Abstract:
An apparatus for improved centering of a device which is intended to penetrate a severe occlusion of a body lumen. The apparatus includes a substantially tubular member having an exit port; an inflatable member having a distal end; wherein the exit port is not distal to the inflatable member. Such an apparatus allows for better fluoroscopic visualization, and therefore placement, of the apparatus with respect to the lesion.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to an apparatus and method for treatment of stenotic or diseased lumens. More particularly, the invention relates to a novel balloon catheter and method of treatment of a chronic total occlusion of a lumen. 
     BACKGROUND OF THE INVENTION 
     Balloon angioplasty, atherectomy, and stent implantation are common procedures for the treatment of stenotic or diseased lumens. Such procedures are performed percutaneously, through an incision site remote from the site of treatment within the lumen. These procedures consequently require tracking of the treatment device from the incision site, through the vasculature and to the lesion. The vasculature is typically tortuous and may have numerous stenoses of varying degrees throughout its length. In order to place the distal end of a catheter at the treatment site, a guidewire is first tracked from the incision, through the stenosis, and across the lesion. Then, a catheter bearing a balloon and/or other device such as, for example, a stent, at its distal end can be tracked over the guidewire to the treatment site. Ordinarily, the distal end of the guidewire is quite flexible in order that, as it is pushed through the lumen, it can “find” its way through the turns of the typically irregular passageway of the lumen without damaging the lumen. 
     In some instances, the extent of occlusion of the lumen is so severe that the lumen is nearly completely obstructed, leaving virtually no passageway for the guidewire. Such a condition may be described as a “total occlusion”. Where such a condition persists longer than six months, the lesion is referred to a “chronic total occlusion”. Further, in the case of diseased blood vessels, the lining of the vessels may be characterized by the prevalence of atheromatous plaques, which may form a total occlusion. The extensive plaque formation of a chronic total occlusion typically has a fibrous cap surrounding softer plaque material. Such a fibrous cap may present a surface which may be difficult to penetrate with a conventional guidewire. In such instances, the typically flexible distal tip of the guidewire may be unable to cross the lesion, and in order to successfully cross and treat a chronic total occlusion, alternative devices may be required. For example, at a minimum, a stiffer guidewire may be required to traverse the stenosis. Or, an atherectomy device may be required to penetrate the occlusion. Hereinafter, Applicants refer to any device intended to penetrate the occlusion, including a guidewire, as a recanalizing device. 
     In the event that a recanalizing device and/or greater force by the clinician are required in order to create a passageway through a chronic total occlusion, additional precautions must be taken to prevent injury to the vessel wall. For example, it is imperative that the guidewire and/or atherectomy device be centered within the vessel to avoid penetration of the vessel wall. Further, visualization of the location of the guidewire or atherectomy device exit port is desirable. Therefore, the device and method for centering the recanalizing device within the vessel must confer a high degree of confidence on the clinician, both in centering and in visualization, in order that a passageway can be safely created. 
     Additionally, in the instance where a stiffer guidewire or other device is required in order to cross the lesion, the guidewire will meet increased resistance upon attempts to penetrate the plaque. Consequently, the guidewire or other device will require increased support proximal of the lesion. That is, when the tip of the guidewire abuts the plaque, and as pressure is exerted upon the guidewire in order to penetrate the lesion, portions of the guidewire proximal of the tip will require the support of a catheter encasing the guidewire. Such “back support” will prevent excessive prolapse of the guidewire or other device within the vessel proximal of the stenosis and will ensure that the recanalizing device remains centered within the lumen. 
     Further, when the tip of the guidewire or recanalizing device meets increased resistance to penetration of the lesion, an additional result may be a tendency of the catheter to slide proximally over the guidewire. Such proximal sliding will result both in a failure to maintain the recanalizing device centered within the vessel and in a failure to provide back support to the device. Such a tendency may be recurring with repeated attempts to traverse the stenosis, rendering the process increasingly frustrating for the clinician. Means for securing the catheter within the vessel may be required during attempts to penetrate an extensive lesion. 
     Angioplasty catheters and stent delivery catheters of the prior art lack means for adequate visualization, centering, support and securement of the catheter for treatment of extensive lesions. Similarly, devices bearing cutting heads or other devices for creating a guide wire passage lack means for sufficiently centering the device prior to penetrating the occlusion. Therefore, the prior art devices lack sufficient safeguards and back support for using a stiffer guidewire and lack the essential safeguards for centering a cutting device intended to penetrate an extensive occlusion. 
     SUMMARY OF THE INVENTION 
     The present invention provides an apparatus for improved centering of a device which is intended to penetrate a severe occlusion of a body lumen. Further, a device according to the present invention allows for better fluoroscopic visualization, and therefore placement, of the device with respect to the lesion. A device according to the present invention also provides back support for a recanalizing device during attempts to penetrate an extensive occlusion. Still further, a device according to the present invention provides a friction fit of the device with the vessel wall during attempts to cross a lesion, preventing proximal sliding of the device during attempts to cross the lesion. According to the present invention, a catheter with a substantially central lumen for receiving a guidewire and/or other recanalizing device is provided. Further, the central lumen of a catheter according to the invention comprises an exit port which is not distal to the inflatable member of the catheter. An alternative embodiment of the invention also comprises a central lumen for receiving a second catheter for the purpose of conducting an angioplasty procedure and/or delivering a stent. Further, a method of making an inflatable member for use in an apparatus according to the invention is provided. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a cut-away view of a first embodiment of the invention. 
     FIG. 2 illustrates a cut-away view of a second embodiment of the invention. 
     FIG. 3 illustrates a cut-away view of a third embodiment of the invention. 
     FIGS. 4-8 illustrate an embodiment of the invention in use. 
     FIG. 9 illustrates a cut-away view of a prior art catheter in use at a bifurcation in a vessel. 
     FIG. 10 illustrates a cut-away view of an embodiment of the invention in use at a bifurcation in a vessel. 
     FIGS. 11-14 illustrate successive steps of one method of manufacturing a balloon for use in a device according to the present invention. 
     FIG. 15 illustrates a side view of an alternative embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, a first embodiment of the invention comprises catheter  10  having lumen  15  with exit port  12 . Catheter  10  further comprises distal end  14 , which includes marker band  19 , and balloon  16  in communication with inflation lumen  17 . Distal portion  18  of balloon  16  is substantially contiguous with exit port  12 . Distal portion  18  and exit port  12  thereby define the distal-most elements of distal end  14  of catheter  10 . Balloon  16  is typically but is not of necessity a low-pressure balloon. Balloon  16  is affixed to the exterior surface of tubular member  11  near proximal region  13  of balloon  16  and at some point proximal of exit port  12 . 
     Turning now to FIG. 2, an alternative embodiment of the invention comprises catheter  20  having lumen  25  with exit port  22 . Distal end  24  of catheter  20  comprises distal portion  28  of balloon  26 , which defines the distal-most element of distal end  24 . Distal portion  28  of balloon  26  extends slightly distally of exit port  22 . Inflation lumen  27  is in fluid communication with balloon  26 . Balloon  26  is affixed to the exterior surface of tubular member  21  near proximal region  23  of balloon  26  and at some point proximal of exit port  22 . 
     FIG. 3 represents yet another embodiment of the invention. Catheter  30  comprises balloon  36  in fluid communication with inflation lumen  37 . Catheter  30  further comprises lumen  35 , guidewire exit port  32 , and marker band  33 . In the embodiment of FIG. 3, marker band  33  is substantially contiguous with exit port  32 , allowing for fluoroscopic visualization of the device at its distal-most region. Inner member  39  is bonded to balloon  36  at seal  34 . Balloon  36  outer member  38  is bonded to balloon  36  at bond site  31 . Laser bonding, thermal bonding, the use of adhesives, or other procedure known in the art can be used to form seal  34  and/or bond site  31 . 
     FIGS. 4-8 demonstrate the advantages of the invention in use within vessel  3 . In FIG. 4, standard guidewire  5  is advanced through vessel  1  via guide catheter  6 , to the site of chronic total occlusion  2 . Used alone, as depicted in FIG. 4, guidewire  5  will not pass chronic total occlusion  2 , and will prolapse into the vessel when pressure is applied. 
     FIG. 5 illustrates prior art catheter  50  comprising prior art balloon  60 , and the resulting limitations encountered when attempting to center a device such as a guidewire at the site of chronic total occlusion  2 . As illustrated in FIG. 5, guidewire  5  is not directed toward the center of chronic total occlusion  2 , and in fact is directed undesirably toward the wall of vessel  3 . Using prior art catheter  50 , it will be difficult to traverse chronic total occlusion  2  and the risk of perforation of the vessel wall is quite high. And catheter  50  confers no advantage upon the procedure of centering a device such as guidewire  5 . However, it will be possible to traverse such a lesion using the instant invention. 
     FIGS. 7-8 illustrate the clinical advantages of the invention set forth herein. According to the invention, catheter  80 , comprising balloon  70 , is advanced over guidewire  5 , to the site of chronic total occlusion  2 . Because standard guidewire  5  cannot traverse the stenosis, guidewire  5  is withdrawn and replaced by stiffer guidewire  7 . Alternatively, a cutting tool, such as an atherectomy device, can be tracked to chronic total occlusion  2 . As illustrated in FIG. 8, balloon  70  is then inflated at nominal pressure. When inflated, balloon  70  centers exit port  72 , thereby centering stiffer guidewire  7 , within the vessel. Distal portion  75  abuts at least a portion of chronic total occlusion  2 . Further, according to the embodiment of FIG. 8, catheter  80  also comprises marker band  72  at its distal-most portion. Therefore, marker band  72  also abuts chronic total occlusion  2 , and enables the clinician to predict the location of the central region of chronic total occlusion  2 . Such improved visualization of the device both at the lesion and at the port where the guidewire emerges from the device confers great advantage on the device over the prior art. Subsequently, stiffer guidewire  7  may be replaced by an alternative tool also designed to penetrate chronic total occlusion  2 , or to for example, perform a balloon angioplasty and/or stent delivery procedure. Any such device will also be centered within the vessel via balloon  75  and exit port  72 . 
     Catheter  80  additionally provides support to guidewire  7  within the vessel. As a result, the force exerted upon guidewire  7  to penetrate the lesion is enhanced. And, additional force can be applied to stiffer guidewire  7  without resulting in excessive prolapse of the guidewire within vessel  3 . Therefore, it is more likely that guidewire  7  will effectively penetrate chronic total occlusion  2 . 
     Further, after inflation, balloon  70  forms a friction fit with interior wall  6  of vessel  3 . Catheter  80  is thereby securely positioned within vessel  3 . Therefore, pressure exerted to advance stiffer guidewire  7  or other tool to traverse chronic total occlusion  2  will not deflect catheter  80 , or cause catheter  80  to slide proximally within vessel  3 . Stable support and consistent centering in conjunction with improved visualization are thereby provided by catheter  80  according to the invention. 
     Turning now to FIGS. 9 and 10, further advantages of the invention are described. FIG. 9 illustrates the use of a prior art catheter at the site of a bifurcation in a vessel. Prior art catheter  405  has been tracked over guidewire  415  and is shown within vessel  400 . Vessel  400  comprises occlusion  410  within first branch  411 . Guidewire  415 , having encountered occlusion  410 , has prolapsed into second branch  420 . And, prior art catheter  405  is not designed to provide support to or enable guidewire  415 , or an alternate device (not pictured) to traverse the lesion. Consequently, it will be difficult, if not impossible, to traverse occlusion  410  utilizing only the prior art devices. 
     In FIG. 10, catheter  505  according to the invention has been tracked over a conventional guidewire (not shown) to occlusion  510  within first branch  511  of bifurcated vessel  500 . Balloon  506  of catheter  505  centers and supports stiffer guidewire  515  in order that guidewire  515  can traverse occlusion  510 . Further, balloon  506  prevents prolapse of guidewire  515  into second branch  520 . 
     FIGS. 11-14 illustrate successive steps of preparing a balloon for use in a device according to the invention. First, as shown in FIG. 9, balloon  110  comprises central portion  111 , distal shaft  100  and proximal shaft  115 . Distal shaft  100  comprises exterior surface  101 , and proximal shaft  115  comprises interior surface  102  and exterior surface  103 . Distal shaft  100  further comprises marker band  116 . Alternatively, marker band  116  can be placed on the catheter as a later step in the manufacturing process. In either case, according to the invention, marker band  116  can be placed at substantially the distal-most portion of balloon  110 , conferring great advantage over the prior art for visualizing the device at the site of total occlusion. As shown in FIG. 10, distal shaft  100  is withdrawn into balloon  110 , until distal shaft  100  is within central portion  111  of balloon  110 , as shown in FIG.  11 . Proximal shaft  115  is then inverted until interior surface  102  is exposed, and exterior surface  103  is adjacent exterior surface  101 . FIG. 12 illustrates the configuration of balloon  110  after proximal shaft  115  is completely inverted over distal shaft  100  of balloon  110 . Balloon  110  is now ready to be affixed to a catheter member (not pictured) using any process known in the art. 
     Turning now to FIG. 15, an alternative embodiment of the invention is shown within vessel  300  at the site of chronic total occlusion  305 . The embodiment depicted in FIG. 13 comprises catheter  209  having balloon  210 . Distal portion  211  of balloon  210  is the distal most element of catheter  209 . Balloon  210  also comprises central lumen  215 . Once catheter  209  is positioned within vessel  300 , balloon  210  is inflated to abut chronic total occlusion  305 . Next, second catheter  225  can be tracked over guidewire  220 , through central lumen  215 . Second catheter  225  can be a more conventional balloon catheter and/or a catheter designed for stent delivery and deployment. In the embodiment depicted in FIG. 13, stent  240  can be delivered to the site of chronic total occlusion  305 . 
     A balloon catheter assembly and method of manufacturing a balloon catheter assembly have been disclosed. Although the present invention has been described in accordance with the embodiments shown, one of ordinary skill in the art will readily recognize that there could be variations to the embodiments and those variations would be within the spirit and scope of the present invention. 
     A wide variety of suitable materials used for balloons and tubular members may be interchanged without diverging from the methods or structures of the invention claimed. Further, the guide wire or atherectomy device type utilized could be varied greatly. The embodiments disclosed herein focus on conventional guidewires, catheters, balloons and stents comprising conventional materials, but alternative structures and materials may also be used. 
     Further, the instant invention can also be used for treatment of conditions other than chronic total occlusions. Other examples of therapies include mitral valvuloplasty, treatment of urethral blockages and blockage of the fallopian tubes. The foregoing embodiments and examples are illustrative and are in no way intended to limit the scope of the claims set forth herein.