Abstract:
A catheter with at least one centering device attached near a distal end of the catheter. The centering device has at least two struts extending between a proximal end and a distal end. The centering device has a variable diameter and tends to center the distal end of the catheter, steering the catheter away from the vessel wall during insertion through the vasculature and toward the treatment site. The centering catheter may facilitate access to tortuous anatomy by preventing the catheter tip from catching on irregularities in the lumenal surface. The centering catheter may also facilitate uniform stent expansion by stabilizing the catheter during stent deployment.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
   1. Technical Background 
   The present invention relates to a catheter, and more particularly to a catheter with a centering tip. 
   2. Discussion 
   Percutaneous transluminal coronary angioplasty (PTCA) and stenting are therapeutic medical procedures used to increase blood flow through the coronary arteries and can often be used as alternatives to coronary bypass surgery. In PTCA procedures, the angioplasty balloon is inflated within the narrowed or stenosed vessel, at the desired location for treatment, such as an atheroma or plaque deposit, in order to obtain an enlarged opening or lumen. In stenting, an endoluminal prosthesis of any appropriate type is implanted in the vessel to maintain patency following the procedure. In order to initiate these procedures, one must first introduce a guidewire into the lumen of the vessel to serve as a conduit for other interventional devices, such as angioplasty balloons and stent delivery systems. This guidewire must be advanced into a position past the location of the stenosis. Additional interventional devices, such as angioplasty balloon catheters and stent delivery systems, are then advanced over the guidewire and positioned at the site of the stenosis, to initiate therapeutic treatment of the lesion. 
   A common treatment method for using such an angioplasty balloon catheter or stent delivery system is to advance the catheter into the body of a patient over the guidewire, by directing the catheter distal end percutaneously through an incision and along a body passage until the device is located within the desired site. One difficulty commonly encountered with the procedure is that irregularities of the lumenal surface and narrowing of the passageway may result in delivery difficulty, because the distal end of the balloon catheter or the stent delivery system may “catch” on the wall surface. This may cause a challenge in reaching the targeted position in the vessel, and therefore may inhibit successful treatment of the lesion. Another difficulty that is encountered with this procedure is that once the target lesion is reached, stent deployment may not be perfectly uniform if the stent delivery system is not centered within the vessel. This lack of centering may result in the stent cells around the circumference of the stent not opening up completely, resulting in non-uniform deployment. The end result may be reduced strength and incomplete stent scaffolding of the vessel, and a less than optimal clinical result. 
   The general concept of a centering catheter for treating a body vessel with a radioactive source is well known in the art. See, for example, U.S. Pat. Nos. 6,224,535 and 6,267,775. 
   However, the art has yet to disclose or suggest any devices for centering a non-radiation source catheter during its entire journey through the vasculature and to the treatment site, to facilitate access to tortuous anatomy, and then to promote uniform deployed stent expansion at the treatment site. 
   The present invention provides for a centering catheter which operates to remain centered during its entire journey through the vasculature and toward the treatment site, as well as at the treatment site, and which overcomes many of the disadvantages associated with the use and operation of prior art devices. 
   An objective of the present invention is to facilitate access to tortuous anatomy, so that a lesion location may be more easily reached and the vessel may be treated. Another objective of the present invention is to facilitate uniform deployed stent expansion by stabilizing the stent delivery system catheter and centering it in the vessel during stent deployment. 
   The centering catheter of the present invention comprises an elongated catheter body having a proximal end and a distal end, and at least one centering device attached near the distal end of the catheter. The centering device comprises a proximal end and a distal end and at least two struts extending therebetween. The centering device has a smaller diameter for insertion into a lumen and a larger diameter for expanding to substantially equal the diameter of the lumen and to center the catheter within the lumen. The centering device also has a plurality of intermediate diameters, between the smaller diameter and the larger diameter. These intermediate diameters may be utilized as the centering device adjusts to diameter variations in the lumen of the vessel during the catheter journey through the vasculature and toward the treatment site. Once the site is accessed, the centering device may also facilitate uniform stent delivery for either balloon expandable or self-expanding stents, by centering the distal end of the catheter during the deployment of the stent. Uniform stent expansion may contribute to a successful clinical outcome by insuring that optimal scaffolding of the vessel has occurred and optimal radial strength has been achieved to resist elastic recoil of the vessel following an interventional procedure. The catheter may then be withdrawn from the lumen of the vessel. 
   In accordance with one aspect, the present invention is directed to a catheter having at least one centering device attached near the distal end of the catheter. Each centering device comprises a proximal end and a distal end and at least two struts extending therebetween. Each centering device preferably has a variable diameter that centers the distal end of the catheter, steering the catheter away from the vessel wall during its insertion through the vasculature to the treatment site. 
   In accordance with another aspect, the present invention is directed to a stent delivery system comprising at least one centering device attached near the distal end of the stent delivery system. Each centering device comprises a proximal end and a distal end and at least two struts extending therebetween. Each centering device preferably has a variable diameter that centers the distal end of the catheter during the process of stent deployment. 
   An advantage of the present invention is that the sometimes-tortuous anatomy of the vasculature may be more easily traversed while avoiding lumen damage, and access to the lesion location may be facilitated by the availability of a centering device that centers the catheter throughout its introduction into the vessel. Another advantage of the present invention is that the centering device may stabilize the distal end of the catheter during stent expansion, and may therefore allow the operator to achieve a more uniform stent expansion with resultant clinical benefits to the patient. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     The foregoing and other aspects of the present invention will best be appreciated with reference to the detailed description of the invention in conjunction with the accompanying drawings, wherein: 
       FIG. 1  is a diagrammatic, partial, enlarged, cross-sectional view of an example embodiment of the centering catheter, with the centering device on a balloon catheter, in accordance with the present invention. 
       FIG. 2  is a diagrammatic, partial, enlarged, cross-sectional view of an example embodiment of the centering device, with the centering device on a stent delivery system, in accordance with the present invention. 
       FIG. 3  is a diagrammatic, partial, enlarged, cross-sectional view of a non-centering stent delivery system catheter in an irregular and narrowed lumen of a tortuous vessel. 
       FIG. 4  is a diagrammatic, partial, enlarged, cross-sectional view of an example embodiment of the centering catheter, with the centering device on a stent delivery system in an irregular and narrowed lumen of a tortuous vessel, in accordance with the present invention. 
     FIGS.  5 — 7  are partial views of struts having examples of hinges. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The centering catheter of the present invention is designed to facilitate access to a treatment site in a lumen of a vessel through tortuous anatomy, and to facilitate uniform stent deployment at the treatment site. The centering catheter of the present invention comprises an elongated catheter body having a proximal end and a distal end, and at least one centering device attached near the distal end of the catheter. The centering device comprises a proximal end and a distal end, and at least two struts extending therebetween. The centering device has a smaller first diameter for insertion into the lumen, a larger second diameter for expanding to substantially equal the diameter of the lumen of the vessel, and a plurality of intermediate diameters therebetween. 
   The centering device may be employed in any type of flexible elongated medical device product, including catheters, cannulae, guidewires and scopes. Although the centering catheter may be utilized in conjunction with any type of device, for ease of explanation, the exemplary embodiments described below will refer to a balloon catheter and stent delivery system. 
   While the present invention may be realized in a number of exemplary embodiments, for ease of explanation, two exemplary embodiments will be described in detail. Referring to the figures, there is illustrated in  FIG. 1  a centering catheter  10  made in accordance with the present invention. The distal end of the centering catheter  10  comprises an inner member  20 , which extends longitudinally through the centering catheter  10 ; a catheter tip  25 ; at least one centering device  40  attached to the circumference of the inner member  20 ; and an angioplasty balloon  30  attached to the inner member  20  proximal to the at least one centering device  40 . Each centering device  40  comprises a proximal end  42  and a distal end  44  and at least two struts  50  extending therebetween. The struts  50  may be equally or unequally spaced. The struts  50  may be longitudinal, as illustrated in  FIG. 1 , or circumferential, or any number of other suitable configurations. As illustrated in  FIG. 1 , the centering device  40  has a larger diameter that substantially equals the diameter of the lumen, and substantially exceeds the diameter of the inner member  20 . Therefore, the centering device  40  may center the tip  25  of the centering catheter  10  in the lumen during and throughout insertion into the vessel, until the treatment location is reached. 
   The at least one centering device  40  may be made from any number of suitable materials, and is preferably made from a superelastic alloy such as Nitinol. The struts  50  may alternatively be hingedly connected struts. The centering device  40  may be coated with any number of suitable materials, and is preferably coated with a lubricious or biologically compatible coating. The centering device  40  may be removably or permanently attached to the inner member  20 . The centering catheter may be any suitable configuration catheter, and may preferably be an over the wire or rapid exchange catheter. 
   As illustrated in  FIG. 1 , the centering catheter may be advanced into the lumen of a vessel with the centering device  40  expanding to make contact with the walls of the lumen. The centering device  40  thus serves to center the distal end of the catheter  10  and its inner member  20  as it is pushed through the vasculature to the treatment site. The struts  50  are compressible and allow the centering device  40  to vary its diameter as the lumenal diameter varies, while always keeping the catheter tip  25  of the centering catheter  10  centered in the lumen. This may facilitate the pushability and trackability of the centering catheter  10  as it traverses the vasculature. 
     FIG. 2  illustrates another exemplary made in accordance with the present invention. In this exemplary embodiment, a centering catheter  10  is a stent delivery system which comprises an inner member  20 , which extends longitudinally through the catheter  10 ; a catheter tip  25 ; at least one centering device  40  attached to the circumference of the inner member  20 ; an angioplasty balloon  30  attached to the inner member  20  proximal to the at least one centering device  40 ; and a stent  60  mounted on the angioplasty balloon  30 . Each centering device  40  comprises a proximal end  42  and a distal end  44  and at least two struts  50  extending therebetween. The struts  50  may be equally or unequally spaced. The struts  50  may be longitudinal, as illustrated in  FIG. 2 , or circumferential, or any number of other suitable configurations. As illustrated in  FIG. 2 , the centering device  40  has a larger diameter that substantially equals the diameter of the lumen, and substantially exceeds the diameter of the inner member  20 . Therefore, the centering device  40  may center the catheter tip  25  of the centering catheter  10  in the lumen during and throughout insertion into the vessel, and during stent deployment. Another centering device may also be added to the centering catheter  10  at the proximal end of the stent  60  to facilitate uniform stent deployment. 
   The at least one centering device  40  may be made from any number of suitable materials, and is preferably made from a superelastic alloy such as Nitinol. The chronic outward force of the Nitinol may be increased, and/or the diameter of the centering device may be increased to enhance the stabilization of the system during stent deployment. The struts  50  may alternatively have hinges near their midpoints. The centering device  40  may also be coated with any number of suitable materials, and is preferably coated with a lubricious or biologically compatible coating. The centering device  40  may be removably or permanently attached to the inner member  20 . The centering catheter  10  may be any suitable configuration catheter, and may preferably be an over the wire or rapid exchange catheter. The stent  60  may be a balloon expandable stent, as illustrated in  FIG. 2 , or a self-expanding stent. 
   As illustrated in  FIG. 2 , the centering catheter  10  may be a stent delivery system that is advanced into the lumen of a vessel, with the centering device  40  expanding to make contact with the walls of the lumen. The centering device  40  thus serves to center the distal end of the catheter  10  and its inner member  20  as it is pushed through the vasculature to the treatment site. The struts  50  are compressible and allow the centering device  40  to vary its diameter as the lumen diameter varies, while always keeping the catheter tip  25  of the centering catheter  10  centered in the lumen. This may facilitate the pushability and trackability of the centering catheter  10  as it traverses the vasculature. When the treatment site is reached, the centering device  40  may stabilize the stent delivery system in the lumen of the vessel to insure uniform stent  60  deployment. 
   There is illustrated in  FIG. 3  a non-centering catheter  100  in an irregular and narrowed lumen of a tortuous vessel  200 . The lumen may be narrowed by plaques and other deposits  210  on the lumenal surface. The tip  110  of the non-centering catheter  100  may therefore become uncentered and may “catch” on the lumenal surface. Delivery of the noncentering catheter  110  to the targeted position in the lumen of the vessel may be difficult. In addition, deployment of a stent  120  (shown mounted on a balloon  130 ) may not be perfectly uniform. 
   There is illustrated in  FIG. 4  a centering catheter  10  with the at least one centering device  40  on a stent delivery system in an irregular and narrowed lumen of a tortuous vessel  200 . The lumen may be narrowed by plaques and other deposits  210  on the lumenal surface. Delivery of the centering catheter  10  to the targeted position in the lumen of the vessel may be facilitated by the presence of the at least one centering device  40 , which tends to center the tip of the catheter  25  in the lumen of the vessel  200 . Deployment of a stent  60 , shown mounted on a balloon  30 , may be facilitated by the presence of the at least one centering device  40 , which tends to center the catheter  10  within the vessel and facilitate uniform stent deployment. 
   Although shown and described are what are believed to be the preferred embodiments, it is apparent that departures from specific designs and methods described and shown will suggest themselves to those skilled in the art and may be used without departing from the spirit and scope of the invention. The present invention is not restricted to the particular constructions described and illustrated, but should be constructed to cover all modifications that may fall within the scope of the appended claims.