Patent Publication Number: US-8123779-B2

Title: Embolic protection device

Description:
RELATED APPLICATIONS 
     This application is a continuation application of U.S. application Ser. No. 10/331,380 filed Dec. 30, 2002, now U.S. Pat. No. 7,625,389. 
    
    
     FIELD OF THE INVENTION 
     The present invention pertains to intravascular filtering devices. More particularly, the present invention pertains to devices for filtering embolic debris generated during intravascular medical interventions. 
     BACKGROUND 
     Heart and vascular disease are majors problem in the United States and throughout the world. Conditions such as atherosclerosis result in blood vessels becoming blocked or narrowed. This blockage can result in lack of oxygenation of the heart, which has significant consequences since the heart muscle must be well oxygenated in order to maintain its blood pumping action. 
     Occluded, stenotic, or narrowed blood vessels may be treated with a number of relatively non-invasive medical procedures including percutaneous transluminal angioplasty (PTA), percutaneous transluminal coronary angioplasty (PTCA), and atherectomy. 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 of 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. 
     During angioplasty and atherectomy procedures, embolic debris can be separated from the wall of the blood vessel. 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. 
     Embolic debris can also be generated when performing an intravascular procedure at a location away from the heart. For example, engaging or treating the renal artery may generate embolic debris. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention incorporates design and manufacturing refinements to embolic protection devices. In some embodiments, a filter can be coupled to an elongate shaft. The shaft may comprise, for example, a guidewire. A proximal stop may be coupled to the shaft. The stop may be adapted and configured to essentially prevent a catheter from passing over the shaft distally beyond the stop and over the filter. The stop may also be configured to release therapeutic drugs or other appropriate substances. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of an embodiment of an embolic protection filtering device; and 
         FIG. 2  is a side view of another embodiment of an embolic protection filtering device. 
     
    
    
     DETAILED DESCRIPTION 
     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 illustrate example embodiments of the claimed invention. 
     Intravascular medical procedures such as angioplasty or atherectomy can generate embolic debris. This debris can travel in the bloodstream and possibly obstruct downstream vascular regions.  FIG. 1  is a side view of an embodiment of an embolic protection filtering device  10  that may be used to filter out embolic debris. Device  10  includes an elongate shaft  12  having a filter  14  coupled thereto. A proximal stop  16  is coupled to shaft  12 . Stop  16  is adapted and configured to stop a medical device such as a therapeutic catheter  117  from being advanced over shaft  12  beyond stop  16 . Stop  16 , thus, can prevent the medical device from being advanced distally over filter  14 . In some embodiments, the distal end of the lumen defined by the medical device is capable of passing at least partially over the filter and is not capable of passing beyond the stop. A therapeutic catheter might be, for example, an angioplasty catheter, stent deployment catheter, atherectomy catheter or other device. 
     The majority of the length of shaft  12  can generally have a constant outside diameter, shown in  FIG. 1  as OD 1 . OD 1  is sized to allow other medical devices to pass over shaft  12  as needed for any given intervention. For example, an angioplasty or other catheter may be passed over shaft  12  in order to perform a medical procedure. According to this embodiment, shaft  12  can pass through a lumen disposed within the catheter. It can be appreciated that the size of OD 1  can be varied for different medical devices without departing from the spirit of the invention. For example, OD 1  may be about 0.014 inches or less. It is worthy of note that shaft  12  may include a region that tapers distally. The tapered region would, thus, have a decreased outside diameter. Generally, OD 1  is the outside diameter of shaft  12  at locations proximal to the tapered region. 
     When using typical guidewire/filter combinations, the potential exists that a catheter may be advanced over or past the filter. If this occurs, the interventional device may engage the proximal end of the filter and close it inadvertently and/or cause jamming of the devices together. Stop  16  has an outside diameter OD 2  that is generally larger than OD 1 . In particular, OD 2  of stop  16  is designed to be large enough to substantially prevent medical devices passing over shaft  12  from passing over and/or damaging filter  14 . For example, OD 2  may be about 0.026 inches or less. 
     In general, a size relationship exists between OD 1 , OD 2 , and the inside diameter of a medical device to passed over shaft  12 . Thus, the inside diameter of the medical device is sized to be larger than OD 1  so that the medical device can be advanced over shaft  12 . Additionally, OD 2  is sized to be larger than the inside diameter of the medical device so that the medical device cannot pass stop  16 . The relative sizes are configured so that OD 2  is the largest (e.g., about 0.022 to 0.030 inches), the inside diameter of the medical device is next largest (e.g., about 0.013 to 0.022 inches), and OD 1  is the smallest (e.g., about 0.010 to 0.016 inches). It can be appreciated that the actual sizes of these elements are not intended to limit the invention and can be varied without altering the contemplated scope of the invention. 
     As stated above, stop  16  is coupled to shaft  12 . Being coupled to shaft  12  is understood to include being directly attached to shaft  12 , being attached to another device disposed adjacent shaft  12  (e.g., tube  18  as described below), or any other suitable attachment. Stop  16  may be coupled to shaft  12  by any suitable technique. For example, stop  16  may be coupled to shaft  12  by adhesive bonding, thermal bonding, soldering, etc. Stop  16  may be comprised of any suitable material. In some embodiments, stop  16  is comprised of a polymer, metal, or metal-polymer composite. Alternatively, stop  16  may be comprised of or be plated with a radiopaque material. Radiopaque materials are understood to generally produce a relatively bright image on a fluoroscopy screen during a medical procedure. This relatively bright image aids the user of device  10  in determining its location. Radiopaque materials include, but are not limited to, gold, platinum, and plastic material loaded with a radiopaque filler. 
     In some embodiments, filter  14  is coupled to a tube  18  slidably disposed over shaft  12 . Tube  18  is adapted and configured to allow filter  14  to be advanced over shaft  12  to a desired location. Tube  18  may be held in position by a first stop  20  (e.g., located near the distal end  22  of shaft  12 ), and a second stop  24  (e.g., generally located proximally of first stop  20 ). In some embodiments, stop  16  may be attached to tube  18 . 
     Stop  16  and/or filter  14  may be adapted and configured to delivery a pharmacological agent. For example, stop  16  may be coated with pharmacological agent such that stop  16  will elute or release the agent. Alternatively, the agent could be releasably encapsulated within stop  16  so that the agent can be released over a period of time within the bloodstream. In another alternative, shaft  12  or another elongate shaft or other suitable element may physically alter stop  16  (e.g., by stimulation with force, electrical current, heat, etc.) so as to cause the agent to be released. Moreover, the physical means for releasing the agent may be controllable by the clinician so that the clinician can release the agent at any desired point in time. 
     A number of different pharmacological agents may be used in conjunction with stop  16 . The therapeutic agent may be generally described as a drug, chemotherapeutic, antibiotic, etc. Additionally, the pharmacological agent may include anti-thrombogenic agents such as heparin, heparin derivatives, urokinase, and PPack (dextrophenylalanine proline arginine chloromethylketone); anti-proliferative agents such as enoxaprin, angiopeptin, or monoclonal antibodies capable of blocking smooth muscle cell proliferation, hirudin, and acetylsalicylic acid; anti-inflammatory agents such as dexamethasone, prednisolone, corticosterone, budesonide, estrogen, sulfasalazine, and mesalamine; antineoplastic/antiproliferative/anti-miotic agents such as paclitaxel, 5-fluorouracil, cisplatin, vinblastine, vincristine, epothilones, endostatin, angiostatin and thymidine kinase inhibitors; anesthetic agents such as lidocaine, bupivacaine, and ropivacaine; anti-coagulants such as D-Phe-Pro-Arg chloromethyl keton, an RGD peptide-containing compound, heparin, antithrombin compounds, platelet receptor antagonists, anti-thrombin anticodies, anti-platelet receptor antibodies, aspirin, prostaglandin inhibitors, platelet inhibitors and tick antiplatelet peptides; vascular cell growth promotors such as growth factor inhibitors, growth factor receptor antagonists, transcriptional activators, and translational promotors; vascular cell growth inhibitors such as growth factor inhibitors, growth factor receptor antagonists, transcriptional repressors, translational repressors, replication inhibitors, inhibitory antibodies, antibodies directed against growth factors, bifunctional molecules consisting of a growth factor and a cytotoxin, bifunctional molecules consisting of an antibody and a cytotoxin; and cholesterol-lowering agents; vasodilating agents; agents which interfere with endogenous vascoactive mechanisms; anti-sense DNA and RNA; and DNA coding for (and the corresponding proteins) anti-sense RNA, tRNA or rRNA to replace defective or deficient endogenous molecules, angiogenic factors including growth factors such as acidic and basic fibroblast growth factors, vascular endothelial growth factor, epidermal growth factor, transforming growth factor α and β, platelet-derived endothelial growth factor, platelet-derived growth factor, tumor necrosis factor α, hepatocyte growth factor and insulin like growth factor, cell cycle inhibitors including CD inhibitors, thymidine kinase (“TK”) and other agents useful for interfering with cell proliferation, and the family of bone morphogenic proteins (“BMP&#39;s”) including BMP-2, BMP-3, BMP-4, BMP-5, BMP-6 (Vgr-1), BMP-7 (OP-1), BMP-8, BMP-9, BMP-10, BMP-11, BMP-12, BMP-13, BMP-14, BMP-15, BMP-16, “hedgehog” proteins. 
     Shaft  12  includes a proximal end  26  and distal end  22 . Shaft  12  may comprise any elongate medical device such as a guidewire, catheter (guide, diagnostic, or therapeutic), endoscopic device, arthroscopic device, etc. Shaft  12  can be made of any material suitable including metals, metal alloys, polymers, or the like, or combinations or mixtures thereof. Some examples of suitable metals and metal alloys include stainless steel, such as 304v stainless steel, nickel-titanium alloy, such as nitinol, nickel-chromium alloy, nickel-chromium-iron alloy, cobalt alloy, or the like, or other suitable material. The word nitinol was coined by a group of researchers at the United States Naval Ordinance Laboratory (NOL) who were the first to observe the shape memory behavior of this material. The word nitinol is an acronym including the chemical symbol for nickel (Ni), the chemical symbol for titanium (Ti), and an acronym identifying the Naval Ordinance Laboratory (NOL). 
     The entire shaft  12  can be made of the same material, or in some embodiments, can include portions or sections made of different materials. In some embodiments, the material used to construct shaft  12  is chosen to impart varying flexibility and stiffness characteristics to different portions of shaft  12 . For example, the material composition adjacent proximal end  26  of shaft  12  may be relatively stiff for pushability and torqueability, and the material composition adjacent distal end  22  of shaft  12  may be relatively flexible by comparison for better lateral trackability and steerability. Relatively stiff materials, for example, may include straightened 304v stainless steel wire, and relatively flexible materials may include, for example, a straightened super elastic or linear elastic alloy (e.g., nickel-titanium) wire. In addition, shaft  12  may generally taper near distal end  22 . 
     Shaft  12  may also include a distal tip  28 . Distal tip  28  may comprise a “spring tip” or “floppy tip” similar to analogous tips known in the art. For example, distal tip  28  may comprise a coil or spring that helps make distal end  22  generally atraumatic to blood vessel walls, body organs, and tissue when advancing device  10  through the vasculature. 
     Filter  14  and/or tube  18  may be disposed near distal end  22  of shaft  12 . Filter  14  may generally comprise a number of configurations known to those skilled in the appropriate art. Filter  14  may include a filter frame  30 , a filter material  32  disposed over frame  30 , and one or more struts  34 . In general, filter  14  operates between a first generally collapsed configuration and a second generally expanded configuration for collecting debris in a body lumen. Frame  30  may be comprised of a “self-expanding” shape-memory material such as nickel-titanium alloy (to bias filter  14  to be in the second expanded configuration). Filter material  32  may be comprised of a polyurethane sheet and include at least one opening that may be, for example, formed by known laser techniques. The holes or openings are sized to allow blood flow therethrough but restrict flow of debris or emboli floating in the body lumen or cavity. 
     Strut  34  may be coupled to tube  18  (or shaft  12 ) by a coupling  36 . Coupling  36  may be one or more windings of strut  34  about tube  18  (or shaft  12 ) or be a fitting disposed over an end of strut  34  to attach it to tube  18 . 
     The position of stop  16  can be described as being generally adjacent filter  14 . In some embodiments, stop  16  is disposed proximally of a nose cone  38  coupled to tube  18 . Stop  16  is generally located proximally of filter  14  but, as described above, could also be described as being attached to shaft  12 , attached to tube  18 , etc. 
       FIG. 2  is a side view of another example embolic protection filtering device  110  that is essentially the same in form and function as device  10  except that the position of stop  116  is altered. It can be seen in  FIG. 2  that stop  16  is positioned just proximal of coupling  36 . This position may allow, for example, filter  114  to collapse to a lower profile. It can be appreciated that the precise location of stop  116  may be altered to essentially any location proximal of the distal end of filter  114  without departing from the spirit of the invention. For example, stop  116  may be attached to shaft  12 , attached to tube  18 , etc. Stop  116  has an OD 2  similar to stop  16  and is designed to be large enough to substantially prevent medical devices passing over shaft  12  from engaging the proximal end of the filter and close it inadvertently and/or cause jamming of the devices together. 
     From  FIG. 2  it can also be seen that the dimensions of device  110  (or device  10 ) and components thereof may be altered. For example, filter  114  has a shape that is more elongated than filter  14 . In general, the length of filter  14 / 114  (measured from the distal end to strut  34 ) may range from about 10 to 30 millimeters. Additionally, the length of distal tip  28  may be varied (e.g., between about 15-40 millimeters), the spacing between filter  14 / 114  and stop  16 / 116  may be varied (e.g., between about 5 to 15 millimeters), the spacing between distal tip  28  and first stop  20  may be varied (e.g., between about 0 to 5 millimeters), and the spacing between the distal end of tip  28  and the proximal end (e.g., at the junction of filter  14 / 114  or at the junction of frame  30  and strut  34 ) of filter  14 / 114  may be varied (e.g., between about 45 and 60 millimeters). The shapes, lengths, and dimensions listed above are provided as examples, and should not be interpreted to limit the claimed invention. 
     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.