Patent Publication Number: US-7914549-B2

Title: Mechanical embolectomy and suction catheter

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     FIELD OF THE INVENTION 
     Embodiments of the 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, embodiments of the invention relates to the use of balloon or expanding catheters for the treatment and/or removal of emboli. 
     BACKGROUND 
     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 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is inserted percutaneously to the vicinity of the clot and expanded, capturing a portion of the clot, which is then withdrawn from the vessel upon removal of the catheter.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. 
     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. 
     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, including coil-shaped and basket-shaped devices, which typically are 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. 
     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. 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. Furthermore, present catheters do not present a low enough profile for easy insertion into extremely small diameter vessels such as those found in the brain. 
     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. In addition, there is a need in the art for devices that can be inserted into extremely small diameter vessels. 
     SUMMARY OF SOME OF THE PREFERRED EMBODIMENTS 
     A novel catheter and methods for using the same are described herein. Embodiments of the catheter utilize sets of expandable members which collapse into recesses which are part of the catheter body. The recesses provide the catheter body with a low profile for insertion of the catheter into small blood vessels. In addition, the recesses may comprise openings for capturing emboli and clots by suction. Further features and advantages of the catheter will be disclosed below, but preferably the invention is not so limited and includes variations to such embodiments as recognized by this skilled in the art. 
     In an embodiment, a catheter comprises a catheter body having an inner lumen, an outer lumen, and one or more recesses disposed along said catheter body. Each recess includes at least one opening to said inner lumen. The inner lumen and outer lumen are sealed from each other. The catheter further comprises one or more expandable members disposed along said catheter body in fluid communication with said outer lumen. Each expandable member has an expanded position and a contracted position. Moreover, each expandable member in said contracted position fits within one of said plurality of recesses. 
     In an additional embodiment, a device for removal of an embolus from a vessel comprises a guiding catheter. The device further comprises a catheter slidably disposed within said guiding catheter. The catheter has an inner lumen, a plurality of radially expandable members disposed axially along said catheter, and a plurality of recesses. Each recess corresponds to one of said plurality of expandable members, and each recess has at least one opening in fluid communication with said inner lumen. 
     In another embodiment, method of removing at least a portion of an embolus from a vessel comprises providing a catheter comprising an inner lumen, an outer lumen, a plurality of radially expandable members in fluid communication with the outer lumen, and a plurality of recesses disposed along said catheter. Each recess includes at least one opening to said inner lumen. The method also comprises inserting the catheter into an occluded vessel. The plurality of members are in a contracted position within the plurality of recesses. In addition, the method comprises engaging an embolus between said members by expanding said plurality of members. Moreover, the method comprises capturing at least a portion of said embolus in said plurality of recesses by contracting said plurality of members. The method further comprises removing the embolus by withdrawing said catheter from the vessel. 
     In an embodiment, the method also comprises applying vacuum through the at least one opening in each recess from the inner lumen to capture at least a portion of the embolus. 
     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 embodiments, and by referring to the accompanying drawings. It should be appreciated by those skilled in the art that the conception and the 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 
       For a detailed description of embodiments of the invention, reference will now be made to the accompanying drawings in which: 
         FIG. 1  is a perspective view of a catheter constructed in accordance with an embodiment of the invention; 
         FIG. 2  illustrates an embodiment of a catheter with sets of expandable members aligned with each other; 
         FIGS. 3A-C  illustrate side views of various embodiments of a catheter with different cross-sectional configurations; 
         FIG. 4  illustrates an embodiment of a catheter with expandable members offset from each other; 
         FIG. 5A  is an end view down the longitudinal axis of an embodiment of a catheter comprising three expandable members per set in which the members disposed at equal angles; 
         FIG. 5B  is an end view down the longitudinal axis of an embodiment of a catheter comprising three expandable members per set in which the members are disposed at different angles; and 
         FIGS. 6A-C  illustrate an embodiment of a method of removing an embolus from a vessel. 
     
    
    
     The following discussion is directed to embodiments of the invention. Although one or more 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. 
     NOTATION AND NOMENCLATURE 
     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. 
     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. 
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Referring initially to  FIG. 1 , according to an embodiment, a catheter  100  comprises an inner lumen  102 , and outer lumen  104 , and a plurality of expandable members  106 . Typically, catheter  100  slides coaxially over a guide wire  131 . Inner lumen  102  and outer lumen  104  are sealed or separate from each other. Thus, inner and outer lumen  102 ,  104  are not in fluid communication with each other. Plurality of expandable members  106  are disposed axially along the shaft or body  114  of catheter  100 . Moreover, outer lumen  104  is in fluid communication with plurality of expandable members  106 . Any suitable number of expandable members  106  may be disposed along the body  114  of catheter  100 . 
     In an embodiment, catheter  100  may be disposed inside a guiding catheter  141 . In general, the outer diameter of guiding catheter  141  is less than the inner diameter of the occluded portion of the vessel and the outer diameter of catheter  100  is less than the inner diameter of guiding catheter  141 . In other words, catheter  100  moves coaxially within lumen of guiding catheter  141 . 
     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 mm, and the middle cerebral artery has a diameter of about 2-3 mm. In certain embodiments, the guiding catheter  141  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  141  may have a diameter of 2-3 mm. In these embodiments, catheter body  114  of catheter  100  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. 
     In an embodiment, plurality of expanded members  106  have an expanded position and a contracted position as seen in  FIG. 6 . The expanded outer diameter of each expandable member  106  in the expanded position is preferably substantially equal to or less than the inner diameter of a target vessel. The target vessel may be any blood vessel. Examples include without limitation, the carotid artery, the basilar artery, or the middle cerebral artery. In an embodiment, expanded outer diameter of each expandable member  106  will equal approximately 2.5 to 5 mm or the diameter of an average carotid artery. 
     Outer lumen  104  and members  106  are in fluid communication with each other and expandable members  106  are expanded by filling outer lumen  104  and members  106  with a fluid or a gas. In an embodiment, the fluid disposed in outer lumen  104  comprises a fluid, such as a radiopaque fluid. However, any suitable fluid or gas known in the art may be utilized. Members  106  expand as fluid travels through outer lumen  104  from proximal end toward distal end  121  of catheter  100 . 
     Referring to  FIG. 3 , in certain embodiments, fluid enters each expandable member  106  from outer lumen  104  through at least one inlet  103 . According to an embodiment, the outer lumen  104  includes two inlets  103  for each member  106 . Inlets are generally spaced around the circumference of catheter body  114  according to the location of each expandable member  106 . Alternatively, inlets may be unevenly spaced or there may be only one inlet  103  for each expandable member  106 . 
     As illustrated in  FIGS. 3A-C  for example, members  106 , when in their expanded position, my form a predetermined profile shape such as curved ( FIG. 3A ), bent ( FIG. 3B ), or straight ( FIG. 3C ). Distal surface  105  of each member  106  forms the inner surface of the cone or cup shape and proximal surface  107  forms the outer surface of the shape. In one embodiment, distal surface  105  forms an acute angle with the catheter body  114  and proximal surface  107  forms an obtuse angle with the catheter body  114  as shown in  FIGS. 3A-C . However, it is to be understood that expandable members  106  may have other shapes, such as concave in the opposite direction, and/or may not all be identically sized or shaped. Furthermore, when viewed down the axial length, the expandable members  106  may comprise a variety of shapes. For instance, in  FIG. 5 , members  106  comprise a trapezoidal shape. In other embodiments, the members  106  may comprise a rectangular, ovoid, or any other suitable shape. 
     In embodiments, each expandable member  106  is preferably concave in profile. That is, when viewed in profile, each member is angled toward the distal end  121  of catheter  100  as shown for example, in  FIG. 3A-C . This concavity or angling, coupled with the axial spacing of the members  106  along the catheter body  114  results in a capture space  109  that is defined between each recess  108  and each member  106 . During an embolectomy, described below, portions of the embolus  300  are captured in capture space  109  between members  106  and recesses  108 . As the catheter  100  is retracted, in some embodiment, distally curving outer edges on the member  106  may help retain the captured portions as seen in  FIG. 3A . Alternatively, each expandable member  106  is concave in profile toward the proximal end of catheter  100  (not shown). In other words, each expandable member is concave facing away from the distal end  121  of catheter  100 . 
     Referring now to  FIG. 1 , according to an embodiment, catheter  100  includes a plurality of recesses  108 . Recesses  108  allow members  106  to fit flush with catheter body  114  when members  106  are in their contracted position. Thus, catheter body  114  presents a low-profile when members  106  are in their contracted position and facilitates ease of insertion into small vessels. Moreover, each recess  108  may also facilitate improved removal of emboli or clot particles by catheter  100  by entrapment of particles within recesses  108  by members  106 . In embodiments, each member  106  has its own or is associated with a corresponding recess  108 . Moreover, recesses  108  are arranged in the same configuration as members  106 . In embodiments, recesses  108  are disposed distal to members  106 . Alternatively, recesses  108  are disposed proximal to member  106 . 
     Movement of members  106  into their contracted position or withdrawal of fluid from each member  106  reduces the overall diameter of catheter  100 , so that it is less than the inner diameter of guiding catheter  102 . When members  106  are in their contracted position, they preferably fit snugly within each recess  108  and cover openings  111 . 
     In embodiments, the bottom or base of each recess  108  comprises one or more openings  111 . Openings  111  allow the inner lumen  102  to be in fluid communication with the interior of the vessel. In general, openings  111  may be of any suitable geometry such as circular, rectangular, oval, etc. Additionally, openings  111  serve as a means to facilitate capture of emboli or clot particles by the application of a vacuum in inner lumen  102  through openings  111 . The application of vacuum in inner lumen  102  may create suction from openings  111  to draw or pull emboli and clot particles into each recess  108 . In some embodiments, openings  111  may have an area large enough entry of captured clot or tissue material. In embodiments with more than one opening  111  per recess  108 , openings  111  may be arranged in any suitable configuration. For example, as shown in  FIG. 1 , the openings  111  may comprise parallel, elongated grooves at the bottom of each recess  108 . 
     In an embodiment, plurality of expanded members  106  are arranged as one or more sets or arrays  116  of members  106  arranged along catheter body  114  as shown for example, in  FIG. 1 . In some embodiments, each set  116  contains a pair of members  106  disposed opposite each other circumferentially around catheter body  114 . See  FIG. 1 . Additionally, in some embodiments, each set  116  of members  106  may comprise two or more members  106  disposed at any suitable angle around catheter body  114 , as shown in  FIGS. 5A-B . Members  106  may be disposed at equal angles (see e.g.  FIG. 5A ) or different angles around catheter body  114  (see e.g.  FIG. 5B ). 
     Furthermore, catheter  100  may comprise multiple sets  116  of members  106  along catheter body  114 . In embodiments, catheter  100  comprises from 1 to 8 sets of members  106 . According to an embodiment, each set  116  of members  106  are offset at different angles from each other as shown in  FIG. 1 . In embodiments, each set  116  of members  106  is aligned at the same angles with each other as shown in  FIG. 2 . The offset sets or arrays  116  may facilitate more efficient trapping of emboli or clots in the vessel. In yet another embodiment, each set  116  may comprise a single member  106  where each member  106  may be offset from the others as shown in  FIG. 4 . 
     Members  106 , according to one embodiment, are constructed of a resilient material that allows for expansion and contraction. 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 a distal surface  105  aid a proximal surface  107 . Members  106  are preferably spaced axially along catheter body  114  with equal distances between distal surface  105  of one member  106  and proximal surface  107  of an adjacent member  106 , but may be spaced according to other configurations. In an embodiment, the distance between members  106  is in the range of about 1 mm to about 5 mm. In addition, members  106  may comprise any suitable thickness. In an embodiment, the thickness of members  106  may range from about 0.5 mm to about 4 mm. 
     In 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. 
     As shown in  FIG. 3 , one or more webs  115  are disposed inside members  106 . The webbing serves to maintain the structural integrity of each member  106 . In embodiments, webbing  115  is composed of a material that is less elastic than members  106 . Webbing  115  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 connect each distal surface wall  105  to proximal surface  107  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 beyond a pre-determined expansion point between distal and proximal surfaces  105 ,  107 . 
     A guide wire  131 , such as is well known in the art, is typically inserted coaxially through inner lumen  102  of catheter  100 . The opening at distal end of catheter  100  may comprise a seal  119 . Seal  119  guides catheter  100  along guide wire  131  for proper placement within vessel  110  as described below and prevents the egress of fluid around the guide wire  131  into inner lumen  102 . Seal  119  further allows vacuum to be applied within inner lumen  102  during removal of emboli or clots from the vessel. 
     Catheter  100 , including members  106 , and guide wire  131  preferably comprise materials that are biocompatible and non-thrombogenic. 
     Embolectomy 
     As illustrated in  FIGS. 6A-C , catheter  100  may be disposed in an occluded branch or vessel  310  and used to remove an embolus  300  therefrom. In an embodiment, guide wire  131  is deployed in the vessel  310  through and preferably proximate to embolus  300 . Catheter  100  is then deployed so that its distal end  121  penetrates the distal edge of the embolus  300  ( FIG. 6A ), or otherwise as desired, using guide wire  131  as a guide. As illustrated in  FIG. 6A , during placement, members  106  are in their contracted position and disposed within their corresponding recesses  108  so as to maintain a low profile for the catheter  100  and facilitate insertion into small diameter vessels. Typically, 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 members  106  can help ensure that the catheter  100  is positioned as desired. 
     Once in the desired position, ideally with members  106  positioned within embolus  300 , members  106  are expanded as fluid flows through outer lumen  104  of catheter  100 . Members  106  gradually expand toward the inner wall of vessel  110 , trapping portions of embolus  300  in between members  106  as seen in  FIG. 6B . 
     In an embodiment, once members  106  have been expanded, openings  111  are exposed to vessel interior. Any type of drug or therapeutic compound may be delivered through openings  111  to the site of the clot or embolus. Thus, catheter  100  is further capable of delivering drugs to an embolus or clot in a site-specific manner. In an embodiment, the drug is capable of dissolving an embolus or clot. Examples of suitable drugs that may be used include without limitation, aspirin, thienopyridines (e.g. ticlopidine and clopidogrel), glycoprotein IIB/IIa inhibitors (e.g. abciximab and eptifibatide), tissue plasminogen activator (tPA), or combinations thereof. 
     In one embodiment, after members  106  are expanded to a desired state and embolus  300  is captured between members  106 , a vacuum may be applied through the openings  111  located in recesses  108 . See  FIG. 6C . The vacuum may be applied by suction from the inner lumen  102 . During application of vacuum, inflatable members  106  maintain patency of the vessel and prevent collapse of the vessel wall due to suction from recesses  108 . In an exemplary embodiment, a vacuum line (not shown) may be attached to proximal end of catheter  100  to apply vacuum. However, it is contemplated that other methods known to those in the art for applying vacuum through a catheter may be used. 
     Vacuum applied through openings  111  may serve several purposes. For example, vacuum may allow for more efficient trapping of embolus particles caught between members  106  into each recess  108 . In some embodiments, openings  111  are large enough to allow passage of trapped clot or embolus particles into the inner lumen  102  for even more effective removal of the embolus or clot. Thus, portions of the embolus or clot may be sucked into the inner lumen  102  via openings  111  and removed. 
     Once it is determined that the embolus  300  is securely trapped either through suction or the action of members  106 , catheter  100  is drawn toward guiding catheter  141 . In an embodiment, as members  106  approach distal opening  143  of guiding catheter  141 , fluid is gradually released from the outer lumen  104  of catheter  100  such that members  106  are contracted sequentially so as to maintain the trapping effect on a portion of the embolus  300  while allowing members  106  to fit within guiding catheter  102  and reducing the overall volume of member  106 , so as to allow capture of a maximum portion of the embolus  300 . In an embodiment, it is envisioned that the contracting of members  106  is due to the combined effect of fluid withdrawal from members  106 , application of vacuum from openings  111 , and withdrawals of catheter  100  into guiding catheter  141 . However, in other embodiments, the contracting of members  106  may be accomplished by each of the aforementioned mechanisms individually. 
     In some instances, collection of the embolus  300  can be facilitated by applying suction to inside of guiding catheter  141 . That is, a vacuum may be further applied to guiding catheter to pull emboli particle captured by member  106  into guiding catheter, thus, enhancing removal of the embolus  300  from vessel  310 . 
     Preferably after distal end  121  is drawn into guiding catheter  141 , catheter  100  is withdrawn proximally from the occluded region, removing at least a portion of the embolus. 
     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. It is envisioned that the methods and devices described herein will not be limited to emboli and clots, but also for removing any obstruction deposited in blood vessels such as atherosclerotic plaque. 
     While embodiments of the invention are shown and described, it will be understood that variations to these embodiments can be made without departing from the scope of the invention. Likewise, the sequential description or claiming of certain steps of disclosed methods are not intended to limit the methods to performance of those steps in that order or in any particular order, unless otherwise stated.