximal guidewire port  30  and/or in instances in which the catheter  10  is an OTW catheter, the proximal guidewire port  28  may not be present. 
     The catheter shaft  12  may also include an inflation lumen  32  extending from an inflation port  34  of the hub assembly  14  to an interior of the balloon  20 . The inflation lumen  32  may be configured for delivering inflation fluid to the balloon  20  to inflate the balloon  20  during a medical procedure. 
     The catheter  10  may also include a flexible tubular member  40  extending from the main catheter shaft  12  through opening  44 . For example, in some instances the opening  44  may be a side opening extending through a sidewall of a tubular member of the main catheter shaft  12 , or the opening  44  may be a distal opening at the distal end of a tubular member of the main catheter shaft  12 . The flexible tubular member  40  may extend along a portion of the exterior of the balloon  20 , such that an exterior surface of the balloon  20  may engage the flexible tubular member  40  when the balloon  20  is inflated. The flexible tubular member  40  may extend from the main catheter shaft  12  at a location proximal of the balloon  20 , and extend distally therefrom, such that the flexible tubular member  40  extends exterior of the proximal waist  46  of the balloon  20 , which may be secured to a portion of the main catheter shaft  12 . In some instances, the distal tip  42  of the flexible tubular member  40  may terminate proximal of the distal waist  48  of the balloon  20 , which may be secured to a portion of the main catheter shaft  12 . 
     The flexible tubular member  40 , which may be considered a deflectable re-entry tube or redirection tube (e.g., a “stinger”) in some instances, may include flexibility characteristics permitting the flexible tubular member  40  to be deflected away from the main catheter shaft  12  (e.g., away from the central longitudinal axis of the main catheter shaft  12 ) into a curved or deflected configuration. In some instances, the flexible tubular member  40  may include one or more, or a plurality of cuts or slits formed through the sidewall of the flexible tubular member  40 , providing the flexible tubular member  40  with a degree of lateral flexibility. For example, the flexible tubular member  40  may include a helical cut or slit formed through the sidewall of the flexible tubular member  40  and extending along a length of the flexible tubular member  40 , an arrangement of a plurality of cuts or slits formed through the sidewall of the flexible tubular member  40  and extending partially around the circumference of the flexible tubular member  40  along a length of the flexible tubular member  40 , or another arrangement of cuts or slits formed in another fashion to provide a desired degree of lateral flexibility. 
     In some embodiments, the flexible tubular member  40  may be formed of a metallic material, including a stainless steel or a nickel-titanium alloy such as nitinol, a polymeric material such as polyamide, polyether block amide, polyethylene, or polyethylene terephthalate, or a combination of metallic and polymeric materials, for example. 
     The flexible tubular member  40  may define a third, device delivery lumen  38  configured for delivering an elongated medical device to a target location via the catheter  10 . The device delivery lumen  38  may extend from an access port  36  in the hub assembly  14  through the main catheter shaft  12  to the distal tip  42  of the flexible tubular member  40 . Accordingly an elongated medical device may be inserted through the device delivery lumen  38  to be advanced from the distal tip  42  of the flexible tubular member  40  during a medical procedure. 
     In some embodiments, as shown in  FIG. 2A , the catheter shaft  12 , or a portion thereof, may include an outer tubular member  50 , a first inner tubular member  52  extending through the outer tubular member  50 , and a second inner tubular member  54  extending through the outer tubular member  50 . The first inner tubular member  52  may define the guidewire lumen  24 , and the second inner tubular member  54  may define the device delivery lumen  38 . The second inner tubular member  54  may be an extension of the flexible tubular member  40  extending into the outer tubular member  50 , or the second tubular member  54  may be secured to the flexible tubular member  40  and extend therefrom, providing the device delivery lumen  38  therein. In such embodiments, the main catheter shaft  12  may be configured such that the proximal waist  46  of the balloon  20  is secured to the distal end of the outer tubular member  50 , while the distal waist  48  of the balloon  20  is secured to the distal end of the first inner tubular member  52 , extending through the interior of the balloon  20 . Furthermore, the inflation lumen  32  may be defined between the outer tubular member  50  and the first and second inner tubular members  52 ,  54 . 
     In other embodiments, as shown in  FIG. 2B , the catheter shaft  12 , or a portion thereof, may be an extruded shaft  56  having a plurality of lumens formed therein. For example, the extruded shaft  56  may include the guidewire lumen  24 , the inflation lumen  32 , and the device delivery lumen  38 . In such embodiments, the main catheter shaft  12  may be configured such that the proximal waist  46  of the balloon  20  is secured to a portion of the extruded shaft  56 , while the distal waist  48  of the balloon  20  is secured to another portion of the extruded shaft  56  or a tubular member extending therefrom, extending through the interior of the balloon  20 . 
     The catheter  10  may also include a distal tip  58  extending distally from the balloon  20 . The distal tip  58  may have a lumen extending therethrough and opening out to the distal port  26  at the distal end thereof to accommodate the guidewire  22  extending from the distal port  26 . In some instances, the distal tip  58  may be an atraumatic tip, such as a flexible, low durometer tip similar to tips provided with typical angioplasty balloon catheters. However, in other embodiments, the distal tip  58  may be configured to facilitate piercing and/or dissection of tissue layers of the blood vessel. For example, the distal tip  58  may include a sharp, rigid and/or piercing feature. In one embodiment, as shown in  FIG. 1 , the distal tip  58  may include an angled distal edge, providing the distal tip  58  with a sharpened cutting or piercing edge. 
       FIG. 3  is a cross-sectional view of the catheter  10  taken through the balloon  20 . As shown in  FIG. 3 , when inflated, the balloon  20  may include a central bulbous portion  60 , a first wing portion  62  extending from the bulbous portion  60  in a first direction, and a second wing portion  64  extending from the bulbous portion  60  is a second direction, generally opposite the first direction. Thus the first and second wing portions  62 ,  64  may extend outwardly in opposing directions from the central bulbous portion  60 . In some instances, the balloon  20  may be formed of a non-distensible or stiffer material, such that when the balloon  20  is inflated, the balloon  20  maintains the bulbous portion  60  and wing portions  62 ,  64  shown in  FIG. 3 . The winged portions  62 ,  64  may be configured to follow the curvature of a vessel wall, and thus generally orient the flexible tubular member  40  toward the center of the true lumen of the vessel during use. Furthermore, the bulbous portion  60  may be configured to contact and press against the flexible tubular member  40 , thereby deflecting the flexible tubular member  40  upon inflation of the balloon  20 . 
       FIGS. 4 and 5  illustrate an exemplary arrangement of the catheter  10  with the balloon  20  deflated and in a delivery configuration. As shown, the deflated balloon  20  may be folded around the flexible tubular member  40  to provide the distal portion of the catheter  10  with a small delivery profile. For example, in some instances, in the folded delivery configuration, the catheter  10  may have an outer diameter of about 3 French (1 mm) to about 5 French (1.67 mm), for example about 3 French (1 mm), about 3.5 French (1.17 mm), about 4 French (1.33 mm), about 4.5 French (1.5 mm) or about 5 French (1.67 mm). In some embodiments, the distal tip  42  of the flexible tubular member  40  may be wrapped within the folds of the balloon  20  to cover and protect the distal tip  42  from inadvertent contact with the vessel wall during delivery of the balloon  20  and flexible tubular member  40  to a target location in the vasculature. For example, as shown in  FIG. 5 , portions of balloon material forming the wings  62 ,  64  may be folded around the flexible tubular member  40  to maintain the flexible tubular member  40  in an elongated configuration generally parallel to the central longitudinal axis of the catheter shaft  12 . 
       FIG. 6  illustrates an alternative embodiment, in which the catheter  10  includes a pull wire  70 , or other actuation mechanism to facilitate deflecting the flexible tubular member  40  into a curved configuration. For example, the pull wire  70  may have a distal end secured to a distal portion of the flexible tubular member  40  proximate the distal tip  42  of the flexible tubular member  40 . Accordingly, the pull wire  70  may extend to the proximal end of the catheter  10 , or be attached to an actuatable component accessible at the proximal end of the catheter  10 , to be manipulated by the operator to deflect the flexible tubular member  40  into a curved configuration. 
     As shown in  FIG. 7 , the flexible tubular member  40  may be configured to be curved or deflected from a generally axially aligned configuration A in which the flexible tubular member  40  extends along a central longitudinal axis Y generally parallel to the central longitudinal axis X of the main catheter shaft  12  to a curved configuration in which the distal portion of the flexible tubular member  40  is curved away from the longitudinal axis Y. For example, in some embodiments, the distal portion of the flexible tubular member  40  may be curved or deflected to a curved configuration B having an angle of curvature (i.e., arc angle) θ 1  of less than 90°, for example about 30°, about 45°, or about 60°, in some instances. In other embodiments, the distal portion of the flexible tubular member  40  may be curved or deflected to a curved configuration C having an angle of curvature (i.e., arc angle) θ 2  of about 90°. In still other embodiments, the distal portion of the flexible tubular member  40  may be curved or deflected to a curved configuration D having an angle of curvature (i.e., arc angle) θ 3  of greater than 90°, for example about 95° or more, about 100° or more, or about 105° or more in some instances. As described herein, the “arc angle” or “angle of curvature” is intended to be the angle through which the distal portion of the flexible tubular member  40  curves through from the point along the longitudinal axis Y in which the flexible tubular member  40  begins to curve away from the longitudinal axis Y to the center of the opening at the distal tip  42  of the flexible tubular member  40 . 
     In some embodiments, such as embodiments in which the distal tip  42  includes a tapered or sharpened tip, the opening of the lumen  38  at the distal tip  42  may face in a proximal direction in the curved configuration. For instance, the opening of the lumen  38  at the distal tip  42  may face in a proximal direction when the distal portion of the flexible tubular member  40  is deflected through an arc angle of 90° or more, 95° degrees or more, 100° degrees or more, or 105° degrees or more. Accordingly, in such an embodiment, an elongate medical device advanced out of the distal opening of the lumen  38  of the flexible tubular member  40  may be directed in a proximal or retrograde direction, for example. 
       FIG. 8  is a cross-sectional view of the distal portion of the catheter  10  positioned in a subintimal space created between two tissue layers of a vessel wall  80 . The blood vessel  80  typically has three tissue layers, an innermost layer or intima layer (i.e., tunica intima)  82 , an intermediate layer or media layer (i.e., tunica media)  84 , and an outermost layer or adventitia layer (tunica adventitia)  86 , with the media layer  84  positioned between the intima layer  80  and the adventitia layer  86 . The intima layer  82  is a layer of endothelial cells lining the lumen  88  of the vessel  80 , as well as a subendothelial layer made up of mostly loose connective tissue. The media layer  84  is a muscular layer formed primarily of circumferentially arranged smooth muscle cells. The adventitia layer  86 , which forms the exterior layer of the vessel wall  80  is formed primarily of loose connective tissue made up of fibroblasts and associated collagen fibers. 
     As will be described further herein, the distal portion of the catheter  10 , including the balloon  20 , may be advanced into a subintimal space (i.e., a space between the intima layer  82  and the adventitia layer  86 ) created in the vessel wall  80 , such as through dissection of the tissue layers of the vessel wall  80 . Once positioned in the subintimal space, the balloon  20  may be inflated between the intima layer  82  and the adventitia layer  86  of the vessel wall  80 . As the balloon  20  is inflated, the wings  62 ,  64  of the balloon  20  may be unfolded and inflated between the intima layer  82  and the adventitia layer  86  to orient the flexible tubular member  40  radially inward of the bulbous portion  60  of the balloon  20 . Furthermore, the bulbous portion  60  of the balloon  20  may be inflated to press against the flexible tubular member  40  to deflect the flexible tubular member  40  toward the true lumen  88  of the vessel  80 . Inflation of the bulbous portion  60  against the flexible tubular member  40  may cause the distal tip  42  of the flexible tubular member  40  to pierce through the intima layer  82  into the true lumen  88  to allow re-entry into the true lumen  88  with an elongate medical device advanced through the lumen  38 . Because the external adventitia layer  86  is more inelastic than the internal intima layer  82 , the forces generated through inflation of the balloon  20  may cause the internal intima layer  82  to yield first, bending or folding towards the true lumen  88 , rather than causing the external adventitia layer  86  to stretch. 
     In some instances, it may be undesired, difficult or impossible to pass through an occlusion, such as a chronic total occlusion (CTO) in a lumen of a blood vessel with a medical device to recanalize the vessel. In such instances, it may be possible to recanalize the blood vessel through a subintimal approach using the catheter  10 . Turning to  FIGS. 9-14 , several aspects of an exemplary method for recanalizing an occluded blood vessel using the catheter  10  are illustrated. As shown in  FIG. 9 , a guidewire  22  may initially be advanced through the lumen  88  of the vessel  80  to a location proximate a proximal end of an occlusion  90  blocking the lumen  88 . The guidewire  22  may then be advanced to penetrate outward through the intima layer  82  at a location proximal of the proximal end of the occlusion  90  into the vessel wall  80 . With the tip of the guidewire  22  located between the intima layer  82  and the adventitia layer  86 , the guidewire  22  may be further advanced distally in a subintimal manner to create a subintimal space between the intima layer  82  and the adventitia layer  86 . As shown in  FIG. 10 , the guidewire  22  may be advanced in a subintimal manner until the distal tip of the guidewire  22  is located distal of the distal end of the occlusion  90  in the subintimal space created, such as by dissection of the tissue layers of the vessel wall  80 . 
     The recanalization catheter  10  may then be advanced distally over the guidewire  22  from the true lumen  88  proximal of the occlusion  90 , into the subintimal space between the intima layer  82  and the adventitia layer  86 , to a position in the subintimal space in which the distal portion of the catheter  10 , including the balloon  20 , is located distal of the distal end of the occlusion  90 , as shown in  FIG. 11 . The recanalization catheter  10  may be advanced through the subintimal space in a delivery configuration, such as with the balloon  20  in a deflated, folded configuration wrapped around the flexible tubular member  40  extending from the main catheter shaft  12 . In some instances in which the distal tip  58  of the catheter  10  is configured to facilitate piercing and/or dissection of tissue layers of the blood vessel, the sharp, rigid or piercing feature of the distal tip  58  may be used to pierce and/or dissect tissue layers of the vessel wall  80  as the catheter  10  is advanced distally. 
     With the balloon  20  positioned distal of the distal end of the occlusion  90 , the balloon  20  may be inflated in the subintimal space formed between the intima layer  82  and the adventitia layer  86 , as shown in  FIG. 12 . As the balloon  20  is inflated, the wings  62 ,  64  of the balloon  20  may be unfolded and inflated between the intima layer  82  and the adventitia layer  86  to orient the flexible tubular member  40  radially inward of the bulbous portion  60  of the balloon  20 . Furthermore, the bulbous portion  60  of the balloon  20  may be inflated to press against the flexible tubular member  40  to deflect the flexible tubular member  40  toward the true lumen  88  of the vessel  80 . Inflation of the bulbous portion  60  against the flexible tubular member  40  may cause the distal tip  42  of the flexible tubular member  40  to pierce through the intima layer  82  and thus re-enter into the true lumen  88  to allow re-entry into the true lumen  88  distal of the occlusion  90  with an elongate medical device advanced through the lumen  38 . In some instances, the pull wire  70  may be actuated to facilitate and/or augment curving the flexible tubular member  40  into a curved configuration. The distal portion of the main catheter shaft  12 , including the distal tip of the main catheter shaft  12  and the balloon  20 , as well as the guidewire  22 , may remain positioned in the subintimal space after the flexible tubular member  40  is deflected into the curved configuration and penetrates into the true lumen  88 . 
     As described above, the flexible tubular member  40  may be configured to be curved or deflected from a generally axially aligned configuration in which the flexible tubular member  40  extends parallel to the main catheter shaft  12  to a curved configuration in which the distal portion of the flexible tubular member  40  is curved away from the longitudinal axis of the main catheter shaft  12 . For example, in some embodiments, as shown in  FIG. 12 , the distal portion of the flexible tubular member  40  may be curved or deflected to a curved configuration having an angle of curvature (i.e., arc angle) of about 90° or greater than 90°, for example about 95° or more, about 100° or more, or about 105° or more in some instances. 
     An elongate medical device  100  may then be advanced through the device delivery lumen  38  of the catheter  10  and exit the flexible tubular member  40  into the true lumen  88  distal of the occlusion  90  through the opening in the distal tip  42  of the flexible tubular member  40 , shown in  FIG. 13 . In the embodiment shown in  FIG. 13 , the flexible tubular member  40  may be curved such that the distal opening of the lumen  38  at the distal tip  42  of the flexible tubular member  40  faces in a proximal direction, and thus faces the distal end of the occlusion  90 . Accordingly, the elongate medical device  100 , upon exiting the flexible tubular member  40 , may be directed or advanced proximally toward the distal end of the occlusion  90 . In instances in which the elongate medical device  100  is an occlusion crossing device, such as an atherectomy device, a needle-tipped catheter, a stylet or a guidewire, the elongate medical device may be directed or advanced proximally from the distal opening of the lumen  38  of the flexible tubular member  40  toward the distal end of the occlusion  90  to penetrate into or through the occlusion  90  in a retrograde manner. 
     As shown in  FIG. 13 , in some instances the elongate medical device  100  may be an atherectomy device having an elongate shaft  104  with a distal cutting tip  102  attached thereto for penetrating into or through the occlusion  90 . For example, in some instances, the distal cutting tip  102  may be a rotatable cutting tip or burr, such as a micro burr, expandable burr, an angled burr, an enhanced wire tip burr, a diamond coated burr, or other cutting device. In other instances, the distal cutting tip  102  may be an ablation electrode or ultrasound transducer configured for ablating a pathway through the occlusion  90 . 
     From the re-entry location distal of the occlusion  90 , the elongate medical device  100  (e.g., occlusion crossing device) may be advanced in a retrograde direction (i.e., proximally) into the distal end of the occlusion  90 . In such a fashion, the elongate medical device  100  may be advanced through the occlusion  90  from the distal end of the occlusion  90  to the proximal end of the occlusion  90  in a retrograde manner, as shown in  FIG. 14 , to create a pathway through the occlusion  90  to recanalize the vessel and provide a pathway through the occlusion  90  for blood to flow therethrough. 
     In a retrograde approach of crossing the occlusion  90  in such a manner, there may be less concern with the fluid flow and circumstances associated therewith. For example, emboli created while boring or ablating through the occlusion  90  may flow distally away from the occlusion  90  as the atherectomy device is advanced through the occlusion  90 . 
     In other embodiments, such as shown in  FIG. 15 , the balloon  20  may be inflated in the subintimal space formed between the intima layer  82  and the adventitia layer  86  to deflect the flexible tubular member  40  into a curved configuration by inflating the bulbous portion  60  of the balloon  20  against the flexible tubular member  40  to deflect the flexible tubular member  40  toward the true lumen  88  of the vessel  80 . Inflation of the bulbous portion  60  against the flexible tubular member  40  may cause the distal tip  42  of the flexible tubular member  40  to pierce through the intima layer  82  and thus re-enter into the true lumen  88  to allow re-entry into the true lumen  88  distal of the occlusion  90  with an elongate medical device advanced through the lumen  38 . In some instances, the pull wire  70  may be actuated to facilitate and/or augment curving the flexible tubular member  40  into a curved configuration. The distal portion of the main catheter shaft  12 , including the distal tip of the main catheter shaft  12  and the balloon  20 , as well as the guidewire  22 , may remain positioned in the subintimal space after the flexible tubular member  40  is deflected into the curved configuration and penetrates into the true lumen  88 . 
     Alternatively, inflation of the bulbous portion  60  against the flexible tubular member  40  may cause the distal tip  42  of the flexible tubular member  40  to be oriented toward the intima layer  82  and an elongate medical device, such as a guidewire, a stylet, a needle, or other device may be advanced through the flexible tubular member  40  to pierce through the intima layer  82  to re-enter into the true lumen  88  distal of the occlusion  90 . 
     As described above, the flexible tubular member  40  may be configured to be curved or deflected from a generally axially aligned configuration in which the flexible tubular member  40  extends parallel to the main catheter shaft  12  to a curved configuration in which the distal portion of the flexible tubular member  40  is curved away from the longitudinal axis of the main catheter shaft  12 . For example, as shown in  FIG. 15 , the distal portion of the flexible tubular member  40  may be curved or deflected to a curved configuration having an angle of curvature (i.e., arc angle) of less than 90° such that the distal opening of the lumen  38  at the distal tip  42  of the flexible tubular member  40  faces in a distal direction. 
     An elongate medical device  100  may then be advanced through the device delivery lumen  38  of the catheter  10  and exit the flexible tubular member  40  into the true lumen  88  distal of the occlusion  90  through the opening in the distal tip  42  of the flexible tubular member  40 , shown in  FIG. 16 . In the embodiment shown in  FIG. 16 , the flexible tubular member  40  may be curved such that the distal opening of the lumen  38  at the distal tip  42  of the flexible tubular member  40  faces in a distal direction, and thus faces away from the distal end of the occlusion  90 . Accordingly, the elongate medical device  100 , upon exiting the flexible tubular member  40 , may be directed or advanced distally through the true lumen  88  away from the distal end of the occlusion  90 . 
     Once a pathway has been created across the occlusion  90 , either through the occlusion  90  and/or around the occlusion  90  via a subintimal track, one or more additional medical devices may be advanced through the blood vessel  80  to enlarge the pathway and/or pass distally of the occlusion  90  to perform a further medical procedure. 
     Those skilled in the art will recognize that aspects of the present disclosure may be manifested in a variety of forms other than the specific embodiments described and contemplated herein. Accordingly, departure in form and detail may be made without departing from the scope and spirit of the present disclosure as described in the appended claims.