Abstract:
The present invention provides an improved medical device delivery catheter. The medical device delivery system comprises a catheter having a medical device receiving portion adapted to receive a medical device near the distal end of the catheter and a medical device such as a stent concentrically arranged around the catheter within the medical device receiving portion. The medical device delivery system further comprises a movable medical balloon disposed about the medical device. In use, the balloon may be inflated to dilate a lesion, retracted to deploy the medical device and subsequently reinflated to seat the medical device.

Description:
FIELD OF THE INVENTION 
     This invention relates to a medical device delivery catheter system, such as the kind used in percutaneous transluminal coronary angioplasty (PTCA) procedures. More particularly, it relates to a medical device delivery catheter employing a movable balloon which is disposed about the medical device. 
     BACKGROUND OF THE INVENTION 
     In typical PTCA procedures, a guiding catheter is percutaneously introduced into the cardiovascular system of a patient and advanced through the aorta until the distal end is in the ostium of the desired coronary artery. Using fluoroscopy, a guide wire is then advanced through the guiding catheter and across the site to be treated in the coronary artery. An over the wire (OTW) balloon catheter is advanced over the guide wire to the treatment site. The balloon is then expanded to reopen the artery. The OTW catheter may have a guide wire lumen which is as long as the catheter or it may be a rapid exchange catheter wherein the guide wire lumen is substantially shorter than the catheter. Alternatively, a fixed wire balloon catheter could be used. This device features a guide wire which is affixed to the catheter and cannot be removed. Following dilatation of the vessel, the balloon catheter is removed from the vessel. 
     To help prevent arterial closure, repair dissection, or prevent restenosis following dilatation, a physician can implant an intravascular prosthesis, or a stent or other such device such as a stent-graft, or a graft, for maintaining vascular patency inside the artery at the lesion. The stent may either be a self-expanding stent or a balloon expandable stent. For the latter type, the stent is often delivered on a balloon and the balloon is used to expand the stent. The self-expanding stents may be made of shape memory materials such as nitinol or constructed of regular metals but of a design which exhibits self expansion characteristics. 
     In certain known stent delivery catheters, a stent and an optional balloon are positioned at the distal end of the catheter, around a core lumen. The stent and balloon are held down and covered by a sheath or sleeve. When the distal portion is in its desired location of the targeted vessel the sheath or sleeve is retracted to expose the stent. After the sheath is removed, the stent is free to self-expand or be expanded with a balloon. 
     This multiple step procedure of dilatation with a balloon catheter, removal of the balloon catheter and use of a separate stent delivery catheter is time consuming and requires the use of many different devices. Moreover, the insertion and removal of multiple device increase the opportunity for hemorrhagic complications and increase the overall trauma to the patient. In an effort to reduce the number of insertions and removals of catheters, a number of devices have been disclosed which combine a dilation balloon and a stent delivery catheter in a single device. These devices reflect a variety of approaches. 
     One approach employs a multiple balloon catheter in which a first balloon is used for dilatation and a second balloon is used for expanding a stent. This approach is disclosed, inter alia, in U.S. Pat. Nos. 5,733,299, 5,632,760, 5,456,694 and 5,725,535. 
     Another approach employs a balloon which is longitudinally displaceable with respect to the stent. This approach is disclosed, inter alia, in U.S. Pat. No. 5,807,398 and 5,634,928. 
     The present invention presents another approach to providing a dilatation balloon in a medical device delivery catheter. 
     For the purpose of this disclosure, the term medical device shall refer to stents, stent-grafts, grafts and vena cava filters. 
     All U.S. patents and patent applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides an improved medical device delivery system. The medical device delivery system comprises a catheter having an inner tube with a medical device disposed about a receiving region at the distal end thereof and a retractable balloon assembly surrounding at least the medical device. The retractable balloon assembly may comprise a medical balloon in mechanical communication with a balloon retraction device and an inflation lumen in fluid communication with the medical balloon. In one embodiment, the balloon retraction device comprises an outer sheath and an inner sheath. The proximal end of the balloon is attached to the distal end of the outer sheath, and the distal end of the balloon is attached to the distal end of the inner sheath. 
     The outer sheath of the catheter may include a proximal outer sheath portion and a retractable distal sheath. An optional collapsible sheath may be located between and adhered to the proximal outer sheath and the retractable distal sheath. During retraction of the distal sheath the collapsible sheath collapses upon itself or accordions upon its preformed pleats or creases, providing room for the distal sheath to retract unencumbered, thereby freeing the loaded stent. The inclusion of the collapsible sheath significantly reduces the sheath length, maintains a reduced system profile, provides good flexibility and provides a protective covering to the w ire pull back mechanism. 
     The outer sheath may also be telescoping. A separate inflation lumen may be provided or the space between an inner and outer sheath may serve as an inflation lumen. 
    
    
     Other objects, features, embodiments and characteristics of the present invention, as well as the methods of operation and functions of the related elements of the structure, and the combination of parts and economics of manufacture, will become more apparent upon consideration of the following description with reference to the accompanying drawings, all of which form a part of this specification. 
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
     FIG. 1 shows a side view of a catheter according to the invention having a loaded stent including a cross-sectional view of the distal portion thereof and a side view of the proximal end of a catheter according to the invention showing the manifold portion thereof. 
     FIG. 2 is an enlarged view of the distal end of the catheter shown in FIG. 1 with a loaded stent. 
     FIG. 3 is a sectional view of the catheter taken along line  3 — 3  in FIG.  1 . 
     FIG. 4 a  shows a side view of the distal end of a catheter according to the invention having an axially collapsible balloon and a loaded stent. 
     FIG. 4 b  shows the catheter of FIG. 4 a  with the balloon partially collapsed. 
     FIG. 4 c  shows the catheter of FIG. 4 a  with the balloon fully collapsed. 
     FIG. 5 is a cross sectional view of a distal end of an inventive catheter with a separate tube for an inflation lumen. 
     FIG. 6 is a sectional view of the catheter taken along line  6 — 6  in FIG.  5 . 
     FIG. 7 a  shows a side view of the distal end of a catheter formed of a dual lumen tube according to the invention. 
     FIG. 7 b  is a cross sectional view of the catheter of FIG. 7 a  taken along line  7   b — 7   b.    
     FIG. 8 a  shows a side view of a catheter according to the invention including a cross-sectional view of the distal portion thereof and a side view of the proximal end of a catheter according to the invention showing the manifold portion thereof. 
     FIG. 8 b  shows a side view of a catheter according to the invention having a partially deployed stent including a cross-sectional view of the distal portion thereof and a side view of the proximal end of a catheter according to the invention showing the manifold portion thereof. 
     FIG. 9 shows a side view of a catheter according to the invention including a cross-sectional view of the distal portion thereof and a side view of the proximal end of a catheter according to the invention showing the manifold portion thereof. 
     FIG. 10 a  shows a side view of the distal end of an inventive catheter with a retractable balloon disposed about a stent. 
     FIG. 10 b  shows the catheter of FIG. 10 a  with the balloon retracted. 
     FIG. 11 a  is a schematic of a telescoping catheter in accordance with the invention. 
     FIG. 11 b  is a schematic showing the catheter of FIG. 11 a  after the stent has been partially deployed. 
     FIG. 12 a  shows an inventive catheter with a balloon made of a rollable material. 
     FIG. 12 b  shows the catheter of FIG. 12 a  with the balloon partially retracted. 
     FIG. 12 c  shows another inventive catheter with a balloon made of a rollable material. 
     FIG. 12 d  shows the catheter of FIG. 12 c  with the balloon partially retracted. 
     FIG. 12 e  shows an inventive catheter including a rolling membrane disposed between the balloon and the stent. 
     FIG. 12 f  shows the catheter of FIG. 12 e  with the balloon partially retracted. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While this invention may be embodied in many different forms, there are described in detail herein specific preferred embodiments of the invention. This description is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated. 
     FIG. 1 shows a cross-section of the distal portion of a specific embodiment of the stent delivery catheter, generally designated as  105 , that is the subject of the present invention. The device generally comprises a proximal outer sheath  110  which covers the majority of the catheter  105  excluding a portion of the distal end of the catheter  105 . This outer sheath  110  is characterized by a flexible tube. Preferably the outer sheath  110  is comprised of a high density polyethylene (HDPE) or TEFLON material. The outer sheath  110  is rigidly disposed about an inner sheath  112 . Inner sheath  112  encloses an inner tube  115  which also serves as a guide wire lumen. Inner tube  115  extends through and terminates with the distal tip  125  of the catheter  105 . Preferably the inner tube  115  encloses a guide wire  120  which aids in the navigation of the catheter  105  through the appropriate vessel. The inner tube  115  is made of flexible, but incompressible construction such as a polymer encapsulated braid or coil. The flexibility of the braid/coil allows the catheter  105  to navigate through body lumens and the incompressibility of the braid/coil aids in maintaining the integrity of the catheter and aids in deployment accuracy when the sheath is being retracted during stent release. The braid/coil may be comprised of stainless steel or nitinol, but preferably stainless steel encased in a polymer such as a polyimide, HDPE, teflon or urethane, but preferably polyimide or teflon. 
     Situated just proximal to the distal tip  125  is the medical device receiving region  130  of inner tube  115  around which the medical device is concentrically carried. As shown in FIG. 1, the medical device is stent  135 . Other medical devices such as stent-grafts, grafts and vena cava filters may also be used. The stent  135  surrounds the inner tube  115 . The stent  135  is preferably a Nitinol™ or mesh self-expanding stent, but may also be any other self-expanding stent or a balloon expandable stent carried by an expansion balloon. Self-expanding and balloon expandable stents are well known in the art and require no further instruction. An enlarged view of the distal end of the catheter is shown in FIG.  2 . 
     A medical balloon  147  is disposed about the exterior of inner sheath  112 . The distal end of the balloon  147  is connected to the distal end of inner sheath  112 . The proximal end of the balloon  147  is connected to the distal end of outer sheath  110 . In combination, outer sheath  110 , inner sheath  112  and balloon  147  comprise a retractable balloon assembly. 
     Medical balloon  147  and/or distal end of inner sheath  112  cover and optionally contain the loaded stent  135 . The medical balloon  147  and/or distal end of inner sheath  112  may be constructed to hold a self-expanding stent in its reduced delivery configuration. The medical balloon and/or distal end of the inner tube will merely contain a balloon expandable stent. In the case of a balloon expandable stent, the catheter comprises an additional medical balloon located underneath the stent and an accompanying inflation lumen as is well known to those of ordinary skill in the art. Details of such features may be found in commonly assigned U.S. Pat. No. 5,772,669. 
     Medical balloon  147  may be used for dilating a vessel as well as for expanding and/or seating a stent. An inflation fluid is supplied to the medical balloon  147  via an inflation lumen  152  which is in fluid communication with the medical balloon. Inflation lumen  152  extends to the proximal end of the catheter where it terminates in balloon inflation port  154 . In the instant embodiment, inflation lumen  152  is formed of the space between outer sheath  110  and inner sheath  112 , as shown in FIG. 3, a cross-sectional view of catheter  105  of FIG. 1, taken along lines  3 — 3 . 
     Outer sheath  110  is just short of a full length sheath in that it extends from manifold  156  to the proximal end of balloon  147 . Inner sheath  112  is a full length sheath, extending to tip  125  of catheter  105 . 
     Balloon  147  may be made of any suitable balloon material, as known in the art Suitable materials included polyethylene, polyethylene terephthalate (PET), Arnitel, Hytrel, polyetherether ketone (PEEK), Pebax, Teflon as well as other polyolefins. Other thermoplastic elastomers may be used as well. More generally, any suitable thermoplastic elastomer may be used. The invention also contemplates the use of materials suitable for rolling membranes and balloons such as those disclosed in commonly assigned, copending U.S. application Ser. No. 09/187947 filed Nov. 6, 1998, now U.S. Pat. No. 6,059,813, and U.S. Pat. No. 4,732,152. 
     In an embodiment of the invention shown in FIGS. 4 a-c , balloon  147  is pleated so that on movement of inner sheath  112  in a proximal direction, balloon  147  compresses into an accordion-like structure. FIG. 4 a  shows the catheter with balloon  147  prior to retraction. FIG. 4 b  shows the catheter as balloon  147  begins to form pleats. When balloon  147  is fully compressed, as shown in FIG. 4 c , further motion of inner sheath  112  in a proximal direction results in proximal motion of outer sheath  110  as well. Suitable materials for such a balloon include TEFLON, PEBAX, or LDPE. Balloon  147  covers stent  135  which is disposed about inner tube  115  adjacent to bumpers  149 . 
     The invention also contemplates embodiments in which a separate tube is provided to serve as an inflation lumen as shown in FIG.  5 . Inflation lumen  152  is in fluid communication with balloon  147  and extends to the proximal end of the catheter (not shown) where it is in fluid communication with an inflation port through which inflation fluid is supplied. With the exception of the presence of a separate inflation lumen and the lack of outer sheath  110 , the catheter of FIG. 5 is identical in design to that of FIG.  1 . The catheter of FIG. 5 is illustrated in cross-sectional view along line  6 — 6  in FIG.  6 . 
     In another embodiment of the invention, as shown in FIG. 7 a , catheter  105  includes a dual lumen tube  113 . Dual lumen  113  includes an inflation lumen  152  and an inner tube lumen  153 . Inner tube lumen  153  houses inner tube  115 . Balloon  147  is mounted on the distal end of dual lumen tube disposed about stent  135 . Proximal end  147   a  and distal end  147   b  of balloon  147  are mounted to dual lumen tube  113 . Balloon  147  is in fluid communication with inflation lumen  152 . Stent  135  is disposed about inner tube  115 . A transverse view of the catheter, taken along line  7   b — 7   b  is shown in FIG. 7 b.    
     In yet another embodiment of the invention, outer sheath  110  and inner sheath  112  may be coupled together via a coupling member  158  at a position proximal to balloon  147 , as shown in FIG. 8 a . In such an embodiment, balloon  147  does not move relative to inner sheath  112  and outer sheath  110 . Balloon  147  may then be withdrawn from over the stent by moving one of the inner and outer sheaths in a proximal direction. 
     The combination of the medical balloon, inner sheath and outer sheath comprises a retractable balloon assembly. In this embodiment, the balloon retraction device is the combination of the inner and outer sheaths. 
     The catheter further includes a hydrating luer  160  extending from manifold  156 . 
     A catheter similar to that shown in FIG. 8 a , with a partially deployed stent is shown in FIG. 8 b.    
     Another embodiment of the invention is shown in FIG.  9 . FIG. 9 shows a partial longitudinal cross-section of the distal portion of a specific embodiment of the stent delivery catheter, generally designated as  105 , that is the subject of the present invention. The device generally comprises a proximal outer sheath  110  which covers the majority of the catheter  105  excluding a portion of the distal end of the catheter  105 . This outer sheath  110  is characterized by a flexible tube which contains a pull wire lumen and an inflation hydrating lumen. Preferably the outer sheath  110  is comprised of a high density polyethylene (HDPE) or TEFLON material. The proximal outer sheath  110  encloses an inner tube  115  which also serves as a guide wire lumen. Inner tube  115  extends through and terminates with the distal tip  125  of the catheter  105 . Preferably the inner tube  115  encloses a guide wire  120  which aids in the navigation of the catheter  105  through the appropriate vessel. The inner tube  115  is made of flexible, but incompressible construction such as a polymer encapsulated braid or coil. The flexibility of the braid/coil allows the catheter  105  to navigate through body lumens and the incompressibility of the braid/coil aids in maintaining the integrity of the catheter and aids in deployment accuracy when the sheath is being retracted during stent release. The braid/coil may be comprised of stainless steel or nitinol, but preferably stainless steel encased in a polymer such as a polyimide, HDPE, teflon or urethane, but preferably polyimide or teflon. 
     Situated just proximal to the distal tip  125  is the medical device receiving region  130  of inner tube  115  around which the stent is concentrically carried. The stent  135  surrounds the inner tube  115 . 
     The present invention further comprises a retractable distal sheath  140  which covers and optionally contains the loaded stent  135 . The retractable distal sheath  140  may be constructed to hold a self-expanding stent in its reduced delivery configuration. The retractable distal sheath will merely contain a balloon expandable stent. 
     A medical balloon  147  is disposed about at least a portion of the exterior of distal sheath  140 . Medical balloon  147  may be used for dilating a vessel as well as for expanding and/or seating a stent. An inflation fluid is supplied to the medical balloon  147  via an inflation lumen  152  which is in fluid communication with the medical balloon. Inflation lumen  152  extends to the proximal end of the catheter. 
     The distal sheath  140  is connected to a retracting member  145 , or pull wire, which allows a physician to retract the distal sheath  140  from the proximal end of the catheter  105 , thus releasing the stent  135  in the targeted area of the vessel. The combination of the medical balloon, distal sheath and retracting member  145  comprises a retractable balloon assembly while the retracting member in combination with the distal sheath comprise a balloon retraction device. 
     The retractable sheath  140  may be flexible or rigid, and is generally used to retain the stent  135  and protect the vessel wall. The distal sheath is preferably formed of a material which provides tensile strength, but is flexible, such as a braid, coil, a super elastic alloy, polymer, stainless steel or other similar composites. The inflation lumen  152  may also be used as a retracting member. The retracting member  145  may also be a rod, a cable, a tube which may also be used to transport fluids, a pull back wire, guide wire or the like, but is preferably a wire. In addition, the retracting member  145  may be tapered along its length to impart varying flexibility. Those skilled in the art will recognize other suitable materials and constructions may be employed to serve substantially the same function. The figure shows a single pull wire. It should be understood that any desired number of pull wires could be utilized. The retracting member  145  extends longitudinally within the proximal outer  110 , optionally through a retracting member lumen (not shown), such as a HDPE, nylon, or polyether block amide (PEBAX) tube. In one embodiment, the retracting member lumen extends longitudinally under the proximal outer  110 , and houses the pull back wire  145 . The retracting member lumen that houses the pull back wire  145  may also carry fluid for purging air from the catheter  105 . 
     The invention additionally comprises a collapsible sheath  150  situated between the proximal outer  110  and the distal sheath  140 . The collapsible sheath  150  covers the exposed area between the proximal outer sheath  110  and the distal sheath  140 , serving to protect the inner tube  115  and the retracting member  145  in this area. The collapsible sheath  150  is adhered to the proximal end of the distal sheath  140  at point  142  and the distal end of the proximal outer  110  at point  148 . These connections between components are preferably made using adhesives such as urethane or cyanoacrylate, and other suitable adhesives that are well known in the art. Connections between polymer components can also be made using other bonding techniques such as thermal welding, ultrasonic welding and the like. 
     Additional information concerning the manufacture of the collapsible sheath has been disclosed in U.S. Pat. No. 5,534,007. 
     As the distal sheath  140  is retracted, the collapsible sheath  150  is forced back, collapsing upon itself into an accordion type configuration to give the distal sheath  140  room to retract. The collapsible sheath  150  is longer than the medical device  135  and is made from a highly flexible material such as TEFLON, PEBAX, or LDPE, but preferably TEFLON. The distal sheath  140  and the collapsible sheath  150  may be two separate sheaths adhered to one another, or they may form one continuous sheath. 
     Further, with the retraction of the distal sheath  140 , stent  135  is exposed for deployment. In the case of a self-expanding stent, as shown in FIG. 9, the stent expands upon retraction of the distal sheath. 
     In yet another embodiment of the invention, catheter  105 , as shown in FIG. 10 a , includes a retractable balloon  147  disposed about stent  135 . Balloon  147  forms the distal end of outer sheath  110 . Balloon  147  may be retracted by moving outer sheath  110  in a proximal direction. Stent sheath  117  may be similarly retracted by moving inner sheath  112  in a proximal direction to release the stent for delivery. Catheter  105  is shown in FIG. 10 b  with balloon  147  retracted and stent sheath  117  covering stent  135 . The region between outer sheath  110  and inner sheath  112  defines an inflation lumen  152  for supplying an inflation fluid to balloon  147 . Distal end of balloon  147  forms a tolerance seal  151  with distal end of inner sheath  112 . 
     In a further embodiment as best illustrated by FIG. 11 a , the outer sheath  110  is capable of telescopic extension by utilizing outer and inner sheath portions  200 ,  202  respectively. Outer sheath portion  200  has a diameter greater than that of the inner sheath portion  202 . Prior to stent deployment inner sheath portion  202  may extend outward from outer sheath portion  200 . When balloon  147  is retracted, inner sheath portion  202  is drawn concentrically into the outer sheath portion  200 . 
     Portion  202  may extend all the way to the proximal end of the catheter or may be movable via a pull wire as rod (not shown) extending to the proximal end of the catheter. FIG. 11 b  shows a schematic depiction of the catheter of FIG. 11 a  following retraction of the balloon lumen telescoping portion  202  has been retracted inward into outer sheath portion  200 . 
     In addition to the embodiment shown, a telescopically expandable outer sheath  110  could include additional telescoping portions depending on the diameter of the catheter, the size of the medical device and the amount of extension or retraction required. 
     The inventive catheters may also incorporate the use of rollable materials. The operation of several such catheters is shown schematically in FIGS. 12 a-f . FIGS. 12 a  and  12   b  show a catheter  105  with a balloon  147  made of a rollable material. Balloon  147  may be retracted by moving inner sheath  112  in a proximal direction causing balloon  147  to roll. FIGS. 12 c  and  12   d  also show a catheter  105  with a balloon  147  made of a rollable material. Balloon  147  may be retracted by moving outer sheath  110  in a proximal direction causing balloon  147  to roll. On proximal motion of the inner sheath, balloon  147  rolls over on itself until the direction of the balloon has been completely reversed. Further proximal motion of the inner sheath results in proximal motion of the outer sheath as well. 
     In another embodiment of the invention, as shown in FIG. 12 e  and  12   f , a rolling membrane  155  is attached to the distal end of inner sheath  112 . Rolling membrane  155  is situated between inner sheath  112  and stent  135 . As inner sheath  112  is retracted, rolling membrane  155  is retracted as well, exposing stent  135 . 
     The inventive catheters may be provided in an over the wire configuration as disclosed above, a fixed wire configuration or a rapid exchange configuration. Suitable features of a fixed wire catheter may be incorporated into the inventive catheter including those features disclosed in commonly assigned U.S. Pat. No. 5,702,364 to Euteneuer et al. Suitable features of a rapid exchange catheter may be incorporated into the inventive including those features disclosed in commonly assigned U.S. Pat. No. 5,534,007 to St. Germain et al. 
     Although the above description specifically relates to stents, including self-expanding and balloon expandable stents, other medical devices including stent-grafts, grafts and vena cava filters may be delivered using the inventive medical device delivery catheter. 
     In addition to being directed to the embodiments described above and claimed below, the present invention is further directed to embodiments having different combinations of the dependent features described above and claimed below. 
     The above disclosure is intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the attached claims. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims attached hereto.