Abstract:
A retrieval catheter operable by a single clinician that will neither displace a deployed stent nor cause undue trauma to the vascular lumen or lesion. The retrieval catheter may be sized to accommodate both a guidewire and a balloon wire. The retrieval catheter is easy to navigate through tortuous passageways and will cross a previously deployed stent or stent-graft easily with minimal risk of snagging on the deployed stent or stent graft. The sheath and dilator are adapted to allow a guidewire or balloon wire to pass through the walls of both and to allow the sheath and dilator to move axially with respect to each other.

Description:
FIELD OF THE INVENTION 
     The present invention relates to catheters used for retrieving, positioning, or repositioning endoluminal devices located distal or adjacent to a stent or other previously implanted device. 
     BACKGROUND OF THE INVENTION 
     The field of endovascular surgery is rapidly becoming an alternative to more traditional surgeries such as carotid endarterectomy, coronary artery bypass grafting, aortic aneurysm repair, and vascular grafting. Percutaneous intervention is becoming the primary means for revascularization in many such procedures. Distal embolization of friable debris from within the diseased conduit remains a risk of endovascular surgery, potentially involving complications such as myocardial infarction and ischemia. Devices such as balloon catheters and embolic filters have been used to control and remove embolic debris dislodged from arterial walls during endovascular procedures, distal to an interventional procedure site. Percutaneous introduction of these devices typically involves access via the femoral artery lumen of the patient&#39;s groin vasculature. An introducer sheath may then be inserted in the wound, followed by a guide catheter that is advanced to the site to be treated. A guidewire is usually introduced into the lumen of the vasculature and advanced distally, via manipulation by the clinician, to cross the lesion or area of treatment. Then a catheter containing the device(s) may be employed to traverse the length of the guidewire to the desired deployment location. Once the distal protection device is deployed, the lesion or stenosis is available for treatment. 
     A common practice for treating the lesion or stenosis is to deploy a stent at the target location to increase the lumen size of the vessel and maintain or increase patency. When feeding a guidewire through the lumen of a stent, there is a possibility that the tip of the wire will become diverted and/or ensnared by the stent. This possibility increases with increasing vessel tortuosity. This problem has been addressed through the use of a soft, flexible, floppy tip at the distal end of the wire to improve steerability and reduce the possibility of engaging the stent or peripheral vasculature. However, a flat-tipped catheter advanced over a guidewire with an inside diameter larger than the outside diameter of the guidewire, presents a sharp edge to the vessel or stent at the point of tangential contact. The exposure of this edge increases with vessel tortuosity and with an increase in differences between the guidewire outside diameter and catheter inside diameter. 
     Embolic filters and balloons are often deployed by traversing the lesion being treated and deploying the device distally. If a balloon wire or embolic filter becomes caught in the patient&#39;s vasculature or is otherwise prevented from removal by a stent, such as the device becoming entrapped within the struts of a stent, then the clinician is typically required to perform higher risk procedures to retrieve them. These include subjecting the device to greater retrieval forces, and removal through invasive surgical techniques. The former increases the risk of the device becoming detached from its guidewire or catheter, whereas the latter exposes the patient to the increased risks of open surgical extraction. Successful retrieval of these devices in situations other than those originally anticipated, without intimal dissection, plaque, hemorrhage, or vessel occlusion, is an important advancement in the field of interventional endovascular surgery. 
     SUMMARY OF THE INVENTION 
     A retrieval catheter assembly is described that may be operated by a single clinician and upon delivery will neither permanently displace a previously deployed stent nor cause undue trauma to the vascular lumen or lesion. The retrieval catheter assembly will enable a tubular retrieval sheath to be advanced over a wire between the outside diameter of a deployed stent and the vessel wall, or over a guidewire through the lumen of a stent and retrieve various devices, e.g., filters, balloons, etc. distal to the stent. The retrieval catheter may also enable a tubular sheath to be directed through the sidewall of a stent. 
     The retrieval catheter assembly comprises a sheath having a balloon wire or guidewire exchange port through the sidewall of the sheath and a dilator, which is positioned in the sheath lumen. The sheath has a body with relatively stiff proximal and distal sections and with a flexible middle section, which aids in the operation of the device. The dilator is adapted to slide axially relative to the sheath between an extended position and a retracted position while a balloon wire or guidewire extends through the exchange port. When the dilator is withdrawn in a proximal direction into the sheath, it provides a space within the lumen of the distal end of the sheath to accommodate a filter or other device retrieved by the wire. 
     The dilator includes a tapered tip, which allows the device to be inserted between the stent and the vasculature for retrieval of devices distal to the stent. The tip may be a soft or hard pliable thermoplastic, metal such as stainless steel, or ceramic and will have a radius, which averts snagging on the stent and vasculature. The inner diameter of the tip is sized to control the clearance between the tip inner diameter and the guidewire outer diameter, which aids in operation of the device. 
     The catheter assembly preferably includes a hydrophilic and/or a lubricious coating applied to the dilator tip and also preferably applied to the sheath from tip to the exchange port. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view of the catheter assembly. 
         FIG. 1B  is a longitudinal cross-sectional view of the catheter assembly tip with guidewire threading tube. 
         FIG. 1C  is a longitudinal cross-sectional view of the catheter assembly tip and relative position of the cooperative opening region during a first stage of device retrieval. 
         FIG. 1D  is a longitudinal cross-sectional view of the catheter assembly tip and relative position of the cooperative opening region during a second stage of device retrieval. 
         FIG. 1E  is a longitudinal cross-sectional view of the catheter assembly tip configured to have a slit type cooperative opening extending to the most distal tip of the assembly. 
         FIG. 2A  is a cross-sectional view of a vascular filter in situ, distal to a vascular lesion. 
         FIG. 2B  is a cross-sectional view of a vascular filter in situ, distal to a vascular lesion that has been covered by a deployed stent. 
         FIG. 2C  is a cross-sectional view of a retrieval catheter of prior art. 
         FIG. 3A  is a cross-sectional view of one embodiment of this invention showing a step in a method of using the retrieval device in a vascular filter retrieval procedure. 
         FIG. 3B  is a cross-sectional view of one embodiment of this invention showing a second step in a method of using the retrieval device in a vascular filter retrieval procedure. 
         FIG. 3C  is a cross-sectional view of one embodiment of this invention showing a third step in a method of using the retrieval device in a vascular filter retrieval procedure. 
         FIG. 3D  is a cross-sectional view of one embodiment of this invention showing a fourth step in a method of using the retrieval device in a vascular filter retrieval procedure. 
         FIG. 4A  is a cross-sectional view of an occlusion balloon with the balloon wire positioned between the deployed stent and the vasculature. 
         FIG. 4B  is a cross-sectional view of a retrieval catheter of prior art. 
         FIG. 4C  is a cross-sectional view of one embodiment of the present retrieval catheter showing a step in a method of using the retrieval device in a balloon retrieval procedure. 
         FIG. 5  is perspective view of one embodiment of the present retrieval catheter showing the retrieval catheter exiting the lumen of a previously placed stent through the sidewall of the stent. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As noted above, this catheter assembly includes a sheath, dilator and guidewire.  FIG. 1A  is a perspective view of catheter assembly  20 , having a sheath  22 , dilator  24 , guidewire threading tube  25 , and guidewire  26 . Guidewire threading tube  25  may be constructed from a variety of polymeric materials such as polyimide. Guidewire threading tube  25  is provided to aid in the insertion of the guidewire  26  through sheath slot  30  and dilator slot  46  (per  FIG. 1B ), prior to use in a patient. This threading tube  25  is typically removed from catheter assembly  20  prior to insertion into a patient. Also shown in  FIG. 1A  is the proximal end of the dilator  24 , or dilator hub  28  extending from the luer hub  29 . 
       FIG. 1A  additionally depicts the distal section  23  of catheter assembly  20 .  FIGS. 1C-1E  are longitudinal cross-sections of distal section  23  showing a sheath  22 , dilator  24 , dilator lumen  27 , sheath slot  30 , dilator slot  46 , and guidewire  26 . Note the relative distal movement of sheath  22  and sheath slot  30  with respect to dilator  24  and dilator slot  46 . The sheath  22  and hubs  28  and  29  may comprise conventional medical grade materials such as nylon, acrylonitrile butadiene styrene, polyacrylamide, polycarbonate, polyethylene, polyformaldehyde, polymethylmethacrylate, polypropylene, polytetrafluoroethylene, polytrifluorochlorethylene, polyether block amide or thermoplastic copolyether, polyvinylchloride, polyurethane, elastomeric organosilicon polymers, and metals such as stainless steels and nitinol. The sheath  22  or dilator  24  may contain either radiopaque markers or contain radiopaque materials commonly known in the art. 
     In one embodiment, the catheter assembly  20  may be used to retrieve a previously placed vascular filter  32 .  FIG. 2A  illustrates a vascular filter  32  with filter wire  34  placed within the vasculature  36 , distal to a lesion  37 . In this application, a stent  38  is placed over the vascular lesion  37  creating a rough, tortuous region across which vascular filter  32  is to be retracted as shown in  FIG. 2B .  FIG. 2C  depicts a retrieval catheter  40  of prior art. Note the relatively inflexible catheter shaft and the inability of the catheter  40  to maintain a concentric position within the lumen of the catheter shaft of filter wire  34 . Also note the significant difference between catheter  40  inner diameter and filter wire  34  outer diameter, creating an opening which provides an opportunity for catheter  40  to engage with the stent  38 . 
       FIGS. 3A through 3D  show sequential cross-sectional views of the retrieval catheter in use. In these figures, the catheter assembly  20  is used to retrieve a previously placed vascular filter  32 . 
       FIG. 3A  illustrates an embodiment of the present retrieval catheter with sheath  22  and dilator  24  navigating the rough, tortuous region through the stent  38  toward the previously placed vascular filter  32 . The sheath  22  may be constructed with varying stiffness along the length. Methods of construction to achieve variable stiffness in a sheath component are well known in the art and include varying cross sectional profile dimensions and/or wall thickness, changing the hardness or modulus of the sheath material, braid modification, and including the use of a removable stylet or stiffening wire. Additional methods of achieving variable stiffness in a sheath component are generally taught by U.S. Pat. No. 6,858,024 and U.S. Pat. Appl. No. 2007/0088323 A1. The sheath  22  may be made with an outer diameter that would vary depending on targeted vascular size. For example, a sheath used with a 0.36 mm guidewire would have an outer diameter that ranges from about 1.57 mm to 1.62 mm. The sheath  22  inner diameter would also vary with application and for use with a 0.36 mm guidewire typically ranges from about 1.22 mm to 1.27 mm. 
     The sheath  22  includes a slot or aperture  30  functioning as a cooperative opening or exchange port through the sidewall of the sheath. The slot  30  may be formed through the side wall of the sheath  22  by methods known in the art which may include skiving by hand with a straight razor or cutting with a suitable tool. One or both ends of slot  30  may be formed to be perpendicular to the longitudinal axis of sheath  22 . Alternately, one or both ends may be formed to have a taper to reduce the angle between the proximal end of slot  30  and the guidewire  26 . As shown in  FIG. 3A , the slot  30  may be a formed to have a length  42  that would vary with application but would preferably range from about 0.20 mm to 0.38 mm. Slot  30  may have a width  44  suitable to provide adequate clearance between the slot  30  and a guidewire  26  or balloon wire. Alternately, slot  30  may be formed as a slit thus providing an interference fit between the guidewire  26  or balloon wire and the slit walls. Slot  30  may also be configured with features to provide positive tactile feedback to a user during device use. These may include such features slot  30  being formed to have a barbell shape that provides stops at the proximal and distal ends of slot  30  for securing guidewire  26  or a balloon wire. Slot  30  may also be provided with rough surfaces or serrations along the edge of the slot  30  to provide enhanced tactile feedback. The slot  30  may be cut at a distance from the distal end of the sheath from about 1 cm to about 50 cm from the distal end of the sheath  22  depending on the specific design requirements. Preferably, the range would be from about 5 cm to about 31 cm from the distal end of the sheath  22 . The most preferred range would be from about 25 cm to about 32 cm from the distal end of the sheath  22 . 
     The outer surface of sheath  22  may be provided with a hydrophilic/lubricious coating. The coating may be applied to the entire outer surface of the sheath. Most preferably, the coating may be applied from the most distal end continuing to about the slot  30  or aperture. The inner surface of sheath  22  component may be provided with a hydrophilic/lubricious coating. The coating may be applied to the entire inner surface of the sheath  22 . Preferably, the coating may be applied to the distal most 40 cm of the sheath  22 . Most preferably, the coating may be applied to the distal most 30 cm of the sheath  22 . The coating may be any biocompatible polymer lubricant as commonly known in the art. 
     Dilator  24  is typically formed from a lubricious plastic material such as polytetrafluoroethylene, polyethylene, polyether block amide or thermoplastic copolyether to provide a high degree of lubricity in the blood vessel as well as with respect to movement of the sheath  22  over the dilator  24 . Dilator  24  may also be formed of a lubricious plastic material in combination with a metal hypo tube. Dilator  24  is typically provided with a hub  28  at its proximal end and is of a length slightly greater than the length of the catheter assembly so that when the hub  28  of the dilator is advanced fully distally against the proximal end of catheter hub  29 , the tip of dilator  24  will project beyond the distal end of the catheter. Thus, the length of dilator  24  will depend on the length of the sheath  22 . The tip of dilator  24  is considered to be the tapered portion located at the distal most tip of dilator  24 . A length of about 1 cm for the tapered portion will be applicable to most applications but could range from about 1 mm to 5 cm. 
     Dilator  24  may be made with an outer diameter sized to pass through the lumen of the sheath  22  with which it is intended to be and may be supplied in various sizes dependent on the application and catheter sheath inner diameter. A typical range of outer diameters for the intended application of retrieving a vascular filter or balloon would be from about 1.14 mm to 1.19 mm. The clearance between a guidewire  26  or balloon wire and the lumen of dilator  24  is relatively small and would vary dependent on intended use. For the intended application involving use over a guidewire, a typical inner tip diameter would be from about 0.38 mm to 0.43 mm. Alternately, dilator  24  may be used with a balloon wire where a typical inner tip diameter would be from about 0.48 mm to 0.53 mm. Dilator  24  has a lumen  27  adapted for passage of a guidewire or balloon wire. Diameters of dilator lumens  27  will vary with intended use. A typical dilator lumen  27 , suitable for use with a guidewire  26 , would be from about 0.48 mm to 0.53 mm. Alternately, dilator  24  may be made with a lumen  27  suitable for balloon wires, typically ranging from about 0.61 mm to 0.66 mm. 
     Dilator  24  may have a tip made of pliable thermoplastic such as Pebax® (polyether block amide or thermoplastic copolyether from Arkema, Beaumont Tex. 77704) or metal such as stainless steel, nitinol or any other material with appropriate stiffness, hardness and other properties suitable for use in the human body. The dilator tip may alternately be constructed of a combination of a biocompatible metal and thermoplastic in a variety of ways. The tip may also be of composite metal or ceramic and/or polymer construction. 
     As shown in  FIG. 3A  (and similar to the slot  30  through the sidewall of sheath  22 ), dilator  24  has a slot  46  through the sidewall of the dilator  24 . The dilator slot  46  may be formed through the sidewall of the dilator  24  by methods well known in the art which may include skiving by hand with a straight razor cutting with a suitable tool. One or both ends of dilator slot  46  may be formed to be perpendicular to the longitudinal axis of dilator  24 . Alternately, one or both ends may be formed to have a taper to reduce the angle between the proximal end of dilator slot  46  and the guidewire  26 . 
     The dilator slot  46  may have a length  48  extending from about 1 cm proximal to the dilator tip to the distal end of the luer hub  29 . Preferably, the dilator slot  46  may extend from about 1 cm proximal to the dilator tip to about 100 cm proximal to the tip. Most preferably, the dilator slot  46  may extend from about 1 cm proximal to the dilator tip to about 33 cm proximal to the tip. In still another embodiment, dilator slot  46  (particularly if configured as a slit as described below) may extend from the tip to about, for example, 33 cm proximal to the tip. 
     Dilator slot  46  may have a width  48  suitable to provide adequate clearance between the dilator slot  46  and a guidewire  26  or balloon wire. Alternately, dilator slot  46  may be formed as a slit thus providing an interference fit between the guidewire  26  or balloon wire and the slit walls. Dilator slot  46  may also be configured with features to provide positive tactile feedback to a user during device use. These may include such features dilator slot  46  being formed to have a barbell shape that provides stops at the proximal and distal ends of dilator slot  46  for securing guidewire  26  or a balloon wire. Dilator slot  46  may also be provided with rough surfaces or serrations along the edge the of dilator slot  46  to provide enhanced tactile feedback. 
       FIG. 3B  shows the distal end of the catheter assembly  20  positioned in vasculature  36  in close proximity to a previously placed vascular filter  32 . The catheter assembly  20  was advanced over the previously placed vascular filter wire  34 . Note that dilator  24  protrudes from the sheath  22 . 
     As shown in  FIG. 3C , the dilator  24  is retracted into sheath  22  in the direction as shown by arrow  50 . Note the axial sliding movement of slot  30  and dilator slot  46  with respect to slot  30  of sheath  22 . 
     As shown in  FIG. 3D , the dilator  24  remains retracted into the sheath  22 . Sheath  22  is advanced in the direction as shown by arrow  52  thereby collapsing the vascular filter  32 . After the filter  32  has been collapsed and contained within the sheath  22 , the catheter assembly  20  is withdrawn from the target site. 
       FIGS. 4A through 4C  show sequential cross-sectional views of a retrieval catheter in use retrieving a balloon  54 . 
       FIG. 4A  shows a stent  38  deployed over a balloon  54  and balloon wire  56 , trapping the balloon  54  and/or balloon wire  56  between the stent  38  and vasculature  36 . 
       FIG. 4B  depicts a retrieval catheter  40  of prior art. Note the relatively inflexible catheter shaft and the inability of the catheter  40  to maintain a concentric position within the lumen of the catheter shaft of balloon wire  56 . 
       FIG. 4C  illustrates an embodiment of the invention with sheath  22  and dilator  24  navigating the rough tortuous region between the stent  38  and the vasculature  36  toward the trapped balloon  54 . The remainder of the balloon retrieval procedure is similar to the procedure described in  FIGS. 3B through 3D . 
     The present invention may also be used to position or reposition a device located distal or adjacent to a stent or other previously implanted device.  FIG. 5  depicts an embodiment of the present invention with sheath  22  and dilator  24  exiting the lumen of a previously placed stent  38  through the sidewall of the stent  38 . This embodiment could be used to deploy or reposition an endoluminal device into the branch vasculature. The same embodiment could alternately be used to retrieve an endoluminal device from branch vasculature. 
     EXAMPLES 
     To construct a sheath, a 1.24 mm PTFE coated mandrel was loaded with a 1.29 mm inner diameter etched PTFE liner (1.29 mm inner diameter.×0.02 mm thick wall) and secured. A braided sleeving (0.25 mm×0.76 mm stainless steel flat wire, 2 over 2 under, 50 ppi) was loaded and secured at the proximal end of mandrel. The braid was stretched to the distal end of the mandrel and carefully trimmed to length with scissors so that the ends of the wires were uniform. Trimming of the braid length may be achieved with any suitable cutting or trimming tool. A marker band (platinum/iridium, 1 mm width minimum, inner diameter 14.7 mm, 0.25 mm minimum thickness) was slid onto the assembly from the proximal end of the loaded mandrel to the distal end. The marker band was carefully brought up to the end of the braid so that the marker band covered the end of the braid and so that no ends of wires were showing at the marker band. The location of the marker band should be from about 5.08 cm to 6.35 cm from the distal end of the mandrel. A hand crimper tool was used to secure the marker band. The braid was then stretched from the proximal end of the mandrel and re-secured. 
     To pre-assemble the proximal and distal body stock components of the sheath, the proximal component (Pebax® 7233, 72 durometer and 1.57 mm inner diameter and 0.10 mm wall, gold pigment) was cut to about 125 cm and the distal body stock component (Pebax® 5533, 55 durometer and 0.157 cm inner diameter and 0.10 mm wall, grey pigment) was cut to about 32.5 cm. The distal body stock component was flared with the end of a pair of small tweezers so that it would slide over the proximal body stock component. The distal and proximal components were loaded onto a 0.15 mm PTFE mandrel (nonporous PTFE) and the two components were overlapped by 1 mm. A 2.54 cm long length of FEP heat shrink (EP4587-10T, Zeus, Orangeburg, S.C. 29116) was positioned over the center of the 1 mm overlap of the two body stock components and a heat gun was used to bond the two components together. The FEP heat shrink tube was removed after the bond had cooled. 
     The pre-assembled body stock component was loaded onto the proximal end of the 1.24 mm PTFE coated mandrel bringing the end of the pre-assembled body stock component to within 2 cm to 3 cm past the marker band. A heat shrink tube (EP4587-10T FEP 1.9 mm minimum expanded inner diameter) was loaded over the entire assembly with the end of the heat shrink tube reaching the end of the pre-assembled body stock component distal end. The two ends were bonded together with a heat gun. The assembly was heated in a convection heat shrink reflow oven. The assembly was allowed to air cool, the heat shrink tube was removed and the ends were trimmed with a razor. The entire assembly was removed from the mandrel. The assembly was cut to a length of about 142 cm and the tip was trimmed. A hole was hand cut at about 29.7 cm from the distal end of the sheath. A female luer hub (Qosina part No. 41426 Qosina, Edgewood, N.Y. 11717) was bonded to the proximal end with adhesive (Loctite® 4011 Adhesive, Henkel Corp., Rocky Hill, Conn. 06067). 
     A stock dilator (Pebax® 7233, light grey pigment, 0.48 mm inner diameter×1.2 mm outer diameter) was tipped down to 0.36 mm inner diameter and 0.66 mm outer diameter with a radio frequency tipping machine (Ameritherm Inc., Scottsville, NY 14546). The dilator was then cut to about 152 cm in length. Any appropriate cutting method may be used. An 4.0 cm slot was hand skived in the dilator starting at about 27.2 cm from the distal end of the dilator. The proximal end of the dilator was heat flared to form a mechanical anchor. A female luer hub (Qosina part. No. 64018) was bonded onto the dilator proximal end with Loctite® 3311 Adhesive. 
     To assemble the catheter assembly  20 , a hemostasis valve (part No. RV0317-000, Qosina part No. 88416) was attached to the hub of the dilator  24 . With the aid of a 0.36 mm guidewire, the sheath  22  and dilator  24  components were assembled and guidewire threading tube  25  (Phelps Dodge part No. Polyimide EP4649-10Z 0.38 mm inner diameter×0.47 mm outer diameter, Phelps Dodge HPC, Trenton, Ga. 30752) was installed in the assembly. The catheter assembly  20  was masked to expose the proximal and distal ends. A flexible mandrel (0.46 mm outer diameter) was inserted into the distal end of the assembly until it exited the cooperative opening  30 . The loaded assembly was then placed into a vacuum plasma system. The entire assembly was plasma treated to enhance attachment of the polymer lubricant. The catheter assembly  20  was removed from plasma system. The sheath  22  and dilator  24  components of the catheter assembly  20  were then dip coated with a biocompatible polymer lubricant to reduce friction. The catheter assembly  20  with lubricious coating was then heat cured. The flexible mandrel was removed and catheter assembly  20  was then placed in a protective polymer coil and packaged for shipment. 
     While particular embodiments of the present invention have been illustrated and described herein, the present invention should not be limited to such illustrations and descriptions. It should be apparent that changes and modifications may be incorporated and embodied as part of the present invention within the scope of the following claims.