Abstract:
Devices and methods for the treatment of chronic total occlusions are provided. One disclosed embodiment comprises a method of facilitating treatment via a vascular wall defining a vascular lumen containing an occlusion therein. The method includes providing an intravascular device having a distal portion with a side port, inserting the device into the vascular lumen, positioning the distal portion in the vascular wall, directing the distal portion within the vascular wall such that the distal portion moves at least partially laterally, and directing the side port towards the vascular lumen.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/716,287, filed Sep. 12, 2005, under 35 U.S.C. §119(e). In addition, this application also claims the benefit of U.S. Provisional Application No. 60/717,726, filed Sep. 15, 2005, under 35 U.S.C. § 119(e). In addition, the application also claims the benefit of U.S. Provisional Application No. 60/727,819, filed Oct. 18, 2005, under 35 U.S.C. §119(e). The entire disclosure of each of the above-referenced applications is incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The inventions described herein relate to devices and associated methods for the treatment of chronic total occlusions. More particularly, the inventions described herein relate  to devices and methods for crossing chronic total occlusions and subsequently performing balloon angioplasty, stenting, atherectomy, or other endovascular methods for opening occluded blood vessels. 
     BACKGROUND OF THE INVENTION 
     Due to age, high cholesterol and other contributing factors, a large percentage of the population has arterial atherosclerosis that totally occludes portions of the patient&#39;s vasculature and presents significant risks to patient health. For example, in the case of a total occlusion of a coronary artery, the result may be painful angina, loss of cardiac tissue or patient death. In another example, complete occlusion of the femoral and/or popliteal arteries in the leg may result in limb threatening ischemia and limb amputation. 
     Commonly known endovascular devices and techniques are either inefficient (time consuming procedure), have a high risk of perforating a vessel (poor safety) or fail to cross the occlusion (poor efficacy). Physicians currently have difficulty visualizing the native vessel lumen, can not accurately direct endovascular devices toward visualized lumen, or fail to advance devices through the lesion. Bypass surgery is often the preferred treatment for patients with chronic total occlusions, but less invasive techniques would be preferred. 
     SUMMARY OF THE INVENTION 
     To address this and other unmet needs, the present invention provides, in exemplary non-limiting embodiments, devices and methods for the treatment of chronic total occlusions. The disclosed methods and devices are particularly beneficial in crossing coronary total occlusions but may also be useful in other vessels including peripheral arteries and veins. In exemplary embodiments, total occlusions are crossed using methods and devices intended to provide a physician the ability to place a device within the subintimal space, delaminate the connective tissues between layers within the lesion or vessel wall, or remove tissues from the chronic total occlusion or surrounding vessel. 
     In an aspect of the disclosure, a subintimal device may be used to guide conventional devices (for example guide wires, stents, lasers, ultrasonic energy, mechanical dissection, or atherectomy) within the vessel lumen. Additionally, a subintimal device may be used to delaminate vessel wall layers and also may be used to remove tissue from the occlusive lesion or surrounding vessel wall. In one example, the positioning of a subintimal device or the establishment of a delamination plane between intima and medial layers is achieved through the use of a mechanical device that has the ability to infuse a fluid (for example saline). Fluid infusion may serve to apply a hydraulic pressure to the tissues and aid in layer delamination and may also serve to protect the vessel wall from the tip of the subintimal device and reduce the chance of vessel perforation. The infusion of fluid may be controlled by pressure or by volume. 
     Subintimal device placement may be achieved with a subintimal device directing catheter. The catheter may orient a subintimal device so that it passes along the natural delamination plane between intima and media. The catheter may orient the subintimal device in various geometries with respect to the vessel. For example, the subintimal device may be directed substantially parallel with respect to the vessel lumen or in a helical pattern such that the subintimal device encircles the vessel lumen in a coaxial fashion. The subintimal device directing catheter may be an inflatable balloon catheter having proximal and distal ends with two wire lumens. One lumen may accept a conventional guide wire while the second lumen may accept the subintimal device. In an alternative embodiment, the wire directing catheter may be a guide catheter with distal geometry that steers the subintimal device with the appropriate orientation to enter the subintimal space. 
     In an additional disclosure, a subintimal device intended to mechanically delaminate tissue layers may use a device that is inserted into the subintimal space in a first collapsed configuration and is released or actuated into a second expanded configuration. The device may then be withdrawn or manipulated to propagate the area of delamination. 
     An additional aspect of the disclosure may allow the physician to remove tissues from the lesion or vessel wall. In one embodiment, a subintimal device is circumferentially collapsed around the total occlusion. Tissue removal is performed through simple device withdrawal or through a procedure that first cuts connective tissues (i.e. the intimal layer proximal and distal of the lesion) and then removes the targeted tissue. In another embodiment, a tissue removal device is passed through the lesion within the native vessel lumen. The targeted tissues may be mechanically engaged and removed through device withdrawal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       It is to be understood that both the foregoing summary and the following detailed description are exemplary. Together with the following detailed description, the drawings illustrate exemplary embodiments and serve to explain certain principles. In the drawings, 
         FIG. 1  shows an illustration of a heart showing a coronary artery that contains a chronic total occlusion; 
         FIG. 2  is a schematic representation of a coronary artery showing the intimal, medial and adventitial layers; 
         FIG. 3  is a partial sectional view of a subintimal device directing balloon catheter embodiment with fluid infusion through the subintimal device lumen within the device directing catheter; 
         FIG. 4  is a partial sectional view of a subintimal device directing balloon catheter embodiment with fluid infusion through the subintimal device; 
         FIG. 5  is a partial sectional view of an additional subintimal device directing guiding catheter embodiment with fluid infusion through the subintimal device; 
         FIGS. 6A  and B are partial sectional views of a expandable delamination catheter; 
         FIGS. 7  A-D are partial sectional views of a circumferential subintimal tissue removal device; 
         FIGS. 8A-C  are an example of subintimal device construction; 
         FIGS. 9A  and B are partial sectional views of an intraluminal rotational engagement tissue removal device; 
         FIG. 10  is a schematic illustration of an alternative subintimal device; 
         FIGS. 11A and 11B  are schematic illustrations of an alternative subintimal device with a re-entry port; 
         FIGS. 12A-12D  are schematic illustrations of a re-entry method using a balloon catheter; and 
         FIGS. 13A and 13B  are schematic illustrations of an alternative subintimal device and associated pumping system. 
     
    
    
     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. 
     Referring to  FIG. 1 , a diseased heart  100  includes a chronic total occlusion  101  of a coronary artery  102 .  FIG. 2  shows coronary artery  102  with intimal layer  200  (for sake of clarity, the multi layer intima is shown as a single homogenous layer). Concentrically outward of the intima is the medial layer  201  (which also is comprised of more than one layer but is shown as a single layer). The transition between the external most portion of the intima and the internal most portion of the media is referred to as the subintimal space. The outermost layer of the artery is the adventitia  202 . 
     In an aspect of the disclosure, a subintimal device may be used to guide conventional devices (for example guide wires, stents, lasers, ultrasonic energy, mechanical dissection, or atherectomy) within the vessel lumen. Additionally, a subintimal device may be used to delaminate vessel wall layers and also may be used to remove tissue from the occlusive lesion or surrounding vessel wall. In one embodiment,  FIG. 3  shows a subintimal device directing catheter is  300  with its distal balloon  301  that has been advanced over a conventional guide wire  302  and inflated proximal to chronic total occlusion  101 . For the sake of clarity,  FIG. 4  shows a subintimal device path that is substantially parallel to the vessel lumen, but other orientations (i.e. helical) may also be considered. Subintimal device lumen  303  is positioned adjacent to the intimal layer  200  and subintimal device  304  has been advanced as to perforate the subintimal layer. A fluid source (i.e. syringe)  305  is in fluid communication with subintimal device lumen  303  through infusion lumen  306 . Fluid may flow from the fluid source  305  through the subintimal device lumen  303  under a controlled pressure or a controlled volume. The infused fluid may enter the subintimal space  307  directly from the subintimal device lumen  303  or from the volume  308  defined by the distal end of the balloon  301  and the proximal edge of the lesion  101 .  FIG. 4  shows an alternative fluid infusion path where fluid source  305  is in fluid communication with a lumen within the subintimal device  304 .  FIG. 5  shows an alternative subintimal device directing guide catheter  500  where the distal end  501  has a predefined shape or the distal end has an actuating element that allows manipulation by the physician intra-operatively. 
     Another aspect of the disclosure may place a subintimal device within the subintimal space in a first collapsed configuration and releases or actuated the subintimal device to a second expanded configuration. The device may then be withdrawn or manipulated to propagate the subintimal dissection. In one embodiment,  FIG. 6A  shows a subintimal device with internal expandable element  600  that contains one or more expanding elements contained in exterior sheath  602 .  FIG. 6B  shows exterior sheath in a retracted position allowing expanding elements  601  to elastically expand. The subintimal device is intended to be delivered through the aforementioned subintimal device delivery catheters. 
     An additional aspect of the disclosure may allow the physician to remove tissues from the lesion or vessel wall.  FIG. 7A  shows an embodiment where subintimal device directing balloon catheter is inflated within coronary artery  102  just proximal to chronic total occlusion  101 . Subintimal device  304  is partially delivered around chronic total occlusion  102  coaxially outside the intimal layer  200  and coaxially inside medial layer  201  in a helical pattern.  FIG. 7B  shows a subintimal device capture catheter  702  positioned across the chronic total occlusion  101  over conventional guide wire  703  and within subintimal device  304 . The distal  704  and proximal  705  ends of the subintimal device have been captured and rotated as to reduce the subintimal device outside diameter and contain the lesion  101  and intima  200  within the coils internal diameter. The device may be withdrawn through the use of a cutting element. For example, FIGS. C and D show the advancement of a cutting element  706  in two stages of advancement showing the cutting of intima  200  proximal of the occlusion  707  and intimal distal of the occlusion  708 . 
     An additional aspect of the subintimal device is the construction of the device body. The flexibility and torquability of the device body can affect the physician&#39;s ability to achieve a subintimal path. The subintimal device body may be constructed in part or in to total of a single layer coil with geometric features along the coil length that allow adjacent coils to engage (for example mechanical engagement similar to the teeth of a gear).  FIG. 8A  shows coil  801  closely wound such that the multitude of teeth  802  along the coil edges are in contact such that the peaks of one coil falls within the valleys of the adjacent coil. A conventional coil reacts to an applied torsional load by diametrically expanding or contracting, thus forcing the wire surfaces within a turn of the coil to translate with respect to its neighboring turn. The construction of coil  801  resists the translation of wire surfaces within the coil thus resisting the diametric expansion or contraction (coil deformation). An increased resistance to coil deformation increases the torsional resistance of the device body while the coiled construction provides axial flexibility. An exemplary construction may include a metallic tube where the coil pattern  801  and teeth  802  are cut from the tube diameter using a laser beam.  FIG. 8B  shows subintimal device body  804  that is for example a continuous metallic tube with distal laser cut coil segment  801  and proximal solid tube  803 . Tube materials include but are not limited to stainless steel and nickel titanium. Alternatively, the coil may be wound from a continuous wire. The wire has a cross section that for example has been mechanically deformed (stamped) to form the teeth and allow coil engagement.  FIG. 8C  shows an example of a laser cut tooth pattern from the circumference of a tube that has been shown in a flat configuration for purposes of illustration. 
     In another embodiment, a tissue removal device may be passed through the lesion within the native vessel lumen.  FIG. 9A  shows corkscrew device  900  with exterior sheath  902  engaging occlusion after delamination of the intimal layer  901  has been performed by the aforementioned methods and devices.  FIG. 9B  shows removal of the occlusion and a portion of the intimal layer through axial withdrawal of the corkscrew device. 
     With reference to  FIG. 10 , an alternative subintimal device  1000  is shown schematically. Subintimal device  1000  is similar to the device shown and described with reference to  FIGS. 8A-8C , and may include any of the variants described previously, such as distal atraumatic tip configurations, fluidic dissection mechanisms, etc. Subintimal device  1000  may be sized and shaped for intravascular navigation and includes an elongate tubular shaft  1004 , at least a distal portion of which includes a helical interlocking gear  1006  and a helical wire coil  1008  disposed thereon. A helically shaped inner mandrel or tube  1010  may be disposed in the tubular shaft  1004  such that the shaft  1004  rotates freely thereon. The shaft  1004  may have a linear or straight configuration in a relaxed state and a helical configuration (shown) when the helically shaped inner member  1010  is disposed therein. The device  1000  may be disposed in a constraining sheath (not shown) and navigated to the intravascular site, such as the site of an occlusion. When the device  1000  is advanced distally out the end of the constraining sheath or when the sheath is pulled proximally relative thereto, the distal portion of the device  1000  assumes a helical shape as shown. The shaft  1004  may be rotated relative to the inner member  1010  to cause rotation of the helical wire threads  1008 , which may be used to engage the vessel wall and advance around an occlusion in a subintimal path as described previously. A bearing (not shown) may be disposed on the inner member  1010  to engage the proximal or distal end of the shaft  1004  to enable the shaft  1004  and the inner member  1010  to be advanced in unison. 
     With reference to  FIGS. 11A and 11B , an alternative subintimal device  1100  is shown schematically. Subintimal device  1100  may be similar to device  1000  described previously, with the helical interlocking gear and helical wire coil eliminated for sake of illustration. Subintimal device  1100  includes an elongate tubular shaft  1102  having a lumen extending therethrough and a re-entry port  1106  disposed distally in the region of the helical shape. In this embodiment, the distal portion of the shaft  1102  may have a helical shape in its relaxed state such that the re-entry port  1106  is always oriented toward the center of the helix as shown in  FIG. 11A . With this arrangement, a re-entry device  1110  such as a guide wire or flexible stylet with a tissue penetrating tip may be advanced through the lumen  1104  of the shaft  1102  to exit the re-entry port  1106  as shown in  FIG. 11B . This arrangement may be used to establish re-entry of the native lumen of a vessel once the device  1100  traverses an occlusion in the subintimal space. 
     With reference to  FIGS. 12A-12D , an alternative re-entry method is schematically shown. In this method, a subintimal device such as guide wire  1210  is advanced into the subintimal space  1202  across an occlusion  1200  in a manner similar to the methods described previously, for example. As shown in  FIG. 12A , the guide wire  1210  extends across an occlusion  1200  disposed in subintimal space  1202  between intimal/medial layers  1204  and adventitial layer  1206 , where re-entry of the native lumen  1208  distal of the occlusion  1200  is desired. A balloon catheter  1220  is then advanced over the guide wire  1210  until the balloon portion is disposed adjacent the distal end of the occlusion as shown in  FIGS. 12B and 12C . The guide wire  1210  is pulled proximally and balloon is then inflated causing radial displacement of the distal end of the balloon catheter  1220  as shown in  FIG. 12C . Inflating the balloon of the balloon catheter  1220  orients the tip of the catheter toward the intimal/medial layers  1204 . The guide wire  1210  may be removed from the balloon catheter  1220  and a sharpened stylet  1230  or the like may be advanced through the guide wire lumen of the catheter  1220  until the distal end of the stylet  1230  penetrates the intimal/medial layers  1204  as shown in  FIG. 12D , thus establishing re-entry from the subintimal path  1202  and into the native lumen  1208 . 
     With reference to  FIGS. 13A and 13B , an alternative fluidic subintimal system  1300  with subintimal device  1310  and associated pumping system  1320  is shown schematically. The fluidic system  1300  is similar in certain aspects to the arrangements described with reference to  FIGS. 3 ,  4  and  5 , the various aspects of which may be combined or used in the alternative as will be appreciated by those skilled in the art. System  1300  includes a subintimal device  1310  which may comprise any of the tubular subintimal devices described herein. Generally, subintimal device  1310  includes a tubular shaft  1312  having a proximal end connected to a pumping mechanism  1320 . A plunger rod  1314  is slidingly disposed in the tubular shaft  1312  as shown in  FIG. 13B  and its proximal end is connected to a linear actuator  1322  of the pumping mechanism as shown in  FIG. 13A . As seen in  FIG. 13B , a ring seal  1315  is disposed in the lumen of shaft  1312  around the rod  1314 . The rod  1314  extends through the tubular shaft  1312  to a point proximal of the distal end thereof to define a pumping chamber  1316 . A source of liquid  1330  (e.g., saline bag) is connected to the proximal end of the subintimal device  1310  via a fluid line  1332  and optional valve  1334  to supply liquid to the annular lumen between the rod  1314  and the inner wall of the tubular shaft  1312 . As the linear actuator moves the rod  1314  back and forth in the tubular shaft  1312 , liquid is caused to be expelled out of the chamber  1316  in a pulsatile fashion, which may be used to hydraulically dissect tissues to define a subintimal path as described previously, for example. The stroke length, stroke rate and stroke volume may be adjusted to achieve the desired effect. For example, the stroke volume of the chamber  1316  may be relatively small (0.01 cc-1.0 cc, for example) such that liquid exits the chamber  1316  with high energy that dissipates quickly to minimize trauma to tissues as they are dissected. 
     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.