Abstract:
A retrieval catheter for retrieving deployed medical devices includes a first guidewire lumen and a second guidewire lumen spaced radially from the first guidewire lumen. The first guidewire lumen has a distal end portion configured to recapture a medical device, such as a collapsed embolic protection device, deployed in a body lumen and secured to a guidewire extending through the first guidewire lumen. The second guidewire lumen receives a second guidewire which may be advanced past a first interventional site to perform a second procedure. The retrieval catheter may be provided with a soft tip to reduce trauma to the body tissue.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application Ser. No. 61/042,131, filed Apr. 3, 2008, the entire content of which is incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention is directed generally to catheters and retrieval methods. More particularly, the present invention is directed to dual-lumen retrieval catheters and methods of retrieving deployed medical devices such as, for example, embolic protection devices. 
       BACKGROUND 
       [0003]    Transcatheter procedures are employed in increasing numbers for opening stenosed or occluded blood vessels in patients caused by deposits of plaque or other materials on the walls of the blood vessels. Such minimally invasive procedures have proven to be advantageous compared to traditional surgical procedures, such as open heart surgery. Stenosis in arteries and other blood vessels can be treated by permanently or temporarily introducing a stent into the stenosed region to open the lumen of the vessel. 
         [0004]    However, embolic material may be released into the blood stream during implantation of a stent or another prosthetic device, placing the patient at great risk. Embolic material formed of calcium deposits, intimal debris, pieces of artheromatous plaque and/or thrombi has the potential of migrating downstream and causing distal tissue damage, for example stroke or myocardial infarction (see Topol, E. J. and Yadav, J. S., “Recognition of the Importance of Embolization in Athereosclerotic Vascular Disease”, Circulation 2000, 101:570). Embolic material which can potentially damage the distal tissue is often released during vascular intervention procedures, such as stenting of an artheromatous region. 
         [0005]    To alleviate this problem, an embolic filter, or other type of embolic protection device (EPD), may be advanced to a site distal to the treatment site to filter and capture undesired embolic material from the blood. The filter is typically inserted over or together with a guidewire using a delivery catheter. Following the treatment procedure, the filter is collapsed and removed from the body over the guidewire or together with the guidewire. Additional treatment devices, such as balloons and stents, can be inserted and/or removed via the same guidewire. 
         [0006]    During some procedures, after treatment with a balloon and/or stent is completed, the surgeon may discover another lesion or stenosis distal of the original treatment site or discover a vessel dissection resulting from the immediately preceding procedure. In such cases, the surgeon must remove the guidewire with the collapsed filter and then re-deploy a new guidewire for treatment of the second site. This procedure of re-inserting a secondary guidewire adds significantly to the patient&#39;s treatment time since deployment of a guidewire is very time consuming. Additionally, re-inserting a secondary guidewire also introduces modest risk of plaque embolization while the guidewire is being position at the diseased artery. 
         [0007]    Referring to  FIG. 1 , a deployed embolic protection device  10 , for example, an embolic filter, is illustrated just distal of a first deployment site  13  of a stent  14 . The device  10  is mounted on a guidewire  12  and is shown in an open (deployed) position. The device  10  may include an EPD with a guidewire locking mechanism of the type described in U.S. patent application Ser. No. 11/873,882, filed on Oct. 17, 2007, and entitled “Guidewire Stop,” and U.S. patent application Ser. No. 11/873,893, filed on Oct. 17, 2007, and entitled “Guidewire Stop,” the disclosures of which are incorporated herein by reference. Consequently, the removal of EPD  10  may require simultaneous retrieval of the guidewire  12  on which the EPD is lockingly deployed. 
         [0008]    Thus, if a second lesion  17  is subsequently discovered, the surgeon would need to retrieve the EPD  10  together with the guidewire  12 , and subsequently replace the guidewire  12  with a new one. For such cases, it would be desired to provide a retrieval catheter that permits delivery of a secondary guidewire while the primary guidewire  12  and EPD  10  are still deployed. In particular, it would be desirable if the retrieval catheter could also serve to introduce a secondary guidewire, prior to recovery of the primary guidewire and EPD. Thus, such an improved retrieval catheter would perform the dual functions of delivery of a secondary guidewire while retrieving a previously-deployed EPD system. 
         [0009]    Retrieving an EPD has posed challenges because of apparently contradictory requirements for the design of the retrieval catheter. On one hand, the collecting tube with which the filter is retrieved needs to have a large inside diameter in order to capture the filter easily and avoid squeezing out the material caught in the filter during the procedure; on the other hand, the size of the collecting tube is limited by the size of the guiding catheter size, the stent size through which the collecting tube must navigate, trauma to vessel, etc. 
         [0010]    A large open-tube design of the collecting tube can be traumatic to the blood vessel. To alleviate trauma and facilitate navigation, the distal part of, for example, balloon catheters has a tapered soft tip which tapers all the way from the maximal tube diameter to the guidewire diameter. In this way, the catheter does not “dig” into the vessel wall, especially in tortuous vessels or get caught when traversing a stent, where struts may protrude toward the center of the blood vessel. 
         [0011]    Several manufacturers have attempted to solve this problem by tapering the distal end of the collecting tube used for retrieval which, however, tends to make retrieval of the full filter more difficult and risks discharging particles back into the blood stream. In addition, the collecting tube and catheter need to be built from a sufficiently rigid material to prevent collapse when the filter is pulled into the tube, which makes it impossible to use a very flexible tube which will track softly through the blood vessels. 
         [0012]    The retrieval catheters and retrieval methods of the present disclosure solve one or more of the problems set forth above. 
       SUMMARY OF THE INVENTION 
       [0013]    According to one aspect of the invention, a catheter for retrieving a medical device deployed in a body lumen includes a first guidewire lumen extending through a distal shaft portion of the retrieval catheter from a first proximal guidewire port to a first distal guidewire port, and a second guidewire lumen extending through the distal shaft portion of the retrieval catheter from a second proximal guidewire port to a second distal guidewire port. The first guidewire lumen has a distal end portion dimensioned to recapture the medical device secured on a first guidewire distal of the distal end portion. The first guidewire passes through the first guidewire lumen. The second guidewire lumen is radially offset from the first guidewire lumen and receives a second guidewire operable separately from the first guidewire for advancement past the distal end portion following recapture of the medical device. 
         [0014]    According to another aspect of the invention, a method of retrieving an embolic protection device deployed in a body lumen at a location distal to a first interventional procedure site and secured to a first guidewire includes the steps of advancing a retrieval catheter along the first guidewire to a location proximal of the embolic protection device, wherein the retrieval catheter has a first guidewire lumen extending through a distal shaft portion of the retrieval catheter from a first proximal guidewire port to a first distal guidewire port. The first guidewire lumen has a distal end portion dimensioned to recapture the embolic protection in a collapsed state, and the first guidewire passes through the first guidewire lumen. The retrieval catheter further has a second guidewire lumen extending through the distal shaft portion of the retrieval catheter from a second proximal guidewire port to a second distal guidewire port. The second guidewire lumen is radially offset from the first guidewire lumen and receives a second guidewire operable separately from the first guidewire. The method includes the additional steps of recapturing the collapsed embolic protection device into the first guidewire lumen of the retrieval catheter, advancing the second guidewire through the second guidewire lumen of the retrieval catheter to a second interventional procedure site, and withdrawing the retrieval catheter with the embolic protection device and the first guidewire, while leaving the second guidewire in place. 
         [0015]    According to one embodiment, the dual-lumen retrieval catheter may include a tipped member having a conical shape with a greatest outside diameter sized to be slidably received in the distal end portion of the first guidewire lumen and a center opening through which the first guidewire passes. The tip of the tipped member may protrude distally from the distal end portion when the retrieval catheter is advanced distally in the body lumen towards the medical device to prevent trauma to the vessel. 
         [0016]    According to yet another aspect of the invention, a catheter for retrieving a medical device deployed in a body lumen includes a guidewire lumen extending through a distal shaft portion of the retrieval catheter from a first proximal guidewire port to a first distal guidewire port. The guidewire lumen has a distal end portion dimensioned to recapture the medical device secured on a guidewire distal of the distal end portion. The guidewire passes through the guidewire lumen. The catheter further includes a tipped member having a conical shape with a greatest outside diameter sized to be slidably received in the distal end portion of the guidewire lumen and a center opening through which the guidewire passes. The tip of the tipped member protrudes distally from the distal end portion when the retrieval catheter is advanced distally in the body lumen towards the medical device. 
         [0017]    According to still another aspect of the invention, a method of retrieving an embolic protection device deployed in a body lumen and secured to a guidewire includes the steps of advancing a retrieval catheter along the guidewire to a location proximal of the embolic protection device. The retrieval catheter has a guidewire lumen extending through a distal shaft portion of the retrieval catheter from a proximal guidewire port to a distal guidewire port. The guidewire lumen has a distal end portion dimensioned to recapture the embolic protection device in a collapsed state. A tipped member having a conical shape is slidably received in a distal end portion of the guidewire lumen, with the pointed end protruding distally from the distal end portion. The guidewire passes longitudinally through the tipped member. The method includes the additional steps of collapsing the embolic protection device, and pulling the collapsed embolic protection device proximally into the guidewire lumen of the retrieval catheter. 
         [0018]    In one embodiment, a pulling wire may be secured to the tipped member, for example by a material connection or a force-transmitting connection, for defining a longitudinal position of the tipped member inside the receiving guidewire lumen. The tipped member may frictionally engage with the distal end portion of the receiving guidewire lumen. 
         [0019]    In one embodiment, a proximal actuator may be provided which has a distal section attached to a proximal shaft portion of the retrieval catheter, and a proximal section movable longitudinally with respect to the distal section and secured to the pulling wire. The tipped member is longitudinally displaced inside the distal end portion of the first guidewire lumen by moving the proximal section relative to the distal section. 
         [0020]    The retrieval catheter may be configured for rapid exchange. 
         [0021]    These and other features and advantages of the present invention will become more readily appreciated from the detailed description of the invention that follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The following figures depict certain illustrative embodiments of the invention in which like reference numerals refer to like elements. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. 
           [0023]      FIG. 1  is a schematic view of an exemplary embolic protection device deployed in a body lumen; 
           [0024]      FIG. 2  is a schematic view of an exemplary dual-lumen retrieval catheter deployed in a body lumen in accordance with various aspects of the invention; 
           [0025]      FIG. 3  is a schematic view of a guidewire deployed in a body lumen; 
           [0026]      FIG. 4A  is a schematic view of an exemplary dual-lumen retrieval catheter deployed in a body lumen in accordance with various aspects of the invention, 
           [0027]      FIGS. 4B and 4C  are schematic views of a proximal end of an exemplary retrieval catheter in accordance with various aspects of the invention, 
           [0028]      FIG. 5  is a schematic view of an exemplary dual-lumen retrieval catheter in accordance with various aspects of the invention, 
           [0029]      FIG. 6  shows schematically a conventional retrieval catheter passing through a stented region of a vessel, 
           [0030]      FIG. 7  is a schematic view of an exemplary retrieval catheter having a soft distal tip in accordance with various aspects of the invention, 
           [0031]      FIGS. 8A-C  show schematically different stages of retrieval of an embolic filter, 
           [0032]      FIGS. 9A  and B show schematically in more detail the mechanism employed with the retrieval catheter for retrieving an embolic filter, 
           [0033]      FIG. 10A  is a schematic view of the dual-lumen retrieval catheter of  FIG. 5A  with a soft tip to ensure non-traumatic passage through a vessel lumen, and 
           [0034]      FIG. 10B  shows schematically an embolic protection device following retrieval from the vessel with the dual-lumen retrieval catheter of  FIG. 5B . 
       
    
    
     DETAILED DESCRIPTION 
       [0035]    Various aspects of exemplary retrieval catheters and methods are disclosed herein which may efficiently and effectively enable a therapeutic procedure to be performed in a blood vessel at an interventional procedure site, for example, stenosis site due to plaque. The exemplary catheters and methods may be part of a therapeutic system and method configured to occlude the blood vessel at a location relative to the interventional procedure site, prevent the flow of blood past the occlusion, and enable the capture and recovery of embolic material which may be released into the blood vessel during the interventional procedure. 
         [0036]    The retrieval catheters and methods are illustrated and described herein by way of example only and not by way of limitation. While the exemplary retrieval catheters and methods are described in detail as applied to the carotid arteries of the patient, those skilled in the art will appreciate that they can also be used in other body lumens as well, such as the coronary arteries, renal arteries, saphenous veins, and other peripheral arteries. Additionally, the exemplary retrieval catheters and methods can be utilized when performing any one of a number of interventional procedures, such as stenting, balloon angioplasty, laser angioplasty, or atherectomy. 
         [0037]    Referring again back to  FIG. 1 , a primary guidewire  12 , for example a guidewire used with a rapid exchange delivery and retrieval system, may be delivered to a first interventional procedure site  13 . As would be appreciated by persons skilled in the art, in accordance with conventional intravascular procedures using the well-known Seldinger Method, a Seldinger wire and introducer sheath may be inserted into the femoral artery at a patient&#39;s groin area. A guide catheter (not shown) can then be inserted into the femoral artery via the introducer sheath, with the distal end of the guide catheter ultimately positioned at a location proximal of the interventional procedure site  13 . For example, in procedures involving the carotid arteries, the guide catheter may be directed through the descending aorta to the aortic arch, with the distal end of the guide catheter being positioned such that the distal end thereof is fixedly positioned and intubating an ostium associated with the desired common carotid artery requiring access and treatment. 
         [0038]    The primary guidewire  12  may then be controllably steered to the site  13  of a lesion or stenosis in a body lumen, for example, a blood vessel, following introduction through a pre-deployed guide catheter. Primary guidewire  12  is manipulated the interventional vascular practitioner into the selected left or right common carotid artery, as appropriate. Primary guidewire  12  is then steered into an appropriately selected internal or external carotid artery, in accordance with the location of the procedure site  13 . Ultimately, the distal tip of primary guidewire  12  is positioned at a location slightly distal of the interventional procedure site  13 . Primary guidewire  12  can then be used to deliver an EPD  10 , such as an embolic protection filter, to a location slightly distal of the interventional procedure site  13 . EPD  10  may preferably be delivered to the treatment site using a rapid exchange embolic protection device delivery catheter (not shown). As previously discussed, the embolic protection device  10  may be configured to lock onto the guidewire  12 , for example, as described in U.S. patent application Ser. Nos. 11/873,882 and 11/873,893. 
         [0039]    The intravascular therapeutic treatment procedure may further include insertion of a balloon dilatation catheter followed by a stent delivery catheter, both catheters utilizing a rapid exchange configuration for ease of access to the site of the stenosis or lesion to be treated. Since all of the aforementioned catheters preferably utilize the rapid exchange configuration, each catheter can easily be substituted and introduced over a standard length interventional guidewire. The balloon and stent catheters are delivered over the guidewire to a position just proximal of the deployed embolic protection device. The balloon and stent may be deployed to treat the stenosis or lesion, as is known by persons skilled in the art. As previously mentioned, if the surgeon notices a second treatment site distal to the first site after the first site has been treated, a dual-lumen retrieval device in accordance with the disclosure may then be delivered to capture the embolic protection device, assist in delivery of a secondary guidewire, and remove the primary guidewire originally introduced, together with the re-captured embolic protection device, from the body lumen. 
         [0040]    A distal portion of an exemplary embodiment of a dual-lumen retrieval catheter  22  is shown in  FIG. 2 . The retrieval catheter  22  includes a first lumen  24  and a second lumen  26 . The first lumen  24  may be configured to receive the embolic protection device  10 , e.g. a filter. For example, referring back to  FIG. 1 , the proximal collar  15  of the embolic protection device  10  may be fixedly coupled to the primary guidewire  12  to stabilize the embolic protection device  10  relative to the guidewire  12  such that the device  10  will collapse for recapture into the first lumen  24  at a distal end  28  of the retrieval catheter  22 . 
         [0041]    In operation, the retrieval catheter  22  may be delivered to the intravascular site where the embolic protection device  10  is deployed. The first lumen  24  of the catheter  22  receives a collapsing or collapsed EPD  10 . As previously described, the embolic protection device  10  may be retrieved with the primary guidewire  18 , upon which it is locked. Removal of the catheter  22  with EPD  10  leaves the secondary guidewire  27  in a therapeutic position associated with the second lesion site  17 , as shown in  FIG. 3   
         [0042]    Referring now to  FIG. 4A , the retrieval catheter  22  may include a rapid exchange (RX) retrieval catheter. The rapid exchange catheter  22  may include a proximal shaft portion  24   a  located at a proximal end  40  of the catheter  22  and a distal shaft portion  24   b.  The proximal shaft portion  24   a  may extend through a guide catheter  41  and preferably have a length sufficient to extend from the site of introduction at the femoral artery to an appropriate distal location such that a distal end of the guide catheter  41  for intubation into an appropriate ostium of the aortic arch. It will be appreciated that the guide catheter  41  may extend further than illustrated in  FIG. 4A  so as to enclose the primary guidewire  18  and the proximal shaft portion  24   a  within the guide catheter  41 ; however, for sake of clarity, these elements are illustrated as not being enclosed by the guide catheter  41 . A hub  45  located at the proximal end of the guide catheter  41  facilitates longitudinal repositioning of the primary guidewire  18  and delivery catheters while maintaining hemostasis via a valve (not shown) on the hub  45 . 
         [0043]    To enable rapid exchange, the distal shaft portion  24   b  includes a first proximal guidewire port  42 , a first distal guidewire port  24 , and a second distal guidewire port  26 . The first proximal guidewire port  42  may be spaced from the proximal end  40  of the catheter  22 . The first guidewire lumen  24  may extend through the distal shaft portion  24   b  from the first proximal guidewire port  42  to the first distal guidewire port  24 . The first guidewire lumen  24  may have a distal end portion (not shown), which is similar to the collecting tube  55  shown in  FIG. 5  and configured to recapture a collapsed embolic protection device  10 . A second guidewire lumen may extend through the distal shaft portion  24   b  from a second proximal guidewire port  36  to the second distal guidewire port  26 . 
         [0044]    The primary guidewire  18 , which extends distally from the distal shaft portion  24   b,  exits a proximal end  24   a  of the distal shaft portion at a rapid exchange port  42  and extends proximally parallel with the proximal shaft portion  24   a  and through the guide catheter  41  and a hub  45  as it exits the patient&#39;s body. 
         [0045]    A secondary guidewire  27  can be introduced through the catheter  22  via the proximal shaft portion  24   a  and extends from the second lumen  26  of the distal shaft portion  24   b  to enter the patient&#39;s blood vessel distal of the catheter  22  ( FIG. 2 ). The proximal shaft portion  24   a  may extend through the introducing sheath  41  and the hub  45 . The secondary guidewire  27  may exit the patient&#39;s body via an exit port  48  of the proximal shaft portion. 
         [0046]    According to some aspects, as shown in  FIGS. 4B and 4C , for example, in order to retrieve the catheter  22  from the patient&#39;s body with a guidewire used in rapid exchange procedures, a shaft  44  of the proximal shaft portion  24   a  may include a slit  47  extending along its length, from the exit port  48  to the rapid exchange port  42 . The slit  47  is configured to open and allow the catheter shaft  44  to be peeled  46  away from the secondary guidewire  27  during retrieval. Alternatively, a longer guidewire, such as a Kaltenbach wire, can be employed in lieu of a catheter with a slit when using a full-length over-the-wire retrieval catheter. 
         [0047]    Another retrieval catheter and retrieval method is shown in and described with reference to  FIG. 5 . According to one aspect, a retrieval catheter  152  may include a first lumen  155  and a second lumen  156 . As shown, a new guidewire  127  may be pre-loaded into catheter  152  prior to insertion of the catheter  152  into a patient&#39;s body. A distal tip  157  of the new guidewire  127  may be close to an exit port  148  of the second lumen  156 . 
         [0048]    The first lumen  155  may be configured to collect a deployed EPD  10  (not shown in  FIG. 5 ) locked onto original guidewire  18  in collecting tube  154 . The catheter  152  may include a rapid exchange port  153  extending from a proximal end of a distal shaft portion to a distal end  159  of the catheter. The catheter  152  may also include a handle  159  and a shaft  158  connecting the handle  159  to the catheter near the rapid exchange port  153 . 
         [0049]    As evident from  FIG. 5 , the retrieval catheter  152  may not be able to traverse a stent  14  ( FIG. 2 ) smoothly, and may easily get caught on protrusions  62  of stent  14 , as depicted in  FIG. 6 . This is shown more clearly for an exemplary single tube retrieval or collection catheter  64  with an indicated radiopaque marker  68 . When pushed from the proximal end, the tube may got caught on a protruding strut  62  of a stent  14  which interrupts passage of the retrieval catheter toward the EPD  66  to be retrieved. When the collection catheter  64  is pushed, it may bend at  65  when getting caught on the strut. Further attempts to push then may cause trauma to the blood vessel, especially at the stent position. 
         [0050]      FIG. 7  shows a retrieval catheter  74  with a tapered soft tip  72  which will alleviate this problem and ensure a smooth and non-traumatic passage along the vessel wall. As indicated in  FIG. 7  and described in more detail hereinafter with reference to  FIGS. 8A-C , the greatest outside diameter of the tapered tip  72  is smaller than the inside diameter if the retrieval catheter, so that the tapered tip  72  is retracted into the retrieval catheter together with the EPD device to be retracted. 
         [0051]      FIGS. 8A-C  show different stages in the retrieval of an embolic protection device (EPD)  85  with the soft-tipped retrieval catheter  74  illustrated in  FIG. 7 . As seen in  FIG. 8A , the retrieval catheter  74  is advanced distally over the guidewire  18  towards the EPD  85  until it comes in contact with the proximal side  86  of EPD  85 . At this stage of the process, the guidewire  18  is coupled to or held, as illustrated in  FIG. 8B  by arrow  81 , against the retrieval catheter&#39;s proximal handle section  87 , which is slidably guided in or with respect to the retrieval catheter&#39;s distal handle section  88 . The guidewire  18  may be coupled to proximal handle section  87  by frictional engagement, for example, with clips affixed to the outside of handle section  87 , or the proximal handle section  87  may be constructed as a collet or chuck through which guidewire  18  passes. 
         [0052]    The guidewire  18  together with the proximal handle section  87  is then pulled proximally away from the stationary distal handle section  88 , as shown in  FIG. 8C , pulling the EPD  85  and the soft tip  72  into the retrieval catheter or collecting tube  74 .  FIG. 8C  shows the filter (obscured from view) after retrieval inside the retrieval catheter or collecting tube  74 , with only the conventional soft tip of the EPD  85  protruding from the distal end of the retrieval catheter or collecting tube  74 . A pulling wire  89  is attached with its proximal end to the proximal handle section  87  and with its distal end to the proximal end of soft tip  72 , as described in more detail with reference to  FIG. 9 . Pulling wire  89  may be a flexible wire and comprise a metal wire or polymer suture, for example. 
         [0053]      FIGS. 9A and 9B  show in more detail the mechanism by which the soft tip  72  is movably held inside the retrieval catheter  74 . As shown in  FIG. 9A , the soft tip  72  is attached at attachment point  92  to pulling wire  89  that extends through the retrieval catheter  74  to the proximal handle  87  (see also  FIG. 8C ). The pulling wire  89  can be attached to the soft tip  72  using various fastening methods, such as a material connection (brazing, welding), or a force-transmitting connection such as an adhesive or a rivet. After soft tip  72  comes in contact with the EDP  85 , both the EPD  85  and the soft tip  72  are pulled out proximally, with the EPD  85  collapsing and assuming the position inside the retrieval catheter  74  indicated in  FIG. 9B . 
         [0054]    It will be appreciated by those skilled in the art that the soft-tipped retrieval catheter depicted in  FIG. 7  can also be employed with the dual-lumen retrieval catheter illustrated in  FIG. 5 . Identical elements or elements performing substantially identical functions are indicated with the same reference numerals. The primary guidewire  18  has been omitted from  FIG. 10A  for sake of clarity, but is shown in  FIG. 10B . With the soft tip  72  in place as shown, the dual-lumen catheter can be advanced through a vessel without causing trauma to the vessel walls. The retraction procedure for the EPD  10  is identical to the procedure described in  FIGS. 8A-C  for a single-lumen retrieval catheter. 
         [0055]    Those of skill in the art will appreciate that the soft tip  72  can also be frictionally held in place inside the collection tube  74 , obviating the need for a separate pull wire. Retraction of the EPD  85  will then also push the soft tip  72  back into the lumen of the retrieval catheter. However, this process may distort the shape of the soft tip  72 , requiring a harder material for the soft tip  72  which could then again disadvantageously induce trauma in the vessel. In addition, the soft tip  72  would not be securely held captive in the collection tube  74  during advancement through the vessel and may become dislodged from its position inside the collection tube  74 , though still being held by the guidewire extending through the soft tip  72 . 
         [0056]    It will be apparent to those skilled in the art that various modifications and variations can be made to the retrieval catheters and methods of the present invention without departing from the scope of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only.