Abstract:
Device and method for capturing guidewires inside blood vessels. The disclosed device enables retrieval of guidewires that need to be pulled from the body at a different location than the guidewire entering location, such as guidewires that have entered in a retrograde direction.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention generally relates to a device and a method for retrograde guidewire retrieval during blood vessel angioplasty, such as below the knee (BTK) blood vessels and other blood vessels (e.g., femoral or iliac), which are partially or totally occluded. 
       BACKGROUND OF THE INVENTION 
       [0002]    A chronic total occlusion (CTO) is an arterial vessel blockage that prevents blood flow beyond the obstruction. CTO&#39;s typically occur in coronary, peripheral, pediatric, and other small arteries. In the coronary and peripheral arteries, they result from the same underlying cause—atherosclerosis. 
         [0003]    Endovascular therapy for arteries below the knee has emerged as a promising revascularization technique for patients with critical limb ischemia (CLI). However, when employing standard angioplasty techniques, angioplasty of BTK arteries fails to achieve revascularization in up to 20% of cases. The main cause for failure is the inability to penetrate the plaque&#39;s proximal cap with the guidewire. 
         [0004]    A new technique of approaching the plaque from below—known as the retrograde approach—is often used to pass the guidewire through the plaque from the other direction. This approach has high success rates, but is technically challenging to perform and has its own complications, especially the danger of vessel perforation. 
         [0005]    In order to use the retrograde technique, the clinician must puncture the small target artery with a needle—usually smaller than a 21 gauge needle. The clinician relies on several angiographic images to aim the needle into the artery, and verifies proper needle tip location by observing blood flow exiting from the needle&#39;s proximal end. 
         [0006]    Puncturing small arteries is not easy; it requires proper manipulation of the C-arm and a gentle needle stick to avoid arterial perforation. Once a small sheath or direct (sheath-less) guidewire is inserted within the needle into the artery, the needle can be removed. 
         [0007]    If retrograde passage of the guidewire through the occlusion is successful transluminally, the guidewire must be snared and pulled through the antegrade or cross-over sheath, using “Lasso” snaring devices or a simple 5 or 6 Fr (1.7-2.0 mm) support catheter. Thereafter, relatively large balloons and stents can be delivered without damaging the small retrograde puncture hole, preventing the risk of small blood vessel perforation. For example, the tibial-peroneal vessels are small, having diameters of about 2 mm (6 Fr) to 3 mm (9 Fr). Therefore, inserting a 6 Fr or even a 5 Fr sheath needed for balloons and stent delivery, will perforate the artery. 
         [0008]    However, although using a “Lasso” device is feasible it is not easy; it requires gentle manipulation, and the guidewire tip often becomes damaged and cannot be used. 
         [0009]    Retrieval of the guidewire with a small support catheter can be very difficult; it takes a long time with many attempts, and has a low rate of success, due to the small catheter lumen compared to the relatively larger vessel lumen at the wire exit area. 
         [0010]    Such guidewire capturing is also needed when treating iliac arteries, which are relative large, but guidewires are often inserted through distant arteries, like radial arteries, to avoid iliac dissection. Such guidewires must be captured near the occlusion for easy delivery of balloons and stents. 
         [0011]    If retrograde passage of the guidewire through the occlusion is performed via a subintimal approach, the true lumen must be reentered, either spontaneously or with a reentry device. Current reentry devices are big, stiff, and require at least a 6 Fr sheath through which to pass. Therefore, they cannot be used from a retrograde approach. 
       SUMMARY OF THE INVENTION 
       [0012]    The present invention is directed to a device and a method for retrograde guidewire retrieval during blood vessel angioplasty. The invention seeks to improve the physician&#39;s technique in treating blood vessel occlusions, and can be used when crossing both new, soft plaque and old, hard plaque. 
         [0013]    In accordance with a non-limiting embodiment of the invention, the retrograde approach may be performed with the following steps:
       a. Insert needle tip into the (small) blood vessel.   b. Insert a standard 0.014″, 0.018″ or 0.035″ guidewire through the needle into the artery, and remove the needle and needle holder.   c. Attempt crossing the plaque with the guidewire alone. If not successful, use the flexible sheath introducer as a support catheter for the guidewire. If a sheath-less technique is used, use a support catheter to support the guidewire passage through the plaque.   d. If the guidewire ultimately crosses the plaque successfully, and must be captured from above/other side into the cross-over or antegrade sheath, insert the guidewire retrieval catheter of the present invention from the other side, to funnel the guidewire out through the sheath via the special conical tip of the guidewire retrieval catheter.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which: 
           [0019]      FIG. 1  is a simplified illustration of a guidewire retrieval catheter, having an elastomeric, conical funnel tip, inserted in an artery, constructed and operative in accordance with a non-limiting embodiment of the present invention. 
           [0020]      FIG. 2  is a simplified illustration of the guidewire retrieval catheter of  FIG. 1  with a cover sheath, in accordance with a non-limiting embodiment of the present invention. 
           [0021]      FIG. 3  is a simplified illustration of a guidewire retrieval catheter, having an elastomeric, conical funnel tip and blood flow blocking balloon, constructed and operative in accordance with a non-limiting embodiment of the present invention. 
           [0022]      FIG. 4  is a simplified illustration of a funnel insertion device, constructed and operative in accordance with a non-limiting embodiment of the present invention. 
           [0023]      FIG. 5  is a simplified illustration of a guidewire retrieval catheter, having a conical funnel tip made of a shape memory material, constructed and operative in accordance with a non-limiting embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
       [0024]    Reference is now made to  FIG. 1 , which illustrates a guidewire retrieval device  10 , constructed and operative in accordance with an embodiment of the present invention. The guidewire retrieval device  10  is also referred to as guidewire retrieval catheter  10 , but it is understood that the device is not limited to the configuration of a catheter. 
         [0025]    The guidewire retrieval device  10  includes a tube  11 , constructed from a suitable, biomedically safe material, such as, but not limited to, PEBAX (trade name for a polyether block amide), nylon, or PTFE (polytetrafluoroethylene). A funnel  12  (preferably cone-shaped, but other shapes are possible) is disposed at a distal end of tube  11 . Funnel  12  may be constructed from a flexible, elastomeric material, such as, but not limited to, polyurethane or silicone.  FIG. 1  shows guidewire retrieval device  10  inserted in a blood vessel  2  from the antegrade direction. Funnel  12  is open capture a guidewire  1  inserted from the retrograde direction. Opposite directions can also be used if desired by the operator. The size of the open mouth of funnel  12  is preferably equal or slightly larger than the blood vessel diameter. 
         [0026]    Guidewire  1  is pushed into funnel  12 , which directs guidewire  1  into tube  11 . Pushing guidewire  1  further allows capturing its distal tip outside of the patient&#39;s body, allowing continuation of the procedure from that side. 
         [0027]    Reference is now made to  FIG. 2 . Optionally, retrieval catheter  10  (or any of the other embodiments of the invention) may include a long sheath  13  to cover and protect funnel  12  during insertion into the blood vessel. Sheath  13  is withdrawn to expose funnel  12 , after funnel  12  has reached its proper location inside the blood vessel  2 . 
         [0028]    Reference is now made to  FIG. 3 , which illustrates a guidewire retrieval catheter  20 , including the elastomeric, conical funnel  12  and an additional blood flow blocking balloon  14 , constructed and operative in accordance with a non-limiting embodiment of the present invention. As with the embodiment of  FIG. 1 , guidewire retrieval catheter  20  includes a tube  11 . 
         [0029]    Balloon  14  is proximal to funnel  12 . An additional coaxial tube  15  is added over tube  11  to create a balloon inflation lumen. Double-lumen tube can be used as well, as is known in the art. Balloon  14  is made from a polymer material, such as a compliant or semi-compliant material, e.g., polyurethane or silicone, but can also be made from nylon or stiffer non-compliant materials. The diameter of balloon  14  is preferably similar or slightly larger than that of the blood vessel lumen in its nominal inflation pressure. Balloon  14  blocks blood flow, preventing possible collapse of funnel  12  due to blood flow and pressure that could close or shrink funnel  12 . 
         [0030]    Balloon  14  is preferably located quite near funnel  12 , so as not only to block blood flow, but also to support centering the relative soft funnel  12  in the blood vessel. (Funnel  12  is relative soft to prevent possible damage to blood vessel  2  during insertion of catheter  20 .) Since blood flow might collapse the soft funnel, balloon  14  is needed to prevent such funnel collapse. In addition, since blood vessels are not always straight, centering funnel  12  in the blood vessel using inflated balloon  14  is important for proper funnel function, assuring that funnel  12  touches the entire inner circumference of the blood vessel. Such funnel centering is required even if the device is used against the blood flow direction, when blood flow might naturally open the funnel. 
         [0031]    Balloon  14  can alternatively be a long, non-compliant balloon that can also be used for blood vessel angioplasty (PTA). 
         [0032]    The guidewire retrieval catheter  20 , or any of the other embodiments of the invention, may include one or more radio-opaque markers  16 , which help the user to verify that guidewire  1  is properly inserted into tube  11 . The markers  16  may be positioned on tube  11  near a neck  17  of funnel  12 , and/or at the middle of balloon  14  if a short balloon is used, or at both sides of balloon  14  if a long balloon is used. 
         [0033]    The proximal side of the retrieval catheter  20  may include a Y connector  18  with female luer connectors, as is known in the art, including a side-arm  18   a  for balloon inflation, and a central arm  18   b  for guidewire passage. 
         [0034]    Since funnel  12  is normally open, a device and method of inserting it into the blood vessel through a standard sheath is provided in accordance with an embodiment of the invention as illustrated in  FIG. 4 . 
         [0035]    In one embodiment, a funnel inserting device  30 , made of a material, such as, but not limited to, PEBAX, nylon, or PTFE, includes a tube with a distal portion  31  extending from a proximal portion  32 . The distal portion  31  has a larger diameter than the proximal portion  32 . Proximal portion  32 , which may be made from the same tube as distal portion  31 , but heat shrunk to a smaller diameter, has a diameter smaller than balloon  14  when folded. This ensures that the funnel inserting device  30  cannot be pushed distally and out by mistake before inserting funnel  12  into a standard sheath. 
         [0036]    Distal portion  31  is used as a balloon protector for balloon  14 , and for housing the folded funnel  12  before inserting into standard sheath. 
         [0037]    The length of distal portion  31  is preferably the distance between the proximal end of balloon  14  and the distal end of funnel  12 , or slightly longer. 
         [0038]    Funnel  12  does not necessarily have to be made from an elastomeric material. Reference is now made  FIG. 5 , in which funnel  12  is made from a shape memory material, such as, but not limited to, nitinol. In the illustrated embodiment, the funnel is made from nitinol wire  62 . Wire  62  is connected to a stiffer (thicker) nitinol wire  63  that is used to open or close funnel  12 . The distal part of wire  62  is pre-shaped like a cone made from a crowded (zero pitch) spiral wire, which circles in an ever reducing diameter at every circle to create the desired cone shape. To prevent possible damage to the blood vessel, the distal end of wire  62  is rounded, and may circle backwards and connect to the distal end of stiff wire  63 .