Abstract:
A balloon catheter for dilating a stenotic region of a patient&#39;s body lumen such as an artery or for the implantation of an expandable stent within a patient&#39;s body lumen. The balloon of the catheter has a plurality of canted wings which are inclined at an angle of about 15° to about 75°, preferably about 30° to about 60° from a line tangent to an inner tubular member extending within the interior of the balloon.

Description:
BACKGROUND OF THE INVENTION 
     This invention generally relates to balloon catheters, particularly balloon catheters for deploying stents, such as after percutaneous transluminal coronary angioplasty (PCTA) procedures. 
     In a typical PTCA procedure a dilatation balloon catheter is advanced over a guidewire to a desired location within the patient&#39;s coronary anatomy where the balloon of the dilatation catheter is properly positioned within a stenosis to be dilated. The balloon is inflated with radiopaque liquid at relatively high pressures (generally greater than 4 atmospheres) to dilate the stenosed region of the diseased artery. One or more inflations may be needed to effectively dilate the stenosis. The catheter may then be withdrawn from the stenosis or advanced further into the patient&#39;s coronary anatomy to dilate additional stenoses. 
     Very frequently the PTCA treatment modality includes the placement of a stent either simultaneously during the angioplasty or after a dilatation of a stenotic arterial region has been completed to provide long term lumen patency. Balloon catheters similar to those described above for dilatation are used to deploy stents within a patient&#39;s body lumen. Typically, an expandable stent is first disposed about the exterior of the deflated balloon on the distal extremity of the catheter in a constricted or otherwise unexpanded condition and then the catheter is advanced within the patient&#39;s body lumen until the stent mounted on the exterior of the balloon is at the location in which the stent is to be deployed, e.g. at the stenotic site of a previous dilatation. The balloon is inflated so as to expand the constricted or otherwise unexpanded stent against the wall defining the body lumen and then the balloon is deflated and the catheter withdrawn from the patient&#39;s body lumen. The expanded stent remains at the lumen site in an expanded condition when the catheter is removed. 
     Advances in material development for relatively non-compliant balloons designed for both dilatation and stent deployment have increased the tensile strength of the balloons allowing thinner balloon walls and thus lower catheter profiles. However, to obtain the benefits of a lower catheter profile, the wings which form when such balloons are deflated are wrapped around the inner member which extends through the interior of the balloon. The wrapped balloon may be covered with a protective sheath at least for handling and storage. Frequently, for stent delivery balloons, the stent is crimped onto a protective sheath covering which is somewhat elastically expansive so as to provide a more uniform expansion of the stent mounted on the sheath. The wrapped wings of the balloon are usually heat set in this condition so that the wings have a memory of the small wrapped dimensions when the balloon is deflated after inflation, e.g. for prepping, dilatation or stent deployment. 
     While some improvement in balloon profile has been obtained with the prior wrapped balloons, the procedures for forming the balloon with the desired memory complicates the manufacturing procedure and the use of the balloon. What has been needed is a catheter structure which simplifies the wrapping and eliminates the folding of the balloon wings and the heat setting thereof. The present invention satisfies these and other needs. 
     SUMMARY OF THE INVENTION 
     This invention is directed to a catheter having a balloon on a distal extremity of the catheter shaft which has a plurality of biased wings and to the method of forming the biased wings on the balloon. 
     The inflatable balloon on the catheter of the invention generally has a plurality of canted wings, each of which have been formed so as to be inclined at an angle of about 15° to about 75°, preferably about 30° to about 60°, with respect to a tangent line extending from the exterior of an inner member about which the wings are wrapped. The wings are formed of the cylindrical and part of the tapered ends of the balloon thus significantly reducing the balloon profile. 
     The inclined or canted wings are formed by pressing suitable shaping tools against the exterior of the balloon while the balloon is inflated at relatively low pressures of about 5 to about 20 psi, preferably about 8 to about 15 psi and, once the wings have been formed by the shaping tool, the interior of the balloon is subjected to a partial vacuum, i.e. a pressure of about 10 to about 29 inches (25.4-73.7 cm) of Hg, preferably about 20 to about 27 inches (51-68.6 cm) of Hg. in order to maintain the balloon in the constricted deflated condition with the canted wings of the balloon inclined and partially wrapped. The canted wings can be more easily wrapped around an inner tubular member extending within the balloon interior to reduce the effective profile of the balloon. The wrapping may be performed manually or by placing the balloon within an appropriate die and rotating either the balloon or the die or both to wrap the wings. A variety of other methods may be employed to wrap the balloons. 
     The vacuum applied within the balloon interior holds the canted wings in a wrapped position long enough so that a sheath or a stent can be mounted about the wrapped wings of the balloon. A stent may also be slid over and crimped onto the sheath for subsequent deployment. The angularity of the wings with respect to a line tangent to the exterior of the inner member greatly facilitates the wrapping of the wings and the reforming thereof when the deflated balloon is pulled back into a sheath or the distal end of a guiding catheter. 
     Details of stents suitable for use with the present invention can be found in U.S. Pat. No. 5,344,426, U.S. Pat. No. 5,423,885, U.S. Pat. No. 5,441,515, U.S. Pat. No. 5,443,458, U.S. Pat. No. 5,443,500 and U.S. Pat. No. 5,514,154, all of which are assigned to the present assignee. They are incorporated herein by reference. Other stent designs may also be employed. 
     In one aspect of the invention, the catheter has an elongated shaft with a proximal end, a distal end, a port in the distal end and guidewire lumen extending through at least the distal portion of the catheter to and in fluid communication with the port in the distal end of the catheter shaft. The balloon of the invention may be mounted on a distal extremity of the catheter shaft in a conventional fashion with a distal skirt secured by fusion bonding or a suitable adhesive to a distal extremity of the inner tubular member extending through the interior of the balloon and a proximal skirt of the balloon is similarly secured to a portion of the catheter shaft which may be the distal extremity of an outer tubular member which in part forms the catheter shaft. 
     The balloon may be made from suitable thermoplastic polymeric materials including high density polyethylene, polyethylene terephthalate (PET), polyamide (e.g. nylon 11 or 12), ionomers such as Surlyn sold by DuPont, polyurethane and polyamide block co-polymers such as PEBAX. 
     The present invention provides an intralumenal catheter with an improved balloon member with multiple wrapped wings which are formed so as to be inclined to predispose the wings to wrapping and subjected to an interior vacuum to hold the wings in the constricted condition. The crease which forms with the wing formation extend well into the tapered ends of the balloon which facilitates mounting a sheath or stent onto the wrapped balloon. A stent may be mounted and then crimped directly onto the wrapped balloon or onto a sheath covering the wrapped balloon for vascular deployment. The inclined wings also facilitate the pullback of the deflated balloon after a vascular or other procedure into the distal tip of the guiding catheter. 
     Long term disposition of the balloon in the wrapped condition and/or thermal treatment of the wrapped balloon effect a set which the balloon tends to stay in for the duration of storage and use. 
     These and other advantages of the invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying exemplary drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational schematic view, partially in section, of a balloon catheter embodying features of the invention. 
     FIG. 2 is a transverse cross-sectional view of the catheter shown in FIG. 2 taken along the lines  2 — 2 . 
     FIGS. 3 and 4 schematically illustrate the forming of multiple canted wings on the balloon. 
     FIG. 5 is a perspective view in section which illustrates the balloon with multiple canted wings. 
     FIG. 6 illustrates the placement of the balloon with multiple canted wings within a die for wrapping the canted wings about an inner tubular member. 
     FIG. 7 illustrates the balloon in the wrapped condition within the die. 
     FIG. 8 is a transverse cross-sectional view which illustrates a stent disposed about the multiwinged balloon shown in FIGS.  1 - 2 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference is made to FIGS. 1-2 which illustrate a balloon catheter  10  embodying features of the invention. Catheter  10  has an elongated shaft  11  with proximal and distal shaft sections  12  and  13 , a multiarm adapter  14  on the proximal end of the shaft and an expandable balloon  15  on the distal shaft section spaced proximal to the distal end  16 . An inflation lumen  17  extends between the proximal end of shaft  11  and a location spaced proximal to the distal end  16  and is in fluid communication with the interior of the balloon  15 . The catheter shaft  11  is provided with an inner tubular member  18  and an outer tubular member  19  of suitable polymeric material. A guidewire receiving lumen  20  extends through the proximal and distal shaft sections  12  and  13  to the port  21  in the distal end  16 . In the distal shaft section  13 , the guidewire receiving lumen  20  is defined at least in part by the inner tubular member  18 . 
     The balloon  15  has a distal skirt  22  which is secured by suitable means such as fusion or adhesive bonding to an exterior portion of the inner tubular member  18  and a proximal skirt  23  which is secured by the same or similar means to the distal end of the outer tubular member  19 . A guidewire  24  is slidably disposed within the guidewire lumen  20 . 
     As shown more clearly in FIG. 2, the balloon  15  has a plurality of canted wings  25  which are deformed so as to be inclined at a suitable angle with respect to a line  26  which is approximately tangent with the exterior surface of the inner tubular member  18 . 
     FIGS. 3 and 4 schematically illustrate the deformation of the balloon  15  so as to form the canted wings  25 . As shown in FIG. 3, a partially inflated balloon  15  (e.g. inflated to an internal pressure of about 5-15psi) is surrounded by three elongated shaping tools  27 . Each of the shaping tools  27  has planar surfaces  30  and  31  and may have an elongated wedge-like deforming element  28  as shown in the drawings. The surface  31  of one shaping tool  27  is configured to press against the underside of a first canted wing  25  and the surface  30  of the same shaping tool is configured to press against the top side of a second canted wing  26  adjacent to the first canted wing. The shaping tools  27  are assembled so that when they are moved radially inwardly the wedge-like deforming elements  28  thereof are off-set from the longitudinal axis  32  as shown to deform the canted wing  25  in the desired manner. 
     While the balloon  15  is inflated at low pressures, the shaping tools  27  are moved inwardly until the surfaces  30  of the shaping tools are pressed against the bottom side of the canted wings  25  and the surfaces  31  of the adjacent shaping tools are pressed against the top side of the wings as shown in FIG. 4. A space of about 0.004 to about 0.008 inch is maintained between the surfaces  30  and  31  but these surfaces do press against the balloon material between these surfaces to form the wings. There is little or no deformation of the outer tip of the wings, i.e. there is no folding as was done in the prior art. The interior of the balloon  15  is then subjected to a partial vacuum which holds the canted wings  25  in a partially wrapped condition as shown in FIGS. 2 and 5. 
     The canted wings  25  of balloon  15  may be wrapped about the inner tubular member  18  by placing the distal extremity of the catheter  10  within a die  33  so that the canted wings  25  of the balloon  15  are disposed within the chambers  34  of the die as shown in FIG.  6 . Relative rotational motion is effected between the die  33  and the distal extremity of the catheter  10  so that the canted wings  25  disposed within the chambers  34  are wrapped about the inner tubular member  18  as shown in FIG.  7 . When wrapped, the tips of the wings may extend over an adjacent wrapped wing depending upon the lengths of the wings and the diameter of the inner tubular member  18  about which the wings are wrapped. Once wrapped, the canted wings  25  have little tendency to unwrap particularly when subjected to an internal vacuum, so a stent  54  may be readily slid over and crimped over the wrapped balloon  15  as shown in FIG.  8 . Typically, when the stent  54  is disposed about the balloon  15 , it is crimped onto the exterior of the balloon  15  to facilitate the introduction of the catheter into a patient&#39;s vascular system, but a protective sheath  53  may be applied to the exterior of the balloon and the stent  54  crimped onto the sheath. 
     When the balloon  15  is in the desired location within the patient&#39;s vascular system, inflation fluid is introduced into the interior of the balloon through the inflation lumen  17  to inflate the balloon and expand the stent  54  crimped onto the balloon. Because of the multiple canted wings  25  on the balloon  15 , when the balloon inflates, it readily and uniformly expands the stent  54  mounted onto the balloon. Once expanded, the stent  54  is secured within the body lumen and the balloon may then be deflated and withdrawn. 
     While the balloon catheter with canted wings has been described herein as a stent delivery catheter, those skilled in the art will recognize that the catheter may be employed as a balloon angioplasty catheter to dilate stenosis within a patient&#39;s coronary artery or other body lumen. When employed as a balloon angioplasty catheter, a sheath may be provided about the balloon with canted wings to hold the canted wings in place. Other modifications and improvements may be made to the invention without departing from the scope thereof.