Abstract:
An apparatus for exchanging over-the-wire balloon catheters engages a guide wire within a guide catheter. In one embodiment the engagement is by an inflatable balloon in the guide catheter. Alternatively, the engagement is accomplished by a captivation wire in the guide catheter that has a collapsible loop portion through which the guide wire extends. Inflation of the balloon or closing the loop portion of the captivation wire within the guide catheter traps the guide wire and restricts its movement relative to the guide catheter. Once the guide wire position is fixed, withdrawal of a first balloon catheter and subsequent introduction of a second balloon catheter over the guide wire is possible without moving the guide wire longitudinally. Thus, the positioning of the guide wire over a stenosis to be dilated is not disturbed.

Description:
REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of Ser. No. 07/398,756 filed Aug. 25, 1989 now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of angioplasty. In particular, the present invention relates to an apparatus and method for facilitating the exchange of a dilatation balloon catheter on a guide wire. 
     2. Description of the Prior Art 
     Angioplasty has gained wide acceptance in recent years as an efficient and effective method for treating types of vascular diseases. In particular, angioplasty is widely used for opening stenoses in the coronary arteries, although it is also used for treatment of stenoses in other parts of the vascular system. 
     The most widely used form of angioplasty makes use of a dilatation catheter which has an inflatable balloon at its distal end. Using fluoroscopy, the physician guides the catheter through the vascular system until the balloon is positioned across the stenosis. The balloon is then inflated by supplying a fluid under pressure through an inflation lumen to the balloon. The inflation of the balloon causes stretching of the artery and pressing of the lesion into the artery wall to re-establish acceptable blood flow through the artery. 
     Two types of dilatation catheters are “over-the-wire” catheters and “non-over-the-wire” catheters. An over-the-wire catheter is one in which a separate guide wire lumen (sometimes called a “thru lumen”) is provided so that a guide wire can be used to establish a path through the stenosis. The dilatation catheter is then advanced over the guide wire until the balloon is positioned across the stenosis. One problem with the over-the-wire catheter is the inability to maintain the position of the guide wire within the vascular system when removing the catheter, and when exchanging it for one of a smaller (or larger) balloon diameter. 
     It is desirable to maintain the position of the guide wire across the stenosis during the exchange of catheters to ensure the safety and speed of the angioplasty procedure. Attempts to alleviate the problem of guide wire movement include the use of long or “exchangeable” guide wires, or extendable guide wires. These guide wires are of a length such that a proximal portion of the guide wire extends outside the patient&#39;s body while a distal portion of the guide wire passes through the body and across the stenosis. Thus, during an exchange of balloon catheters on the wire, the guide wire position across the stenosis is maintained by holding onto a proximal segment of the guide wire from outside of the body. However, guide wire movement relative to the stenosis still occurs despite such external fixation of the guide wire. These guide wires also have the disadvantage of being cumbersome and difficult to handle while maintaining the guide wire position across the stenosis. For example, a length of guide wire of approximately 150 cm must be maintained outside the body (either by an extension or by a 300 cm long base guide wire). Furthermore, x-ray fluoroscopy must be used during the exchange in order for the operator to see the wire being held in position across the stenosis. This use of fluoroscopy results in an undesirable, excessive exposure of x-ray radiation to the patient and also to the attendant medical personnel. 
     A non-over-the-wire catheter (also called a “fixed wire” catheter) acts as its own guide wire, so that the exchange of catheters necessarily requires removal of the catheter/guide wire assembly from the stenosis area. Thus, when accomplishing an exchange with the “non-over-the-wire” catheter, the path to the stenosis must be re-established when replacing the catheter with one having a different balloon diameter. 
     In both types of catheter/guide wire systems, it is difficult to effectively maintain or realign the guide wire across the stenosis. In addition, the exchange often requires more than one person to perform the procedure and requires extensive use of fluoroscopy resulting in excessive x-ray exposure to the patient. 
     SUMMARY OF THE INVENTION 
     Unlike previous catheter exchange systems which allow guide wire movement during an exchange at the distal end of the guide catheter and near the stenosis, the present invention has the advantage of fixing the guide wire position directly at the distal end of guide catheter and near the stenosis, thereby preventing guide wire movement relative to the stenosis. 
     The present invention is an improved apparatus for use in exchanging an over-the-wire balloon catheter on a guide wire, with the guide wire running through a guide catheter. The improved apparatus is a means for selectively engaging the guide wire within the guide catheter to restrict longitudinal movement of the guide wire relative to the guide catheter. The means for selectively engaging further include a means for urging a portion of the guide wire against an inner portion of the guide catheter. 
     In some preferred embodiments of the present invention, an inflation lumen extends longitudinally within the guide catheter. The inflation lumen has a proximal end and a distal end, with the distal end of the inflation lumen being within and adjacent to a distal end of the guide catheter. An inflatable balloon is in fluid communication with the distal end of the inflation lumen, and the inflatable balloon is of a size such that inflation of the balloon within the guide catheter restricts longitudinal movement of the guide wire relative to the guide catheter. 
     In one preferred embodiment, the inflation lumen is integral with a wall of the guide catheter and in fluid communication with an inflatable balloon that is fixed to a wall of the guide catheter. The inflation lumen provides a fluid path between the proximal end of the guide catheter and the inflatable balloon, wherein the balloon is inflated when pressure is applied to the fluid through the lumen. Upon inflation of the balloon, the guide wire is trapped between the balloon and the inner portion of the guide catheter, and longitudinal guide wire movement with respect to the guide catheter is limited. 
     In another preferred embodiment, the inflation lumen and an inflatable balloon both are separate from the guide catheter, and are thus movable longitudinally within the guide catheter. The inflation lumen provides a fluid path between the proximal end of the guide catheter and the inflatable balloon, wherein the balloon is inflated when pressure is applied to the fluid through the lumen. Upon inflation of the balloon, the guide wire is captured between the balloon and the guide. catheter, and longitudinal guide wire movement with respect to the guide catheter is limited. 
     In another preferred embodiment of the present invention, a captivation wire extends longitudinally within the guide catheter. The captivation wire has a distal end, a loop portion, and a proximal end. The distal end of the captivation wire is secured to the guide catheter, and the loop portion of the captivation wire is within and just proximal to the distal end of the guide catheter. The loop portion has an open loop state, whereby unrestricted longitudinal movement of the guide wire through the loop portion and relative to the guide catheter is permitted. The loop portion also has a closed loop state, whereby longitudinal movement of the guide wire relative to the guide catheter is limited. 
     In one embodiment, the captivation wire extends longitudinally through and is slidably received in a lumen formed in a wall of the guide catheter. A spiraled recess is formed within an inner wall of the guide catheter to receive the loop portion of the captivation wire when in its open loop state. A tab member is connected to the proximal end of the captivation wire and is mounted to the proximal end of the guide catheter. The tab member is movable longitudinally with respect to the guide catheter between a first distal position and a second proximal position. When the tab member is in its first distal position, the captivation wire is in the open loop state and when the tab member is in its second proximal position, the captivation wire is in the closed loop state. The tab member also includes detent means to selectively retain the tab member in the first distal position or the second proximal position. 
     The unique and inventive method for limiting a guide wire in a guide catheter from longitudinal movement with respect to the guide catheter involves two simple steps: (1) providing a means for selectively engaging the guide wire within the guide catheter, and (2) manipulating the means for engaging to force the guide wire against an inner portion of the guide catheter, thereby fixing the guide wire position with respect to the guide catheter. Preferably, the means for engaging the guide wire is positioned within the guide catheter adjacent a distal end of the guide catheter. The guide wire position is thus fixed at a location somewhat close to the stenosis, as opposed to trying to hold the guide wire in position by grasping the guide wire adjacent its proximal end, at a location outside of the body and very remote from the stenosis. 
     In one embodiment of the inventive method, the means for engaging the guide wire is an inflatable wire-captivation balloon. The wire-captivation balloon is provided within the guide catheter and inflated to a size such that the balloon forces the guide wire against an inner portion of the guide catheter, thereby fixing the guide wire position with respect to the guide catheter. 
     To exchange a first over-the-wire catheter on a guide wire in a patient&#39;s vascular system for a second over-the-wire catheter on the guide wire, this inventive exchange method includes a first step of providing the inflatable wire-captivation balloon within the guide catheter. Next, a proximal end of the guide wire is held outside the vascular system to maintain position of the guide wire longitudinally relative to the guide catheter, while the balloon of the first over-the-wire catheter is moved on the guide wire into the guide catheter to a position that is proximal of the wire-captivation balloon. The wire-captivation balloon is then inflated to maintain the position of the guide wire relative to longitudinal movement with respect to the guide catheter. Once the guide wire position is fixed within the guide catheter, the proximal end of the guide wire is released. Then, the first over-the-wire catheter is withdrawn from a proximal end of the guide wire, and a second over-the-wire catheter is installed onto the proximal end of the guide wire. The balloon of the second over-the-wire-catheter is moved to a position just proximal of the wire-captivation balloon, and then the proximal end of the guide wire is again held outside of the vascular system to maintain position of the guide wire longitudinally relative to the guide catheter and vascular system. Next, the wire-captivation balloon is deflated to release the guide wire from its fixed position relative to the guide catheter, and finally the second over-the-wire catheter is moved distally of the wire-captivation balloon and across the lesion for further dilatation. 
     In another embodiment of the inventive method, the means for engaging the guide wire is a wire-captivation wire. The wire-captivation wire is provided within the guide catheter and when a loop portion of the wire-captivation wire is closed, the guide wire is forced against an inner portion of the guide catheter, thereby fixing the guide wire position relative to the guide catheter. 
     An exchange of over-the-wire catheters by the inventive method using the wire-captivation wire requires a wire-captivation wire within the guide catheter that has a looped portion through which the guide wire extends. In use, the looped portion closes to trap the guide wire against an inner portion of the guide catheter and opens to release the guide wire. The wire-captivation wire replaces the wire-captivation balloon of the previous exchange method and in particular, the looped portion of the wire-captivation wire effectively replaces the inflatable wire-captivation balloon. All the steps of the previous exchange method are duplicated except for the following: (1) instead of inflating the balloon to a size such that movement of the guide wire longitudinally relative to the guide catheter is limited, the looped portion of the captivation wire is closed to a size such that movement of the guide wire longitudinally relative to the guide catheter is limited, and (2) instead of deflating the inflatable balloon to release the guide wire from its fixed position relative to the guide catheter, the looped portion is opened to release the guide wire. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagrammatic view of an angioplasty balloon catheter system incorporating the present wire-captivation invention. 
     FIG. 2 is an enlarged fragmentary sectional view of a portion of FIG. 1 which shows guide wire captivation. 
     FIG. 3A is an enlarged elevational view showing one preferred embodiment of an inflation lumen and an inflatable captivation balloon, with some parts shown in section. 
     FIG. 3B is an enlarged fragmentary sectional view of another preferred embodiment of the inflatable captivation balloon. 
     FIG. 4 is a sectional view of another preferred embodiment of the present invention, showing an inflation lumen and an inflatable balloon, in combination with a guide catheter. 
     FIG. 5 is a sectional view as taken on line  5 — 5  in FIG.  4 . 
     FIG. 6 is a sectional view of another preferred embodiment of the present invention, showing a captivation wire in combination with a guide catheter. 
     FIG. 7 is an enlarged fragmentary sectional view of a portion of FIG. 6 which shows guide wire captivation. 
     FIG. 8 is a sectional view as taken on line  8 — 8  in FIG.  6 . 
     FIG. 9 is a diagrammatic view similar to FIG. 1 illustrating use of the wire-captivation invention with another intravascular device. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Basic Angioplasty Components and Procedure 
     A vascular system  10  and a balloon catheter system  20  are shown in FIG.  1  and shown in FIG. 2 in fragmentary detail. In an angioplasty procedure, entry into the vascular system is typically through the femoral artery in the thigh. The proximal portion of the vascular system  10  is not shown, but will be described for anatomical reference. Continuing up from the femoral artery is an iliac artery and, then an abdominal aorta, which extends into a thoracic aorta. The distal portion of the vascular system  10  as shown in FIG. 1 begins just distal of the thoracic aorta (not shown) and extends into a descending aorta  12 , an arch of aorta  14 , and an ascending aorta  16 . Extending from the ascending aorta  16  is a coronary artery  18 , in which a stenosis  19  is formed. The stenosis  19  is a formation of plaque within the coronary artery  18  which restricts blood flow. 
     The balloon catheter system  20  includes a guide catheter  22 , a guide wire  24  extending through the guide catheter  22 , and a dilatation catheter  25  with a distal balloon  26  mounted on a balloon catheter main shaft  28 . The dilatation catheter  25  is an over-the-wire catheter, with its main shaft  28  extending over the guide wire  24 . A proximal end of the main shaft  28  is connected to an inflation manifold  29 , out of which a proximal portion of the guide wire  24  protrudes. 
     The basic angioplasty procedure consists of inserting the guide catheter  22  into the vascular system  10  at the femoral artery (not shown). The guide catheter  22  is pushed up through the previously described (and not shown) proximal portion of the vascular system  10  until the descending aorta  12  is reached. Thereafter, the guide catheter  22  is further pushed through the arch of aorta  14 , the ascending aorta  16 , and up to the mouth of the coronary artery  18 , where the stiffness of the guide catheter  22  is such that the guide catheter  22  cannot be extended through the tortuous lumens of the artery tree to the stenosis  19 . 
     Next, the distal end of dilatation catheter  25  is loaded onto and over the proximal end of guide wire  24  and pushed up the guide wire  24  until a distal end of dilatation catheter  25  is adjacent to a distal end of the guide wire  24 . Then, the assembled combination of guide wire  24  and dilatation catheter  25  are inserted into and pushed up through the proximal end of guide catheter  22 , retracing the already established path of the guide catheter  22  through the patient&#39;s vascular system  10 . The guide wire  24  and dilatation catheter  25  are pushed until they both extend out of a distal end of the guide catheter  22 . The tip of the guide wire  24  with the loaded dilatation catheter  25  is then manipulated into the artery tree to the stenosed artery and then finally, across the stenosis  19 . 
     The stenosis  19  as shown in FIG. 1 is adjacent the ostium of the coronary artery  18 . Frequently, the stenosis  19  is farther from the ostium of the coronary artery  18  and is found in an arterial branch extending from the coronary artery  18 . The route from the coronary artery to the stenosis/arterial branch is often a tortuous path of turns and twists through several blood vessels in an arterial tree. In such a case, the guide catheter  22  is too stiff to be guided down the tortuous path, so the guide wire  24  and the dilatation catheter  25  must extend some distance beyond the distal end of the guide catheter  22  down the tortuous arterial path in order to reach the stenosis  19 . 
     Dilatation Catheter Exchange—Prior Art Techniques 
     The profile of the deflated balloon  26  of a dilatation catheter  25  is sometimes too large to fit through the stenosis  19 , or the balloon diameter is so small that upon inflation of the balloon  26 , the stenosis  19  is not sufficiently dilatated. When this difficulty occurs, the balloon  26  must be exchanged for one of a different size (smaller or larger), so that the stenosis  19  can be crossed and properly treated upon inflation of the balloon  26 . The dilatation catheter  25  may also have poor control or low flexibility resulting in an inability to track to the stenosis  19 . In this case, the dilatation catheter  25  must be exchanged for one with better tracking characteristics so that the stenosis  19  may be reached and crossed. 
     A balloon catheter exchange with an extended or extendable guide wire begins by a physician holding onto the extended guide wire  24  extending outside the body at the femoral artery (to fix the position of the guide wire across the stenosis). Then, a second physician withdraws the dilatation catheter  25  proximally from the stenosis  19  and back through the tortuous path of arterial branches to the distal end of the guide catheter  22 . The second physician must incrementally remove the dilatation catheter  25  proximally over the guide wire  24  while the first physician grasps an exposed proximal portion of the guide wire  24 . As the dilatation catheter  25  is moved proximally, the first physician must continually change the grasping location of the wire  24  to a position proximal of the proximal end of the dilatation catheter  25  in order to maintain the position of the guide wire  24  relative to the stenosis  19 . This is necessary since the removal of the catheter  25  by the second physician urges the guide wire  24  proximally back out of the vascular system. Therefore, the first physician must continually urge or “advance” the guide wire  24  distally into the catheter  25  at the same time and in equal length movements that the second physician is withdrawing the catheter  25  proximally from the wire  24  and vascular system  10 . 
     It is desirable to hold the guide wire  24  in place across the stenosis  19  during withdrawal of dilatation catheter  25  to eliminate the need to re-establish the position of the guide wire  24  down the tortuous path and across the stenosis  19  after the catheter on the wire is exchanged. More importantly, being able to hold the guide wire  24  in place prevents excess movement of the distal end of the guide wire  24 , which can result in the guide wire  24  damaging the heart. 
     To complete the exchange process, the dilatation catheter  25  is further withdrawn proximally through the vascular system  10  in the path established by the guide catheter  22  until the dilatation catheter  25  is removed from the body at the femoral artery. Upon removal of the dilatation catheter  25  from the femoral artery, a portion of the guide wire  24  is exposed between the proximal end of the guide catheter and the distal end of the dilatation catheter  25 . The first physician grasps the guide wire  24  at this exposed portion to hold the guide wire  24  in position across the stenosis  19  while the dilatation catheter  25  is continually withdrawn proximally relative to the guide wire until it is completely removed from the proximal end of the guide wire. 
     A second dilatation catheter is then placed on the proximal end of the guide wire  24  and moved distally over the guide wire  24  up through the guide catheter  22  and down the tortuous path of arterial branches until the balloon of the second dilatation catheter is pushed across the stenosis  19 . As required during withdrawal of the original dilatation catheter  25 , the guide wire  24  must be held in position across the stenosis  19  at all times during the insertion of the second dilatation catheter. Again, this prevents the guide wire  24  from moving distally so as to damage the heart, as well as avoiding the difficulty of re-establishing a path to and across the stenosis  19 . 
     During the exchange of dilatation catheters as described, the guide wire  24  must continually and skillfully be manipulated from outside the body to maintain its position across the stenosis  19 . Note that the reference point to fix the position of the guide wire  24  is outside of the body (the thigh) at a location far removed from the area of the stenosis  19  (the chest). This remote point of control for the guide wire  24  makes the exchange of dilatation catheters very difficult, necessitating the use of two persons to perform the exchange. 
     The longitudinal position of the guide wire  24  relative to the stenosis  19  must be maintained while simultaneously moving the dilatation catheters over the guide wire  24  longitudinally. To do so, the guide wire  24  must be held in position from outside the body by the first physician while the second physician removes the dilatation catheter  25  from the guide wire  24 . This is further complicated by the necessary length (perhaps 150 cm) of the guide wire  24  to facilitate such an exchange which extends outside of the body and is difficult to control during the removal or insertion of a dilatation catheter. Not only is this extra guide wire length quite flexible, but it must be kept sterile, on the table and off the floor. 
     Furthermore, x-ray fluoroscopy must be used during the exchange for the first physician to know that the guide wire  24  is being held in place across the stenosis  19 . The x-ray exposure effectively illuminates the image of a radiopaque tip of the guide wire  24  so that its position within the coronary artery may be observed. This prolonged, continuous x-ray exposure to the patient and the physician/and medical team during the exchange is undesirable due to the limited capability of humans to withstand x-ray radiation. However, without x-ray fluoroscopy this vital exchange procedure would not be possible. 
     THE PRESENT INVENTION 
     First Embodiment (FIGS.  1 - 3 ) 
     The present invention, as shown in FIGS. 1-3, employs a guide wire captivation catheter  30  which has an inflatable balloon  31  mounted on a distal end of an elongated flexible shaft  32 . The shaft  32  is formed from a flexible hollow tube to provide an inflation fluid path between the inflatable balloon  31  and a proximal end of the shaft  32 , which is connected to a suitable inflation device (not shown). 
     As seen in. FIGS. 1 and 2, guide wire captivation catheter  30  is inserted into the guide catheter  22  and its balloon  31  (in an uninflated state) is advanced distally to a position adjacent the distal end of the guide catheter  22 . The dilatation catheter  25  is moved proximally on the guide wire  24  (which is held in place by hand) until its balloon  26  (also uninflated) is positioned proximally of the balloon  31 . Radiopaque markers on the balloons or their respective shafts permit relative positioning of these components. The guide wire  24  is thus exposed and uncovered distally of the balloon  26  and adjacent the balloon  31  within the distal end of the guide catheter. Inflation of the balloon  31  (as seen in FIGS. 2 and 3) therefore limits longitudinal movement of the guide wire  24  relative to the guide catheter  22 . The balloon  31  is of size such that the pressure exerted by its inflation pushes the guide wire  24  against an inner wall of the guide catheter  22 . The guide wire  24  is thus captivated or trapped at the distal end of the guide catheter  22 , which is near the stenosis  19 . This is in contrast to the guide wire “captivation” systems described above (i.e., grasp the guide wire at a point outside the body), where the area of guide wire captivation (grasping) is far removed from the stenosis  19 . As such, a distinct advantage of the present invention for guide wire captivation over prior arrangements is more direct and local control over the position of the guide wire  24  at its distal end. 
     A preferred embodiment for the guide wire captivation catheter  30  of the present invention is shown in FIG.  3 A. An inflation manifold  34  is bonded to a strain relief member  35  at a strain relief bond surface  36  and bonded to proximal end  37  of the shaft  32  at another bond surface  38 . The inflation manifold  34  is connected to an inflation device (not shown) to provide positive fluid pressure to the inflation lumen in the shaft  32  for inflatable balloon  31  inflation, and negative fluid pressure for balloon  31  deflation. The shaft  32  extends from the inflation manifold  34  to a lumen/balloon joint  42 , where a distal end  44  of the shaft  32  is connected to a proximal portion  46  of the balloon  31 . 
     FIG. 3B shows an alternative structure of the distal end of the captivation catheter  30 . The structures vary due to the differing types of material used to construct the main shaft  32 . As shown in FIG. 3A, when the main shaft  32  is made of a flexible stainless steel material, the distal end  44  of shaft  32  has a support wire  48  secured thereto to extending within the balloon  31  from its proximal end to its distal end. The support wire  48  adds rigidity to the balloon  31 , so that upon insertion and movement of the balloon  31  within the guide catheter  22 , the balloon will not fold back on itself, and is capable of being forced through a tight area. 
     As shown in FIG. 3B, when the main shaft  32   a  is made of a plastic polyethylene material, the distal end  44   a  of shaft  32   a  is necked down in order to receive the proximal portion  46  of balloon  31 . This arrangement creates a more stable bonding structure for balloon  31  when the main shaft.  32   a  is a plastic material. In either case, the distal end of the shaft may optionally be extended in a necked fashion to the distal end of balloon to provide additional structural support to the balloon. The extended necked shafts would thus include inflation paths therethrough to allow the inflation fluid to fill the balloon chamber since the shaft would extend through the entire length of the balloon. 
     The inflation balloon  31 , in its deflated state, preferably has a profile under 0.030 inches in diameter, with a length of approximately 2.5 cm. The inflatable balloon  31  is preferably a polymer material such as a polyolefin. Upon inflation of the balloon  31 , its maximum outer diameter is preferably 0.090 inches or just larger than the guide catheter  22  in which it is being utilized. In FIGS. 3A and 3B, the balloon is shown inflated in phantom. 
     The shaft  32  is preferably formed from an elongated flexible thin-walled tube, preferably of stainless steel, polyethylene or polyamide with a low friction coating on its outer surface such as Teflon or silicone. The shaft  32  preferably has a 0.014 inch inner diameter and a 0.019 inch outer diameter, with a total length of approximately 100 cm. The tube defining shaft  32  preferably has a wall thickness of 0.0025 inch. 
     The inflation fluid is preferably a saline solution or a solution consisting of fifty percent saline and fifty percent contrast media, where the contrast media may be remagrafin  76 . The fifty percent contrast media solution is used when it is desirable to view the balloon expansion using fluoroscopy. 
     Incorporating this preferred embodiment of the present invention, the basic angioplasty procedure as previously described is followed until it becomes necessary to effect a dilatation catheter exchange on the guide wire. 
     The inventive method of balloon catheter exchange begins by inserting the guide wire captivation catheter  30  into the guide catheter  22  at the femoral artery (not shown) and moving it distally until the balloon  31  is adjacent and just proximal to the distal end of the guide catheter  22 . Next, a proximal end of the guide wire  24  is held outside of the vascular system  10  to maintain the position of the guide wire  24  longitudinally relative to the guide catheter  22  and vascular system  10 . The dilatation catheter  25  is then withdrawn proximally from the stenosis  19  and coronary arteries until its balloon  26  is within the distal end of the guide catheter  22  and proximal to the balloon  31 . The balloon  31  is manually positioned by manipulating that portion of the shaft  32  outside the body. Once the balloon  31  is positioned, it is then inflated as seen in FIG.  2 . The balloon  31  inflates to a diameter which fills the guide catheter  22  inner diameter and pushes the guide wire  24  against an inner wall of the guide catheter  22 , thereby limiting longitudinal movement of the guide wire  24  relative to the guide catheter  22  and relative to the stenosis  19  (assuming the guide catheter  22  is not moved within the vascular system). Inflation of the balloon  31  is accomplished by introducing a fluid under pressure into the inflation manifold  34 , through the inflation lumen of the shaft  32 , and into the balloon  31 . 
     After the guide wire  24  position is fixed by inflation of the balloon  31 , the proximal end of the guide wire is released and the dilatation catheter  25  is moved proximally over the guide wire  24 , out of the body and removed off of the proximal end of the guide wire  24 . Likewise, a second dilatation catheter is placed on the proximal end of the guide wire  24  and moved distally over the guide wire  24  through the guide catheter  22  to a point just proximal of the balloon  31 . The balloon  31  is then deflated, thereby freeing the guide wire  24  from its captive or fixed-position state. The second dilatation catheter is then further moved distally along the guide wire  24  past the distal end of the guide catheter  22  and through the arterial branches up to the stenosis  19 . This occurs while the proximal end of the guide wire  24  extending out of the proximal end of the second dilatation catheter is manipulated by hand to prevent its advancement within the vascular system  10  during the distal movement of the second dilatation catheter. The balloon of the second dilatation catheter is then positioned across the stenosis  19 , so that upon inflation of that balloon, the stenosis  19  is further dilated. The dilatation catheter exchange procedure has now been completed, and the guide wire captivation catheter  30  can be left in the guide catheter  22  until no further exchanges are necessary (i.e., until the guide wire  24  can be withdrawn from across the stenosis). 
     During the dilatation catheter removal and installation procedure, the position of the guide wire is maintained relative to the guide catheter and, more importantly, relative to the stenosis, without the previously required task of holding the guide wire by hand from outside of the body. Since the guide wire no longer must be continually manipulated, the previously required extension or exchange wires used to facilitate handling of the guide wire are no longer necessary (i.e. the guide wire can be shorter). Additionally, the procedure may be performed without a second skilled physician, who was previously necessary to continually manipulate the guide wire. Finally, the dangerously prolonged use of x-ray fluoroscopy used to observe the position of the guide wire is no longer necessary since the guide wire is held stationary by use of the present invention and thus its position need not be continuously observed. 
     In addition to the above described method of operation, there are other alternative embodiments of the method for the use and operation of the captivation catheter. According to another embodiment of the method of operation, the guide catheter  22  is advanced into the vascular system  10  via the femoral artery so that the distal portion thereof is at or proximate to the coronary artery  18 . Next, the guide wire  24  is advanced through the guide catheter  22  out the distal end thereof. The guide wire  24  is advanced before the dilation catheter  25  is loaded over it. Then, an attempt is made to cross the stenosis with the guide wire  24 . If the guide wire  24  can be successfully positioned in the coronary site, the guide wire position is secured by use of the captivation catheter  30 . The captivation catheter  30  is advanced into the guide catheter  25  adjacent to the guide wire  24  so that the balloon portion  31  of the captivation catheter  30  is proximate to the distal end of the guide catheter  22 . The captivation catheter  30  may be advanced into the guide catheter  22  after the guide wire  24  is successfully positioned in place in the coronary site. Alternatively, the captivation catheter  30  may be advanced through guide catheter  22  along with the guide wire  24 . According to this latter method, the guide wire  24  and captivation catheter  30  are advanced together until the balloon portion  31  of the captivation catheter  30  is at the distal portion of the guide catheter  22  and then the guide wire  24  is advanced further for positioning in the coronary site. 
     After the guide wire  24  has been successfully positioned in the coronary site and its positioned secured by the captivation catheter  30 , the dilation catheter  25  is loaded over the proximal end of the guide wire  24 . The dilation catheter  25  is advanced over the guide wire  24  through the guide catheter  22  until the proximal end extends from the proximal end of the guide wire lumen of the dilation catheter  25 . Depending upon the lengths of the guide wire and the dilation catheter guide wire lumen, the distal end of the dilation catheter may be just proximate of the balloon of the captivation catheter. When the proximate end of the guide wire can be grasped, the captivation balloon  31  may be deflated. Then, the dilation catheter  25  can be advanced over the guide wire past the distal end of the guide catheter and across the stenosis. The captivation catheter  30  may be left in place at this stage. The dilation catheter may be inflated to dilate and treat the stenosis in a manner as is well known in the art. 
     If it is determined that a dilation catheter of a different size or type is needed, the first dilation catheter  25  can be exchanged for another, in the manner as described above. The captivation catheter  30  is already in place in the guide catheter  22  so that as the first dilation catheter is withdrawn proximally past the captivation catheter, the guide wire can be secured in position across the stenosis. A second dilation catheter can be installed over the guide wire while the captivation catheter is secures the distal position of the guide wire. 
     The above described procedure has several advantages. First, because the captivation catheter is installed in the guide catheter prior to an attempt to position the first dilation catheter, if it becomes necessary to exchange the first dilation catheter for another, the captivation catheter is already in place and ready to use. This saves the time that would otherwise be needed to prep and position the captivation catheter in the guide catheter. Thus, this method of operation could be indicated when the physician considers it a strong possibility that a dilation catheter exchange would be likely. 
     Another advantage of this embodiment of operation is that if the attempt to cross the stenosis with the guide wire is unsuccessful, the time of prepping the dilation catheter and the expense of the dilation catheter would not be wasted. With the present embodiment of operation, the dilation catheter (which would likely be more expensive than the captivation catheter), would not be opened or prepped until the guide wire had been successfully positioned across the stenosis. 
     As mentioned above, the guide wire and the captivation catheter may be advanced together into the guide catheter or alternatively the guide wire may be advanced all the way across the stenosis first and then the captivation catheter may be advanced into the guide catheter. An advantage of advancing the guide wire first is that if the guide wire cannot cross the stenosis, the captivation catheter need not be opened and prepped. An advantage of advancing the guide wire and captivation catheter into the guide catheter together is that the position of the guide wire in the coronary site can be secured as soon as it is obtained thereby reducing the possibility of that the guide wire position may be lost during positioning of the captivation catheter in the guide catheter. 
     Alternatively, the captivation catheter may be positioned in the guide catheter before the guide wire is advanced into the guide catheter. In yet other alternative embodiments of operation, the above alternative sequences can be combined, e.g. to provide for partial positioning of one or the other of the guide wire and the captivation catheter. 
     Second Embodiment (FIGS.  4  and  5 ) 
     The embodiment of the present invention depicted in FIGS. 4 and 5 may also be used according to the alternative method of operation described above. Specifically, the guide wire  54  may be advanced through the guide catheter  50  and across the stenosis before the dilation catheter  51  is positioned over the guide wire. Then, as described above, if the guide wire  54  is successfully positioned, the annular inflatable balloon  68  located at the distal end of the guide catheter is inflated to secure the guide wire position. Then, the dilation catheter  51  is prepped and inserted over the guide wire  54  up to just proximal of the annular balloon  68 . Then the annular balloon is deflated and the dilation catheter  51  may be advanced to the site of the stenosis. 
     Another embodiment of the guide wire captivation catheter of the present invention is shown in FIGS. 4 and 5. A guide catheter  50  provides a partial path through the arterial system for a dilatation catheter  51  having a main inflation lumen shaft  52  and a distal dilatation balloon  53 . The dilatation catheter  51  is an over-the-wire catheter, which is movable along a guide wire  54  which is positioned within the guide catheter  50 . As is typical, the proximal end of the shaft  52  is mounted to an inflation manifold  55  through which the guide wire extends. A guide catheter manifold  56  is affixed on the proximal end of the guide catheter  50 . 
     In this embodiment, the wire captivation balloon is fixed to the guide catheter. An inflation lumen  62  is formed in the wall of the guide catheter  50 , between an inner wall surface  64  and an outer wall surface  66 . At a proximal end of the guide catheter  50  an inflation device (not shown) is connected to the inflation lumen  62 , either directly or via a coupling  67 . An annular inflatable balloon  68  is mounted within the guide catheter  50  adjacent its distal end, and is in fluid communication with the inflation lumen  62 . The inflation lumen  62  thus provides a fluid path to the inflatable balloon  68  located adjacent the guide catheter distal end  70 . Upon inflation, the inflatable balloon  68  expands to a size that limits longitudinal movement of the guide wire  54  relative to the guide catheter  50 . 
     The method of dilatation catheter exchange incorporating this preferred embodiment of the present invention is very similar to the previously described, improved method of dilatation catheter exchange. However, in this embodiment of the present invention, the inflation lumen  62  and the inflatable balloon  68  are integral with or fixed to the guide catheter  50  so that neither the inflation lumen  62  nor the balloon  68  need be inserted or removed from the guide catheter. The inflatable balloon  68  is used in the same way -as in the previous improved method of the dilatation. catheter exchange, but is not movable longitudinally relative to the guide catheter. 
     Of course, other configurations for the guide wire captivation catheter of the present invention are contemplated. For instance, the inflatable balloon  68  can be a shape other than annular—it could extend out from only one side of the inner wall of the guide catheter  50 , pushing the guide wire  54  against the opposite side of the inner wall of the guide catheter  50 . 
     In another variation, the inflation lumen  62  may be separate from the guide catheter  50 , so that it extends through the lumen of the guide catheter  50 , as does the guide wire  54 . However, in this configuration, the inflation lumen  62  is connected to an inflatable balloon  68  which is fixed to the guide catheter  50 . 
     The embodiment of the present invention depicted in FIGS. 6-8 may also be used according to the alternative method of operation described above. Specifically, the guide wire  84  may be advanced through the guide catheter  80  and across the stenosis before the dilation catheter  81  is positioned over the guide wire. Then, as described above, if the guide wire  84  is successfully positioned, the loop portion  100  located at the distal end of the guide catheter  80  is operated to move it into its closed state to secure the guide wire position. Then, the dilation catheter  81  is prepped and inserted over the guide wire  84  up to just proximal of the loop portion  100 . Then, the loop portion  100  is operated to move it in its open state and the dilation catheter  81  may be advanced to the site of the stenosis. 
     Third Embodiment (FIGS.  6 - 8 ) 
     Another embodiment of the present invention, as shown in FIGS. 6-8, employs a guide wire captivation wire  98  positioned within a guide catheter  80 . The guide catheter  80  provides a partial path through the arterial system for a dilatation catheter  81  having a main inflation lumen shaft  82  and a distal dilatation balloon  83 . The dilatation catheter  81  is an over-the-wire catheter, which is movable along guide wire  84  positioned within the guide catheter  80 . As is typical, the proximal end of the shaft  82  is mounted to an inflation manifold  85  through which the guide wire extends. A guide catheter manifold  86  is affixed to the proximal end of the guide wire  80 . 
     In this embodiment, a lumen  90  is formed in a wall of the guide catheter  80 , between an inner wall surface  92  and an outer wall surface  94  (see FIG.  8 ). The lumen  90  has a distal end adjacent the distal end of the guide catheter  80  and a proximal end adjacent the proximal end of the guide catheter  80 . The distal end of the guide wire captivation wire  98  is fixed to the distal end of guide catheter  80  at wire receptor  99 . The guide wire captivation wire  98  has a looped portion  100  extending out of the lumen  90 , positioned just proximal of the distal end of the guide catheter  80 . 
     A spiraled recess  102  is formed within the wall of the guide catheter  80 , positioned just proximal of the distal end of guide catheter  80  and aligned to receive the looped portion  100  of the wire-captivation wire  98 . The guide wire captivation wire  98  extends out of a distal end  103  of the lumen  90  and forms an open loop within the spiraled recess  102 , with its distal end received in and fixed to the guide catheter  80  at wire receptor  99 . The looped portion  100  of the captivation wire  98  thus is flush or below the inner wall surface of the guide catheter inside diameter. Thus, the loop portion  100  of wire-captivation wire  98  in its open loop state does not interfere with the movement and functioning of guide wire  84  or dilatation catheter  81  within the guide catheter  80 . 
     A proximal end of the captivation wire  98  is connected to a tab member  104  which is slidably mounted relative to the guide catheter manifold  86  at the proximal end of guide catheter  80 . A detent  108  is formed on the proximal end of tab member  104  and forcibly fits within a distal groove  110  or a proximal groove  112  of the guide catheter manifold  86 . 
     The loop portion  100  of wire-captivation wire  98  is capable of being in either an open loop state (FIG. 6) or a closed loop state (FIG.  7 ). The loop state is changed by the longitudinal movement of tab member  104  relative to the manifold  86 . The tab member  104  is connected to the proximal end of the wire-captivation wire  98  such that longitudinal movement of tab member  104  causes longitudinal movement of wire  98 , except for its fixed distal end. Pushing the tab member  104  distally relative to the guide catheter pushes the wire-captivation wire distally thereby moving the loop portion  100  to its open loop state. Pulling the tab member  104  proximally relative to the guide catheter pulls the wire-captivation wire  98  proximally, thereby pulling the wire forming the loop portion  100  into the lumen  90  via its distal end  103 . This effectively moves the loop portion  100  to its closed loop state. The detent  108  of tab member  104  fits into distal groove  110  and proximal groove  112  such that tab member  104  is selectively retained into one of the two grooves to place the captivation wire  98  in its open loop state and closed loop state, respectively. 
     FIGS. 6 and 7 show the relative positions of a guide wire and dilatation catheter positioned within the distal end of the guide catheter  80  for a dilatation catheter exchange. The guide wire  84  extends through the open loop portion  100  of captivation wire  98  and the dilatation catheter  81  is moved proximally on the guide wire  84  (which is held in place by hand, outside of the body) until the balloon  83  is positioned proximally of the loop portion  100 . Radiopaque markers on the balloon or catheter shaft and on the captivation wire  98  permit relative positioning of the balloon  83  and the loop portion  100 . As illustrated in FIG. 6, the guide wire  84  is thus exposed and uncovered distally of balloon  83  and within the loop portion  100  adjacent the distal end of the guide catheter  80 . 
     To fix the position of the guide wire  84  for exchange purposes, the tab member  104  is moved proximally to engage proximal grove  112  thereby shrinking the open loop portion  100  down onto the guide wire  84 . The captivation wire  98  is drawn taut, urging the guide wire  84  against the inner wall of the guide catheter  80 . In its closed state (as seen in FIG. 7) the captivation wire  98  limits longitudinal movement of the guide wire  84  relative to the guide catheter  80 . The loop portion  100  in its closed loop state is reduced to a size such that the guide wire  24  is trapped at the distal end of the guide catheter  80 . 
     The method of dilatation catheter exchange incorporating this third embodiment of the present invention is very similar to the previously-described, improved methods of dilatation catheter exchange. once the guide wire  84  has been fixed in place by manipulation of the tab member  104 , the dilatation catheter  81  is withdrawn and a second dilatation catheter inserted onto the guide wire  84 . Thus, the majority of the exchange procedure is accomplished without the necessity of holding onto the guide wire at a position outside the body and quite remote from the lesion. In this embodiment of the present invention, the loop portion  100  of wire-captivation  98  is fixed within the distal end of guide catheter  80 . Thus, as opposed to other variations of the invention, the means for engaging the guide wire need not be inserted or removed from the guide catheter during the exchange procedure. The loop portion  100  of wire-captivation wire  98  is used to trap the guide wire  84  in a similar fashion as the inflatable captivation balloon of the other preferred embodiments. The loop portion  100  of wire  98  closes to trap the guide wire  84  within the guide catheter  80  whereas in the previously described methods, inflation of the captivation balloon effectively trapped the guide wire. Also, the loop portion  100  when opened allows longitudinal movement of the guide wire  84  relative to the guide catheter  80 , whereas in the previously described inventive method, the deflated captivation balloon allowed relatively unrestricted longitudinal movement of the guide wire within the guide catheter. 
     Although the examples included herein specifically describe use of embodiments of the invention in conjunction with angioplasty procedures with a dilation balloon catheter, in alternative embodiments, embodiments of the present invention may be used in conjunction with other intravascular therapeutic or diagnostic devices or procedures (e.g. atherectomy, laser, ultrasound, bail-outs, optical fiber, ultrasound, etc). Also, although the above methods describe use with over-the-wire catheters, the methods and apparatuses of the present invention may be used with fixed wire catheter devices or with single-operator-exchange catheter devices in which a proximal end of a guide wire lumen of the catheter device communicates with the exterior of the device at a location normally within the patient&#39;s body during use so that a guide wire is adjacent to the device proximally of the proximal opening inside the patient&#39;s body. 
     CONCLUSION 
     The present invention offers the advantages of allowing pre-angioplasty dilatation catheter selection and guide wire selection, with the ability to later exchange dilatation catheters quickly and without longitudinal guide wire movement in the guide catheter. Another advantage is the ability of one person to perform the dilatation catheter exchange. Previously, more than one person was usually necessary to perform the dilatation catheter exchange, since one person must be available to manipulate the guide wire to hold it in position while the another person exchanges the catheters. Also, the cumbersome, long or extendable exchange wires, which were used to maintain guide wire position, are no longer required to perform a dilatation catheter exchange using the inventive structure and exchange method of the present invention. Finally, the dangerously prolonged use of x-ray fluoroscopy is no longer necessary to continuously observe the movable guide wire position, since the guide wire can now be fixed in position. 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.