Abstract:
A guidewire navigable through body vessels of a human subject for delivery of a catheter or the like is provided. The guidewire includes an expandable segment movable between a collapsed state and an expanded state. If the catheter encounters resistance in a vessel and cannot be advanced further, the medical professional can move the expandable segment to the expanded state in which the expandable segment engages an inner surface of the catheter. The expandable segment locks onto the catheter, which allows the guidewire and catheter to be advanced through the vessel together as a single unit. An inflatable balloon catheter movable along the guidewire requires only a single tube and is sealed by the expandable segment of the guidewire for subsequent inflation.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention generally relates to medical devices that are navigable through body vessels of a human subject. More particularly, this invention relates to guidewires used to position a catheter or the like within a body vessel.  
       DESCRIPTION OF RELATED ART  
       [0002]     Vessel defects, such as blockages and stenoses, within the human vasculature system are often diagnosed and treated by the intraluminal delivery of diagnostic catheters, treatment fluids or expansion devices and stents. Expansion devices can take any of a number of forms, but are all generally delivered by a flexible catheter that, once properly positioned, deploys the expansion device. The path to the diseased site is typically tortuous and may additionally pass through other constricted lumens, so catheters cannot be used to define their own path through the vasculature. As such, a more rigid guidewire is first passed through the vasculature to the desired site, then the catheter is passed over the guidewire. A stent delivery system or catheter usable in such a procedure is commonly referred to as an “over-the-wire” or OTW catheter.  
         [0003]     An alternative stent delivery system commonly referred to as a “rapid exchange” or RX catheter also uses a guidewire to properly position the distal end of a catheter. Examples of known RX catheters and methods of using the same are illustrated in U.S. Pat. No. 5,061,273 to Yock, which is hereby incorporated herein by reference.  
         [0004]     Catheters must be flexible in order for them to follow the path defined by a guidewire through tortuous portions of the human anatomy. However, while catheters generally are capable of being pushed through tortuous paths, they cannot easily navigate an overly constricted vessel. When a catheter encounters resistance from a stenosed region of a vessel, rather than passing through, the downstream pushing force provided by an operator at the proximal end of the catheter is lost due to compression and “snaking” of the flexible catheter. Thereafter, the catheter must be backed out of the ostium to prevent further exasperation of the problem.  
         [0005]     Another problem is that some stent delivery systems must be provided with an overly intricate construction in order to ensure proper operation, which increases the stiffness of the catheter. While this increased stiffness is useful in pressing the catheter through a stenosed region, it increases the diameter of the catheter and prevents the use of longer stents. Thus, rather than delivering a single elongated stent to a target site, the operator must instead deliver several shorter stents to the site.  
         [0006]     For example,  FIG. 1  illustrates a typical balloon catheter  10  on a typical guidewire  12 , which catheter is subject to the above-described problem. The catheter  10  requires an outer tube  14  with an inflatable section  16  and an inner tube or inner body  18  to seal the inflatable section  16  at a distal portion  20 . Further discussion of such a double-tube catheter can be found in U.S. Patent Application Publication No. 2003/0229307 to Muni et al., which is hereby incorporated herein by reference.  
         [0007]      FIGS. 6 and 7  of that Muni et al. patent publication show an inner tubular member  15  having a thin wall section  22  which is said to collapse onto guidewire  18  to secure same into the catheter. This type of passive grasping feature creates a problem of not being able to reliably reverse the grasping action. Thus, to the extent the balloon  13  of that patent publication inflates to effect the passive grasping action, balloon deflation will not totally undo the grasping of the guidewire  18 . A balloon catheter needing only a single tube could have a smaller diameter. This is useful in providing an inflatable section that is more flexible than a double-wall catheter. This flexibility facilitates delivery of longer stents which add a degree of bulk and stiffness. In addition, a grasping approach that avoids the disadvantages of a passive system such as in Muni et al. would be desirable.  
         [0008]     Accordingly, a general aspect or object of the present invention is to provide a guidewire usable with standard catheters for navigation through a stenosed region of a body lumen.  
         [0009]     Another aspect or object of this invention is to provide a guidewire facilitating the use of lower profile stent delivery systems.  
         [0010]     Another aspect or object of this invention is to provide a method for navigating a medical device through a body vessel using a guidewire.  
         [0011]     Another aspect or object of the present invention is to provide a guidewire and system that effects an active grasping action and that avoids the shortcomings of a passive grasping system.  
         [0012]     Other aspects, objects and advantages of the present invention, including the various features used in various combinations, will be understood from the following description according to preferred embodiments of the present invention, taken in conjunction with the drawings in which certain specific features are shown.  
       SUMMARY OF THE INVENTION  
       [0013]     In accordance with one aspect of the present invention, a guidewire is provided with an expandable segment movable between a collapsed state and an expanded state. In the collapsed state, the guidewire operates as a standard guidewire and facilitates the delivery of medical devices, such as stent delivery systems, to body vessels. If the medical device encounters resistance and cannot be advanced further, the operator can move the expandable segment to the expanded state in which the expandable segment engages an inner surface of the medical device. The expandable segment locks onto the medical device, which allows the guidewire and medical device to be advanced through the vessel together as a single unit. Thus, the stiffness of the guidewire is used to effectively enhance the pushability and hence crossability of a flexible catheter.  
         [0014]     According to an embodiment of the present invention, the expandable segment is comprised of an elastic material, such as an elastomeric o-ring, which can be compressed in order to radially expand. According to yet another embodiment of the present invention, the expandable segment is comprised of a balloon that can be inflated in order to radially expand.  
         [0015]     According to another aspect of the present invention, a guidewire is provided with a plurality of longitudinally spaced expandable segments. The segments would be designed to impart a longitudinal displacement to the overriding component with respect to the guidewire. The segments may be activated in such a manner as to “inchworm” an engaged medical device through a body vessel. This is preferred when the guidewire has already been properly positioned at the target site and it is undesirable to advance the guidewire further into the vessel. Such “inchworm” motion is characterized by a leading expandable segment that is typically stationary with respect to the guidewire and a trailing expandable segment that is typically axially movable with respect to the guidewire. Both expandable segments are expanded to engage the medical device, and then the trailing expandable segment is moved toward the leading expandable segment. At this stage, the leading expandable segment is collapsed, which causes the medical device to move through the vessel. Finally, the trailing expandable segment is collapsed and moved away from the leading expandable segment and the process is repeated. This process can be automated or carried out manually.  
         [0016]     Special application for the present invention has been found for guidewire delivery of OTW and RX catheters to vessels of the human vascular system. However, the present invention is also applicable to guidewire delivery of stent delivery systems and other medical devices to other body lumens, so it will be understood that the products described herein are not limited to particular medical devices or particular surgical applications. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1  is a cross-sectional view of a prior art double-tube balloon catheter and guidewire;  
         [0018]      FIG. 2  is a cross-sectional view of a guidewire according to the present invention disposed within a single-tube balloon catheter in a body vessel;  
         [0019]      FIG. 3  is a cross-sectional view of a guidewire with an elastic expandable segment in a collapsed state;  
         [0020]      FIG. 4  is a cross-sectional view of the guidewire of  FIG. 3  with the expandable segment in an expanded state;  
         [0021]      FIG. 5  is a cross-sectional view of another embodiment of a guidewire according to the present invention, with a balloon expandable segment in a collapsed state;  
         [0022]      FIG. 6  is a cross-sectional view of the guidewire of  FIG. 5  with the expandable segment in an expanded state;  
         [0023]      FIG. 7  is a cross-sectional view of the guidewire of  FIG. 6  disposed within a single-tube balloon catheter;  
         [0024]      FIG. 8  is a cross-sectional view of a guidewire having a locking mechanism; and  
         [0025]      FIG. 9  is a cross-sectional view of a guidewire having a plurality of expandable segments. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriate manner.  
         [0027]      FIG. 2  illustrates the general structure and function of a guidewire  22  according to the present invention, as well as a medical device  24  deliverable with the guidewire  22 . The illustrated medical device  24  is an OTW catheter, but the present invention can be applied to RX catheters and other medical devices with a lumen suitable for delivery using a guidewire.  
         [0028]     The guidewire  22  has a proximal portion  26  and a distal portion  28  that are separated by expandable segment  30 . The proximal portion  26  is relatively rigid for pushing the guidewire  22  to the target site and providing tactile feedback to the operator, while the distal portion  28  includes a tip  32  with a flexible coiled spring for navigation through tortuous body vessels. The proximal and distal portions  26  and  28  may be made of stainless steel, a nitinol, or any other suitable material.  
         [0029]     Typically, the expandable segment  30  remains in a collapsed state during use, illustrated in  FIG. 3 . As shown, the diameter of the expandable segment  30  in a collapsed state is preferably no greater than the diameter of the proximal and distal portions  26  and  28  of the guidewire  22 . This allows the guidewire  22  to operate as a standard guidewire when the expandable segment  30  is in a collapsed state.  
         [0030]     If there are no difficult-passage locations, such as stenosed or constricted regions, in the path defined by the guidewire  22 , then the catheter  24  can be passed over the guidewire  22  and delivered to the target site without activating the expandable segment  30 . However, if the guidewire  22  and catheter  24  must traverse a difficult-passage location such as a stenosed region S of a body vessel V, then the expandable segment  30  is radially expanded by active action to move it from the collapsed state of  FIG. 3  to the expanded state of  FIGS. 2 and 4 . As illustrated, the diameter of the expandable segment  30  increases until it engages an inner surface  34  of the catheter  24 . Preferably, the expandable segment  30  is sized and configured to expand sufficiently to lock onto the inner surface  34  without damaging the catheter  24 .  
         [0031]     In order for optimal functionality, a high coefficient of friction should exist between the guidewire expandable segment  30  and catheter inner surface  34 ; otherwise the catheter  24  will slide away from the expandable segment  30  and resist passage further into the vessel V. Accordingly, the expandable segment  30  may be comprised of a material providing enhanced friction when engaging the inner surface  34 . Alternatively, a surface treatment may be provided at and/or applied to the expandable segment  30  or inner surface  34  for enhanced frictional engagement.  
         [0032]     The expandable segment  30  is preferably generally adjacent to the flexible tip  32  of the guidewire  22  in order to facilitate engagement of the expandable segment  30  at a distal end of the catheter  24 . The problem of a catheter “snaking” against a constricted vessel region is caused by pushing it from a proximal end, so the problem is minimized by causing the expandable segment  30  to actively grip the inner surface  34  at a distal end of the catheter  24  and move the guidewire distally so as to effectively have the guidewire “pull” the catheter through the difficult-passage location of the vascular system.  
         [0033]     Preferably, the guidewire  22  is provided with a radiopaque marker  36  for locating and properly positioning the expandable segment  30 . Most preferably, the guidewire  22  includes a radiopaque marker  36  at each end of the expandable segment  30  for better locating the expandable segment  30 . Alternatively, the expandable segment  30  could be comprised of a radiopaque material or receive a radiopaque surface treatment.  
         [0034]     More particularly, when the expandable segment  30  has locked onto the catheter  24 , the guidewire  22  is advanced through the vasculature and effectively pulls the catheter  24  through any stenosed or constricted regions S or the like and to the target site. Thus, a guidewire according to the present invention allows for navigation of a flexible catheter through virtually any stenosed region of a body vessel that is navigable by a guidewire.  
         [0035]     The expandable segment  30  does not need to grip an entire perimeter of the inner surface  34  in order to function. Preferably, the entire perimeter of the interior surface  34  is gripped by the expandable segment  30  in order to provide a stronger frictional engagement to achieve the needed pulling action.  
         [0036]     A further advantage of providing an expandable segment  30  that engages a perimeter of the inner surface  34  is that it allows for the use of a simplified catheter. As illustrated in  FIGS. 2 and 7 , a simplified catheter  24  having a single outer tube  38  and an inflatable section  40  may be provided. When desired, a stent  41  can be positioned over the inflatable section  40 . In contrast to the catheter  10  of  FIG. 1 , the simplified catheter  24  has no inner body  18  or distal sealing section  20 , because the distal end of the inflatable section  40  is sealable by the expandable segment  30  in an expanded state, as shown in  FIGS. 2 and 7 , with a proximal seal that is achieved by a similar expandable segment  30  proximal of the inflation port or a seal integral to the simplified catheter  24  proximal of the inflation port. The combination of at least two seals will provide a means to create a chamber capable of pressurization to inflate section  40 . A prior art catheter such as shown in  FIG. 1  typically has a relatively large minimum outer diameter or profile of approximately 0.042 inch.  
         [0037]     Due to its simplified design, the catheter  24  may have a smaller outer diameter and decreased stiffness of the inflation section, when compared with a double-tube catheter as shown in  FIG. 1 . This allows for the delivery of longer stents to hard-to-reach lesions. This also allows for delivery of devices previously not possible due to a variety of reasons such as profile, tortueosity, and bending stiffness. In particular, an outer diameter or profile of approximately 0.032 inch is achievable for current POBA, SDS and DES catheters used with the present guidewire. Such systems are capable of having flexibility similar to that of a fixed wire catheter. However, a guidewire and catheter combination according to the present invention is preferable to a fixed wire catheter, because the present guidewire can be positioned independently of the catheter.  
         [0038]     In use, the guidewire  22  and catheter  24  are passed through the vasculature to a target site according to the above-described process. Thereafter, the expandable segment  30  is oriented distally of the inflatable section  40  of the catheter  24  and radially expanded to the expanded state of  FIGS. 2 and 7 . When a suitable seal has been provided around the perimeter of the inner surface  34 , an inflation fluid is introduced to the inflation section  40  through a catheter balloon inflation lumen  42 . The inflation fluid causes the inflation section  40  to expand for engagement with the body vessel or for expansion of a stent  41  surrounding the inflation section  40 .  
         [0039]      FIGS. 3 and 4  illustrate a first embodiment of a guidewire  22   a  according to the present invention. The guidewire  22   a  has a proximal portion  26   a  and a distal portion  28   a  that are separated by expandable segment  30   a.  Expandable segment  30   a  is comprised of an elastic material that is radially expanded from the collapsed state of  FIG. 3  to the expanded state of  FIG. 4  by axial compression. Preferably, the expandable segment  30   a  is an elastomeric o-ring. In an illustrated embodiment, the o-ring has an inner diameter of approximately 0.010 inch and an outer diameter of approximately 0.014 inch. A full ring is not necessary, provided that the elastic material of the expandable segments is capable of expanding to provide sufficient friction against a medical device, but a full ring is preferred in order to create a complete perimeter seal, which allows the use of a simplified catheter, as described above.  
         [0040]     In order to axially compress the o-ring  30   a , the proximal portion  26   a  and the distal portion  28   a  are movable relative to each other. The proximal portion  26   a  is substantially tubular and movably receives a shaft extension  44  of the distal portion  28   a.  The outer diameter of the proximal and distal portions  26   a  and  28   a  in the illustrated embodiment are approximately 0.014 inch to coincide with the outer diameter of the o-ring  30   a  in the collapsed state of  FIG. 3 . The shaft  44  extends through the center of the o-ring  30   a  and proximal portion  26   a  and terminates in a diameter ramp-up section  46  located proximally of the proximal portion  26   a.  The outer diameter of the diameter ramp-up section  46  is greater than the inner diameter of the proximal portion  26   a , which prevents excess movement of the distal portion  28   a  away from the proximal portion  26   a.    
         [0041]     In order to actively radially expand the o-ring  30   a , the diameter ramp-up section  46  or a handle associated with the diameter ramp-up section  46 , not illustrated, is moved proximally or upstream from the position of  FIG. 3  to the position of  FIG. 4  or to an intermediate position between those illustrated in  FIGS. 3 and 4 . Proximal or upstream movement of the diameter ramp-up section  46  also moves the shaft  44  and distal portion  28   a  proximally or upstream with respect to the proximal portion  26   a  of the guidewire  22   a.  The resulting movement of the distal portion  28   a  closer to the proximal portion  26   a  compresses the o-ring  30   a  and causes it to radially expand until it engages an inner surface of a surrounding medical device, as generally shown in  FIG. 2 . The distal portion  28   a  is thereafter moved away from the proximal portion  26   a  in order to return the o-ring  30   a  to its collapsed state and proceed with further medical treatment action as desired.  
         [0042]     Preferably, the guidewire includes a locking mechanism for selectively preventing movement from the orientation of  FIG. 4  to the orientation of  FIG. 3 . One possible locking mechanism is achieved by providing a guidewire  22   a ′ having a threaded shaft length  44 ′ with threads that mate with a proximal portion threaded length  26   a ′ of the guidewire  22   a ′, as illustrated in  FIG. 8 . This allows for axial advancement of the shaft  44 ′ by rotation, in addition to serving as a locking mechanism.  
         [0043]     In a preferred arrangement for such a locking mechanism, the threaded lengths are coordinated so that the shaft and guidewire engage each other to prevent any further axial movement in the distal direction that would cause excess compression of the expandable segment  30   a  and possible damage to the expandable segment or otherwise damage the distal portion of the device. For example, a radially extending proximal edge  53  of the shaft  44 ′ can engage a radially extending distal edge  54  of the ramp-up section  46  precisely when the expandable segment  30   a  is expanded to the maximum or optimum extent.  
         [0044]     Other suitable locking mechanisms include a ratcheting member associated with diameter ramp-up section  46 . This can include markings or other indicators (not shown) that correspond to a degree or degrees of rotation needed to achieve one or more levels of expansion of the expandable segment. Other locking mechanisms may also be used without departing from the scope of the present invention.  
         [0045]      FIGS. 5-7  illustrate another embodiment of a guidewire according to the present invention. The guidewire generally designated as  22   b  has a proximal portion  26   b  and a distal portion  28   b  that are separated by expandable segment  30   b.  Expandable segment  30   b  can take the form of a balloon that is radially expanded from the collapsed state of  FIG. 5  to the expanded state of  FIGS. 6 and 7  by inflation. The preferred embodiment includes a balloon  30   b  that is inflatable to engage a complete perimeter of a lumen or inner surface  34  of a catheter  24 , which allows the use of a simplified standard catheter design, as described above. However, the balloon  30   b  could instead expand to engage a smaller portion of the inner surface  34 , provided that it supplies sufficient friction.  
         [0046]     The illustrated guidewire  22   b  is further provided with a removable luer  48 , a guidewire inflation lumen  50 , and an inflation chamber  52  in fluid communication with the guidewire inflation lumen  50 . An inflation fluid, typically a saline solution, is injected into the guidewire inflation lumen  50  from a syringe, not illustrated, and the inflation fluid fills the inflation chamber  52  in order to inflate the balloon  30   b  and radially expand it from the collapsed state of  FIG. 5  to the expanded state of  FIGS. 6 and 7 . Thereafter, the inflation fluid may be removed from the guidewire  22   b  in order to deflate the balloon  30   b  and return it to the collapsed state of  FIG. 5 .  
         [0047]     Preferably, the guidewire  22   b  includes a locking mechanism for selectively preventing unintentional deflation of the balloon  30   b.  Means for preventing the premature deflation of a balloon catheter and the like are well known to those skilled in the art and may be applied to a guidewire  30   b  according to the present invention as a suitable locking mechanism. Examples for this embodiment are known mechanisms for applying inflation pressure to the inflation fluid which apply the pressure to the fluid at a desired level so as to achieve and maintain balloon inflation levels that are maximal and/or optimal for the particular device and use. As for the locking mechanism of the o-ring embodiment, the locking mechanism for the balloon embodiment can be arranged so as to control expansion and stop such expansion when a selected extent of expansion has been attained and overexpansion has been avoided.  
         [0048]     The illustrated embodiments of  FIGS. 2-7  show a guidewire having a single expandable segment, but a guidewire having a plurality of expandable segments  30   c ,  30   d  also is within the scope of the present invention. The expandable segments are designed to impart a longitudinal displacement to the ID of the component. The expandable segments may be disposed at different positions along the length of the guidewire  22   b , as shown in  FIG. 9 , and/or at different angular locations. The expandable segments need not be identical, but may be differently sized and/or shaped, and a combination of balloons and o-rings may also be employed. The various expandable segments may be actuated simultaneously, e.g., by providing a plurality of balloons associated with a single inflation lumen according to the embodiment of  FIG. 9 , or independently of each other, or in series. Typically, inflation will be controlled by the surgeon so as to effect an “inch-worm” type of action. Automated operation could be possible, especially when the segments are activated in series.  
         [0049]     It will be understood that the embodiments of the present invention which have been described are illustrative of some of the applications of the principles of the present invention. Numerous modifications may be made by those skilled in the art without departing from the true spirit and scope of the invention, including those combinations of features that are individually disclosed or claimed herein.