Abstract:
A microsurgical balloon, with at least one incising component mounted to the surface of the balloon, includes a protective pad to prevent the outer surface of the incising component from coming into contact with and damaging the balloon surface. In particular, the protective pad is positioned on the outer surface of the balloon substantially parallel to and juxtaposed with the incising component. When the balloon is in a deflated configuration, either for insertion into the vasculature system or removal from the patient, the protective pad engages the outer surface of the incising component thereby protecting the balloon from being punctured or damaged by the incising component. The protective pad may be bonded to the outer surface of the balloon, or it may be an integral part of a homogeneous balloon structure.

Description:
FIELD OF THE INVENTION 
     The present invention pertains generally to interventional medical devices. More particularly, the present invention pertains to microsurgical balloons that are used to insert incising components into the vasculature system of a patient. The present invention is particularly, but not exclusively, useful as a device and method for protecting the surface of the microsurgical balloon from damage or puncture caused by the balloon outer surface coming into contact with the incising component. 
     BACKGROUND OF THE INVENTION 
     Angioplasty is a well known technique that is commonly used in the treatment of vasculature diseases. An integral part of an angioplasty procedure is the insertion of an inflatable balloon on a catheter into the vasculature of a patient to position the balloon in a vessel at the site of a stenosis. The balloon is then inflated to dilate the stenosis. 
     A recent innovation in angioplasty procedures involves ablation of a stenosis by an inflated balloon with an incising component mounted on the outer surface of the balloon. Typically the so-called “cutting balloon” will have a plurality of atherotomes (blades) mounted on its outer surface. Once the “cutting balloon” is inflated inside the vessel, the blades create small incisions in the lesion which facilitate dilation of the stenosis and reduce barotrauma. Such a “cutting balloon” is disclosed and claimed in U.S. Pat. No. 5,797,935 which issued to Barath for an invention entitled “Balloon Activated Force Concentrators for Incising Stenotic Segments” and which is assigned to the same assignee as the present invention. While the “cutting balloon” is one example of an interventional medical device that has been developed for performing certain in situ procedures, it is possible for other external components to be mounted on a catheter balloon for therapeutic or diagnostics purposes. 
     Regardless of the specific incising component that may be mounted on the balloon, a recurring problem is damage that may happen to the balloon during insertion of the catheter or after the balloon inflation and deflation sequence. Prior to insertion, the balloon is typically folded into a so-called “taco shape” or “spiral fold” configuration to reduce its overall profile. Typically, the balloon will come from the manufacturer in this folded configuration. An incising component mounted on the surface of the balloon may, however, prevent the balloon from being folded into its most compact configuration, and may damage the balloon. In addition, damage may occur as the balloon is being maneuvered through the vasculature of a patient. Despite careful manipulation of the catheter through the vasculature system, balloon material may be pushed against the incising surface, damaging the balloon and causing an unwanted rupture. 
     Yet another opportunity for damage occurs after the balloon has been used for its intended purpose, and is subsequently deflated and withdrawn from the vessel. After deflation, the balloon again collapses inwardly toward its center, for example into a modified “X” configuration. When blades or other incising components are mounted on the balloon, to be located between the legs of the “X”, the balloon is particularly vulnerable to damage. Specifically, damage can occur in this configuration if the balloon material is pushed against the incising component during passage through tortuous anatomy or during a twisting of the catheter. 
     In addition to the problems discussed above, balloon material may have a tendency to fold back on itself, along the axis of the balloon, as the distal end of the balloon contacts the vessel wall or obstructions in the vessel. Importantly, a balloon with an incising component mounted on the outer surface will be more rigid in the area of the incising component. As such, the balloon will tend to fold back, or “kink”, in less rigid areas, potentially causing balloon material to fold over and come into contact with the incising component. 
     In light of the above, it is an object of the present invention to provide a reinforced balloon to protect the areas of the balloon that are likely to be damaged by an incising component. Another object of the present invention is to provide a reinforced balloon that helps to minimize collateral damage to the tissue of a patient. Still another object of the present invention is to provide a balloon that helps to minimize balloon damage resulting from the balloon folding back on itself. Yet another object of the present invention is to provide a reinforced balloon with components mounted on its surface that is easy to use, relatively simple to manufacture, and comparatively cost effective. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an inflatable microsurgical balloon having an incising component mounted on an outer surface of the balloon. A protective pad is positioned on the balloon surface to protect the balloon from being inadvertently cut by the incising component. Specifically, the protective pad is positioned on the outer surface of the balloon such that prior to inflation, and after deflation in the vessel, the protective pad engages the outer cutting surface of the incising component. The balloon is thereby protected from being punctured or otherwise damaged by the incising component. As envisioned for the present invention, an “incising component” may include any component mounted on the outer surface of the balloon with a protrusion capable of cutting, puncturing or otherwise damaging the balloon. 
     In detail, the balloon is an elongated, inflatable balloon that defines a longitudinal axis. When fully inflated, the surface of the balloon is distanced radially from the longitudinal axis. For the present invention, at least one incising component is mounted on the outer surface of the balloon. Juxtaposed with, and parallel to, the incising component is a protective pad. The protective pad may be manufactured from a substantially impenetrable material or from a semi-penetrable material. Importantly, the protective pad may have an extended length, greater than the length of the incising component, to provide additional stiffness to the balloon in the longitudinal direction. The protective pad is positioned to engage the outer cutting surface of the incising component when the balloon is folded prior to insertion into the patient, or when the balloon is deflated after use in the vasculature. In an alternate embodiment of the present invention, a protective pad may also be positioned at one or both ends of the incising component, to engage the incising component in those instances when the balloon “kinks” or folds back along itself in a longitudinal direction. 
     In the preferred embodiment of the present invention, the incising component comprises an elongated blade with an outer cutting surface running the length of the blade. Further, the protective pad is a single, continuous pad mounted on the outer surface of the balloon, juxtaposed with and parallel to the elongated blade. In an alternate embodiment of the present invention, the protective pad comprises a plurality of axially aligned sections, wherein adjacent sections are separated by a depression. In yet another embodiment, the pad is a localized area of thicker balloon material, manufactured as an integral part of a homogeneous balloon structure. 
     With regard to the incising component, it is within the contemplation of the present invention that a plurality of incising components may be mounted axially, parallel to the longitudinal axis of the balloon. Further, a plurality of incising components may be axially aligned but azimuthally separated on the balloon. In yet another embodiment of the present invention, the incising component comprises an elongated blade and a base, with the base mounted on the outer surface of the balloon, and the blade mounted on the base. When the balloon is folded or deflated, the protective pad may engage either the base or the blade, thereby preventing the elongated blade from coming into contact with the balloon outer surface. The base may be shaped to increase the stiffness of the balloon in the longitudinal direction, thereby minimizing the possibility that the balloon will “kink” or fold back along itself. In addition, the base may be manufactured with one or more longitudinal stiffeners molded into the base. It is further contemplated by the present invention that the incising component may include an elongated tab at the proximal and distal end of the blade to increase the longitudinal stiffness of the balloon. The tab is an axial extension of the blade, and it is bonded to the outer surface of the base. 
     Prior to use, the inflatable balloon may be delivered by the manufacturer in a deflated, “folded” configuration. When folded, balloon material is wrapped circumferentially around the axis defined by the balloon. As contemplated by the present invention, when the balloon is folded, the protective pad engages the cutting surface of the incising component. This engagement effectively prevents the cutting surface of the incising component from coming into contact with, and damaging, the outer surface of the balloon. 
     In operation, the folded balloon is inserted and advanced into the vasculature of a patient to perform a vessel dilation procedure. The increased longitudinal stiffness of the balloon helps to prevent “kinking” during insertion and removal, as the balloon strikes the vasculature wall or other obstructions. Once the balloon is properly positioned, a fluid source is used to inflate the balloon. This inflation then forces the incising component into the vessel wall of the patient to assist in the dilation of the vessel. After the dilation has been completed, the balloon is then deflated for removal from the vasculature system. When deflated, the balloon will collapse inwardly toward its longitudinal axis, returning the balloon to a modified “folded” configuration. As the balloon deflates, the protective pad again engages the cutting surface of the incising component to prevent an unwanted and inadvertent rupture of the balloon surface by the incising component. In this configuration, the incising component is also prevented from damaging the vessel wall of the patient. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which: 
         FIG. 1  is a perspective view of an inflatable balloon catheter system incorporating an incising component and a protective pad, in accordance with the present invention; 
         FIG. 2  is a perspective view of a protective pad and incising component mounted on the outer surface of a balloon; 
         FIG. 3A  is a cross-sectional view of a balloon in a “folded” configuration, as would be seen along the line  3 - 3  in  FIG. 1 , when the balloon is deflated prior to use; 
         FIG. 3B  is a cross-sectional view of a balloon in its fully inflated configuration, as would be seen along line  3 - 3  in  FIG. 1 ; 
         FIG. 3C  is a cross-sectional view of a deflated balloon, after use in a patient, as would be seen along the line  3 - 3  in  FIG. 1 ; 
         FIG. 3D  is a cross-sectional view of a deflated balloon having a protective pad on either side of an incising component; 
         FIG. 3E  is a cross-sectional view of an alternate embodiment of a balloon in a “folded” configuration, as would be seen along the line  3 - 3  in  FIG. 1 , when the balloon is deflated prior to use; 
         FIG. 4A  is a perspective view of an alternate embodiment of a protective pad with extensions positioned at either end of an incising component; 
         FIG. 4B  is a perspective view of an alternate embodiment of a protective pad positioned at either end of an incising component; 
         FIG. 5  is a perspective view of an alternate embodiment of a protective pad and an incising component; 
         FIG. 6  is a side view of an incising component comprising an elongated blade mounted on a base; 
         FIG. 7A  is a top view of an alternate embodiment of a base mounted to the surface of a balloon; and 
         FIG. 7B  is a side view of an alternate embodiment of an incising component bonded to a base with two stiffeners. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A system in accordance with the present invention is shown in  FIG. 1  and is generally designated  10 . As shown, the system  10  has a catheter  12 , and an inflatable microsurgical balloon  14  that is attached to the catheter  12 . The balloon  14  is an elongated, inflatable balloon  14  that defines a longitudinal axis  16 . Mounted on the outer surface  18  of the balloon  14  is an incising component  20 . As shown in  FIG. 1 , positioned substantially parallel to and juxtaposed with the incising component  20  is a protective pad  22 . In the preferred embodiment of the present invention, the incising component  20  and the protective pad  22  are mounted on the outer surface  18  of the balloon  14  in a manner well known in the pertinent art, such as by adhesive bonding. The protective pad  22  may be manufactured from a substantially impenetrable or a semi-penetrable material. As further shown in  FIG. 1 , the system  10  includes an extracorporeal fluid pump  24  that is connected to the catheter  12 . The extracorporeal fluid pump  24  is used to selectively inflate and deflate the balloon  14  by introducing fluid into, or in the alternative extracting fluid from, the system  10 . In detail, the structure of the protective pad  22  and the incising component  20  will be best appreciated by referring to  FIG. 2 . 
     As shown in  FIG. 2 , the protective pad  22  and the incising component  20  are mounted on the outer surface  18  of the balloon  14 . In an alternate embodiment of the present invention, the incising component  20  may be mounted on a base  26  (not shown in  FIG. 2 ), which in turn is mounted on the outer surface  18  of the balloon  14 . The incising component  20  is mounted on the balloon  14  with a gap  28  between the incising component  20  and the protective pad  22 . Importantly, the width of the gap  28  must be sufficiently small to ensure the incising component  20 , as it rotates toward the protective pad  22 , engages the protective pad  22 , and does and not engage the surface  18  of the balloon  14 . In the preferred embodiment of the present invention, the incising component  20  comprises a blade  30  with an outer cutting surface  32  running the length of the elongated blade  30 . In addition, the protective pad  22  is a single, continuous pad mounted parallel to, and juxtaposed with, the incising component  20 . Variations in the relative position of the protective pad  22  and the incising component  20  can best be appreciated by referring to the cross-sectional views in  FIGS. 3A-3E . 
     In  FIG. 3A , it will be noted that when the balloon  14  is folded prior to insertion into the vasculature of a patient, the cutting surfaces  32   a ,  32   b ,  32   c , and  32   d  of the incising components  20   a ,  20   b ;  20   c , and  20   d  are engaged by the outer surfaces  33   a ,  33   b ,  33   c , and  33   d  of the protective pads  22   a ,  22   b ,  22   c , and  22   d . As shown in  FIG. 3B , when the balloon  14  is fully inflated, the protective pads  22   a - d  and the incising components  20   a - d  are distanced radially from the axis  16 . The outer surfaces  33   a - d  of the protective pads  22   a - d , and the cutting surfaces  32   a - d  of the incising components  20   a - d , are oriented substantially normal to the outer surface  18  of the balloon  14 . Further, as is shown in  FIG. 3C , when the balloon  14  is deflated after use, the balloon  14  will collapse inwardly towards the axis  16 . As the balloon  14  deflates, it will return to a modified version of the pre-insertion, folded configuration. Specifically, the protective pad  22   a  falls inwardly towards the longitudinal axis  16  and rotates towards the incising component  20   a . Likewise, the incising component  20   a  falls inwardly and rotates toward the protective pad  22   a . Consequently, the outer surface  33   a  of the protective pad  22   a  engages the cutting surface  32   a  of the incising component  20   a . In a like manner, the remaining protective pads  22   b - d  and incising components  20   b - d  fall, rotate and engage. 
     In an alternate embodiment of the present invention, as shown in  FIG. 3D , two protective pads, of which pads  22   a  and  22   b  are exemplary, are mounted juxtaposed with, and parallel to, an incising component  20 . In this configuration the incising component  20  engages a protective pad  22   a  and  22   b , regardless of the direction of rotation of the incising component  20 . 
     Referring now to  FIG. 3E  it can be seen that the incising component  20  comprises a base  26  with an outer surface  34 , and an elongated blade  30  with an outer cutting surface  32 . As contemplated by the present invention, two protective pads  22   a  and  22   b  are positioned to engage the outer surface  34  of the base  26 . When the protective pads  22   a  and  22   b  engage the base  26 , the cutting surface  32  of the incising component  20  does not contact the outer surface  18  of the balloon  14 . 
     With regard to the protective pad  22 , as shown in  FIGS. 3A-3E , the pad  22  may be bonded to the outer surface  18  of the balloon  14 . In an alternate embodiment of the present invention, the protective pad  22  may be a localized area of thicker, or reinforced, balloon  14  material, manufactured as an integral part of a homogeneous balloon  14  structure. In addition, as shown in  FIGS. 4A and 4B , protective pads, of which  23   a  and  23   b  are exemplary, may be positioned to engage the incising component  20  when the balloon  14  “kinks” or folds back on itself. 
     Considering now  FIG. 5 , in yet another embodiment of the present invention, the protective pad  22 ′ comprises a plurality of axially aligned sections, wherein adjacent sections are separated by a depression  36 . The depression  36  has a side wall  38   a  and a side wall  38   b  that extend vertically at an angle from the outer surface  18  of the balloon  14 . In addition, the depression  36  has a floor  40 . The floor  40  is substantially parallel to, and located radially outward from, the outer surface  18  of the balloon  14 . The floor  40  connects adjacent sections of the pad  22 ′. Additionally, as shown in  FIG. 5 , a plurality of elongated blades (e.g. blades  30   a ,  30   b  and  30   c ) are axially oriented and substantially parallel to the axis  16  of the balloon  14 . It can be contemplated by referring to  FIG. 5  that the system  10 , with a protective pad  22 ′, and a plurality of elongated blades  30   a - c , will have increased axial flexibility. Increased flexibility in the axial direction, along the length of the balloon  14 , provides for greater ease of movement of the catheter  12  through the vasculature system of the patient. 
     As shown in  FIG. 6 , the incising component  20  may comprise a base  26  and a blade  30  with an outer cutting surface  32 . The base  26  is mounted on the outer surface  18  of the balloon  14 , and the blade  30  is mounted to the base  26 . Further, as shown in  FIG. 6 , the blade  30  includes a tapered region  42 , and an elongated tab  44  at both the proximal and distal ends of the blade  30 . The tapered region  42  of the blade  30  extends from the outer surface  46  of the tab  44  to the outer cutting surface  32  of the blade  30 , at an angle “α” measured from a line drawn normal to the outer surface  46  of the tab  44 . Referring still to  FIG. 6 , the tab  44  extends axially from the bottom of the tapered region  48  for an elongated distance “X”, thereby providing increased stiffness to the blade-base combination. The tab  44  may be bonded on the outer surface  34  of the base  26 . 
     Referring now to  FIGS. 7A and 7B , the base  26  may be shaped to provide the balloon  14  increased longitudinal stiffness. As shown in  FIG. 7A , the base  26  has an increased surface area at either end of the base  26 . The increased surface area provides the balloon  14 , to which the base  26  is bonded, increased stiffness in the longitudinal direction, which is to say along the longitudinal axis  16 . In addition, as shown in  FIG. 7B , the incising component  20  may be inset into the base  26 , thereby providing additional stiffness to the base  26 , and hence the balloon  14 . Also, as shown in  FIG. 7B , the base  26  may be manufactured with a plurality of stiffeners  50   a  and  50   b  molded into the interior of the base  26 . A shaped base  26 , as in  FIGS. 7A  and B, or a base  26  with added stiffeners  50   a  and  50   b  ( FIG. 7B ), will provide the balloon  14  increased stiffness in the longitudinal direction. The increased stiffness minimizes the possibility that the balloon  14  will “kink”, or fold back on itself when contacting structure within the vasculature. 
     While the particular microsurgical balloon and system as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.