Abstract:
The present invention relates generally to devices and methods for treating occluded or stenoic blood vessels. More particularly, the present invention relates to devices and methods for delivering or retrieving an embolic protection device from the vasculature of a patient. In an embodiment, a catheter for retrieval or delivery of an embolic protection device comprises an inner shaft and an outer sheath. In addition, a method for retrieving and delivering an embolic protection device is disclosed.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to devices and methods for treating occluded or stenoic blood vessels. More particularly, the present invention relates to devices and methods for delivering or retrieving an embolic protection device from the vasculature of a patient.  
       BACKGROUND OF THE INVENTION  
       [0002]     Atherosclerosis is a major problem wherein blood vessels become blocked or narrowed. This blockage can result in lack of oxygenation to the heart. It is critical that the heart muscle be well oxygenated so that the blood pumping action of the heart is not impaired.  
         [0003]     Occluded or stenotic blood vessels may be treated with a number of medical procedures including, for example, angioplasty and atherectomy. Angioplasty techniques such as percutaneous transluminal angioplasty (PTA) and percutaneous transluminal coronary angioplasty (PTCA) are relatively non-invasive methods of treating a stenotic lesion. These angioplasty techniques typically involve the use of a balloon catheter. The balloon catheter is advanced over a guidewire such that the balloon is positioned adjacent a stenotic lesion. The balloon is then inflated and the restriction in the vessel is opened. During an atherectomy procedure, the stenotic lesion may be mechanically cut away from the blood vessel wall using an atherectomy catheter.  
         [0004]     During atherectomy procedures, stenotic debris that is separated from the stenosis may be free to flow within the lumen of the vessel. If this debris enters the circulatory system, it could block other vascular regions including the neural vasculature, or in the lungs. An occlusion in the neural vasculature may cause a stroke, and an occlusion in the lungs may interfere with the oxygenation of the blood. During angioplasty procedures, stenotic debris may also break loose due to manipulation of the blood vessel. Because of this debris, a number of devices termed embolic protection devices have been developed to filter out this debris.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention relates generally to devices and methods for treating occluded or stenoic blood vessels. More particularly, the present invention relates to devices and methods for delivering or retrieving an embolic protection device from the vasculature of a patient.  
         [0006]     An embodiment of the invention includes a filter retrieval catheter. The filter retrieval catheter may comprise an inner shaft slidably disposed within an outer sheath. The inner shaft may include a proximal end, a mid-region, and a tapered distal end. The distal end may include a tubular member. A guidewire can be adapted to pass through the tubular member of the inner shaft. The guidewire may include an embolic protection device coupled to a distal end thereof.  
         [0007]     The outer sheath may further comprise an opening. In addition, a cover sheath may be disposed about the outer sheath, for example over the opening. The cover sheath may further comprise a slot that may allow the guidewire to be disposed therein. Retrieval of the embolic protection device may including shifting the position of the inner shaft relative to the opening in the outer sheath.  
         [0008]     Preparation of the retrieval catheter may comprise elimination of air from vacant space between the inner shaft and the outer sheath. Air may be substantially eliminated from the vacant space by flushing the vacant space with a fluid. Fluid can be additionally flushed through the proximal end of the catheter and through the opening. In addition to the vacant spaces, distant vacant spaces may need to be flushed. According to this embodiment, the tubular member may further comprise a plurality of flush holes. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a cross sectional view of a filter retrieval catheter in an arrangement suitable for advancement through the vasculature;  
         [0010]      FIG. 2  is a cross sectional view of a filter retrieval catheter in an arrangement suitable for removal from the vasculature;  
         [0011]      FIG. 3  is a side view of an alternate embodiment of an outer sheath further comprising a cover sheath;  
         [0012]      FIG. 4  is a top view of the cover sheath according an embodiment;  
         [0013]      FIG. 5  is a cross sectional view for preparation of a filter retrieval catheter according to an embodiment of the invention; and  
         [0014]      FIG. 6  is an alternate cross sectional view for preparation of a filter retrieval catheter according to an embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]     The following description should be read with reference to the drawings wherein like reference numerals indicate like elements throughout the several views. The detailed description and drawings represent select embodiments and are not intended to be limiting.  
         [0016]      FIG. 1  is a cross sectional view of a filter retrieval and delivery catheter  10  in an arrangement suitable for advancement through the vasculature. In an embodiment, a filter retrieval catheter  10  may comprise an inner shaft  12  slidably disposed within an outer sheath  14 .  
         [0017]     Inner shaft  12  may include a proximal end  16 , a mid-region  18 , and a distal end  20 . Proximal end  16  may comprise an elongate tube. The elongate tube may be comprised of materials including, but not limited to, thermoplastics, high performance engineering resins: fluorinated ethylene propylene (FEP), polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), polyurethane, polytetrafluoroethylene (PTFE), polyether-ether ketone (PEEK), polyimide, polyamide, polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polysufone, nylon, perfluoro(propyl vinyl ether) (PFA), metals: stainless steel, nickel alloys, nickel-titanium alloys, and combinations thereof.  
         [0018]     Proximal end  16  may be held to secure inner shaft  12  relative to outer sheath  14 , for example be a lock wire  22 . Alternatively, inner shaft  12  may be held in place relative to a guidewire  24 . According to this embodiment, movement of guidewire  24  results in substantially similar movement of inner shaft  12 . Moreover, movement of either guidewire  24  or inner shaft  12  may occur independently of movement of outer sheath  14 .  
         [0019]     Mid-region  18  may comprise an opening on each of two opposite ends. The openings may be appropriate for coupling mid-region  18  to proximal end  16  and distal end  20 . Mid-region  18  may comprise a polymer or metal, including those listed above. In an exemplary embodiment, mid-region  18  comprises polyethylene.  
         [0020]     Distal end  20  may comprise a tubular member  26  having a proximal region  28 , a distal region  30 , and a lumen  32  extending therethrough. Lumen  32  may be a guidewire lumen adapted for housing guidewire  24 . Distal end  20  may comprise polyimide. Alternatively, distal end  20  may comprise materials similar to those listed above. Tubular member  26  is coupled to mid-region  18 . For example, tubular member  26  may be disposed within an opening within mid-region  18  and bend to exit a second opening within mid-region  18 . The bend in tubular member  26  when exiting mid-region  18  may define a port  34  that may be disposed at proximal region  28 . A tip  36  can be disposed at distal region  30  of tubular member  26 . Tip  36  is comprised of generally soft or atraumatic materials. For example, tip  36  may be comprised of materials including polymers. In addition, tip  36  may be comprised of materials similar to those listed above.  
         [0021]     Outer sheath  14  may be disposed around inner shaft  12 . Outer sheath  14  may be comprised of materials including, but not limited to, metals, alloys, nickel alloys, nickel titanium alloys, polymers, and combinations thereof. Alternatively, outer sheath  14  may be comprised of materials similar to those listed above.  
         [0022]     Outer sheath  14  includes a proximal end  38 , a distal end  40 , and a lumen  42  extending therethrough. Lumen  42  is sized to allow inner shaft  12  to be slidably disposed therein.  
         [0023]     Outer sheath  14  may include an opening  44 . Opening  44  can be, for example, about 2 inches long. Opening  44  can be, for example, less than about 4 inches long. Opening  44  may further comprise a proximal region  46  and a distal region  48 . In an exemplary embodiment, inner shaft  12  is disposed within lumen  42  such that port  34  is disposed substantially proximate opening  44 .  
         [0024]     Guidewire  24  may further include a proximal end  50  and a distal end  52 . An embolic protection device  54 , such as a distal protection filter, may be disposed at distal end  52 . Embolic protection device  54  is adapted to prevent embolic debris from travelling away from a treatment site. According to this embodiment, embolic protection device  54  can substantially prevent embolic debris from occluding a blood vessel down stream from a treatment site.  
         [0025]     Catheter  10  may be used as a filter retrieval catheter or a filter delivery catheter. When used to retrieve embolic protection device  54 , catheter  10  is configured relative to guidewire  24  and inner shaft  12  is configured relative to outer sheath  14 . As to configuring catheter  10  relative to guidewire  24 , catheter  10  is generally passed over guidewire  24 . According to this embodiment, guidewire  24  passes through lumen  32  of tubular member  26 , through port  34 , and through opening  44 . Proximal end  50  of guidewire  24  extends proximally out of outer sheath  14  at opening  44 . Distal end  52  of guidewire  24  extends distally out of tip  36  of distal region  30  of inner shaft  12 .  
         [0026]     When configured for retrieving embolic protection device  54  (or when generally configured for advancing through the vasculature) guidewire  24  may be locked relative to inner shaft, for example by locking wire  22 . Moreover, guidewire  24  is generally disposed at a location near distal region  48  of opening  44  (as shown in  FIG. 1 ). Disposing guidewire  24  near distal region  48  of opening  44  may be advantageous when using catheter  10  for retrieval. For example, positioning guidewire  24  near distal region  48  during retrieval (or generally during advancement of catheter  10  through the vasculature) makes available space for guidewire  24  to shift (proximally) within opening  44 . This feature is important because guidewire  24  and inner shaft  12  may be locked. Thus, allowing space for guidewire  24  to proximally shift may allow movement or shifting of inner shaft  12  relative to sheath  14  (as described in more detail below).  
         [0027]     As to configuring inner shaft  12  relative to outer sheath  14 , inner shaft  12  may be oriented in a first position (as shown in  FIG. 1 ). In the first position, inner shaft  12  is positioned distally within sheath  14  such that at least a portion of tip  36  extends out from outer sheath  14 . In an exemplary embodiment, a tapered portion of tip  36  extends out of outer sheath  14  when inner shaft  12  is in the first position. Generally, the first position is appropriate for advancing catheter  10  through the vasculature and provides a generally tapered or atraumatic distal end to catheter  10 .  
         [0028]     Retrieval of embolic protection device  54  may then be accomplished by advancing catheter  10  through the vasculature to a position near embolic protection device  54  (for example, as shown in  FIG. 1 ). Once located near embolic protection device  54 , inner shaft  12  can be shifted from the first position to a second position. Shifting can occur by advancing sheath  14  distally relative to inner shaft  12 . Shifting inner shaft  12  to the second position results in sheath  14  moving distally over inner shaft  12  such that tip  36  is disposed a distance proximally of distal end  40  of sheath  14  (as shown in  FIG. 2 ).  
         [0029]     Because guidewire  24  may be locked relative to inner shaft  12 , shifting the position of inner shaft  12  results in shifting of guidewire  24  relative to sheath  15 . In general, when inner shaft  12  shifts to the second position, guidewire  24  shifts such that it becomes disposed near proximal end  46  of opening. Because embolic protection device  54  is coupled to guidewire  24 , shifting inner shaft  12  to the second position results in sheath  14  passing distally over at least a portion of embolic protection device  54  (as shown in  FIG. 2 ). When at least a portion of embolic protection device  54  is disposed within sheath  14 , catheter  10  (and, thus, embolic protection device  54 ) may be removed from the vasculature.  
         [0030]     Catheter  10  may also be used to deliver embolic protection device  54 . For example, inner shaft  12  may be in the second position (as shown in  FIG. 2 ) and advanced through the vasculature. While advancing, embolic protection device  54  may be at least partially collapsed within sheath  14 . Upon reaching a desired location, sheath  14  may be shifted (in the proximal direction) relative to inner shaft  12  and guidewire  24  such that embolic protection device  54  emerges from distal end  40  of sheath  14 . Generally, embolic protection device  54  is designed to be self-expanding such that when device  54  emerges from sheath  14  it assumes the expanded configuration appropriate for filtering embolic debris. Thus, the shift of sheath  14  in the proximal direction allows embolic protection device  54  to expand and be delivered. Once embolic protection device  54  is delivered, catheter  10  may be removed from the vasculature.  
         [0031]      FIG. 2  is a cross sectional view of a filter retrieval catheter in an arrangement suitable for removal from the vasculature. Inner shaft  12  can be shifted from the first position to a second position relative to outer sheath  14  as shown. In the second position tip  36  may be substantially contained within lumen  42  of outer sheath  14 . In addition, a portion of embolic protection device  54  may be disposed within outer sheath  14  after shifting from the first position to the second position. Shifting results in inner shaft  12  (specifically proximal region  28  and/or port  34 ) becoming disposed near proximal region  46  of opening  44 . Subsequent to shifting, guidewire  24  may be secured in place during relative to sheath  14  and both can be removed proximally from the patient&#39;s vasculature.  
         [0032]      FIG. 3  is a side view of an alternate embodiment of an outer sheath further comprising a cover sheath. A cover sheath  56  may be disposed on outer sheath  14  over opening  44 . Cover sheath  56  may be comprised of a number of materials including polymers. Alternatively, cover sheath  56  may be comprised of materials similar to those listed above.  
         [0033]     Cover sheath  56  may be coupled to outer sheath  14  in a number of differing manners. For example, cover sheath  56  may be coupled to outer sheath  14  by an adhesive. Alternative methods for coupling cover sheath  56  would be familiar to those of ordinary skill in the art.  
         [0034]      FIG. 4  is a top view of the cover sheath according an embodiment. Cover sheath  56  can further comprise a slot  58 . Slot  58  may be sized appropriately for passage of guidewire  24 . In addition, slot  58  may be substantially self-resealing. Self-resealing is understood to mean that slot  58  essentially prevents the passage of fluids therethrough but allows guidewire  24  to be moveable therein.  
         [0035]      FIG. 5  is a cross sectional view for preparation of a filter retrieval catheter according to an embodiment of the invention. Preparation of filter retrieval catheter  10  may include the step of substantially eliminating of air from vacant space  60  within inner shaft  12 . Air may be substantially eliminated from vacant space  60  by flushing vacant space  60  with a fluid, such as saline. Alternative flushing mediums may be used without departing from the spirit of the invention.  
         [0036]     To prepare filter retrieval catheter  10 , fluid may be flushed through distal region  30  of tubular member  26  and throughout tubular member  26 . Fluid can be additionally flushed through proximal end  38  of outer sheath  14 , distal end  40  of outer sheath  14 , and through opening  44 . Flushing substantially eliminates air from vacant space  60 .  
         [0037]      FIG. 6  is a cross sectional view for preparation of a filter retrieval catheter according to an embodiment of the invention. In addition to vacant spaces  60 , distant vacant spaces  62  may be present. According to some embodiments of the invention, distant vacant spaces  62  may not be adequately flushed by the using the preparation strategy shown in  FIG. 5 .  
         [0038]     To address this issue, an alternate filter retrieval catheter  110  may be constructed including an alternate inner shaft  112 . Inner shaft  112  may comprise tubular member  126 . Tubular member  126  can further comprise a plurality of flush holes  164 . According to this embodiment, flushing fluid through inner shaft  112  and through tubular member  126  may result in substantial flushing of distant vacant spaces  62  by allowing fluid to be flushed through holes  164 .  
         [0039]     It should be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of steps without exceeding the scope of the invention. The invention&#39;s scope is, of course, defined in the language in which the appended claims are expressed.