Abstract:
A dilatation catheter is disclosed having an inflation balloon and a catheter shaft with an inflation channel. A first guidewire channel is disposed along the dilatation catheter and has a distal exit at the distal end of the catheter shaft. A second guidewire channel is disposed along the dilatation catheter and has a distal exit attached along the inflation balloon. Guidewires are slideably disposed within the first and second guidewire channels. An oblique ended expandable stent is disposed about the inflation balloon and used to treat bifurcated and sidebranched arteries and ostial lesions.

Description:
TECHNICAL FIELD 
     This invention relates to a stent and its implantation into blood vessels. More particular, it relates to a stent and an application catheter used to implant the stent into vascular bifurcations, side branches and ostial lesions. 
     BACKGROUND ART 
     Stents are prostheses to support the lumen of hollow organs, primarily to acutely maintain the lumen of blood vessels after mechanical interventions such as balloon angioplasty and to achieve a better long term result after such mechanical interventions. While implantation of stents into straight vessel segments poses little technical problems, implantation of stents into ostial lesions, sidebranches or into vessel bifurcations represents a challenge to the operator and carries increased risks of acute and long-term failure, in particular due to misplacement or imprecise placement. 
     In ostial lesions, the proximal end of the stent must be precisely placed at the ostium of the artery so that the stent is not protruding into the aortic lumen. In order to avoid the above risk, the stent is sometimes advanced too far into the artery causing the initial segment of the diseased ostium to remain unstented. 
     A similar problem exists with stenting of sidebranches and vessel bifurcations. For both situations, precision placement techniques are required for optimal results. However, the operator must rely on visual assessment during fluoroscopy with and without contrast injections. Contrast injections are of little help for stenting in ostial lesions, since opacification of the target artery is usually inadequate and identification of the aortic lumen and the ostial takeoff is very limited. In sidebranch and bifurcational lesions, precise placement is similarly difficult due to poor identification of the exact beginning of the sidebranch ostium and the often non-perpendicular nature of the plane of the sidebranch in relation to the axis of the major vessel. The beating heart makes maintaining of a catheter position with current techniques even more difficult if not impossible. 
     The current invention offers a unique solution to the technical problems as described above. 
     SUMMARY OF THE INVENTION 
     A dilation catheter has a distal exit of a first guidewire channel located distally from an inflatable balloon portion and a distal exit of a second guidewire channel located proximally from the distal exit of the first guidewire channel. The distal exit of the second guidewire channel is located along the inflatable balloon portion or other expandable portion of the dilatation catheter. An oblique ended expandable stent is mounted therearound and used to treat bifurcated and sidebranched arteries and ostial lesions. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1A shows a dilatation catheter of the present invention; 
     FIG. 1B shows an alternate embodiment of the catheter of the present invention; 
     FIG. 1C shows another embodiment of the catheter of the present invention; 
     FIG. 1D shows another embodiment of the catheter of the present invention; 
     FIG. 1E shows still another alternate embodiment of the present invention having guidewire exits at the proximal end of the dilatation catheter. 
     FIG. 1F shows yet another alternate embodiment of the present invention having two guidewire channels in fluid communication. 
     FIG. 2A shows the catheter of the present invention having a stent mounted therearound; 
     FIG. 2B shows a prior art stent having its end axis perpendicular to its longitudinal axis; 
     FIG. 2C shows an oblique ended stent used with the catheter of the present invention; 
     FIG. 3A illustrates prior art showing a non-oblique ended stent in a bifurcated artery having a lesion formed thereupon which is not covered by the non-oblique ended stent; 
     FIG. 3B illustrates prior art showing a non-oblique ended stent in a bifurcated artery having a lesion formed thereupon which is covered by the non-oblique ended stent but permits an end of the stent to protrude into the main artery; 
     FIG. 3C shows an oblique ended stent used in the present invention which is capable of covering the lesion but prohibits an end portion of the stent from protruding into the main artery; 
     FIG. 4A shows the catheter of the present invention being used to insert an oblique ended stent into a bifurcated artery; 
     FIG. 4B shows the catheter of the present invention being used to insert an oblique ended stent, the catheter depicted outside an artery; 
     FIG. 4C is a top plan view, partially in section, of the configuration depicted in FIG. 4B showing the distal exit of the second guidewire channel located along the balloon catheter; 
     FIG.  5 A 1  shows a sinusoidal ring configuration of a stent used in the present invention; 
     FIG.  5 A 2  shows a more detailed view of the FIG.  5 A 1 ; 
     FIG.  5 B 1  shows a non-expanded closed loop configuration used to form an oblique end of a stent in the present invention; 
     FIG.  5 B 2  shows an expanded closed loop configuration used to form an oblique end of a stent in the present invention; 
     FIG.  5 C 1  shows a non-expanded ratcheting band configuration used to form an oblique end of a stent in the present invention; and 
     FIG.  5 C 2  shows an expanded ratcheting band configuration used to form an oblique end of a stent in the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A balloon catheter as used for vascular dilatation commonly has a balloon inflation channel along the whole length of a pliable shaft of the balloon catheter up to the beginning or the mid-portion of the balloon, and a so called first guidewire channel  16  through which a first guidewire  12  is fed. The first guidewire channel  16  commonly exits at the distal end  10  of the balloon catheter (very distal catheter tip). Depending on whether the first guidewire channel  16  is running through the whole length of the balloon catheter shaft and exiting proximally at the proximal end  17  of the balloon catheter shaft or whether the first guidewire channel  16  is exiting via a side-exit  20  proximal to the balloon (i.e., the first guidewire channel  16  being substantially shorter than the whole catheter length), the balloon catheters are termed over the wire or monorail balloon catheters. 
     In order to create a technique to assist to mechanically self-position an application catheter, in an ostial, side branch or bifurcational lesion, or to orient the application catheter to a certain direction within a 360 degree circumference of the vessel, the application catheter must have a mechanical means to limit its advancement beyond a certain point and/or to direct the application catheter to the desired target. This is realized, as seen in FIGS. 1A-1D, by a distal exit  11  of a second guidewire channel  14  located along an inflatable portion of a balloon catheter (or other expandable means) used for stenosis dilatation (within the distal and proximal end of the balloon catheter) or along the respective portion used for stenosis dilatation or stent, drug or radiation application of any other application catheter or located within a short portion of length (i.e., 1-30 mm) beginning just proximal to the functional segment of a stent application catheter or other application catheter of other therapeutics and extending proximally. 
     The second guidewire channel  14  may run along the whole length of the balloon chatheter shaft, allowing the proximal exit of the second guidewire channel  14  to be located at the proximal end  17  of the balloon catheter shaft (over the wire fashion). Alternatively, the second guidewire channel  14  may be significantly shorter than the balloon catheter shaft, allowing the proximal exit of the second guidewire channel  14  to be located between the balloon inflation segment or the functional segment and the proximal end  17  of the balloon catheter shaft. A second guidewire  15  is threaded through the second guidewire channel  14 . Preferably, but not necessarily, the proximal exit of the second guidewire channel  14  is within the distal half of the catheter so that easy monorail handling of the second guidewire channel  14  and second guidewire  15  is possible, as seen in FIG.  1 A. In further reference to FIG. 1A, it is shown that the catheter has a distal end  10  through which a first guidewire  12  exits. A radiopaque marker  13  can be employed on the balloon catheter at the level of the distal exit  11  of the second guidewire channel  14 . FIG. 1C illustrates the distal exit  30  of the first guidewire  12 . 
     In an alternate embodiment, the second guidewire channel  14  merges with the first guidewire channel  16  over a certain distance or its total length and may use the same side exit  20  as the first guidewire channel  16 , as seen in FIG. 1B, or the same exit at the proximal end  17  of the balloon catheter shaft (FIG.  1 E). 
     In yet another alternate embodiment, as seen in FIG. 1D, the distal exit  11  of the second guidewire channel  14  is located on the first guidewire channel  16  intermediately positioned between the proximal end  17  of the catheter shaft and the distal end  10  of the catheter shaft; the first guidewire channel  16  is mounted to the outside of the balloon or other inflation means. Thus, the first guidewire channel  16  and the second guidewire channel  14  are the same channel over a certain segment. 
     To insert the stent of the present invention using a monorail type balloon catheter for bifurcational (or sidebranch) dilatation and stenting, the preferred steps include: placing the first guidewire  12  in the target artery (sidebranch); placing the second guidewire  15  in the main artery; advancing the balloon catheter over the first guidewire  12  (placed in the target lesion) which is threaded through the distal exit  30  of the first guidewire channel  16  at the distal end  10  of the balloon catheter and over the second guidewire  15  (main artery), which is threaded through the distal exit  11  of the second guidewire channel  14 . The balloon is then advanced until the distal exit  11  of the second guidewire channel  14  reaches the bifurcation and prohibits any further advancement. However, an alternate sequence of steps is possible depending on the individual situation and types of catheter configuration used. It may be possible to partially or totally pre-load the second guidewire  15  into the second guidewire channel  14  and advance it through the distal exit  11  of the second guidewire channel  14  with the application catheter already inside the patient and/or coronary arteries. One or more radiopaque markers  13  make the location of the distal exit  11  of the second guidewire channel  14  visible to the operator. 
     This procedure permits stable positioning of a balloon catheter within a bifurcated vessel. But, more importantly, it orients the distal exit  11  of the second guidewire channel  14  automatically into the direction of the opening to the main artery, prohibiting any further rotation of the balloon, which may carry a stent or other therapeutic means. Thereby,.stents with oblique ends may be placed precisely into sidebranches. 
     For stable balloon placement in ostial lesions, prepositioning of the second guidewire  15  is not necessary. In these cases, the second guidewire channel  14  may be pre-loaded and the second guidewire  15  may be advanced through the distal exit  11  of the second guidewire channel  14  once the balloon is approaching the target ostium. For ostial lesions, a plurality of guidewire channels  14  may be helpful and the guidewires used need no steerability but rather an atraumatic distal configuration and floppy property, e.g. mini-pigtail shape  100  (see FIG.  4 A.), super-elasticity (e.g. use of the material Nitinol). 
     The longitudinal axis of sidebranches are almost never perpendicular to the longitudinal axis of the vessel from which they are taking off. Therefore, the current stent  40  configurations of cylindrical tubular shape with the crosssectional plane of the ends of the stent being perpendicular to the longitudinal axis of the cylinder stent  40  are inadequate. This configuration does not permit full stent coverage of the ostium of a sidebranch, as there is always the risk of protrusion of one edge of the end of the stent  40  into the lumen of the main artery  70 , as shown in FIG.  3 B. Stents with at least one oblique end are needed to better adapt to bifurcational anatomies, in particular the vessel takeoff angles. 
     An oblique stent  90  is described, where one end of the stent cylinder is cut in a plane which is non perpendicular to the longitudinal axis of the stent, (i.e. oblique), preferentially in an angle of 80 to 45 degrees to the longitudinal axis of the stent (or 10 to 45 degrees to the axis perpendicular to the longitudinal axis of the stent), as seen in FIG.  2 C. This configuration is defined by the short side  61  of the stent with a minimum length and the long side  64  of the stent with a maximum length. This configuration is further defined by a cross-sectional plane  60  representing the oblique stent end  62  which is non perpendicular to the longitudinal axis  65  of the stent. This is compared to a prior art stent  40  of FIG. 2B wherein the cross-sectional plane  51  of the stent end is perpendicular to the longitudinal axis  50  of the stent. 
     Placement and use of the oblique ended stent  90  is achieved if the stent carrying instrument, e.g. balloon catheter, can be directed so that the long and short sides,  64  and  61  respectively, of the stent are placed correctly in the ostium. This can be accomplished by the self-orienting catheter with a distal exit  11  of a second guidewire channel  14  of the present invention. The bifurcational stent will be mounted on the balloon such that the short side  61  of the stent  90  is closest to the distal exit  11  of the second guidewire channel  14 . As seen in FIG. 3C, an oblique ended stent  90  of the present invention covers a lesion  92  and is placed properly in the bifurcated artery. 
     FIGS.  5 A 1  and  5 A 2  illustrate a sinusoidal ring configuration of a stent used in the present invention. The oblique end  62  of the stent  90  is non-perpendicular to the longitudinal axis  65  of the stent. 
     FIG.  5 B 1  illustrates a non-expanded closed loop configuration  150  used to form an oblique end of a stent in the present invention. FIG.  5 B 2  illustrates an expanded closed loop configuration  160  used to form the oblique end of the stent. 
     FIG.  5 C 1  illustrates a non-expanded ratcheting band configuration  170  used to form an oblique end of a stent in the present invention. FIG.  5 C 2  illustrates an expanded ratcheting band configuration  180  used to form the oblique end of the stent. 
     Equivalent elements and steps can be substituted for the elements and steps employed in this invention to obtain substantially the same results in substantially the same way.