Abstract:
A discrete segmented balloon catheter for removal of an embolus. In an embodiment, the catheter comprises a catheter having a proximal and a distal end, a fluid inlet at the proximal end, and discrete expandable segments placed along the shaft of the catheter. In addition, the segments are expanded through dispersal of fluid that flows from the catheter&#39;s proximal inlet. It follows that the segments are contracted through withdrawal of fluid from the catheter&#39;s proximal inlet.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims benefit of U S. Provisional Application Ser. No. 60/688,824, filed on Jun. 9, 2005, which is incorporated herein by reference in its entirety. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not applicable  
       FIELD OF THE INVENTION  
       [0003]     The present invention relates generally to catheters and more particularly, to catheters for use as embolectomy catheters and angioplasty catheters for treating diseases including but not limited to stroke Still more particularly, the present invention relates to the use of balloon or expanding catheters for the treatment and/or removal of emboli.  
       BACKGROUND  
       [0004]     Expanding catheters are commonly used in surgical procedures to remove emboli or blood clots from an occluded branch or vessel. An embolus is most frequently a blood clot, but it can also be a plaque broken off from an atherosclerotic blood vessel or a number of other substances including fat, air, and even cancerous cells Typically, the catheter is inserted percutaneously to the vicinity of the clot and expanded, capturing a portion of the clot, which is then withdrawn from the vessel upon removal of the catheter. One mechanism for expansion of a catheter is inflation,  
         [0005]     Catheters with inflatable balloon means have been provided for blood clot removal. U.S. Pat. No. 4,762,130 to Fogarty discloses such a catheter. The Fogarty device uses a single, spiral-configured balloon. U.S. Pat. No. 6,254,571 to Hart discloses a second type of catheter for removing occlusive materials from body passages, in which a plurality of mechanically activated expandable segments are disposed on the distal end of a catheter.  
         [0006]     Embolectomy catheters have also been provided with balloons having small flexible protrusions adapted to bite into the clot upon inflation of the balloons, enabling a portion of the clot to be pulled free by withdrawal of the catheter. Such a catheter is shown in U.S. Pat. No, 3,635,223 to Klieman. Various other means for removing emboli exist, include coil-shaped and basket-shaped devices, which typically constructed of wire or the like. None of these are consistently effective for clot removal, largely because new clots tend to be less organized and therefore more delicate.  
         [0007]     Existing expandable catheters may suffer from several other problems. For example, if such a catheter comprises a single balloon and it is inflated near a well-organized clot, expansion of the balloon may result in the application of excessive force to the delicate vessel wall. Second, if a single expanded balloon catches the clot and the clot is large, the process of removing the clot may also create excessive forces on the vessel. Such procedures may damage the wall of the vessel. In addition, expanding catheters that do not engage most of the clot mass may not trap and retain a large portion of the clot, especially upon withdrawal of the catheter from the vessel.  
         [0008]     Accordingly, there remains a need in the art for an angioplasty or embolectomy catheter that can capture, retain, and remove all or a significant portion of the blood clot without producing excessive pressure on the vessel.  
       SUMMARY OF SOME OF THE PREFERRED EMBODIMENTS  
       [0009]     These and other needs in the art are addressed in one embodiment by a discrete segmented balloon catheter. In an embodiment, the present embolectomy catheter comprises a first catheter having a proximal and a distal end, a fluid inlet at the proximal end, and discrete expandable segments placed along the shaft of the catheter. In addition, the segments are expanded through dispersal of fluid that flows from the catheter&#39;s proximal inlet. The segments can be contracted through withdrawal of fluid from the catheter&#39;s proximal inlet.  
         [0010]     An additional embodiment includes a guiding catheter in combination with the aforementioned first catheter, where a portion of the first catheter is inside the guiding catheter. Upon contraction or partial contraction of the expandable segments, some or all of the first catheter may be drawn into the guiding catheter, so as to allow at least a portion of the clot mass to be drawn into the guiding catheters.  
         [0011]     At least a portion of an embolus may be removed by deploying the first catheter, with its segments contracted, along a guide wire into the embolus. Once positioned in the embolus, the segments may be expanded to capture a substantial amount of the embolus between the segments The first catheter is then withdrawn, removing the expanded segments and the embolus trapped between them from the occluded branch.  
         [0012]     Thus, embodiments described herein comprise a combination of features and advantages intended to address various shortcomings associated with certain prior devices. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments, and by referring to the accompanying drawings. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the embodiments described herein. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings in which:  
         [0014]      FIG. 1  is a side cross-section through the longitudinal axis of a segmented balloon catheter constructed in accordance with a first embodiment the inventions  
         [0015]      FIG. 2  is a cross-section nodal to the tool axis, taken through an expanded member of the catheter of  FIG. 1   
         [0016]      FIG. 3  illustrates three sequential views of the process for removing an embolus using the catheter.  
         [0017]      FIG. 4  is a side cross-section through the longitudinal axis of a second embodiment of a segmented balloon catheter 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]     The following discussion is directed to various embodiments of the invention. Although one or mote of these embodiments may be preferred, the embodiments disclosed should not be interpreted, or otherwise used, as limiting the scope of the disclosure, including the claims. In addition, one skilled in the art will understand that the following description has broad application, and the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to intimate that the scope of the disclosure, including the claims, is limited to that embodiment.  
         [0019]     Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.  
         [0020]     In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to. . . ” Also, the term “distal” is intended to refer to positions relatively away from the operator of the catheter when it is in use, while the term “proximal” is intended to refer to positions relatively near the operator when the catheter is in use. As a result, the distal end of a device is relatively near the embolus as compared to the proximal end of the device, which is relatively away from the embolus In addition, the term “radial” is intended to refer to movement toward or away from the longitudinal central axis of the catheter The term “axial” is meant to refer to positions lengthwise along the central axis of the catheter. The term “discrete” is intended to describe members that are individually disposed and separately inflatable. If one discrete member is obstructed and unable to fully expand, the next discrete member is not affected and may be expanded to its predetermined shape without regard to other members.  
         [0021]     Referring initially to  FIG. 1 , according to a preferred embodiment, a catheter  100  is disposed inside a vessel  110  In preferred embodiments, catheter  100  includes a guiding catheter  102  and an inner catheter  104 . A portion of inner catheter  104  may be disposed inside guiding catheter  102 . The outer diameter of guiding catheter  102  is preferably less than the inner diameter of the occluded portion of the vessel and the outer diameter of inner catheter  104  is less than the inner diameter of guiding catheter  102 .  
         [0022]     By way of example only, in most adults, the common carotid artery has a diameter of about 6-10 mm, the internal carotid artery has a diameter of about 5-6 mill, and the middle cerebral artery has a diameter of about 2-3 mm. In embodiments of the present invention, the guiding catheter may be positioned upstream of the embolus, in the common or internal carotid artery, which has a diameter of 5-6 mm, so the guiding catheter may have a diameter of 2-3 mm. In these embodiments, the inner microcatheter  104  may have a diameter of 0.5 to 1 mm, so that it can enter the smaller vessel or branch where the embolus is located.  
         [0023]     In a preferred embodiment, inner catheter  104  includes a plurality of separate or discrete annular expandable members  106  that are disposed axially along the shaft of the distal end  120  of inner catheter  104 . The expanded outer diameter, R, of expandable members  106 , is preferably approximately equal to vessel  110 &#39;s inner diameter. Thus, in some embodiments, R will equal approximately 25 to 5 mm.  
         [0024]     Inner catheter  104  and members  106  are in fluid communication with each other and expandable members  106  are expanded by filling inner catheter  104  and members  106  with fluid. In a preferred embodiment, the fluid disposed in inner catheter  104  may be comprised of radiopaque fluid, such as is well known in the art. As fluid travels from proximal end  122  toward distal end  120  of inner catheter  104 , members  106  expand.  
         [0025]     Members  106 , according to a preferred embodiment, are constructed of a resilient material that allows for expansion and contraction, such as are known in the art. In an embodiment the resilient material comprises a polymer. In other embodiments, members  106  comprise a flexible material that does not appreciably stretch. Members  106  each include an inner wall  116  and an outer wall  114  Members  106  are preferably spaced axially along the shaft of catheter with a distance X between the inner wall I  16  of one member  106  and the outer wall  114  of an adjacent member  106  and a distance Y between the inner wall  116  and outer wall  114  of a given member  106 . In some embodiments, X may be in the range of 1 to 5 mm and Y is in the range of 0.5 to 4 mm.  
         [0026]     Referring now to  FIG. 2 , in certain embodiments, fluid enters each expandable member  106  from catheter  104  through at least one port  105  According to a preferred embodiment, the shaft of catheter  104  includes two opposing ports  105  for each member  106 , as shown in  FIG. 2 . Ports  105  may be evenly spaced around the circumference of catheter shaft  104 . Alternatively, ports  105  may be unevenly spaced or there may be only one port  105  for each expandable member  106 . The axial extent of ports  105  may be equal to Y, or may be to 0.25 Y or less.  
         [0027]     In a preferred embodiment, members  106 , when expanded, form a predetermined shape such as circular, conical, or cup-shaped. Inner wall  116  forms the inner or distal surface of the cone or cup shape and outer wall  114  forms the outer surface of the shape. In the preferred expanded cup-shape, inner wall  116  will form an acute angle with the shaft of catheter  104  and outer wall  114  will form an obtuse angle with the shaft of catheter  104 . While the figures illustrate a preferred embodiment, it will be understood that expandable members  106  may have other shapes, may be concave in the opposite direction, and/or may not all be identically sized or shaped.  
         [0028]     Contraction of members  106  reduces the overall diameter of inner catheter  104 , so that it is less than the inner diameter of guiding catheter  102 . When members  106  are contracted, inner surface  116  is drawn toward the central axis of inner catheter  104 .  
         [0029]     In preferred embodiments, catheter  100  includes a radiopaque mark (not shown) on at least the most distal segment and the most proximal segment. Such radiopaque marks aid in visualization during placement and extraction, as described below.  
         [0030]     In some embodiments, one or more webs  108  are disposed inside members  106 . In preferred embodiments, webbing  108  is composed of a material that is less stretchy than members  106 . Webbing  108  may be disposed in one or a plurality of places inside each member  106  and shaped such that it prevents deformation of members  106  beyond their predetermined shape. In the embodiment shown, multiple webs  108  connect each inner wall  116  to the outer wall  114  of the same expandable member  106 , thereby limiting the ability of the member  106  to expand beyond the desired shape and more specifically limiting the ability of each member  106  to deform such that the distance between its inner and outer walls  116 ,  114  exceeds the desired distance, Y.  
         [0031]     In preferred embodiments, each expandable member  106  is preferably concave when viewed from the distal end of the tool. Thus, as in the embodiment illustrated in  FIG. 1 , the outer edge  107  of each member  106  is closer to the distal end of the tool than is the central portion of each member. This concavity, coupled with the axial spacing of the members along the tool results in a capture space  109  that is defined between each adjacent pair of members  106 . During an embolectomy, described below, portions of the embolus are captured in spaces  109 . As the tool is retracted, the distally curving outer edges  107  help retain the captured portions.  
         [0032]     A guide wire  112 , such as is well known in the art, extends through the distal end of inner catheter  104  at seal  118 . Seal  118  allows inner catheter  104  to travel along guide wire  112  for proper placement within vessel  110  as described below and prevents the egress of fluid around the guide wire during inflation of members  106 .  
         [0033]     In an alternative embodiment, as shown in  FIG. 4 , inner shaft  400  is disposed inside inner catheter  104 , forming inner lumen  402 . Guide wire  112  extends through inner lumen  402 . The distal end of inner shaft  400  is sealed with the shaft of inner catheter  104 , so as to maintain the sealed fluid chamber defined by members  106  and inner catheter  104 . Inner shaft  400  can be made of the same resilient or flexible material as inner catheter  104 .  
         [0034]     Catheter  100 , including members  106 , and guide wire  112  preferably comprise materials that are biocompatible and non-thrombogenic.  
         [0035]     As illustrated in FIGS.  3 ( a )-( d ), catheter  100  may be disposed in an occluded branch or vessel and used to remove an embolus  300  therefrom. To begin this operation, guide wire  112  is deployed in the vessel through and preferably somewhat beyond the embolus. Inner catheter  104  is then deployed so that its distal end  120  is disposed in the distal edge of the embolus  300 , or otherwise as desired. During placement, members  106  are contracted and disposed adjacent to inner catheter  104  and guide wire  112 . In a preferred embodiment, fluoroscopy or an equivalent technique is used to monitor the position of catheter  100  relative to embolus  300 . In particular, radiopaque marks on the expandable segments can help ensure that the devices is positioned as desired.  
         [0036]     Once in the desired position, ideally with members  106  fully embedded in embolus  300 , members  106  are expanded as fluid flows from proximal end  122  to the distal end  120  of the device,. Members  106  gradually expand toward the inner wall of vessel  110 , trapping portions of embolus  300  in spaces  109  between members  106 .  
         [0037]     After members  106  are expanded to a desired state and embolus  300  is captured between members  106 , inner catheter  104  is drawn toward guiding catheter  102 . As members  106  approach passage  124 , fluid is gradually released from the distal end such that members  106  are contracted sequentially so as to maintain the trapping effect on a portion of the embolus while reducing R to allow members  106  to fit within guiding catheter  102  and reducing the overall volume of member  106 , by also reducing Y, so as to allow capture of a maximum portion of the embolus. In some instances, collection of the embolus can be facilitated by applying suction to inside of guiding catheter  102 .  
         [0038]     Preferably after distal end  120  is drawn into guiding catheter  102 , catheter  100  is withdrawn proximally from the occluded region, removing at least a portion of the embolus.  
         [0039]     If embolus  300  is larger than can be removed by members  106  with one procedure, then the procedure may be repeated to remove the occlusion.  
         [0040]     While a preferred embodiment of the invention is shown and described, it will be understood that variations to the embodiment can be made without departing from the scope of the present invention. Likewise, the sequential description or claiming of certain steps of the present method is not intended to limit the present method to performance of those steps in that order or in any particular order, unless otherwise stated.