Patent Publication Number: US-2007100372-A1

Title: Embolic protection device having a filter

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims the benefit of U.S. Provisional Application No. 60/732,883 filed on Nov. 2, 2005, entitled “EMBOLIC PROTECTION DEVICE HAVING A FILTER,” the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION  
      The present invention relates to medical devices. In particular, the present invention relates to embolic protection devices for capturing emboli during treatment of a stenotic lesion in a body vessel.  
      Embolic protection to capture emboli within the vasculature is a growing concern in the medical industry. Currently, there are a number of approaches for embolic protection to prevent emboli from traveling within the vasculature to create an undesirable embolism, e.g., pulmonary embolism. For example, filters are more commonly being used for trapping emboli in the filter to prevent pulmonary embolism. Also, anti-platelet agents and anticoagulants may be used to breakdown blood clots. Moreover, snares and baskets (e.g., stone retrieval baskets) are more commonly used for retrieving urinary calculi. Additionally, occlusion coils are commonly used to occlude aneurysms and accumulate thrombi in a body vessel.  
      Treatments for a stenotic lesion provide a potential in releasing blood clots and other thrombi plaque in the vasculature of the patient. One example is the treatment for a carotid artery stenosis. Generally, carotid artery stenosis is the narrowing of the carotid arteries, the main arteries in the neck that supply blood to the brain. Carotid artery stenosis (also called carotid artery disease) is a relatively high risk factor for ischemic stroke. The narrowing is usually caused by plaque build-up in the carotid artery. Plaque forms when cholesterol, fat and other substances form in the inner lining of an artery. This formation process is called atherosclerosis.  
      Depending on the degree of stenosis and the patient&#39;s overall condition, carotid artery stenosis has been treated with surgery. The procedure (with its inherent risks) is called carotid endarterectomy, which removes the plaque from the arterial walls. Carotid endarterectomy has proven to benefit patients with arteries substantially narrowed, e.g., by about 70% or more. For people with less narrowed arteries, e.g., less than about 50%, an anti-clotting drug may be prescribed to reduce the risk of ischemic stroke. Examples of these drugs are anti-platelet agents and anticoagulants.  
      Carotid angioplasty is a more recently developed treatment for carotid artery stenosis. This treatment uses balloons and/or stents to open a narrowed artery. Carotid angioplasty is a procedure that can be performed via a standard percutaneous transfemoral approach with the patient anesthetized using light intravenous sedation. At the stenosis area, an angioplasty balloon is delivered to predilate the stenosis in preparation for stent placement. The balloon is then removed and exchanged via catheter for a stent delivery device. Once in position, a stent is deployed across the stenotic area. If needed, an additional balloon can be placed inside the deployed stent for post-dilation to make sure the struts of the of the stent are pressed firmly against the inner surface of the vessel wall.  
      During the stenosis procedure however, there is a risk of such blood clots and thrombi being undesirably released into the blood flow within the vasculature. Embolic or distal protection devices have been implemented to capture emboli from a stenotic lesion undergoing angioplasty. However, many current embolic protection devices restrict flow when deployed within the vasculature of the patient. Moreover, many embolic protection devices are relatively difficult to collapse and retrieve after the need for such device in the vasculature passes.  
      Thus, there is a need to provide a device and method for distally protecting and capturing emboli within a body lumen during a stenosis procedure, without relatively restricting flow and with relatively easy retrievability.  
     BRIEF SUMMARY OF THE INVENTION  
      The present invention generally provides an embolic protection device that minimizes restricted flow when deployed within the vasculature of a patient and that is relatively easy to retrieve.  
      In one embodiment, the present invention provides an embolic protection device for capturing emboli during treatment of a stenotic lesion in a body vessel. The device comprises a filter and filter portion circumferentially attached to the filter. The filter comprises a plurality of struts having first ends attached together at a center portion along a longitudinal axis. Each strut has an arcuate segment extending from the first end to a second end. The struts are configured to move between an expanded state for engaging with the body vessel and a collapsed state for filter retrieval or delivery. The filter portion is circumferentially attached to the filter at each of the second ends. The filter portion is configured for allowing blood to flow therethrough and for capturing emboli when the filter is in the expanded state.  
      In another embodiment, the present invention provides an embolic protection assembly for capturing emboli during treatment of a stenotic lesion in a body vessel. The assembly comprises a balloon catheter having a tubular body portion and an expandable balloon attached to and in fluid communication with the tubular body portion for angioplasty at the stenotic lesion. The expandable balloon has distal and proximal portions. The assembly further comprises the emboli protection device coaxially disposed within the catheter during treatment of the stenotic lesion in the body vessel.  
      In another example, the present invention provides a method for embolic protection during treatment of stenotic lesion in a body vessel. The method comprises percutaneously introducing the balloon catheter in the body vessel and deploying the embolic protection device in a deployed state downstream from the stenotic lesion to capture emboli during treatment of the stenotic lesion.  
      In yet another example, the embolic capture device comprises a ring attached to the second ends and is configured to expand between the expanded and collapsed states. The filter portion is circumferentially attached to the ring. The filter portion is configured for allowing blood to flow therethrough and for capturing emboli when the filter is in the expanded state.  
      Further objects, features, and advantages of the present invention will become apparent from consideration of the following description and the appended claims when taken in connection with the accompanying drawings.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an environment view of an embolic capture device having a filter in an expanded state in accordance with one embodiment of the present invention;  
       FIG. 2  is a perspective side view of the embolic capture device in  FIG. 1 ;  
       FIG. 3  is another environmental view of the device in the expanded state;  
       FIG. 4  is a side perspective view of the device in the expanded state;  
       FIG. 5  is a side view of the device in a collapsed state within a delivery member;  
       FIG. 6   a  is a side view of an embolic capture assembly for capturing emboli during treatment of a stenotic lesion in a body vessel in accordance with one embodiment of the present invention;  
       FIG. 6   b  is an exploded view of the assembly in  FIG. 6   a;    
       FIG. 7  is a flow chart of one method for capturing emboli during treatment of a stenotic lesion in a body vessel; and  
       FIGS. 8 and 9  are side views of an embolic capture device in accordance with another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      The present invention generally provides an embolic capture device that minimizes restricted flow when deployed within the vasculature of a patient and that is relatively easy to retrieve after the risk of releasing blood clots and thrombi within the vasculature has passed. Embodiments of the present invention generally provide an embolic protection device comprising a filter including a plurality of struts having first ends attached together along a longitudinal axis. In one example, the device further comprises a filter portion made of an extracellular matrix and that is circumferentially attached to the filter at each of the second ends. When deployed in the body vessel, the filter portion opens to an expanded state of the device allowing blood to flow therethrough for capturing emboli. The struts of the filter allow for relatively easy removal from the body vessel. This may be accomplished by distally threading a catheter over the struts until the filter is collapsed within the catheter.  
       FIG. 1  illustrates an embolic protection device  10  for capturing emboli during treatment of a stenotic lesion in a body vessel in accordance with one embodiment of the present invention. As shown in  FIGS. 1 and 2 , the device  10  comprises a filter  12  including a plurality of struts  14  having first ends  20  attached together at a center portion along a longitudinal axis X. In this embodiment, each strut  14  has an arcuate segment  15  extending from the first end  20  to a second end  22 . The arcuate segment  15  may take on any arcuate shape as it extends between the first and second ends.  
      As shown, each arcuate segment  15  has a soft S-shape. Each arcuate segment  15  is formed with a first curved portion that is configured to softly bend away from the longitudinal or central axis of the filter  12  and a second curved portion that is configured to softly bend toward the longitudinal axis of the filter. Due to the soft bends of each arcuate segment  15 , a prominence or a point of inflection on the strut  14  is substantially avoided to aid in non-traumatically engaging the vessel wall. In the expanded state, each arcuate segment  15  extends arcuately along a longitudinal axis and linearly relative to a radial axis from the first end  14  to the anchoring ends. In this embodiment, the struts  14  extend linearly relative to the radial axis and avoid entanglement with other struts.  
      The struts  14  preferably are configured to move between an expanded state for engaging the body vessel and a collapsed state for filter  12  retrieval or delivery. In this embodiment, the filter  12  in the expanded state comprises four primary struts  14 . As shown, the first ends  20  of the struts  14  emanate from a hub  24  that attaches the struts  14  together at the center point. In this embodiment, the struts  14  are preferably formed from wire having a round cross-section. Of course, it is not necessary that the struts  14  have a round or near round cross-section. For example, the struts  14  could take on any shape with arcuate edges to maintain non-turbulent blood flow therethrough.  
      As shown in  FIGS. 3 and 4 , each of the struts  14  terminates at the second or anchoring end  22 . Each of the arcuate segments  15  and the anchoring ends  22  will engage the vessel wall when the filter  12  is deployed at a delivery location in the blood vessel. As shown, the struts  14  are configured to move between a collapsed state for filter delivery and retrieval and an expanded state for engaging the blood vessel and capturing emboli during angioplasty. The filter  12  preferably extends longitudinally as shown in  FIG. 4 , defining the longitudinal axis of the filter  12 . The filter  12  further radially expands and collapses, defining the radial axis of the filter  12 . In this embodiment, the hub  24  houses and attaches the first ends  20  of the struts  14 . The first ends  20  attach at the center point in the hub  24 .  
      Although the embodiments of this device  10  have been disclosed as being constructed from wire having a round cross section, it could also be cut from a tube of suitable material by laser cutting, electrical discharge machining or any other suitable process.  
       FIGS. 3 and 4  illustrate a filter portion  28 , e.g., an extracellular matrix portion. In this embodiment, the filter portion  28  is circumferentially attached to the filter  12  at each of the second ends  22 . The filter portion  28  is configured for allowing blood to flow therethrough and for capturing emboli when the filter  12  is in the expanded state. As shown, the filter portion  28  includes a lip  25  attached to each of the second ends  22  defining an opening of the filter portion when the filter  12  is in the expanded state. The lip  25  extends to a closed end for capturing emboli.  
      The filter portion  28  may be comprised of any suitable material to be used for capturing emboli from the stenotic lesion during treatment thereof. In one embodiment, the filter portion  28  is made of connective tissue material for capturing emboli. In this embodiment, the connective tissue comprises extracellular matrix (ECM). As known, ECM is a complex structural entity surrounding and supporting cells that are found within mammalian tissues. More specifically, ECM comprises structural proteins (e.g., collagen and elastin), specialized protein (e.g., fibrillin, fibronectin, and laminin), and proteoglycans, a protein core to which are attached are long chains of repeating disaccharide units termed of glycosaminoglycans.  
      Most preferably, the extracellular matrix is comprised of small intestinal submucosa (SIS). As known, SIS is a resorbable, acellular, naturally occurring tissue matrix composed of ECM proteins and various growth factors. SIS is derived from the porcine jejunum and functions as a remodeling bioscaffold for tissue repair. SIS has characteristics of an ideal tissue engineered biomaterial and can act as a bioscaffold for remodeling of many body tissues including skin, body wall, musculoskeletal structure, urinary bladder, and also supports new blood vessel growth. In many aspects, SIS is used to induce site-specific remodeling of both organs and tissues depending on the site of implantation. In theory, host cells are stimulated to proliferate and differentiate into site-specific connective tissue structures, which have been shown to completely replace the SIS material in time.  
      In this embodiment, SIS is used to temporarily adhere the filter portion  28  to the walls of a body vessel in which the device  10  is deployed. SIS has a natural adherence or wettability to body fluids and connective cells comprising the connective tissue of a body vessel wall. Due to the temporary nature of the duration in which the device  10  is deployed in the body vessel, host cells of the wall may adhere to the filter portion  28  but not differentiate, allowing for retrieval of the device  10  from the body vessel.  
      In other embodiments, the filter portion may also be made of a mesh cloth, woven nitinol, nylon, polymeric material, teflon, or woven mixtures thereof without falling beyond the scope or spirit of the present invention.  
      In use, the device  10  expands from the collapsed state to the expanded state, engaging the filter  12  with the body vessel. In turn, the lip  25  of the filter portion  28  expands to open the filter portion  28  for capturing emboli during treatment of the stenotic lesion. After a need for such device  10  in the vasculature passes, the device  10  may be easily retrieved. In one embodiment, a catheter may be used to move longitudinally about the filter  12  to engage and move the struts  14  radially inwardly to collapse the device  10 , thereby moving the device  10  toward the collapsed state.  
       FIGS. 6   a  and  6   b  depict an embolic protection assembly  40  for capturing emboli during treatment of a stenotic lesion in a body vessel in accordance with another embodiment of the present invention. As shown, the assembly  40  comprises a balloon catheter  42  having a tubular body  44  and an expandable balloon  46  attached to and in fluid communication with the tubular body  44  for angioplasty at a stenotic lesion. In this embodiment, the assembly  40  comprises the embolic protection device  10  mentioned above. The tubular body  44  is preferably made of soft flexible material such as silicon or any other suitable material. In this embodiment, the balloon catheter  42  may include an outer lumen and an inner lumen. The outer lumen may be in fluid communication with the balloon for inflating and deflating the balloon. The inner lumen may be formed therethrough for percutaneous guidance through the body vessel.  
      As shown, the assembly  40  further includes an inner catheter  50  having a distal end  52  through which the balloon catheter  42  is disposed for deployment in the body vessel. The inner catheter  50  is preferably made of a soft, flexible material such as silicon or any other suitable material. Generally, the inner catheter  50  further has a proximal end  54  and a plastic adaptor or hub  56  to receive the embolic protection device  10  and balloon catheter  42  to be advanced therethrough. The size of the inner catheter  50  is based on the size of the body vessel in which it percutaneously inserts, and the size of the balloon catheter  42 .  
      As shown, the assembly  40  may also include a wire guide  60  configured to be percutaneously inserted within the vasculature to guide the inner catheter  50  to a location adjacent a stenotic lesion. The wire guide  60  provides the inner catheter  50  (and balloon catheter  42 ) a path during insertion within the body vessel. The size of the wire guide  60  is based on the inside diameter of the inner catheter  50 .  
      In one embodiment, the balloon catheter  42  has a proximal fluid hub  62  in fluid communication with the balloon via the outer lumen for fluid to be passed therethrough for inflation and deflation of the balloon during treatment of the stenotic lesion. The embolic protection device  10  is preferably coaxially disposed through the inner lumen of the balloon catheter  42  prior to treatment of the stenotic lesion in the body vessel. The distal protection device  10  may be guided through the inner lumen preferably from the hub and distally beyond the balloon of the balloon catheter  42 , exiting from the distal end  52  of the balloon catheter  42  to a location within the vasculature downstream of the stenotic lesion.  
      In this embodiment, the assembly further includes a polytetrafluoroethylene (PTFE) introducer sheath  64  for percutaneously introducing the wire guide  60  and the inner catheter  50  in a body vessel. Of course, any other suitable material may be used without falling beyond the scope or spirit of the present invention. The introducer sheath  64  may have any suitable size, e.g., between about three-french to eight-french. The introducer serves to allow the inner and balloon catheters to be percutaneously inserted to a desired location in the body vessel. The introducer sheath  64  receives the inner catheter  50  and provides stability to the inner catheter  50  at a desired location of the body vessel. For example, the introducer sheath  64  is held stationary within a common visceral artery, and adds stability to the inner catheter  50 , as the inner catheter  50  is advanced through the introducer sheath  64  to a dilatation area in the vasculature.  
      When the distal end  52  of the inner catheter  50  is at a location downstream of the dilatation area in the body vessel, the balloon catheter  42  is inserted therethrough to the dilatation area. The device  10  is preferably loaded through the proximal end of the balloon catheter  42  to a location therein adjacent the expandable balloon  46 . The balloon catheter  42  is then advanced through the inner catheter  50  for deployment through its distal end  52 . In this embodiment, when the device  10  is passed through the dilatation area, the device may be deployed downstream of the stenotic lesion.  
      It is understood that the assembly described above is merely one example of an assembly that may be used to deploy the embolic protection device in the body vessel. Of course, other apparatus, assemblies and systems may be used to deploy any embodiment of the embolic protection device without falling beyond the scope or spirit of the present invention.  
       FIG. 7  illustrates a flow chart depicting one method  110  for capturing emboli during treatment of a stenotic lesion in a body vessel, implementing the assembly mentioned above. The method comprises percutaneously introducing a balloon catheter having an expandable balloon for angioplasty of the stenotic lesion in the body vessel in box  112 . Introduction of the balloon catheter may be performed by any suitable means or mechanism. As mentioned above, an introducer sheath and a wire guide may be used to provide support and guidance to the balloon catheter. For example, the wire guide may be percutaneously inserted through the introducer sheath to the stenotic lesion in the body vessel. The inner catheter and balloon catheter may then be place over the wire guide for percutaneous guidance and introduction to the stenotic lesion.  
      The method  110  further comprises disposing the embolic protection device coaxially within the balloon catheter in box  114 . The device may be disposed coaxially within the balloon catheter before or after percutaneous insertion of the balloon catheter. For example, once the balloon catheter is placed at the stenotic lesion, the wire guide may be removed therefrom, and the device may then be disposed within the balloon catheter for guidance and introduction in the body vessel. In this example, the expandable balloon is positioned at the stenotic lesion and the device, in its collapsed state, is disposed through the distal end of the balloon catheter downstream from the expandable balloon.  
      The method  110  further includes deploying the device in a deployed state downstream from the stenotic lesion to capture emboli during treatment of the stenotic lesion in box  116 . In the expanded state, the open end of the filter portion is expanded to a proximally facing concave shape for capturing emboli during angioplasty.  
      The method may further include treating the stenotic lesion in the body vessel with the balloon catheter. In this example, the expandable balloon may be injected with saline and expanded for predilatation. As desired, additional balloon catheters may be used for pre-dilatation treatment, primary dilatation treatment, and post-dilatation treatment of the stenotic lesion while the device is in its expanded state within the body vessel.  
       FIGS. 8 and 9  illustrate an embolic capture device  210  in accordance with another embodiment of the present invention. As shown, the device  210  comprises components similar to the components of the device  10  shown in  FIGS. 2 and 4 . For example, the filter  212  including struts  214 , arcuate segment  215 , first ends  220 , second ends  222 , and hub  224  of  FIGS. 8 and 9  are similar to filter  12  including struts  14 , arcuate segment  15 , first ends  20 , second ends  22 , and hub  24  of  FIGS. 2 and 4 . As shown, each of the second ends  222  has an anchoring hook  223  extending therefrom. In the expanded state, each anchoring hook  223  is configured to engage the wall of a body vessel, thereby lessening the chance of migration of the device  210 . The device  210  further comprises a ring  230  that is attached to the second ends  222 , allowing the anchoring hooks  223  to distally extend therefrom. In this embodiment, the ring  230  is configured to be collapsible in the collapsed state and expandable in the expanded state of the device  210 . This may be accomplished by any suitable manner. For example, the ring may be comprised of superelastic material such as Nitinol, thereby allowing the ring to collapse when the device is collapsed and to expand when the device is expanded.  
      As shown, the device  210  further comprises a filter portion  228  having a lip  225  circumferentially attached to the ring  230 . The filter portion  228  may be attached to the ring by any suitable means including thermal bonding and sonic bonding. The filter portion is configured for allowing blood to flow therethrough and for capturing emboli when the filter  212  is in the expanded state.  
      The filter  12  may be comprised of any suitable material such as a superelastic material, stainless steel wire, cobalt-chromium-nickel-molybdenum-iron alloy, or cobalt-chrome alloy. It is understood that the filter  12  may be formed of any other suitable material that will result in a self-opening or self-expanding filter, such as shape memory alloys. Shape memory alloys have a property of becoming rigid, that is, returning to a remembered state, when heated above a transition temperature. A shape memory alloy suitable for the present invention may comprise Ni—Ti available under the more commonly known name Nitinol. When this material is heated above the transition temperature, the material undergoes a phase transformation from martensite to austenic, such that material returns to its remembered state. The transition temperature is dependent on the relative proportions of the alloying elements Ni and Ti and the optional inclusion of alloying additives.  
      In one alternate embodiment, the filter  12  may be made from Nitinol with a transition temperature that is slightly below normal body temperature of humans, which is about 98.6° F. Although not necessarily a preferred embodiment, when the filter  12  is deployed in a body vessel and exposed to normal body temperature, the alloy of the filter  12  will transform to austenite, that is, the remembered state, which for one embodiment of the present invention is the expanded configuration when the filter  12  is deployed in the body vessel. To remove the filter  12 , the filter  12  is cooled to transform the material to martensite which is more ductile than austenite, making the filter  12  more malleable. As such, the filter  12  can be more easily collapsed and pulled into a lumen of a catheter for removal.  
      In another alternate embodiment, the filter  12  may be made from Nitinol with a transition temperature that is above normal body temperature of humans, which is about 98.6° F. Although not necessarily a preferred embodiment, when the filter  12  is deployed in a body vessel and exposed to normal body temperature, the filter  12  is in the martensitic state so that the filter  12  is sufficiently ductile to bend or form into a desired shape, which for the present invention is an expanded configuration. To remove the filter  12 , the filter  12  is heated to transform the alloy to austenite so that the filter  12  becomes rigid and returns to a remembered state, which for the filter  12  in a collapsed configuration.  
      While the present invention has been described in terms of preferred embodiments, it will be understood, of course, that the invention is not limited thereto since modifications may be made to those skilled in the art, particularly in light of the foregoing teaching.