Abstract:
Devices, systems and methods are provided for performing intra-lumenal medical procedures in a desired area of the body. Thrombectomy systems and methods of performing medical procedures to re-establish the intravascular flow of blood are provided for the treatment of ischemic disease states.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Prov. Ser. 61/525,362 filed Aug. 19, 2011 which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The field of intralumenal therapy for the treatment of vascular disease states has for many years focused on the use of many different types of therapeutic devices. While it is currently unforeseeable that one particular device will be suitable to treat all types of vascular disease states, it may however be possible to reduce the number of devices used for some disease states while at the same time improve patient outcomes at a reduced cost. To identify potential opportunities to improve the efficiency and efficacy of the devices and procedures it is important for one to understand the state of the art relative to some of the more common disease states. 
     For instance, one aspect of cerebrovascular disease in which the wall of a blood vessel becomes weakened. Under cerebral flow conditions the weakened vessel wall forms a bulge or aneurysm which can lead to symptomatic neurological deficits or ultimately a hemorrhagic stroke when ruptured. Once diagnosed a small number of these aneurysms are treatable from an endovascular approach using various embolization devices. These embolization devices include detachable balloons, coils, polymerizing liquids, gels, foams, stents and combinations thereof. 
     The most widely used embolization devices are detachable embolization coils. These coils are generally made from biologically inert platinum alloys. To treat an aneurysm, the coils are navigated to the treatment site under fluoroscopic visualization and carefully positioned within the dome of an aneurysm using sophisticated, expensive delivery systems. Typical procedures require the positioning and deployment of multiple embolization coils which are then packed to a sufficient density as to provide a mechanical impediment to flow impingement on the fragile diseased vessel wall. Some of these bare embolization coil systems have been describe in U.S. Pat. No. 5,108,407 to Geremia, et al., entitled, “Method And Apparatus For Placement Of An Embolic Coil” and U.S. Pat. No. 5,122,136 to Guglielmi, et al., entitled, “Endovascular Electrolytically Detachable Guidewire Tip For The Electroformation Of Thrombus In Arteries, Veins, Aneurysms, Vascular Malformations And Arteriovenous Fistulas.” These patents disclose devices for delivering embolic coils at predetermined positions within vessels of the human body in order to treat aneurysms, or alternatively, to occlude the blood vessel at a particular location. Many of these systems, depending on the particular location and geometry of the aneurysm, have been used to treat aneurysms with various levels of success. One drawback associated with the use of bare embolization coils relates to the inability to adequately pack or fill the aneurysm due to the geometry of the coils which can lead to long term recanalization of the aneurysm with increased risk of rupture. 
     Some improvements to bare embolization coils have included the incorporation of expandable foams, bioactive materials and hydrogel technology as described in the following U.S. Pat. No. 6,723,108 to Jones, et al., entitled, “Foam Matrix Embolization Device”, U.S. Pat. No. 6,423,085 to Murayama, et al., entitled, “Biodegradable Polymer Coils for Intraluminal Implants” and U.S. Pat. No. 6,238,403 to Greene, et al., entitled, “Filamentous Embolic Device with Expansible Elements.” While some of these improved embolization coils have been moderately successful in preventing or reducing the rupture and re-rupture rate of some aneurysms, the devices have their own drawbacks. For instance, in the case of bioactive coils, the materials eliciting the biological healing response are somewhat difficult to integrate with the coil structure or have mechanical properties incompatible with those of the coil making the devices difficult to accurately position within the aneurysm. In the case of some expandable foam and hydrogel technology, the expansion of the foam or hydrogel is accomplished due to an interaction of the foam or hydrogel with the surrounding blood environment. This expansion may be immediate or time delayed but is generally, at some point, out of the control of the physician. With a time delayed response the physician may find that coils which were initially placed accurately and detached become dislodged during the expansion process leading to subsequent complications. 
     For many aneurysms, such as wide necked or fusiform aneurysms the geometry is not suitable for coiling alone. To somewhat expand the use of embolization coils in treating some wide necked aneurysms, stent like scaffolds have been developed to provide support for coils. These types of stent like scaffolds for use in the treatment of aneurysms have been described in U.S. Pat. No. 6,605,111 to Bose et al., entitled, “Endovascular Thin Film Devices and Methods for Treating Strokes” and U.S. Pat. No. 6,673,106 to Mitelberg, et al., entitled, “Intravascular Stent Device”. While these stent like devices have broadened the types of aneurysms amenable to embolization therapy, utilization of these devices in conjunction with embolization devices is technically more complex for the physician, may involve more risk to the patient and have a substantial cost increase for the healthcare system. 
     To further expand the types of aneurysm suitable for interventional radiological treatment, improved stent like devices have been disclosed in U.S. Pat. No. 5,824,053 to Khosravi et al., entitled, “Helical Mesh Endoprosthesis and Method”, U.S. Pat. No. 5,951,599 to McCrory, entitled, “Occlusion System for the Endovascular Treatment of and Aneurysm” and U.S. Pat. No. 6,063,111 to Hieshima et al., entitled, “Stent Aneurysm Treatment System and Method.” When placed across the neck of an aneurysm the proposed stent like devices purport to have a sufficient density through the wall of the device to reduce flow in the aneurysm allowing the aneurysm to clot, while at the same time having a low enough density through the wall to allow small perforator vessels adjacent to the aneurysm to remain patent. Stent devices of this nature while having the potential to reduce treatment costs have not been realized commercially due to the difficulty in manufacturing, reliability in delivering the devices to the treatment site and an inability to properly position the denser portion of the stent device accurately over the neck of the aneurysm. 
     Another cerebrovascular disease state is ischemia resulting from reduced or blocked arterial blood flow. The arterial blockage may be due to thrombus, plaque, foreign objects or a combination thereof. Generally, soft thrombus created elsewhere in the body (for example due to atrial fibrillation) that lodges in the distal cerebrovasculature may be disrupted or dissolved using mechanical devices and or thrombolytic drugs. While guidewires are typically used to disrupt the thrombus, some sophisticated thrombectomy devices have been proposed. For instance U.S. Pat. No. 4,762,130 to Fogarty et al., entitled, “Catheter with Corkscrew-Like Balloon”, U.S. Pat. No. 4,998,919 of Schepp-Pesh et al., entitled, “Thrombectomy Apparatus”, U.S. Pat. No. 5,417,703 to Brown et al., entitled “Thrombectomy Devices and Methods of Using Same”, and U.S. Pat. No. 6,663,650 to Sepetka et al., entitled, “Systems, Methods and Devices for Removing Obstructions from a Blood Vessel” discloses devices such as catheter based corkscrew balloons, baskets or filter wires and helical coiled retrievers. Commercial and prototype versions of these devices have shown only marginal improvements over guidewires due to an inability to adequately grasp the thrombus or to gain vascular access distal to the thrombus (i.e. distal advancement of the device pushes the thrombus distally). 
     Plaque buildup within the lumen of the vessel, known as atherosclerotic disease, is not generally responsive to thrombolytics or mechanical disruption using guidewires. The approach to the treatment of neurovascular atherosclerotic disease has been to use modified technology developed for the treatment of cardiovascular atherosclerotic disease, such as balloons and stents, to expand the vessel at the site of the lesion to re-establish blood flow. For instance, U.S. Pat. No. 4,768,507 to Fischell et al., entitled, “Intravascular Stent and Percutaneous Insertion Catheter System for the Dilation of an Arterial Stenosis and the Prevention of Arterial Restenosis” discloses a system used for placing a coil spring stent into a vessel for the purposes of enhancing luminal dilation, preventing arterial restenosis and preventing vessel blockage resulting from intimal dissection following balloon and other methods of angioplasty. The coil spring stent is placed into spiral grooves on an insertion catheter. A back groove of the insertion catheter contains the most proximal coil of the coil spring stent which is prevented from springing radially outward by a flange. The coil spring stent is deployed when an outer cylinder is moved proximally allowing the stent to expand. Other stent systems include those disclosed in U.S. Pat. No. 4,512,338 to Balko, et al., entitled, “Process for Restoring Patency to Body Vessels”, U.S. Pat. No. 5,354,309 to Schnepp Pesch et al., entitled, “Apparatus for Widening a Body Cavity” and U.S. Pat. No. 6,833,003 to Jones et al., entitled, “Expandable Stent and Delivery System”. While the aforementioned devices may have the ability to access the cerebrovasculature, they lack sufficient structural coverage of the lesion to achieve the desired patency of the vessel without the use of a balloon device. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present invention there is provided a medical device system for restoring patency of a body lumen in a mammal. The thrombectomy system includes a thrombectomy catheter having proximal and distal ends including a proximal hub, a balloon member having proximal and distal ends, including a longitudinally extending portion and a radially expanding retrieval portion, where the balloon member proximal end is coupled to the catheter distal end and an inflation source member coupled to the proximal hub. The extending portion of the balloon member has an inflated diameter which is smaller than the inflated diameter of the retrieval portion. An elongate tether member is positioned within the catheter lumen and preferably coupled to the balloon member distal end. The tether member extends proximally through the thrombectomy catheter lumen and proximal to the proximal end of the hub assembly. 
     For delivery to a desired target site, the balloon member is everted and positioned within the lumen of the thrombectomy catheter such that the distal end of the balloon member is proximal to the distal end of the catheter. The balloon member of the delivery catheter is typically formed of a thin walled polymeric tube in which the distal end of the tube has been enlarged and sealed and the proximal end of the balloon member is coupled to the distal end of the catheter such that the lumen of the catheter is in fluid communication with the interior surface of the balloon. The balloon member is preferably formed of a high strength non-compliant polymeric material such as nylon, polyester and others, however, metallic materials such as thin-film nitinol or other alloys may also be suitable. The inflation source member is coupled to the proximal end of the catheter and used to apply fluid pressure to the lumen of catheter at a level sufficient to cause the balloon member extending portion to extend longitudinally from the catheter lumen and subsequently deploy and expand the capture portion of the balloon member. The preferred fluids include liquids such as saline although gases such as carbon dioxide gas may be suitable for some system configurations. The amount of fluid pressure required to inflate the balloon member is related to the friction force between the balloon member inner surface and the interior wall of the catheter lumen. The inflation source member preferably takes the form of a syringe (threaded or non-threaded), however other inflation sources such as a pressurized fluid source having a valve assembly or a controllable fluid delivery pump are also suitable. 
     In accordance with another aspect of the present invention there is provided a balloon member for a thrombectomy system having a longitudinally extending portion formed of a non-compliant material and a radially expanding retrieval portion formed of a compliant material. Suitable compliant materials include polymeric elastomers such as silicones, urethanes, polyether block amide (PEBAX) and synthetic rubbers including polyisoprene, nitrile, chloroprene and ethylene propylene diene rubber. 
     In accordance with another aspect of the present invention there is provided a balloon member for a thrombectomy system having a longitudinally extending portion and a radially expanding retrieval portion coupled to a thrombectomy catheter where the inflated diameter of the extending portion is larger than the outer diameter of the thrombectomy catheter. 
     In accordance with another aspect of the present invention there is provided a balloon member for a thrombectomy system having a longitudinally extending portion and a radially expanding retrieval portion coupled to a thrombectomy catheter where the inflated diameter of the extending portion is smaller than the outer diameter of the thrombectomy catheter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partial cross-sectional view of a thrombectomy system according to an embodiment of the present invention. 
         FIG. 2A  is an enlarged partial cross-sectional view of the distal end of the thrombectomy system according to an embodiment of the present invention. 
         FIG. 2B  is an enlarged partial cross-sectional view of the distal end of a thrombectomy system according to another embodiment of the present invention. 
         FIG. 3A  is a partial cross sectional view of a deployed thrombectomy system according to an embodiment of the present invention. 
         FIG. 3B  is a partial cross sectional view of a deployed thrombectomy system according to another embodiment of the present invention. 
         FIG. 3C  is a partial cross sectional view of a deployed thrombectomy system according to yet another embodiment of the present invention. 
         FIGS. 4A through 4F  partial cross-sectional views illustrating a method of delivering and deploying a thrombectomy system within a vessel at a target site according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Methods and systems for capturing and removing an embolus or thrombus from an area of the body are herein described. While the terms “thrombectomy” and “thrombus” generally refer to removal of a specific type of embolus, the usage herein should be considered more broadly to include the removal additional types of emboli such as plaque, solid tissue fragments, clots and foreign objects that may block or restrict the normal flow of blood within the vasculature.  FIG. 1  illustrates a thrombectomy system  10  according to an embodiment of the present invention. Thrombectomy system  10  includes an elongate catheter  20  having distal end  22 , proximal end  24  including hub member  26  and lumen  28  extending therethrough. Coupled to distal end  22  of catheter  20  is balloon member  30 . An elongate flexible tether member  32  coupled to balloon member  30  is slidably positioned within lumen  28  and extends through hub member  26 . Balloon member  30  has a delivery configuration in which it is everted and positioned within lumen  28  of catheter  20  at distal end  22 . Proximal end  24  of catheter  20  is coupled to hub member  26  which includes sealable valve  34  and inflation port  36 . 
     A partial cross sectional view of distal end  22  of catheter  20  is shown in  FIG. 2A . While not shown, the construction of catheter  20  may utilize known catheter technologies that incorporate braiding and or coiling using metallic or non-metallic reinforcing filamentous materials to provide high strength while maintaining catheter flexibility. The incorporation of lubricious hydrophilic and or hydrophobic materials on the inner and or outer surface of the catheter is considered to be within the scope of known catheter construction techniques and suitable for use in a thrombectomy system according to embodiments of the present invention. Retaining member  38  is used to affix proximal end  40  of balloon member  30  to catheter distal end  22 . The inner diameter of balloon member proximal end  40  is slightly larger than the outer diameter of catheter distal end  22  thereby allowing distal end  22  to be inserted within proximal end  40 . Retaining member  38  is shown as a flexible filament (preferably polymeric) wound around proximal end  40  and catheter distal end  22  securing balloon member  30  to catheter  20 . Balloon member proximal end  40  and distal end  22  may be secured using other means such as heat fusing, multifilament winds, ultrasonic welding and or gluing to insure a good bond and seal. The distal end  42  of balloon member  30  is completely sealed using any of the aforementioned techniques and positioned everted within catheter lumen  28  proximal to balloon member proximal end  40 . Balloon member  30  includes a proximally located longitudinally extending portion  44  and a distally located radially expanding retrieval portion  50 . 
       FIG. 2B  illustrates an alternate embodiment of the present invention showing thrombectomy system  110 . Thrombectomy system  110  includes an elongate catheter  120  having delivery portion  122  and guidewire portion  124 . Guidewire portion  124  having through lumen  126  extends proximally to the proximal end of catheter  120 . Alternatively guidewire portion  124  and lumen  126  may extend proximally only a portion of the length of catheter  120  and have a configuration suitable for use as a “rapid exchange” system allowing system  110  to reach a target site over a guidewire that has already been positioned at the target site. Delivery portion  122  includes lumen  128  extending from the proximal end to the distal end of catheter  120 . An elongate flexible tether member  132  is coupled to balloon member  130  and extends proximally through catheter lumen  128 . Securing member  138 , shown as a wound filament, affixes balloon member proximal end  140  to the distal end of delivery portion  122 . Balloon member proximal end  140  and the distal end of delivery portion  122  may be secured using other means such as heat fusing, ultrasonic welding, multifilament winds and or gluing to insure a good bond and seal. The distal end  142  of balloon member  130  is completed sealed using any of the aforementioned techniques and positioned everted within catheter lumen  128  proximal to proximal end  140 . 
       FIG. 3A  shows an enlarged partial cross sectional view of the distal portion of thrombectomy system  10  including catheter  20  having distal end  22 . Balloon member  30  is shown in an inflated configuration longitudinally extending distal to catheter distal end  22 . In this configuration, balloon member distal end  42  is positioned distal to balloon member proximal end  40 . Extending portion  44  of balloon member  30  has a diameter slightly smaller than catheter  20  and ranges from about 0.4 to about 0.99 times the diameter of catheter  20  and has a preferred range from about 0.5 to 0.9 times the diameter of catheter  20 . Typically, the expanded diameter of retrieval portion  50  is slightly larger than the inner diameter of the vessel at a target site to insure that the retrieval portion stays in contact with the vessel wall during the thrombus removal process. Balloon member  30  is typically formed of a thin walled polymeric tube having a proximal non-compliant portion defining extending portion  44  coupled to a distal compliant portion defining retrieval portion  50  that has been sealed. The tube portions may be joined using known joining techniques such as, thermal fusing, ultrasonic welding, gluing, and solvent bonding. Suitable materials for the extending portion of balloon member  30  include high strength non-compliant polymeric material such as nylon, polyester and others, however, metallic materials such as thin-film nitinol or other alloys may also be suitable. Suitable materials for the retrieval portion  50  of balloon member  30  includes compliant polymeric elastomers such as silicones, urethanes, polyether block amide (PEBAX) and synthetic rubbers including polyisoprene, nitrile, chloroprene and ethylene propylene diene rubber. 
       FIGS. 3B and 3C  are partial cross sectional views of thrombectomy systems according to alternate embodiments of the present invention that illustrate different configurations of inflated extended balloon members.  FIG. 3B  shows an enlarged partial cross sectional view of the distal portion of thrombectomy system  210  including catheter  220  having distal end  222 . Balloon member  230  is shown in an inflated configuration longitudinally extending distal to catheter distal end  222 . In this configuration, balloon member distal end  242  is positioned distal to balloon member proximal end  240 . Extending portion  244  of balloon member  230  has a diameter slightly smaller than catheter  220  and ranges from about 0.4 to about 0.99 times the diameter of catheter  220  and has a preferred range from about 0.5 to 0.9 times the diameter of catheter  220 . Typically, the expanded diameter of retrieval portion  250  is slightly larger than the inner diameter of the vessel at a target site to insure that the retrieval portion stays in contact with the vessel wall during the thrombus removal process. Balloon member  230  is typically formed of a thin walled polymeric tube in which the distal end of the tube has been enlarged and sealed. Balloon member  230  is preferably formed of a high strength non-compliant polymeric material such as nylon, polyester and others, however, metallic materials such as thin-film nitinol or other alloys may also be suitable. 
       FIG. 3C  shows an enlarged partial cross sectional view of the distal portion of thrombectomy system  310 . Balloon member  330  is shown in an inflated configuration longitudinally extending distal to catheter distal end  322 . In this configuration, balloon member distal end  342  and retrieval portion are positioned distal to balloon member proximal end  340  and extending portion  344 . Extending portion  344  of balloon member  330  has a diameter slightly larger than catheter  320  and ranges from about 1.0 to about 1.5 times the diameter of catheter  320  and has a preferred range from about 1.05 to 1.3 times the diameter of catheter  320 . Typically, the expanded diameter of retrieval portion  350  is slightly larger than the inner diameter of the vessel at a target site to insure that the retrieval portion stays in contact with the vessel wall during the thrombus removal process. Balloon member  330  is typically formed of a thin walled polymeric tube in which the distal end of the tube has been enlarged and sealed. Balloon member  330  is preferably formed of a high strength non-compliant polymeric material such as nylon, polyester and others, however, metallic materials such as thin-film nitinol or other alloys may also be suitable. 
       FIGS. 4A through 4F  illustrate a method of deploying a retrieval assembly at a target site within a body lumen according to one embodiment of the present invention. The thrombectomy system  10  is positioned within a vessel  400 . Catheter distal end  22  including extendable balloon member  30  are positioned at a target site adjacent to thrombus  410 . An inflation source member (not shown) is coupled to the proximal end of the catheter  20  and used to apply fluid pressure to the lumen of catheter. The inflation source member preferably takes the form of a syringe (threaded or non-threaded), however other inflation sources such as a pressurized fluid source having a valve assembly or a controllable fluid delivery pump are also suitable. The preferred fluids include liquids such as saline and radiopaque contrasts solutions however gases such as carbon dioxide gas may be suitable for some system configurations. As the applied fluid pressure increases to a sufficient level, balloon member  30  begins to extend longitudinally from the catheter lumen. As balloon member  30  extends longitudinally from catheter  20 , leading edge  415  of the balloon member  30  may encounter thrombus  410 . While shown as large particle, thrombus  410  may have a varied composition that could comprise organized clot, tissue, plaque soft clot or even foreign objects. Dependant somewhat upon the size and composition of thrombus  410  balloon member  30  may extend longitudinally through a soft and compliant thrombus or between the inner vessel wall and a more rigid thrombus. Leading edge  415  of balloon member  30  is well suited to extend longitudinally between the more rigid thrombus and the vessel wall without perforating the vessel. With continued application of fluid pressure, balloon member  30  continues to extend longitudinally until retrieval  50  is deployed and positioned distal to thrombus  410 . Once retrieval portion  50  is appropriately deployed, application of additional fluid pressure is unnecessary. As shown in  FIG. 4E , thrombectomy system  10  including tether member  32  is pulled proximally causing retrieval portion  50  to engage the distal side of thrombus  410 . Tether member  32  ensures that sufficient retraction force is applied directly to retrieval portion  50  to move thrombus  410 . Thrombectomy system  10  with thrombus  410  may then be removed from the body. Alternatively, thrombectomy system  10  with captured thrombus  410  may be pulled proximally within larger catheter  420  having distal end  422  and lumen  424 . Suction may then be applied to lumen  424  thus aiding retention of thrombus  410  during removal or to fragment and remove thrombus  410 . 
     Novel devices, systems and methods have been disclosed to re-establish flow in a lumen of mammal. Although preferred embodiments of the invention have been described, it should be understood that various modifications including the substitution of elements or components which perform substantially the same function in the same way to achieve substantially the same result may be made by those skilled in the art without departing from the scope of the claims which follow.