Abstract:
According to a first aspect of the invention there is provided a catheter assembly. A lumen extends through the catheter assembly and terminates with an exit port. The lumen being configured to receive a guide wire therein. The catheter assembly comprises a flexible distal segment having a predetermined length and a first predetermined outer diameter, a proximal segment having a second outer diameter greater than that of the first outer diameter, and an intermediate tapered section between the first proximal segment and the distal segment.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Patent Application 60/554,876 filed Mar. 19, 2004. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates generally to intra-luminal devices for the treatment of stenotic or diseased lumens, and more particularly, to a catheter assembly and method for the treatment of chronic total occlusions (CTO) in a lumen.  
       BACKGROUND OF THE INVENTION  
       [0003]     Stenotic lesions may comprise a hard, calcified substance and/or a softer thrombus material, each of which forms on the lumen walls of a blood vessel and restricts blood flow therethrough. Intra-luminal treatments such as balloon angioplasty, stent deployment, atherectomy, and thrombectomy are well known and have proven effective in the treatment of such stenotic lesions. These treatments often involve the insertion of a therapy catheter into a patient&#39;s vasculature which may be torturous and may have numerous stenoses of varying degrees throughout its length. In order to place the distal end of a catheter at the treatment site, a guidewire is typically introduced and tracked from an incision, through the stenosis, and across the lesion. Then, a catheter (e.g. a balloon catheter), perhaps containing a stent at its distal end can be tracked over the guidewire to the treatment site. Ordinarily, the distal end of the guidewire is quite flexible so that as it is pushed through the lumen, it can find its way through the turns of the typically irregular passageway without damaging the lumen.  
         [0004]     In some instances, the extent of occlusion of the lumen is so severe that the lumen is completely or nearly completely obstructed, leaving virtually no passageway for the guidewire. Such a condition may be described as a total occlusion. If this occlusion persists for a long period of time, the lesion is referred to as a chronic total occlusion or CTO. Furthermore, in the case of diseased blood vessels, the lining of the vessels may be characterized by the prevalence of atheromatous plaque, which may form total occlusions. The extensive plaque formation of a chronic total occlusion typically has a fibrous cap surrounding softer plaque material. This fibrous cap may present a surface that is difficult to penetrate with a conventional guidewire, and the typically flexible distal tip of the guidewire may be unable to cross the lesion. In such cases, a recanalizing device such as a stiffer guidewire may be employed to traverse the stenosis. In such cases, additional precautions must be taken to prevent injury to the vessel wall. For example, it is imperative that the guidewire or other recanalizing device be centered within the vessel to avoid penetration of the vessel wall.  
         [0005]     Accordingly, it would be desirable to provide an improved intraluminal device or catheter assembly for use in the treatment of chronic total occlusions, the device being capable of penetrating the proximal cap of the occlusion, finding and navigating through the true lumen, and exiting the distal cap of the occlusion.  
       BRIEF SUMMARY OF THE INVENTION  
       [0006]     According to a first aspect of the invention there is provided an improved catheter assembly. A lumen extends through the catheter assembly and terminates with an exit port. The lumen is configured to receive a guidewire therein. The catheter assembly comprises a flexible distal segment having a predetermined length and a first predetermined outer diameter, a proximal segment having a second outer diameter greater than that the first outer diameter, and an intermediate tapered section between the flexible proximal segment and the distal segment.  
         [0007]     According to a further aspect of the invention there is provided a catheter assembly comprising a first flexible tube having a lumen therethrough and having a first distal exit port configured to receive a guidewire therein. The first flexible tubular member may include blades or ribs on a distal outer surface. A second flexible tube has a second distal exit port and is configured to slidingly receive the first flexible tube therein. An expandable membrane is coupled proximate a distal end of the second flexible tube for substantially centering the guidewire when the membrane is expanded. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and  
         [0009]      FIGS. 1 and 2  are cross-sectional views illustrating potential problems associated with the treatment of chronic total occlusions;  
         [0010]      FIG. 3  illustrates a guiding catheter assembly positioned within a patient&#39;s vasculature;  
         [0011]      FIG. 4  is a cross-sectional view of a guidewire catheter in accordance with a first embodiment of the present invention;  
         [0012]      FIGS. 5 and 6  illustrates the use of steering elements or wires in the catheter shown in  FIG. 4 ;  
         [0013]      FIG. 7  illustrates the use of four steering elements or wires in the catheter shown in  FIG. 4  so as to permit steering in two planes;  
         [0014]      FIG. 8  illustrates how the guidewire shown in  FIG. 4  may be utilized to open a channel in a total occlusion;  
         [0015]      FIGS. 9, 10  and  11  are cross-sectional views of yet another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]     The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and use of the invention. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description.  
         [0017]      FIGS. 1 and 2  are cross-sectional views illustrating potential problems associated with the treatment of chronic total occlusions. Referring to  FIG. 1 , a standard guidewire  10  is advanced through a vessel  12  via a catheter (not shown) to the site of a chronic total occlusion  14 . As depicted in  FIG. 1 , guide wire  10  may be unable to penetrate the proximal cap of occlusion  14  and may prolapse into vessel  12  when pressure is applied.  
         [0018]      FIG. 2  illustrates a prior art catheter  16  having a balloon  18  mounted thereon and the limitations of such when attempting to center a device such as guidewire  10  at the site of chronic total occlusion  14 . As can be seen, guidewire  10  is not directed toward the center of occlusion  14 , but in fact is undesirably directed toward the wall of vessel  12 . Thus, difficulties will be encountered during attempts to traverse occlusion  14 , and the risk of perforating vessel  12  is high. It should be appreciated that in the arrangement shown in  FIG. 2 , catheter  16  confers no advantage with regard to the centering of guidewire  10 .  
         [0019]     Referring to  FIG. 3 , a guiding catheter assembly  20  is shown positioned within a patient&#39;s vasculature. Typically, the guiding catheter assembly  20  is first inserted through an incision (not shown) and into a femoral artery  22  of a patient. The assembly  20  is then advanced through artery  22  into the patient&#39;s aorta  24  and then into the ostium  26  of the selected carotid artery or vessel; for example, the left carotid  28 . Guiding catheter assembly  20  is positioned by a physician, preferably proximal to the stenotic lesion or occlusion.  
         [0020]      FIG. 4  is a cross-sectional view of a guidewire catheter assembly in accordance with a first embodiment of the present invention. Catheter assembly  30  comprises a catheter  32  having a guide wire lumen  33  therethrough and terminating at exit port  34 . Guidewire  36  may be telescopically inserted into guidewire lumen  33  in the well known manner. As can be seen, catheter assembly  30  has a proximal end  38  and a distal end  40 . Catheter  32  includes a distal segment  46 , a proximal segment  48 , and an intermediate tapered section  44 . Tapered region  44  acts as a transition between distal region  46  and a proximal region  48 . An additional tapered segment  42  is provided at the distal end of distal segment  46 .  
         [0021]     As can be seen, the inner diameter of catheter  32 , in this embodiment, is substantially constant (0.016 inches) throughout its length whereas the outer diameter of proximal region  48  is significantly larger than that of outer region  46 . For example, proximal segment  48  may have an outer diameter of approximately 0.030 inches, and distal segment  46  may have an outer diameter of 0.022 inches. Thus, distal region  46  provides a low profile flexible segment having a length of, for example, 5 to 15 millimeters, that may be advanced into a lesion with minimum trauma and facilitates steering of wire  36  in the lesion. The larger proximal section  48  may be pushed through the lesion after the wire to dilate the lesion in preparation for the introduction of, for example, a balloon. The distal portion of proximal tip  40  may be provided with a radiopaque substance  50  such as barium sulfate without compromising tracking profile.  
         [0022]     As stated previously, the inner diameter of wire lumen  33  is relatively constant along the length of catheter  32 . However, it may be desirable to increase the inner diameter of proximal region  48 , for example to 0.022 inches-0.024 inches, in order to improve wire movement and facilitate the injection of dye through wire lumen  33 . Furthermore, a standard PTCA balloon  52  may be added. The distal tip can be tracked into the lesion, and when through the lesion, balloon  52  can be brought into the lesion to open the path for further dilation.  
         [0023]     If desired, steering elements (e.g. wires  54  and  56 ) may be imbedded into lumen shaft  32  to provide a steering capability at the distal end of the shaft  40  as is shown in  FIG. 5 . Wires  54  and  56  may be anchored at the distal end thus enabling the distal tip of the shaft to be deflected as is shown in  FIG. 6 . That is, if wires  54  and  56  are anchored at their distal ends as is shown at  62  and  64  respectively, pushing wire  54  at its proximal end as is indicated by arrow  58  and/or pulling wire  56  at its proximal end as is indicated by arrow  60  will cause the distal tip of the catheter to bend. It should be understood that while  FIGS. 5 and 6  illustrates the use of two steering wires  54  and  56 , four steering wires could be employed to provide steering in two planes instead of a single plane as is shown in  FIG. 7 . These steering elements facilitate both the positioning of the guidewire in the proximal cap and the further steering of the guidewire through the lesion. Furthermore, by repeatedly flexing the tip of the guidewire in, for example, a back and forth motion, it could be used to locally open a micro-channel as is shown in  FIG. 8 .  
         [0024]      FIGS. 9 and 10  illustrate yet another embodiment of the present invention which substantially reduce the problems described in connection with  FIGS. 1 and 2  above. As can be seen, flexible tubular guidewire catheter  46  acts as an inner shaft which is slidably mounted within an outer flexible tubular balloon-catheter  68  equipped with an expandable membrane (e.g. a compliant balloon)  70 . Inner shaft  46  may further include blades or ribs  80  mounted on a distal section as shown in  FIG. 11 . Blades  80  are housed within outer shaft  68  to protect the vessel from damage until inner shaft  46  is advanced. Sliding inner shaft  46  is advanced over wire  36  and into chronic total occlusion  14  in order to score the lesion and potentially facilitate controlled expansion or opening of the lesion. As can be seen, balloon  70  may be inflated by means of inflation channel  72 . Inner shaft  46  may have an outer diameter of 0.023 inches and an inner diameter of 0.016 inches. Outer shaft  68  may have an inner diameter of 0.041 inches and an outer diameter of 0.047 inches.  
         [0025]     Compliant balloon  70 , when inflated or expanded, serves to center wire lumen  46  and therefore guidewire  36  within the vessel to be treated. For example, referring to  FIG. 10 , balloon  70  centers exit port  34  thereby centering guidewire  36  within vessel  12 . Distal portion  77  of balloon  70  substantially abuts at least a portion of chronic total occlusion  14 . If desired, catheter  68  may be provided with a marker band  34  on its distal portion. Therefore, marker band  34  also substantially abuts chronic total occlusion  14  and enables a clinician to predict the location of the central region of chronic total occlusion  14 . Subsequently, guidewire  36  may be replaced by an alternative tool designed, for example, to penetrate occlusion  14  or, for example, perform a balloon angioplasty and/or stent delivery procedure. In a further example, after sliding catheter shaft  46  is retracted into outer shaft  68 , a balloon catheter can then be advanced into the scored lesion and inflated to dilate the lesion. Ideally, a single device can be used to support wire crossing of the lesion, score the lesion surface and dilate the lesion. Any such device will also be centered within vessel  12  by means of balloon  70 . For a more complete discussion, the interested reader is directed to U.S. Pat. No. 6,533,753 issued Mar. 18, 2003 and entitled “APPARATUS AND METHOD FOR TREATMENT OF AN OCCLUDED LUMEN”.  
         [0026]     While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient roadmap for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.