Abstract:
A vascular catheter including a radially expandable segment, such as an inflatable balloon, and an expanded distal tip having an increased storage volume is disclosed. The inflatable balloon segment of the catheter may be used to provide traditional balloon angioplasty to a portion of a blood vessel narrowed by stenosis, and the expanded distal tip of the catheter apparatus may be used to safely capture, store, and remove a thromboembolic protection device such as an embolic filter used to catch pieces of plaque and other embolic material dislodged during the balloon angioplasty procedure. The catheter of the present invention provides an effective means for dilating a narrowed portion of a blood vessel, as well as preventing the need for deploying a second catheter system to capture and retrieve the embolic filter. The present invention also greatly reduces the chance for plaque and other thromboembolic material to escape from the embolic filter and enter the patient&#39;s bloodstream.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Serial No. 60/363,310 filed Mar. 12, 2002. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to transluminal angioplasty, and more particularly relates to a vascular catheter for providing balloon angioplasty while at the same time providing improved thromboembolic protection. Methods of utilizing the catheter apparatus to provide balloon angioplasty and thromboembolic protection are also provided.  
         BACKGROUND INFORMATION  
         [0003]    It is common practice today to open occluded (i.e. blocked) or stenotic (i.e. narrowed) blood vessels by inserting a guide wire and then a catheter carrying a balloon shaped segment and inflating the balloon, which exerts a radial force to press stenosis outward against the wall of the blood vessel. This procedure is called balloon angioplasty. Frequently, an implantable metallic stent will also be used to provide greater radial strength at the stenotic portion of the blood vessel, and to provide longer-term patency.  
           [0004]    In order to help deliver balloon catheters and stent devices, special guiding catheters or sheaths are often used. These guiding catheters or sheaths are placed away (or upstream) from the targeted lesion or stenotic area. A guide wire may be advanced past the stenotic area, allowing the subsequent balloon catheters and stents to be advanced through the guiding catheter or sheath to the target area of the blood vessel.  
           [0005]    During the balloon angioplasty procedure and stent placement at the stenotic lesion, there may exist the risk of dislodging fragments of plaque, thrombus (blood clots) and/or other material. These fragments may become dislodged from the stenotic lesion when the balloon segment is inflated. If the lesion involves arterial circulation, then the dislodged particles could flow into smaller vessels in the brain, other organs, or extremities, resulting in disastrous complications. Likewise, if the lesions involve the venous circulation, then the dislodged fragments could flow into the heart and lungs, possibly resulting in the demise of the patient.  
           [0006]    Embolic protection devices are typically used to provide protection from such dislodged fragments of plaque and thrombus. These protection devices often consist of a small umbrella-like filter or lasso-shaped device attached to the end of a guide wire. The guide wire with the filter may be advanced across a stenotic lesion in an unexpanded state and then may be expanded in an area of the blood vessel past the stenotic lesion or downstream therefrom. When expanded, the filter can capture dislodged particles while still allowing blood to freely flow. The filter may stay expanded during all major parts of the procedure including pre-dilation of the stenotic lesion with a small balloon catheter, advancement and deployment of a stent, and post dilation with a large balloon catheter. When the procedure is completed, often a separate retrieval catheter will be advanced through the stented artery and be used to collapse and retrieve the embolic protection device.  
           [0007]    There are many disadvantages to the retrieval catheters that are often used to collapse and remove embolic protection filters and other devices. If the targeted blood vessel is tortuous and the newly placed stent is at an angle, it is often difficult to pass a retrieval catheter into position to effectively and safely collapse the embolic filter. The distal tip of the retrieval catheter may often become snagged or caught on the edge of the stent as the retrieval catheter attempts to pass through the newly placed stent. Since retrieval catheters are usually straight, it is also often difficult to turn and advance off of obstructions, such as a newly placed stent.  
           [0008]    Since a retrieval catheter usually requires a lumen that is larger than the dimensions of a filter wire, the retrieval catheter may cause scraping and/or focal dissection of the blood vessel wall as it passed through the diseased portion of the blood vessel.  
           [0009]    Often the distal lumen of a retrieval catheter will be too small to safely collapse, store, and remove an embolic protection device. A partially collapsed filter or a filter not properly stored is at high risk for catching upon the edges of the newly placed stent as the retrieval catheter is removed, and/or for causing the embolic filter material to accidentally become removed from the support struts of the filter. As a result, the captured plaque and other thrombus may become free from the filter and enter into the blood stream. Moreover, the use of a retrieval catheter is an additional procedure that must be performed, requiring removal of the post-dilation balloon catheter and subsequent advancement of the retrieval catheter.  
           [0010]    A need exists for a catheter that serves the dual purpose of providing balloon angioplasty to a stenotic lesion of a blood vessel, while at the same time providing an effective means for safely collapsing, storing, and removing an embolic protection filter or other device containing dislodged plaque and thromboembolic material.  
           [0011]    The present invention has been developed in view of the foregoing, and to address other deficiencies of the prior art.  
         SUMMARY OF THE INVENTION  
         [0012]    The invention relates to an apparatus and method for providing balloon angioplasty while at the same time providing improved thromboembolic protection. The apparatus includes an inflatable balloon segment for providing balloon angioplasty and a distal tip with an increased volume which can safely and effectively store a thromboembolic protection device, such as an embolic filter, filled with embolic material, such as plaque or thrombus. The apparatus of the present invention can be advanced along a guide wire to provide balloon angioplasty to a stenotic portion of a blood vessel, and can then be further advanced along the guide wire to retrieve and store an embolic filter filled with embolic material in the expanded distal tip of the apparatus. The apparatus of the present invention may be advanced coaxially along a guide wire in a monorail system, or may be used in a standard over-the-wire system, both of which are well known in the art.  
           [0013]    An aspect of the present invention is to provide a vascular catheter including a shaft having an expanded distal tip structured and arranged to receive at least a portion of a thromboembolic protection device, and a radially expandable segment disposed on the shaft.  
           [0014]    Another aspect of the present invention is to provide a catheter assembly including a shaft having an expanded distal tip, a radially expandable segment disposed on the shaft, and a thromboembolic protection device at least partially receivable in the expanded distal tip.  
           [0015]    A further aspect of the present invention is to provide a vascular catheter including a shaft having an expanded distal tip for storing at least a portion of a thromboembolic protection device, and a radially expandable segment disposed on the shaft.  
           [0016]    Another aspect of the present invention is to provide a method of dilating blood vessels and protecting a patient from embolic material including the steps of inserting a guide wire including a thromboembolic protection device into a blood vessel and guiding the guide wire and the thromboembolic protection device past a stenotic portion of the blood vessel, expanding the thromboembolic protection device, guiding a catheter into the blood vessel along the guide wire, wherein the catheter includes a shaft having an expanded distal tip and a radially expandable segment, expanding the segment to dilate the stenotic portion of the blood vessel, guiding the catheter further along the guide wire to receive at least a portion of the thromboembolic protection device within the expanded distal tip, and removing the catheter and the thromboembolic protection device from the blood vessel.  
           [0017]    A further aspect of the present invention is to provide a method of dilating blood vessels and protecting a patient from embolic material including the steps of inserting a guide wire including a thromboembolic protection device into a blood vessel and guiding the guide wire and the thromboembolic protection device past a stenotic portion of the blood vessel, expanding the thromboembolic protection device, guiding a catheter into the blood vessel along the guide wire, wherein the catheter includes a shaft having an expanded distal tip and a radially expandable segment, expanding the segment to dilate the stenotic portion of the blood vessel, retracting the guide wire until at least a portion of the thromboembolic protection device is received within the expanded distal tip, and removing the catheter and the thromboembolic protection device from the blood vessel.  
           [0018]    These and other aspects of the present invention will be more apparent from the following description. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    [0019]FIG. 1 is a partially schematic longitudinal sectional view of a catheter apparatus in accordance with an embodiment of the present invention.  
         [0020]    [0020]FIG. 2 is a longitudinal side view of the apparatus of FIG. 1.  
         [0021]    [0021]FIG. 3 is a sectional view taken along the line  3 - 3  of the apparatus of FIG. 2.  
         [0022]    [0022]FIG. 4 is a sectional view taken along the line  4 - 4  of the apparatus of FIG. 2.  
         [0023]    [0023]FIG. 5 is a longitudinal side view of the apparatus of FIG. 1, with the balloon segment in a deflated position.  
         [0024]    [0024]FIG. 6 is a partially schematic longitudinal sectional view of a proximal end of a catheter apparatus in accordance with an embodiment of the present invention.  
         [0025]    [0025]FIG. 7 is a longitudinal side view of the apparatus of FIG. 1 shown in conjunction with a guide wire and a thromboembolic protection device mounted on the guide wire.  
         [0026]    [0026]FIG. 8 is a longitudinal side view of the apparatus of FIG. 1 shown in conjunction with a guide wire and a thromboembolic protection device mounted on the guide wire, with the thromboembolic protection device being retracted into the distal end of the catheter apparatus.  
         [0027]    [0027]FIG. 9 is a longitudinal side view of the apparatus of FIG. 1 shown in conjunction with a guide wire and a thromboembolic protection device mounted on the guide wire, with the thromboembolic protection device retracted and partially stored within the distal end of the catheter apparatus.  
         [0028]    [0028]FIG. 10 is a partially schematic longitudinal side view of a catheter apparatus in accordance with another embodiment of the present invention.  
         [0029]    [0029]FIG. 11 is a sectional view taken along the line  11 - 11  of the apparatus of FIG. 10.  
         [0030]    [0030]FIG. 12 is a sectional view taken along the line  12 - 12  of the apparatus of FIG. 10.  
         [0031]    [0031]FIG. 13 is a partially schematic longitudinal side view of a catheter apparatus in accordance with another embodiment of the present invention.  
         [0032]    [0032]FIG. 14 is a sectional view taken along the line  14 - 14  of the apparatus of FIG. 13.  
         [0033]    [0033]FIG. 15 is a sectional view taken along the line  15 - 15  of the apparatus of FIG. 13.  
         [0034]    [0034]FIG. 16 is a sectional view taken along the line  16 - 16  of the apparatus of FIG. 13.  
         [0035]    [0035]FIG. 17 is a partially schematic longitudinal side view of a catheter apparatus in accordance with another embodiment of the present invention.  
         [0036]    [0036]FIG. 18 is a sectional view taken along the line  18 - 18  of the apparatus of FIG. 17.  
         [0037]    [0037]FIG. 19 is a sectional view taken along the line  19 - 19  of the apparatus of FIG. 17.  
         [0038]    [0038]FIG. 20 is a longitudinal sectional view of the apparatus of FIG. 17.  
         [0039]    [0039]FIG. 21 shows the apparatus of FIG. 1 being used to treat a stenosis of a blood vessel. FIG. 21 also shows the apparatus of FIG. 1 being used in conjunction with a guide wire and a thromboembolic protection device mounted on the guide wire, the thromboembolic protection device being in a substantially open position.  
         [0040]    [0040]FIG. 22 shows the apparatus of FIG. 1 being used to treat a stenosis of a blood vessel in accordance with an embodiment of the present invention. FIG. 22 shows that a stent has been placed in the stenotic portion of the blood vessel, the catheter apparatus has been advanced further along the guide wire towards the thromboembolic protection device, and the thromboembolic protection device is beginning to collapse into the distal tip of the catheter apparatus.  
         [0041]    [0041]FIG. 23 shows the apparatus of FIG. 1 being used to treat a stenosis of a blood vessel in accordance with an embodiment of the present invention. FIG. 23 shows that the thromboembolic protection device has been collapsed and partially stored within the distal tip of the apparatus of FIG. 1, and the apparatus is being removed from the blood vessel. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0042]    The apparatus of the present invention includes a catheter with a radially expandable segment, such as an inflatable balloon disposed on the shaft of the catheter, and an expanded distal tip that houses a thromboembolic protection device. As used herein, the term “expanded distal tip” means a distal portion of a shaft of a catheter that has a larger interior storage volume when compared a proximal portion of the shaft. This larger volume allows the expanded distal tip to effectively capture, store, and remove a thromboembolic protection device from a patient.  
         [0043]    In the exemplary embodiments described herein, the catheter may be used in conjunction with a guide wire having the thromboembolic protection device attached near the end of the guide wire. The protection device may be extendable outward toward the interior wall of a blood vessel of a patient to trap embolic material typically broken lose by dilation or stenting of a stenotic portion of a blood vessel. As used herein, the term “thromboembolic protection device” includes filters, strainers, lassos, nets, traps, or any other assembly or device capable of capturing embolic material during an interventional procedure such as transluminal angioplasty or stenting. Embolic material includes plaque, thrombus, thromboembolic fragments, or any other material that may be dislodged from a blood vessel or released into the blood stream during an interventional procedure such as transluminal angioplasty.  
         [0044]    In a preferred form of the invention, the guide wire and thromboembolic protection device combination may be inserted into a blood vessel to be treated, and the thromboembolic protection device may be extended outward to a substantially open position. The catheter of the present invention may then be advanced along the guide wire, and the radially expandable segment of the catheter may be used to dilate and provide stent placement to a stenotic portion of the blood vessel, as is commonly known in the art. When the procedure is completed and embolic material has collected in the thromboembolic protection device, the catheter of the present invention may be advanced further along the guide wire until the expanded thromboembolic protection device substantially meets the distal tip of the catheter. The thromboembolic protection device may then be collapsed and pulled into the expanded distal tip of the catheter via the guide wire, or the catheter may be advanced further along the guide wire until the collapsed protection device is sufficiently stored within the distal tip. The expanded distal tip of the catheter has a volume which is capable of safely and effectively storing the thromboembolic protection device filled with embolic material. The catheter and the collapsed thromboembolic protection device may then safely be removed from the blood vessel of the patient together, as a unit.  
         [0045]    [0045]FIG. 1 is a partially schematic longitudinal sectional view of a vascular catheter  100  in accordance with an embodiment of the present invention. The catheter  100  may include a shaft  102 , and the shaft includes an intermediate portion  103  and an expanded distal tip  104 . The shaft of the catheter apparatus  100  may be made out of any suitable material, such as polyethylene, polyamide, polytetraflurethylene, or any other polyester compounds. In this embodiment, the expanded distal tip may be substantially cylindrical shaped, as shown in FIG. 1. FIG. 1 also illustrates that the transition from the intermediate portion of the shaft  103  to the expanded distal tip  104  may be a substantially gradual and substantially smooth transition. FIG. 1 shows that the shaft  102  includes inner wall  106  and outer wall  108 . As shown in FIG. 1, the expanded distal tip  104  has a cross-sectional diameter measured with respect to the inner wall  106  that is greater than a cross-sectional diameter of the intermediate portion of the shaft  103  measured with respect to the inner wall  106 . As also shown in FIG. 1, the expanded distal tip  104  has a cross-sectional diameter measured with respect to the outer wall  108  that is greater than a cross-sectional diameter of the intermediate portion of the shaft  103  measured with respect to the outer wall  108 . FIGS. 1, 2 and  5  also show that the expanded distal tip  104  may include one or more tip apertures  114  running radially outward from the inner wall  106  of the shaft  102  to the outer wall  108  of the shaft, which may be used to receive various diagnostic instruments and/or for aspirating embolic debris. The distal tip  104  may optionally include a soft and substantially flexible atraumatic material  116  near the distal end  107  of the distal tip  104 . The atraumatic material  116  may be made out of any suitable material, such as polyethyltetrafluride (PET), polytetraflurethylene (PTFE), polyamide, or any other polyester compounds. This atraumatic portion  116  of the distal tip  104  may optionally be coated or constructed with a material of higher atomic density to aid in visualizing the distal tip  104 , for instance, under fluoroscopy.  
         [0046]    [0046]FIGS. 1, 2 and  5  show that the catheter apparatus  100  may include a radially expandable segment, such as an inflatable balloon segment  118 , disposed on the intermediate portion  103  of the shaft  102 . The inflatable balloon segment  118  may be made out of any suitable material, such as but not limited to, PET, polyethylene, polyamide, PTFE, or other suitable materials that can exert a sufficient radial force to expand a stent or dilate a stenotic portion of an artery. FIGS. 1 and 2 show the inflatable balloon segment  118  in a substantially inflated position and FIG. 5 shows the inflatable balloon segment  118  in a substantially deflated position. FIGS. 1, 2 and  5  also show that the intermediate portion  103  of the shaft  102  containing the inflatable balloon segment  118  may include one or more shaft apertures  120  to allow for the inflatable balloon segment  118  to be inflated and/or deflated. The intermediate portion  103  containing inflatable balloon segment  118  may also include one or more radiopaque markers  122  constructed with a material of higher atomic density to help show the location of the inflatable balloon segment  118  on the shaft  102 . The inflatable balloon segment  118  may be used to provide traditional balloon angioplasty to a blood vessel narrowed by stenosis, however, the inflatable balloon segment may also be lightly inflated or deflated to help align the expanded distal tip  104  of the catheter apparatus  100  with a thromboembolic protection device when such a device is being retrieved. Such an alignment may be needed if a blood vessel is tortuous, preventing the catheter apparatus  100  from naturally aligning with a thromboembolic protection device.  
         [0047]    As most clearly shown in FIGS. 1 and 6, the shaft  102  may include an interior cavity defining a first lumen  124  running inside the catheter  100  substantially from a proximal end  126  of the catheter  100 , as shown in FIG. 6, and extending substantially to the expanded distal tip  104  of the catheter  100  as shown in FIG. 1. The first lumen  124  may be used to accommodate guide wires and/or other diagnostic devices or instruments. As also shown in FIGS. 1 and 6, the shaft  102  also may include an interior cavity defining a second lumen  128  running adjacent to the first lumen  124  substantially from the proximal end  126  of the catheter  100 , as shown in FIG. 6, and extending substantially to the intermediate portion  103  of the shaft  102  containing the inflatable balloon segment  118 , as shown in FIG. 1. This second lumen  128  may be used, for example, to provide gases, liquids, and/or other materials via the shaft apertures  120  to the inflatable balloon segment  118  for the purposes of inflating or deflating the balloon segment.  
         [0048]    [0048]FIG. 3 is a cross-sectional view of the intermediate portion  103  of the shaft  102  of the catheter apparatus  100  shown in FIG. 2 taken along the line  3 - 3 . The cross section of the catheter  100  shown in FIG. 3 may have an inner diameter D 1  defined and measured with respect to the inner wall  106  of the shaft  102 , an outer diameter D 2  defined and measured with respect to the outer wall  108  of the shaft  102 , and a thickness T 1  defined as the distance between the inner wall  106  and the outer wall  108  of the shaft  102 . The inner diameter D 1  may range from about 0.4 mm to about 0.6 mm, preferably from about 0.45 mm to about 0.55 mm. A particularly preferred diameter D 1  may be about 0.48 mm. The outer diameter D 2  may range from about 0.9 mm to about 3 mm, preferably from about 1.5 mm to about 3 mm. A particularly preferred diameter D 2  may be about 2.5 mm. The thickness T 1  may range from about 0.25 mm to about 1.2 mm, preferably from about 0.5 mm to about 1.2 mm. A particularly preferred thickness T 1  may be about 1 mm. Although a particular cross-sectional piece of the intermediate portion  103  of the catheter shaft  102  is shown in FIG. 3, it is to be understood that the diameters D 1  and D 2 , and the thickness T 1  may be measured at other locations along the intermediate portion of the catheter shaft, such as the portion of the shaft  102  containing the inflatable balloon segment  118 . The first lumen  124  and the second lumen  128  are both illustrated in the cross section of the catheter  100  shown in FIG. 3.  
         [0049]    [0049]FIG. 4 shows a cross-sectional portion of the expanded distal tip  104  of the catheter  100  shown in FIG. 2 taken along the line  4 - 4 . As shown in FIG. 4, an inner diameter D 3  may be defined and measured with respect to the inner wall  106  of the shaft  102 , an outer diameter D 4  may be defined and measured with respect to the outer wall  108  of the shaft  102 , and a thickness T 2  may be defined as the distance between the inner wall  106  and the outer wall  108  of the shaft  102 . The inner diameter D 3  may range from about 0.8 mm to about 1.2 mm, preferably from about 0.95 mm to about 1.1 mm. A particularly preferred diameter D 3  may be about 1 mm. The outer diameter D 4  may range from about 1.3 mm to about 3.6 mm, preferably from about 2 mm to about 3.3 mm. A particularly preferred diameter D 4  may be about 3 mm. The thickness T 2  may range from about 0.25 mm to about 1.2 mm, preferably from about 0.5 mm to about 1.1 mm. A particularly preferred thickness T 2  may be about 1.0 mm. The first lumen  124  is also shown in FIG. 4. FIGS. 3 and 4 illustrate that the inner cross-sectional diameter D 3  of the expanded distal tip  104  is greater than the inner cross sectional diameter D 1  of the intermediate portion  103  of the shaft  102 , and that the outer cross-sectional diameter D 4  of the expanded distal tip  104  is greater than the outer cross-sectional diameter D 2  of the intermediate portion  103  of the shaft  102 . FIGS. 3 and 4 also illustrate that the thickness T 2  is substantially equal to the thickness T 1 .  
         [0050]    In this embodiment, a ratio of the diameter D 3  to D 1  may be defined as D 3 :D 1 . D 3 :D 1  may range from about 1.6:1 to about 2.4:1, preferably from about 1.8:1 to about 2.2:1. In a particularly preferred embodiment, D 3 :D 1  may be about 2:1. In this embodiment, a ratio of the diameter D 4  to the diameter D 2  may also be defined as D 4 :D 2 . D 4 :D 2  may range from about 1.1:1 to about 1.4:1, preferably from about 1.1:1 to about 1.3:1. In a particularly preferred embodiment, D 4 :D 2  may be about 1.2:1.  
         [0051]    [0051]FIG. 2 shows that the length of the expanded distal tip  104  may be defined as L 1 . The length L 1  may range from about 0.3 cm to about 1 cm, preferably from about 0.5 cm to about 0.7 cm. A particularly preferred length L 1  may be about 0.7 cm. In this embodiment, a ratio of the diameter D 3  of the expanded distal tip  104  to the length L 1  of the expanded distal tip  104  may be defined as D 3 :L 1 . D 3 :L 1  may range from about 0.27:1 to about 0.12:1, preferably from about 0.19:1 to about 0.13:1. In a particular embodiment, D 3 :L 1  may be about 0.14:1. In this embodiment, a ratio of the diameter D 4  of the expanded distal tip  104  to the length L 1  of the distal tip  104  may be defined as D 4 :L 1 . D 4 :L 1  may range from about 0.44:1 to about 0.36:1, preferably from about 0.4:1 to about 0.39:1. In a particular embodiment of the invention, D 4 :L 1  may be about 0.4:1.  
         [0052]    [0052]FIG. 6 shows a proximal end  126  of the catheter apparatus  100 . The proximal end  126  of the catheter  100  includes a first port  130  in flow communication with the first lumen  124 , and a second port  132  in flow communication with the second lumen  128 . The first port  130  and the second port  132  may both be substantially enclosed in a Y-shaped housing  134  as illustrated in FIG. 6. FIG. 6 shows that the Y-shaped housing  134  may also include a reinforcing lip or ridge  136  for providing the Y-shaped housing  134  with added structural support. As shown in FIG. 6, the Y-shaped housing  134  may be attached to the shaft  102  with any suitable fastening means, or optionally may be formed as an integral part of the catheter  100  during manufacture. The first port  130  may be used to supply the first lumen  124  with guide wires, suction for aspirating embolic material, and/or other diagnostic instruments, and the second port  132  may be used to supply the second lumen  128  with materials for inflating and deflating the inflatable balloon segment  118 , such as, but not limited to, various gases and liquids.  
         [0053]    FIGS.  7 - 9  show the catheter apparatus  100  in conjunction with a guide wire  138  and a thromboembolic protection device, such as an embolic filter assembly  140 , mounted substantially near a distal end  142  of the guide wire  138 . The guide wire  138  may be made of any suitable material, such as stainless steel, nickel titanium alloy (Nitinol), coiled spring stainless steel or other related alloys, and the first lumen  124  of the catheter apparatus  100  may be structured and arranged to receive the guide wire  138  within the first lumen  124 . In one embodiment, the guide wire  138  may run substantially along the entire length of the first lumen  124 , and a proximal end (not shown) of the guide wire  138  may protrude from the first port  130  of the first lumen  124 . Although a guide wire is shown in this embodiment, other types of flexible tubing may also be used. The tubing or guide wire preferably has an outer diameter of greater than about 0.05 cm and less than 0.25 cm, however guide wires with other suitable diameters may be used. For example, the guide wire  138  may have an outer diameter of about 0.09 cm.  
         [0054]    The embolic filter assembly  140  may be of any suitable construction for collecting and containing embolic material that is well known in the art. In one embodiment, as most clearly illustrated in FIG. 7, the embolic filter assembly  140  may include a plurality of ribs  144  spaced around the external circumference of the guide wire  138 . More or less ribs may be used. For example, although four ribs are shown, a device with six ribs may be constructed, and the ribs may be spaced at various intervals around the circumference of the guide wire  138 , for example, in an equiangular fashion. The ribs  144  are preferably formed of a resilient material, such as stainless steel, or Nitinol memory metal or plastic, which is pre-stressed or pre-formed resulting in an expandable or outward bias. The tips  146  of the ribs  144  may be preferably curved inward to minimize trauma to the blood vessel wall.  
         [0055]    A filter material  148  spans the gaps between and is secured to the ribs  144 . The filter material  148  is preferably a finely porous mesh capable of trapping embolic material broken loose from interventional procedures, but coarse enough to allow blood to pass through. Suitable filter materials include porous PTFE, fabrics and metals. When metal such as Nitinol memory metal is used as the filter material, it preferably has a low profile and facilitates trackability of the filter during use. The filter material  148  may be attached to the ribs  144  by any suitable means such as sutures, pockets, adhesives and the like. In one embodiment, the filter material  148  may be tied to the ribs  144  by sutures which also may act as control strings of the embolic filter assembly  140 .  
         [0056]    In many medium sized blood vessels, the embolic filter assembly  140  may expand to a diameter against the wall of the vessel from about 4 mm to about 10 mm, often from about 6 mm to about 8 mm. In larger vessels such as the aorta, the embolic filter assembly  140  may expand to a diameter from about 10 mm to about 30 mm, often from about 12 mm to about 20 mm.  
         [0057]    As most clearly illustrated in FIG. 7, the tips  146  of the ribs  144  may be attached to a collar  150  via a plurality of control strings  152 . The control strings  152  may be made of any suitable material such as metal wires, sutures or suture-like materials. The diameter of each control string  152  is preferably 0.03 cm or less. The collar  150  is preferably in sliding engagement with the guide wire  138 , so that the collar may move freely along the guide wire. In another embodiment, a collar is not used, and instead the control strings  152  may be attached directly to the guide wire  138  by any suitable means.  
         [0058]    In one embodiment, the embolic filter assembly  140  may be introduced into a blood vessel with an introducer sheath (not shown). In this embodiment, the introducer sheath may encase the embolic filter assembly  140 , keeping the embolic filter assembly in a substantially closed position. Once the embolic filter assembly  140  has been placed in a blood vessel at an appropriate location, the introducer sheath may be removed from the embolic filter assembly, thereby allowing the resilient ribs  144  to naturally expand, in turn causing the embolic filter assembly  140  to open to a substantially expanded position, as shown in FIG. 7. In one embodiment, the introducer sheath may be “peeled” away from the embolic filter assembly  140  and removed from the patient using a string, cord, suture, or other appropriate peeling means. In another embodiment, the guide wire may be held in a substantially stationary position, and the introducer sheath may be slideably removed from the embolic filter assembly  140  and subsequently removed from the patient.  
         [0059]    [0059]FIGS. 8 and 9 illustrate how the catheter apparatus  100  may be used to retract the embolic filter assembly  140 . Once the interventional procedure is complete, such as a balloon angioplasty procedure, and the embolic filter assembly  140  has captured any loose or dislodged embolic material, the catheter  100  may be advanced towards the distal end  142  of the guide wire  138  until the distal tip  104  of the catheter  100  meets the control strings  152  of the embolic filter assembly  140 . As shown in FIG. 8, the catheter apparatus  100  may then continue to be advanced towards the distal end  142  of the guide wire  138 , and the operator may pull on a proximal end (not shown) of the guide wire  138  which may protrude from the first port  130  of the first lumen  124 , which will preferably cause the collar  150  and the control strings  152  to be pulled into the distal tip  104  of the catheter  100 , thereby causing the embolic filter assembly  140  to begin to collapse. As shown in FIG. 9, the guide wire  138  may continue to be pulled until the embolic filter assembly  140  and the captured embolic material (not shown) are safely retracted and stored within the distal tip  104  of the catheter apparatus  100 . As shown in FIG. 9, only a portion of the embolic filter assembly  140  need be stored in the distal tip  104 . In another embodiment, the guide wire  138  may be pulled until the entire embolic filter assembly  140  is stored within the distal tip  140 . In another embodiment, the guide wire  138  may remain substantially stationary, and the catheter apparatus  100  may be advanced towards the distal end  142  of the guide wire  138  until a portion of the embolic filter assembly  140  or the entire embolic filter assembly  140  is safely stored within the distal tip  104  of the catheter apparatus  100 .  
         [0060]    In another embodiment of the invention, an embolic filter assembly and guide wire combination may be used with the present invention as disclosed in copending commonly owned U.S. patent application Ser. No. 09/476,829 filed Jan. 3, 2000, which is hereby incorporated by reference. In this embodiment, an embolic filter assembly may be substantially structured and arranged as described above, however, multiple control strings may be attached to an actuator located near a proximal end of a guide wire. The control strings may run inside the guide wire and may exit the guide wire through holes located in a collar, such as the collar  150  described above. The control strings may then be secured to the tips of a plurality of ribs of the embolic filter assembly. To open the embolic filter assembly, the actuator may be pushed forward, releasing tension upon the control strings and allowing the embolic filter assembly to self-expand. When the interventional procedure is complete, the actuator may be pulled, tensioning the control strings and causing the embolic filter assembly to retract, allowing the dislodged embolic material to be retained in a deep pocket formed by the filter material of the embolic filter assembly. The catheter apparatus  100  may then be advanced toward a distal end of the guide wire until the collapsed embolic filter assembly is safely stored within the distal tip  104  of the catheter apparatus  100 , or the guide wire  138  may be pulled until the collapsed embolic filter assembly is safely stored within the distal tip  104  of the catheter apparatus  100 .  
         [0061]    FIGS.  10 - 12  show a catheter apparatus  200  in accordance with another embodiment of the present invention. The catheter  200  includes a shaft  202 , and the shaft includes an intermediate portion  203  and an expanded distal tip  204 . In this embodiment the distal tip may be substantially conical shaped, as shown in FIG. 10, with the diameter of the distal tip  204  gradually increasing towards the distal end  207  of the distal tip  204 . FIG. 10 shows that the distal tip  204  may include one or more tip apertures  214  running radially outward from an inner wall  206  of the shaft to an outer wall  208  of the shaft, which may be used for diagnostic purposes such as aspirating or removing thromboembolic material or other particles from a blood vessel. The distal tip  204  may optionally include a soft and substantially flexible atraumatic material  216  near the distal end  207  of the distal tip  204 . This atraumatic material  216  may optionally be coated or constructed with a material of higher atomic density to aid in visualizing the distal tip  204 , for instance, under fluoroscopy.  
         [0062]    [0062]FIG. 10 shows that the catheter apparatus  200  may include a radially expandable segment, such as an inflatable balloon segment  218 , disposed on the intermediate portion  203  of the shaft  202 . FIG. 10 also shows that the intermediate portion  203  of the shaft  202  containing the inflatable balloon segment  218  may include one or more shaft apertures  220  to allow for the inflatable balloon segment  218  to be inflated and/or deflated. The intermediate portion  203  of the shaft  202  containing inflatable balloon segment  218  may also include one or more radiopaque markers  222  constructed with a material of higher atomic density to help show the location of the inflatable balloon segment  218  on the shaft  202 .  
         [0063]    The shaft  202  also includes an interior cavity defining a first lumen  224 , of which a cross-sectional portion is shown in FIGS. 13 and 14, running inside the catheter substantially from a proximal end (not shown) of the catheter and extending substantially to the distal tip  204  of the catheter  200 . The first lumen  224  may be used to accommodate guide wires and/or other diagnostic devices or instruments. The shaft  202  also may include an interior cavity defining a second lumen  228  running adjacent to the first lumen  224  substantially from the proximal end (not shown) of the catheter  200  and extending substantially to the intermediate portion  203  of the shaft  202  containing the inflatable balloon segment  218 . This second lumen  228  may be used, for example, to provide gases, liquids, or other materials via the shaft apertures  220  to the inflatable balloon segment  218  for the purposes of inflating or deflating the balloon segment.  
         [0064]    [0064]FIG. 11 is a cross-sectional view of the intermediate portion  203  of the shaft  202  of the catheter apparatus  200  shown in FIG. 10 taken along the line  11 - 11 . FIG. 11 shows that the shaft  202  includes inner wall  206  and outer wall  208 . The cross section of the catheter  200  shown in FIG. 11 may have an inner diameter D 5  defined and measured with respect to the inner wall  206  of the shaft  202 , an outer diameter D 6  defined and measured with respect to the outer wall  208  of the shaft  202 , and a thickness T 3  defined as the distance between the inner wall  206  and the outer wall  208  of the shaft  202 . The inner diameter D 5  may range from about 0.4 mm to about 0.6 mm, preferably from about 0.45 mm to about 0.55 mm. A particularly preferred inner diameter D 5  may be about 0.48 mm. The outer diameter D 6  may range from about 0.9 mm to about 3 mm, preferably from about 1.5 mm to about 3 mm. A particularly preferred outer diameter D 6  may be about 2.5 mm. The thickness T 3  may range from about 0.25 mm to about 1.2 mm, preferably from about 0.5 mm to about 1.2 mm.  
         [0065]    A particularly preferred thickness T 3  may be about 1 mm. Although a particular cross-sectional piece of the intermediate portion  203  of the catheter shaft  202  is shown in FIG. 11, it is to be understood that the diameters D 5  and D 6 , and the thickness T 3  may be measured at other locations along the intermediate portion of the catheter shaft, such as the intermediate portion  203  of the shaft  202  containing the inflatable balloon segment  218 . The first lumen  224  is illustrated in the cross section of the shaft  202  shown in FIG. 11.  
         [0066]    [0066]FIG. 12 shows a cross-sectional portion of the expanded distal tip  204  of the catheter  200  shown in FIG. 10 taken along the line  12 - 12 . An inner diameter D 7  may be defined and measured with respect to the inner wall  206  of the shaft  202 , an outer diameter D 8  may be defined and measured with respect to the outer wall  208  of the shaft  202 , and a thickness T 4  may be defined as the distance between the inner wall  206  and the outer wall  208  of the shaft  202 . The inner diameter D 7  may range from about 0.8 mm to about 1.2 mm, preferably from about 0.95 mm to about 1.1 mm. A particularly preferred diameter D 7  may be about 1 mm. The outer diameter D 8  may range from about 1.3 mm to about 3.6 mm, preferably from about 2 mm to about 3.3 mm. A particularly preferred diameter D 8  may be about 3 mm. The thickness T 4  may range from about 0.25 mm to about 1.2 mm, preferably from about 0.5 mm to about 1.1 mm. A particularly preferred thickness T 4  may be about 1 mm. The first lumen  224  is also shown in FIG. 12.  
         [0067]    [0067]FIGS. 11 and 12 illustrate that the inner cross-sectional diameter D 7  of the expanded distal tip  204  is greater than the inner cross-sectional diameter D 5  of the intermediate portion  203  of the shaft  202 , and that the outer cross-sectional diameter D 8  of the expanded distal tip  204  is greater than the outer cross-sectional diameter D 6  of the intermediate portion  203  of the shaft  202 . FIGS. 11 and 12 also illustrate that the thickness T 4  is substantially equal to the thickness T 3 .  
         [0068]    In this embodiment, a ratio of the diameter D 7  to D 5  may be defined as D 7 :D 5 . D 7 :D 5  may range from about 1.6:1 to about 2.4:1, preferably from about 1.8:1 to about 2.2:1. In a particularly preferred embodiment, D 7 :D 5  may be about 2:1. In this embodiment, a ratio of the diameter D 8  to the diameter D 6  may also be defined as D 8 :D 6 . D 8 :D 6  may range from about 1.1:1 to about 1.4:1, preferably from about 1.1:1 to about 1.3:1. In a particularly preferred embodiment, D 8 :D 6  may be about 1.2:1.  
         [0069]    [0069]FIG. 10 shows that the length of the expanded distal tip  204  may be defined as L 2 . The length L 2  may range from about 0.3 cm to about 1 cm, preferably from about 0.5 cm to about 0.7 cm. A particularly preferred length L 2  may be about 0.7 cm. In this embodiment, a ratio of the diameter D 7  of the distal tip  204  to the length L 2  of the distal tip  204  may be defined as D 7 :L 2 . D 7 :L 2  may range from about 0.27:1 to about 0.12:1, preferably from about 0.19:1 to about 0.13:1. In a particular embodiment, D 7 :L 2  may be about 0.14:1. In this embodiment, a ratio of the diameter D 8  of the distal tip  204  to the length L 2  of the distal tip  204  may be defined as D 8 :L 2 . D 8 :L 2  may range from about 0.44:1 to about 0.36:1, preferably from about 0.4:1 to about 0.39:1. In a particular embodiment of the invention, D 8 :L 2  maybe about 0.4:1.  
         [0070]    FIGS.  13 - 16  show a catheter apparatus  300  in accordance with another embodiment of the present invention. The catheter apparatus  300  includes a shaft  302 , and the shaft includes an intermediate portion  303  and an expanded distal tip  304 . In this embodiment the distal tip  304  is substantially bulb-shaped. As used herein, the term “bulb-shaped” refers to an expanded distal tip having at least a portion of the inner and/or outer walls curved. FIG. 13 shows that the expanded distal tip  304  may include one or more tip apertures  314  running radially outward from an inner wall  306  of the shaft to an outer wall  308  of the shaft, which may be used for diagnostic purposes such as aspirating or removing thromboembolic material or other particles from a blood vessel. The expanded distal tip  304  may optionally include a soft and substantially flexible atraumatic material  316  at the distal end  307  of the distal tip  304 . This atraumatic material  316  may optionally be coated or constructed with a material of higher atomic density to aid in visualizing the distal tip  304 , for instance, under fluoroscopy.  
         [0071]    [0071]FIG. 13 shows that the catheter  300  may include a radially expandable segment, such as an inflatable balloon segment  318 , disposed on the intermediate portion  303  of the shaft  302 . FIG. 13 also shows that the intermediate portion  303  of the shaft  302  containing the inflatable balloon segment  318  may include one or more shaft apertures  320  to allow for the inflatable balloon segment  318  to be inflated and/or deflated. The intermediate portion  303  of the shaft  302  containing inflatable balloon segment  318  may also include one or more radiopaque markers  322  constructed with a material of higher atomic density to help show the location of the inflatable balloon segment  318  on the shaft  302 .  
         [0072]    The catheter shaft  302  also preferably includes an interior cavity defining a first lumen  324 , of which a cross-sectional portion is shown in FIGS.  14 - 16 , running inside the catheter  300  substantially from a proximal end (not shown) of the catheter  300  and extending substantially to the expanded distal tip  304  of the catheter  300 . The first lumen  324  may be used to accommodate guide wires and/or other diagnostic devices or instruments. The catheter shaft  302  also may include an interior cavity defining a second lumen  328  running adjacent to the first lumen  324  substantially from the proximal end (not shown) of the catheter  300  and extending substantially to the intermediate portion  303  of the shaft  302  containing the inflatable balloon segment  318 . This second lumen  328  may be used, for example, to provide gases, liquids, or other materials via the shaft apertures  320  to the inflatable balloon segment  318  for a purpose such as inflating and/or deflating the balloon segment.  
         [0073]    [0073]FIG. 14 is a cross-sectional view of the intermediate portion  303  of the shaft  302  of the catheter  300  shown in FIG. 13 taken along the line  14 - 14 . FIG. 14 shows that the shaft  302  includes inner wall  306  and outer wall  308 . The cross section of the catheter  300  shown in FIG. 14 may have an inner diameter D 9  defined and measured with respect to the inner wall  306  of the shaft  302 , an outer diameter D 10  defined and measured with respect to the outer wall  308  of the shaft  302 , and a thickness T 5  defined as the distance between the inner wall  306  and the outer wall  308  of the shaft  302 . The inner diameter D 9  may range from about 0.4 mm to about 0.6 mm, preferably from about 0.45 mm to about 0.55 mm. A particularly preferred diameter D 9  may be about 0.48 mm. The outer diameter D 10  may range from about 0.9 mm to about 3 mm, preferably from about 1.4 mm to about 3 mm. A particularly preferred diameter D 10  may be about 2.5 mm. The thickness T 5  may range from about 0.25 mm to about 1.2 mm, preferably from about 0.5 mm to about 1.2 mm. A particularly preferred thickness T 5  may be about 1 mm. Although a particular cross-sectional piece of the intermediate portion  303  of the catheter shaft  302  is shown in FIG. 14, it is to be understood that the diameters D 9  and D 10 , and the thickness T 5  may be measured at other locations along the intermediate portion of the catheter shaft, such as the intermediate portion  303  of the shaft  302  containing the inflatable balloon segment  318 . The first lumen  324  is illustrated in the cross section of the shaft  302  shown in FIG. 14.  
         [0074]    [0074]FIG. 15 illustrates a cross-sectional portion of the expanded distal tip  304  of the shaft  302  of the catheter apparatus  300  shown in FIG. 13 taken along the line  15 - 15 , which is at the approximate midpoint  309  of the length of the expanded distal tip  304 . In this embodiment, the cross-sectional diameter of the distal tip  304 , measured with respect to the inner wall  306  and outer wall  308  of the shaft, gradually increases from a proximal end  305  of the expanded distal tip to approximately the midpoint  309  of the expanded distal tip, and then gradually decreases slightly from approximately the midpoint  309  of the expanded distal tip to the distal end  307  of the expanded distal tip  304 . FIG. 15 shows that an inner diameter D 11  may be defined and measured with respect to the inner wall  306  of the shaft  302 , an outer diameter D 12  may be defined and measured with respect to an outer wall  308  of the shaft  302 , and a thickness T 6  may be defined as the distance between the inner wall  306  and the outer wall  308  of the shaft  302 . The inner diameter D 11  may range from about 1 mm to about 1.5 mm, preferably from about 1.15 mm to about 1.3 mm. A particularly preferred diameter D 11  may be about 1.2 mm. The outer diameter D 12  may range from about 1.5 mm to about 3.8 mm, preferably from about 2.2 mm to about 3.5 mm. A particularly preferred diameter D 12  may be about 3.2 mm. The thickness T 6  may range from about 0.25 mm to about 1.2 mm, preferably from about 0.5 mm to about 1.1 mm. A particularly preferred thickness T 6  may be about 1.0 mm. The first lumen  324  is also illustrated in FIG. 15.  
         [0075]    [0075]FIG. 16 shows a cross-sectional portion of the expanded distal tip  304  of the catheter  300  shown in FIG. 13 taken along the line  16 - 16 , which is approximately at the distal end  307  of the expanded distal tip  304 . As shown in FIG. 16, an inner diameter D 13  may be defined and measured with respect to the inner wall  306  of the shaft  302 , an outer diameter D 14  may be defined and measured with respect to the outer wall  308  of the shaft  302 , and a thickness T 7  may be defined as the distance between the inner wall  306  and the outer wall  308  of the shaft  302 . The inner diameter D 13  may range from about 0.8 mm to about 1.2 mm, preferably from about 0.95 mm to about 1.1 mm. A particularly preferred diameter D 13  may be about 1 mm. The outer diameter D 14  may range from about 1.3 mm to about 3.6 mm, preferably from about 2 mm to about 3.3 mm. A particularly preferred diameter D 14  may be about 3 mm. The thickness T 7  may range from about 0.25 mm to about 1.2 mm, preferably from about 0.5 mm to about 1.1 mm. A particularly preferred thickness T 7  may be about 1.0 mm. The first lumen  324  is also shown in FIG. 16.  
         [0076]    [0076]FIGS. 14 and 15 illustrate that the diameter D 11  of the expanded distal tip  304  is greater than the diameter D 9  of the intermediate portion  403  of the shaft  302 , and that the diameter D 12  of the expanded distal tip  304  is greater than the diameter D 10  of the shaft  302 . FIGS. 14 and 15 also illustrate that the thickness T 5  is substantially equal to the thickness T 6 .  
         [0077]    [0077]FIGS. 14 and 16 illustrate that the diameter D 13  of the expanded distal tip  304  is greater than the diameter D 9  of the shaft  302 , and that the diameter D 14  of the expanded distal tip  304  is greater than the diameter D 10  of the shaft  302 . FIGS. 14 and 16 also illustrate that the thickness T 5  is substantially equal to the thickness T 7 .  
         [0078]    In this embodiment, a ratio of the diameter D 11  to D 9  may be defined as D 11 :D 9 . D 11 :D 9  may range from about 2.3:1 to about 2.5:1, preferably from about 2.4:1 to about 2.5:1. In a particularly preferred embodiment, D 11 :D 9  may be about 2.5:1. In this embodiment, a ratio of the diameter D 12  to the diameter D 10  may also be defined as D 12 :D 10 . D 12 :D 10  may range from about 1.3:1 to about 1.7:1, preferably from about 1.3:1 to about 1.6:1. In a particularly preferred embodiment, D 12 :D 10  may be about 1.2:1.  
         [0079]    [0079]FIG. 13 shows that the length of the expanded distal tip  304  may be defined as L 3 . The length L 3  may range from about 0.3 cm to about 1 cm, preferably from about 0.5 cm to about 0.7 cm. A particularly preferred length L 3  may be about 0.7 cm. In this embodiment, a ratio of the diameter D 11  of the distal tip  304  to the length L 3  of the distal tip  304  maybe defined as D 11 :L 3 . D 11 :L 3  may range from about 0.38:1 to about 0.14:1, preferably from about 0.23:1 to about 0.19:1. In a particular embodiment, D 11 :L 3  maybe about 0.17:1. In this embodiment, a ratio of the diameter D 12  of the distal tip  304  to the length L 3  of the distal tip  304  may be defined as D 12 :L 3 . D 12 :L 3  may range from about 0.5:1 to about 0.38:1, preferably from about 0.44:1 to about 0.5:1. In a particular embodiment of the invention, D 12 :L 3  may be about 0.46:1.  
         [0080]    FIGS.  17 - 20  show a catheter apparatus  400  in accordance with another embodiment of the present invention. The catheter apparatus  400  includes a shaft  402 , and the shaft includes an intermediate portion  403  and an expanded distal tip  404 . In this embodiment the expanded distal tip  404  may have an outer diameter that is substantially equal to an outer diameter of the intermediate portion of the shaft  403 , as shown in FIGS. 17 and 20. FIGS. 17 and 20 illustrate that the expanded distal tip  404  may include one or more tip apertures  414  running radially outward from an inner wall  406  of the shaft to an outer wall  408  of the shaft, which may be used for diagnostic purposes such as aspirating or removing thromboembolic material or other particles from a blood vessel. The expanded distal tip  404  may optionally include a soft and substantially flexible atraumatic material  416  at the distal end  407  of the distal tip  404 . This atraumatic material  416  may optionally be coated or constructed with a material of higher atomic density to aid in visualizing the distal tip  404 , for instance, under fluoroscopy.  
         [0081]    [0081]FIG. 17 shows that the catheter  400  may include a radially expandable segment, such as an inflatable balloon segment  418 , disposed on the intermediate portion  403  of the shaft  462 . FIG. 17 also shows that the intermediate portion  403  of the shaft  402  containing the inflatable balloon segment  418  may include one or more shaft apertures  420  to allow for the inflatable balloon segment  418  to be inflated and/or deflated. The intermediate portion  403  of the shaft  402  containing inflatable balloon segment  418  may also include one or more radiopaque markers  422  constructed with a material of higher atomic density to help show the location of the inflatable balloon segment  418  on the shaft  402 .  
         [0082]    The catheter shaft  402  also preferably includes an interior cavity defining a first lumen  424 , of which a cross-sectional portion is shown in FIGS. 18 and 19, running inside the catheter  400  substantially from a proximal end (not shown) of the catheter  400  and extending substantially to the expanded distal tip  404  of the catheter  400 . The first lumen  424  may be used to accommodate guide wires and/or other diagnostic devices or instruments. The catheter shaft  402  also may include an interior cavity defining a second lumen  428  running adjacent to the first lumen  424  substantially from the proximal end (not shown) of the catheter  400  and extending substantially to the intermediate portion  403  of the shaft  402  containing the inflatable balloon segment  418 . This second lumen  428  may be used, for example, to provide gases, liquids, or other materials via the shaft apertures  420  to the inflatable balloon segment  418  for the purposes of inflating and/or deflating the balloon segment.  
         [0083]    [0083]FIG. 18 is a cross-sectional view of the intermediate portion  403  of the shaft  402  of the catheter  400  shown in FIG. 17 taken along the line  18 - 18 . FIG. 18 shows that the shaft  402  includes inner wall  406  and outer wall  408 . The cross section of the catheter  400  shown in FIG. 18 may have an inner diameter D 15  defined and measured with respect to the inner wall  406  of the shaft  402 , an outer diameter D 16  defined and measured with respect to the outer wall  408  of the shaft  402 , and a thickness T 8  defined as the distance between the inner wall  406  and the outer wall  408  of the shaft  402 . The diameter D 15  may range from about 0.4 mm to about 0.6 mm, preferably from about 0.45 mm to about 0.55 mm. A particularly preferred diameter D 15  may be about 0.48 mm. The diameter D 16  may range from about 0.9 mm to about 3 mm, preferably from about 1.5 mm to about 3 mm. A particularly preferred diameter D 16  may be about 2.5 mm. The thickness T 8  may range from about 0.25 mm to about 1.2 mm, preferably from about 0.5 mm to about 1.2 mm. A particularly preferred thickness T 8  may be about 1 mm. Although a particular cross-sectional piece of the intermediate portion  403  of the catheter shaft  402  is shown in FIG. 18, it is to be understood that the diameters D 15  and D 16 , and the thickness T 8  may be measured at other locations along the intermediate portion of the catheter shaft, such as the intermediate portion  403  of the shaft  402  containing the inflatable balloon segment  418 . The first lumen  424  is illustrated in the cross section of the shaft  402  shown in FIG. 18.  
         [0084]    [0084]FIG. 19 shows a cross-sectional portion of the expanded distal tip  404  of the shaft  402  of the catheter apparatus  400  shown in FIG. 17 taken along the line  19 - 19 . As shown in FIGS. 19 and 20, an inner diameter D 17  may be defined and measured with respect to the inner wall  406  of the shaft  402 , an outer diameter D 18  may be defined and measured with respect to the outer wall  408  of the shaft  402 , and a thickness T 9  may be defined as the distance between the inner wall  406  and the outer wall  408  of the shaft  402 . The inner diameter D 17  may range from about 0.65 mm to about 1.8 mm, preferably from about 0.95 mm to about 1.65 mm. A particularly preferred diameter D 17  may be about 1.48 mm. The outer diameter D 18  may range from about 0.9 mm to about 3 mm, preferably from about 1.5 mm to about 3 mm. A particularly preferred diameter D 18  may be about 2.5 mm. The thickness T 9  may range from about 0.125 mm to about 0.6 mm, preferably from about 0.25 mm to about 0.55 mm. A particularly preferred thickness T 9  may be about 0.5 mm. The first lumen  424  is also shown in FIG. 19.  
         [0085]    FIGS.  18 - 20  illustrate that the inner diameter D 17  of the expanded distal tip  404  is greater than the diameter D 15  of the intermediate portion  403  of the shaft  402 . However, in this embodiment, the diameter D 18  of the expanded distal tip  404  is substantially equal to the diameter D 16  of the intermediate portion  403  of the shaft  402 . FIGS.  18 - 20  also illustrate that the thickness T 8  is greater than the thickness T 9 .  
         [0086]    In this embodiment, a ratio of the diameter D 17  to D 15  may be defined as D 17 :D 15 . D 17 :D 15  may range from about 1.63:1 to about 3:1, preferably from about 2.1:1 to about 3:1. In a particularly preferred embodiment, D 17 :D 15  may be about 3:1. In this embodiment, a ratio of the thickness T 8  to the thickness T 9  may also be defined as T 8 :T 9 . T 8 :T 9  may range from about 1.5:1 to about 2.5:1, preferably from about 1.75:1 to about 2.25:1. In a particularly preferred embodiment, T 8 :T 9  may be about 2:1.  
         [0087]    [0087]FIGS. 17 and 20 show that the length of the distal tip  404  may be defined as L 4 . The length L 4  may range from about 0.3 cm to about 1 cm, preferably from about 0.5 cm to about 0.7 cm. A particularly preferred length L 4  may be about 0.7 cm. In this embodiment, a ratio of the diameter D 17  of the expanded distal tip  404  to the length L 4  of the expanded distal tip  404  may be defined as D 17 :L 4 . D 17 :L 4  may range from about 0.22:1 to about 0.18:1, preferably from about 0.22:1 to about 0.19:1. In a particular embodiment, D 17 :L 4  may be about 0.21:1. In this embodiment, a ratio of the thickness T 9  to the length L 4  of the expanded distal tip  404  may be defined as T 9 :L 4 . T 9 :L 4  may range from about 0.04:1 to about 0.08:1, preferably from about 0.05:1 to about 0.08:1. In a particular embodiment of the invention, T 9 :L 4  may be about 0.07:1.  
         [0088]    It will be appreciated that catheter apparatus  200 ,  300  and  400  may all be used in conjunction with a guide wire and embolic filter assembly as disclosed and described herein.  
         [0089]    In one embodiment, the catheter  100  may be used to open an occluded blood vessel narrowed by stenosis as shown in FIGS.  21 - 23 . As illustrated in FIG. 21, a guiding sheath  154  may be inserted into a blood vessel such as a common carotid artery  156  located proximal to a bifurcation  158  between an internal carotid artery  160  and an external carotid artery  162 . A guide wire  138  containing an embolic filter assembly  140  may be advanced through the guiding sheath  154  and past a stenotic section  164  of the internal carotid artery  160  that is affected by stenosis  166 , with the embolic filter assembly  140  in a substantially collapsed position.  
         [0090]    The embolic filter assembly  140  may then be opened or expanded. A vascular stent  168  may then be deployed via the guide wire  138  to the location of the stenosis  166 . The catheter  100  of the present invention may then be advanced over the guide wire  138  via the guiding sheath  154  and into the internal carotid artery  160 . The catheter  100  may be positioned along the guide wire  138  so that the inflatable balloon segment  118  is substantially lined up with the stent  168  and the stenotic section  164  of the internal carotid artery  160 . Radiopaque markers  122  located at a portion of the shaft  102  containing the inflatable balloon segment  118  may aid in positioning the inflatable balloon segment  118  relative to the stent  168  and the stenotic section  164  of the internal carotid artery  160 . The inflatable balloon segment  118  may then be substantially inflated by supplying any suitable gas or liquid to the inflatable balloon segment  118  via the second port  132 , second lumen  128 , and shaft apertures  120 . As the inflatable balloon segment  118  is substantially inflated, the stenotic section  164  of the internal carotid artery  160  preferably will become dilated and the stent will preferably become effectively embedded into the wall  170  of the internal carotid artery  160 . As the stenotic section  164  of the internal carotid artery  160  is dilated with the inflatable balloon segment  118 , pieces of stenotic material and other embolic material may become dislodged and may flow through the internal carotid artery  160  and be captured by the expanded embolic filter assembly  140 .  
         [0091]    Once the vascular stent  168  is in place, the inflatable balloon segment  118  may be substantially deflated via the second port  132 , second lumen  128 , and shaft apertures  120 , and the catheter  100  may be further advanced coaxially along the guide wire  138  towards the distal end  142  of the guide wire  138 . Alternatively, the guide wire  138  may be retracted towards the expanded distal tip  104  of the catheter  100 . As shown in FIG. 22, as the expanded distal tip  104  of the catheter  100  meets the control strings  152  of the embolic filter assembly  140 , the proximal end (not shown) of the guide wire  138  may be pulled or the catheter  100  may be pushed, preferably causing the embolic filter assembly  140  to begin to collapse into the expanded distal tip  104  of the catheter  100 . As shown in FIG. 23, once the embolic filter assembly  140  is substantially collapsed and safely stored within the expanded distal tip  104  of the catheter apparatus  100 , the catheter  100  may be retracted into the guiding sheath  154 , and the guiding sheath  154  containing the catheter  100  and the potentially debris filled collapsed embolic filter assembly  140  may be removed from the patient as a unit.  
         [0092]    It will be appreciated that the catheter apparatus  200  shown in FIGS.  10 - 12 , the catheter apparatus  300  shown in FIGS.  13 - 16 , and the catheter apparatus  400  shown in FIGS.  17 - 20  may all operate in substantially the same manner as described above.  
         [0093]    Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.