Abstract:
A removable, low profile, vascular filter system for capture and retrieval of emboli while allowing continuous perfusion of blood, comprising a guidewire having proximal and distal markers, a filter delivery and deployment system, having an outer member and an inner member, and a filter removably attached near the distal end of the inner member. The filter comprises proximal and distal basket sleeves which position the filter between the proximal and distal markers on the guidewire, after the guidewire is in position past the vessel occlusion. The guidewire placement prior to filter delivery may facilitate access to the interventional site, especially through tortuous anatomy. Also, retrievability of the filter from the wire may avoid loss of guidewire position, which may occur following removal of filters permanently attached to guidewires.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a Continuation-in-Part application of U.S. patent application Ser. No. 09/249,377 now U.S. Pat. No. 6,391,044 filed Feb. 12, 1999. 

   BACKGROUND OF THE INVENTION 
   I. Field of the Invention 
   The present invention relates to the treatment of vascular disease, and more particularly to a vascular filter system for use during medical procedures. 
   II. Discussion of the Related Art 
   Percutaneous transluminal coronary angioplasty (PTCA), stenting and atherectomy are therapeutic medical procedures used to increase blood flow through the coronary arteries. These procedures may often be performed as alternatives to coronary bypass surgery. Percutaneous transluminal angioplasty (PTA) and stenting may often be performed as alternatives to carotid endarterectomy, and femoral-popliteal bypass procedures. In PTCA or PTA procedures, the angioplasty balloon is inflated within the stenosed vessel, at the location of an occlusion, in order to shear and disrupt the wall components of the vessel to obtain an enlarged lumen. In stenting, an endoluminal prosthesis is implanted in the vessel to maintain patency following the procedure. In atherectomy, a rotating blade is used to shear plaque from the arterial wall. 
   One of the potential complications associated with all these techniques is the accidental dislodgment of plaque, thrombus or other embolic particulates generated during manipulation of the vessel, thereby potentially causing occlusion of the narrower vessels downstream and ischemia or infarct of the organ which the vessel supplies. Such emboli may be extremely dangerous to the patient, and may result in myocardial infarction, stroke or limb ischemia. In 1995, Waksman et al. disclosed that distal embolization is common after directional atherectomy in coronary arteries and saphenous vein grafts. See Waksman et al., American Heart Journal 129(3): 430–5 (1995). This study found that distal embolization occurs in twenty-eight percent (31 out of 111) of the patients undergoing atherectomy. In January 1999, Jordan, Jr. et al. disclosed that treatment of carotid stenosis using a percutaneous angioplasty with stenting procedure is associated with more than eight times the rate of microemboli seen using carotid endarterectomy. See Jordan, Jr. et al., Cardiovascular Surgery 7(1): 33–8 (1999). Microemboli, as detected by transcranial Doppler monitoring in this study, have been shown to be a potential cause of stroke. The embolic materials include calcium, intimal debris, atheromatous plaque, and thrombi. 
   In order to initiate these procedures, one must first introduce a guidewire into the lumen of the vessel to serve as a conduit for other interventional devices, such as angioplasty balloons and stent delivery systems. This guidewire must be advanced into a position past the location of the occlusion. Guidewires must be capable of traversing tortuous pathways within the body, consisting of bends, loops and branches. For this reason, guidewires need to be flexible, but they should also be sufficiently stiff to serve as conduits for other devices. In addition, they must be “torqueable” to facilitate directional changes as they are guided into position. 
   Guidewires are well known in the art, and are typically made of stainless steel, tantalum or other suitable materials, in a variety of different designs. For example, U.S. Pat. Nos. 4,545,390 and 4,619,274 disclose guidewires in which the distal segment is tapered for greater flexibility. The tapered section may be enclosed in a wire coil, typically a platinum coil, which provides increased column strength and torqueability. Another design is identified in U.S. Pat. No. 5,095,915, where the distal segment is encased in a polymer sleeve with axially spaced grooves to provide bending flexibility. 
   Vascular filters are also well known in the art, especially vena cava filters, as disclosed in U.S. Pat. Nos. 4,727,873 and 4,688,553. There is also a substantial amount of medical literature describing various designs of vascular filters and reporting the results of clinical and experimental use thereof. See, for example, the article by Eichelter and Schenk, entitled “Prophylaxis of Pulmonary Embolism,” Archives of Surgery, Vol. 97 (August, 1968). See, also, the article by Greenfield, et al., entitled “A New Intracaval Filter Permitting Continued Flow and Resolution of Emboli”, Surgery, Vol. 73, No. 4 (1973). 
   Vascular filters are often used during a postoperative period, when there is a perceived risk of a patient encountering pulmonary embolism resulting from clots generated peri-operatively. Pulmonary embolism is a serious and potentially fatal condition that occurs when these clots travel to the lungs. The filter is therefore typically placed in the vena cava to catch and trap clots before they can reach the lungs. 
   Many of the prior art vascular filters are intended to be permanently placed in the venous system of the patient, so that even after the need for the filter has passed, the filter remains in place for the life of the patient. U.S. Pat. No. 3,952,747 discloses a stainless steel filtering device that is permanently implanted transvenously within the inferior vena cava. This device is intended to treat recurrent pulmonary embolism. Permanent implantation is often deemed medically undesirable, but it is done because filters are implanted in patients in response to potentially life-threatening situations. 
   To avoid permanent implantation where possible, it is highly desirable to provide an apparatus and method for preventing embolization associated with angioplasty, stenting or other procedures. In particular, it is desirable to provide a device which may be temporarily placed within the vascular system to collect and retrieve plaque, thrombus and other embolic particulates which have been dislodged during angioplasty, stenting or other procedures. Such a device is removed at the end of the procedure. U.S. Pat. Nos. 6,179,861 and 6,001,118 disclose guidewire-based filters where the filter resembles a windsock and is supported by one or more articulated support hoops. U.S. Pat. Nos. 5,814,064 and 5,827,324 disclose guidewire-based filter devices, wherein the filter is expanded to a predetermined diameter through the introduction of a fluid or a gas. U.S. Pat. Nos. 6,168,604 and 6,152,946 disclose guidewire-based filters, wherein the diameter of the filter is controlled by advancing and retracting a sheath over the filter component. 
   One concern commonly encountered with these devices is that the filter is attached to the guidewire, which increases the profile or diameter thereof, making it is difficult to push and track these devices through the vasculature, to reach the treatment site. A related concern commonly encountered with these devices is that if the filter becomes clogged with emboli, such that distal perfusion is no longer possible, the filter must be removed and replaced, thereby losing guidewire position. 
   The prior art fails to disclose any guidewire-based vascular filters which may be used to address the clinical problems of poor pushability and trackability through the vasculature, and loss of guidewire position upon removal of filters permanently attached to guidewires. 
   SUMMARY OF THE INVENTION 
   The present invention provides a vascular filter system which may be used to address the clinical problems of poor pushability and trackability through the vasculature, and loss of guidewire position upon removal of filters permanently attached to guidewires, as briefly described above. 
   An objective of the present invention is to provide a vascular filter which is positioned on a guidewire after the distal end of the guidewire has crossed the lesion and is in position past an occlusion in a lumen of a vessel. Therefore, the present invention enables the physician to successfully reach the treatment site with a low profile device. Then, the present invention provides a filter to capture embolic particulates that may be released during the procedure, while also allowing perfusion of distal vessels. A further objective of the present invention is to provide a vascular filter that is retrievable while maintaining guidewire position. 
   The filter system of the present invention comprises a guidewire having proximal and distal markers; a filter deployment and delivery system comprising an inner member and an outer member, with a filter removably attached near the distal end of the inner member; proximal and distal basket sleeves attached near the proximal and distal ends of the filter; and a retrieval catheter coaxially disposable around the guidewire and the filter. The low profile guidewire of the present invention, comprising proximal and distal markers near its distal end, but without an attached filter, is used to access the interventional site. If the anatomy is tortuous, such that access would be difficult if not impossible with a filter attached, access may still be achieved with this low profile guidewire. Then, the filter deployment and delivery system of the present invention, comprising an inner member and an outer member, is introduced, with the filter removably attached to the inner member of the filter deployment and delivery system. The outer member collapses and constrains the filter, allowing it to achieve a smaller first diameter. The filter of the present invention comprises proximal and distal basket sleeves. The distal basket sleeve is sized to successfully ride over the proximal marker on the guidewire, but not the distal marker, so the filter is positioned between these two markers. Then, the outer member of the filter deployment and delivery system is retracted to deliver the filter. The inner member is then withdrawn, and the filter remains positioned on the guidewire, between the proximal and distal markers. The filter captures embolic particulates during the procedure. The retrieval catheter is then employed to retrieve the filter and the guidewire, if the procedure is complete. If the procedure is incomplete, but the filter is full and is prohibiting distal perfusion, the filter alone may be removed, so that guidewire position is not lost, and the remainder of the procedure may be completed. 
   In accordance with one aspect, the present invention is directed to a low profile vascular filter system comprising a guidewire having proximal and distal markers. The low profile vascular filter system further comprises a filter deployment and delivery system coaxially disposed around the guidewire, with the filter deployment and delivery system comprising an inner member and an outer member, a filter removably attached near the distal end of the inner member, and proximal and distal basket sleeves attached near the proximal and distal ends of the filter. The low profile vascular filter system further comprises a retrieval catheter coaxially disposable around the guidewire and the filter. The retrieval catheter is used to collapse the filter, and to remove the filter and the guidewire from the lumen of the vessel. 
   In accordance with another aspect, the present invention is directed to a low profile vascular filter system comprising a guidewire having proximal and distal markers. The low profile vascular filter system further comprises a filter deployment and delivery system coaxially disposed around the guidewire, with the filter deployment and delivery system comprising an inner member and an outer member, a filter removably attached near the distal end of the inner member, and proximal and distal basket sleeves attached near the proximal and distal ends of the filter. The low profile vascular filter system further comprises a retrieval catheter coaxially disposable around the guidewire and the filter. The retrieval catheter is used to collapse the filter, to remove the filter from the guidewire, and to withdraw the filter from the lumen of the vessel. The guidewire position is thus maintained, to complete the interventional procedure. 
   An advantage of the present invention is that the filter is delivered to the guidewire after the low profile guidewire has been used to gain access to the interventional site, thereby facilitating access to the site through tortuous anatomy. Another advantage of the present invention is that a full filter may be collapsed and retrieved without removing the guidewire, thereby allowing the operator to maintain guidewire position if the interventional procedure is incomplete. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be apparent upon consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which the reference characters refer to like parts throughout, and in which: 
       FIG. 1  illustrates an enlarged, cross-sectional view of an exemplary embodiment of the low profile vascular filter system, with the filter in the collapsed position, in accordance with the present invention. 
       FIG. 2  illustrates an enlarged, partial, cross-sectional view of an exemplary embodiment of the filter of the low profile vascular filter system, with the filter in the open position, in accordance with the present invention. 
       FIG. 3  illustrates an enlarged, partial, cross-sectional view of an exemplary embodiment of the guidewire of the low profile vascular filter system, in accordance with the present invention. 
       FIG. 4  illustrates an enlarged, partial, cross-sectional view of an exemplary embodiment of the filter and guidewire of the low profile vascular filter system, with the filter in the open position, in accordance with the present invention. 
       FIG. 5  illustrates an enlarged, partial, simplified, cross-sectional view of an exemplary embodiment of the proximal basket sleeve and proximal marker of the low profile vascular filter system, in accordance with the present invention. 
       FIG. 6  illustrates an enlarged, partial, cross-sectional view of an exemplary embodiment of the retrieval catheter of the low profile vascular filter system, in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention relates to a low profile vascular filter system for use in percutaneous angioplasty and stenting, and substantially reduces the risk of distal embolization during interventional procedures. The low profile vascular filter system is designed to address the clinical problems of poor pushability and trackability through the vasculature, and loss of guidewire position upon removal of guidewire-based filters. The low profile vascular filter system comprises a guidewire having proximal and distal markers, and a filter deployment and delivery system coaxially disposed around the guidewire. The filter deployment and delivery system comprises an inner member and an outer member, with a filter removably attached near the distal end of the inner member, and proximal and distal basket sleeves attached near the proximal and distal ends of the filter. The low profile vascular system also comprises a retrieval catheter coaxially disposable around the guidewire and the filter. 
     FIG. 1  illustrates an exemplary embodiment of the low profile vascular filter system in accordance with the present invention. In this exemplary embodiment, the low profile vascular filter system comprises a guidewire  7 , and a filter deployment and delivery system  12 , coaxially disposed around the guidewire  7 . The filter deployment and delivery system  12  comprises an outer member  13  and an inner member  15 , with the outer member  13  coaxially disposed around the inner member  15 , and the inner member  15  coaxially disposed around the guidewire  7 . The inner member  15  comprises a filter  1 , removably attached near the distal end of the inner member  15 . The filter  1  is collapsed into and constrained by the distal end of the outer member  13 . 
   As illustrated in  FIG. 2 , the filter  1 , in the exemplary embodiment, comprises a proximal basket sleeve  2  and a distal basket sleeve  6 , and a plurality of struts  3  therebetween to form a filter membrane support structure. The filter  1  further comprises at least one marker  4  attached to at least one strut  3 . The filter  1  further comprises a permeable filter membrane  5  attached near the distal basket sleeve  6  and attached to the plurality of struts  3 , as illustrated in  FIG. 2 . The filter  1  has a smaller first diameter for delivery, as illustrated in  FIG. 1 , and a larger second diameter for deployment, as illustrated in  FIG. 2 . 
   As illustrated in  FIG. 3 , the low profile vascular filter system in this exemplary embodiment comprises a guidewire  7 , having a floppy tip  11 , a distal marker  10  and a proximal marker  9 . These markers  10 ,  9  serve two purposes. First, the markers  10 ,  9  identify the future location of the filter  1 , under fluoroscopy, after the guidewire  7 , without the filter  1 , is inserted into the lumen. Secondly, as illustrated in  FIG. 4 , the distal marker  10  serves as a stop for the distal basket sleeve  6  after the filter has been positioned onto the guidewire  7 . The distal basket sleeve  6  has a diameter greater than the maximum diameter of the proximal marker  9 , but not greater than the maximum diameter of the distal marker  10 . The proximal basket sleeve  2  has a diameter that is not greater than the maximum diameter of the proximal marker  9 . Accordingly, the filter may be positioned between the distal marker  10  and the proximal marker  9 , as illustrated in  FIG. 4 . 
     FIG. 5  illustrates another exemplary embodiment of the present invention, wherein the proximal basket sleeve  2  and a modified proximal marker  9   a  lock together to minimize longitudinal movement of the device, while still allowing rotational movement of the device. The modified proximal marker  9   a  comprises a protruding ridge  9   b  which is engaged by an indentation  9   c  within the proximal basket sleeve  2 . This may minimize movement of the filter  1  within the lumen, thereby avoiding potential vessel damage and/or accidental release of embolic particulates. 
   As illustrated in  FIG. 6 , the exemplary embodiment of the present invention further comprises a retrieval catheter  16 . The retrieval catheter  16  is coaxially disposable around the guidewire  7  ( FIG. 1 ). The distal end  20  of the retrieval catheter  16  has a larger diameter than the body of the retrieval catheter  16 . The distal end  20  of the retrieval catheter  16  may be inserted over the filter  1  ( FIG. 1 ) to capture and collapse the filter  1 , and to remove the filter  1  from the lumen. 
   As illustrated in  FIGS. 1 ,  2 ,  3 ,  4  and  6 , the low profile vascular filter system may be used to introduce a low profile guidewire into the lumen of a vessel, followed by delivery and deployment of a filter to capture embolic particulates released during the procedure. The guidewire and/or filter may then be retrieved and removed from the lumen. The guidewire  7 , as illustrated in  FIG. 3 , may be introduced into the lumen of a vessel through femoral access. The guidewire  7 , with a floppy tip  11 , is positioned past an occlusion in a vessel, with distal marker  10  and proximal marker  9  identifying the future position of the filter under fluoroscopy. Then, as illustrated in  FIG. 1 , the filter deployment and delivery system may be introduced over the guidewire  7  and advanced through the lumen of the vessel. The filter  1  is removably attached near the distal end of the inner member  15 , and the filter  1  assumes a smaller first diameter when collapsed and constrained within the distal end of the outer member  13 . As illustrated in  FIG. 4 , the distal basket sleeve  10  is advanced over the proximal marker  9 , but not the distal marker  10 . In the exemplary embodiment, the distal marker  10  serves as a stop to prevent the filter  1  from advancing distally. The filter  1  is now in position between proximal marker  9  and distal marker  10 , and the outer member  13  may be retracted to allow the filter  1  to achieve its larger second diameter. The inner member  15  may also be retracted, and the filter  1  remains in position on the guidewire. At this point, additional interventional devices, such as balloon catheters and stent delivery systems, may be advanced over the guidewire to complete the interventional procedure. The filter remains in position capturing embolic particulates. Then, the retrieval catheter  16 , as illustrated in  FIG. 6 , may be advanced over the guidewire  7  to collapse and retrieve the filter  1 . If the filter  1  has become filled with embolic particulates, and the procedure is incomplete, the retrieval catheter may retrieve filter  1  only, and allow the guidewire  7  to remain in position for the balance of the procedure. 
   The guidewire  7  may be made from any number of suitable materials, and may preferably be made from stainless steel or Nickel-Titanium alloy. The filter struts  3  may be made from any number of suitable materials, and are preferably made from Nickel-Titanium alloy. The filter markers  4  may be made from any number of suitable materials, and are preferably made from a radiopaque material such as gold, platinum, tantalum, niobium, molybdenum, rhodium, palladium, silver, hafnium, tungsten or iridium. The proximal marker  9  and the distal marker  10  on the guidewire  7  may be made from any number of suitable materials, and are preferably made from radiopaque materials such as gold, platinum, tantalum, niobium, molybdenum, rhodium, palladium, silver, hafnium, tungsten or iridium. The proximal basket sleeve  2  and the distal basket sleeve  6  on the filter  1  may be made from any number of suitable materials, and are preferably made from radiopaque materials such as gold, platinum, tantalum, niobium, molybdenum, rhodium, palladium, silver, hafnium, tungsten or iridium. The filter  1  may also comprise coatings or any other suitable means for enhancing the radiopacity of the device. The permeable filter membrane  5  may be made from any number of suitable materials, and is preferably made from a flexible polymeric material with elastomeric properties including, polyurethane, polyethylene or a co-polymer thereof, as well as combinations thereof. The permeable filter membrane  5  may comprise any number and configuration of openings/holes and preferably comprises openings/holes wherein the hole size is from about twenty to about three hundred microns in diameter. The openings/holes may be created by any suitable means, and may preferably be created by laser drilling. In alternate embodiments, the filter membrane  5  may comprise a porous material rather than manufactured openings/holes. The outer member  13  and the retrieval catheter  16  may be made from any number of suitable materials, and are preferably made from a polymeric material. The inner member  15  may be made from any number of suitable materials, and is preferably made from a polymeric or metallic material. The filter  1  may be removably attached to the inner member  15  by any suitable means, and may preferably be attached via a friction fit or a releasable latch. The permeable filter membrane  5  may be attached to the struts  3  by any suitable means, and may preferably be attached by a bonding or welding process. The struts  3  may be attached to the basket sleeves  2 ,  6  by any suitable means, and may preferably be attached by a bonding or welding process. The filter markers  4  may be attached to the struts by any suitable means, and are preferably attached to the struts by a bonding or welding process. The guidewire distal marker  10  and the guidewire proximal marker  9  may be attached to the guidewire by any suitable means, and are preferably attached to the guidewire by a bonding or welding process. 
   Although shown and described is what is believed to be the most practical and preferred embodiments, it is apparent that departures from specific designs and methods described and shown will suggest themselves to those skilled in the art and may be used without departing from the spirit and scope of the invention. The present invention is not restricted to the particular constructions described and illustrated, but should be constructed to cohere with all modifications that may fall within the scope of the appended claims.