Abstract:
A system used in a blood vessel when an interventional procedure is being performed in a stenosed or occluded region, which is capable of accurately treating an affected area in a blood vessel while preventing adverse effects for healthy tissue. The system includes a catheter which is positionable in a blood vessel at the interventional procedure site. The system further includes an interventional instrument such as a self-expandable stent which may be deployed in the blood vessel at the interventional procedure site. The system also includes an extendable member, adapted to be about the interventional instrument for delivery of the interventional instrument to the interventional procedure site, and to be retractable from extending about the interventional instrument for enabling the interventional instrument to expand at the interventional procedure site. The system further includes movement preventing elements, for preventing axial movement of the interventional instrument in a support region of a catheter elongated shaft, during retraction of the extendable member from extending about the interventional instrument, for enabling accurate deployment of the interventional instrument.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to a system which can be used when an interventional procedure is being performed in a stenosed or occluded region of a blood vessel to substantially retain the unexpanded axial dimension of an expandable interventional instrument upon expansion thereof. The system of the present invention is particularly useful when performing stenting procedures in critical vessels, such as the carotid arteries. 
     A variety of non-surgical interventional procedures have been developed over the years for opening stenosed or occluded blood vessels in a patient caused by the build up of plaque or other substances on the walls of the blood vessel. Such procedures usually involve the percutaneous introduction of the interventional device into the lumen of the artery, usually through a catheter. One widely known and medically accepted procedure is balloon angioplasty in which an inflatable balloon is introduced within the stenosed region of the blood vessel to dilate the occluded vessel. The balloon catheter is initially inserted into the patient&#39;s arterial system and is advanced and manipulated into the area of stenosis in the artery. The balloon is inflated to compress the plaque and press the vessel wall radially outward to increase the diameter of the blood vessel. 
     Another procedure is laser angioplasty which utilizes a laser to ablate the stenosis by super heating and vaporizing the deposited plaque. Atherectomy is yet another method of treating a stenosed blood vessel in which a cutting blade is rotated to shave the deposited plaque from the arterial wall. A vacuum catheter is usually used to capture the shaved plaque or thrombus from the blood stream during this procedure. 
     In another widely practiced procedure, the stenosis can be treated by placing an expandable interventional instrument such as an expandable stent into the stenosed region to hold open and sometimes expand the segment of blood vessel or other arterial lumen. Stents are particularly useful in the treatment or repair of blood vessels after a stenosis has been compressed by percutaneous transluminal coronary angioplasty (PTCA), percutaneous transluminal angioplasty (PTA) or removal by atherectomy or other means. Stents are usually delivered in a compressed condition to the target site, and then are deployed at the target location into an expanded condition to support the vessel and help maintain it in an open position. 
     Prior art stents typically fall into two general categories of construction. The first type of stent is expandable upon application of a controlled force, often through the inflation of an expandable member such as an expandable balloon in a dilatation catheter which, upon inflation of the balloon or other expansion means, expands the compressed stent to a larger diameter to be left in place within the artery at the target site. The second type of stent is a self-expanding stent formed from, for example, shape memory metals or super-elastic nickel-titanum (NiTi) alloys, which will automatically expand from a compressed state when the stent is advanced out of the distal end of the delivery catheter into the body lumen. Such stents manufactured from expandable heat sensitive materials allow for phase transformations of the material to occur, resulting in the expansion and contraction of the stent. 
     Self-expanding stents are typically delivered to an interventional procedure site for deployment thereof mounted on a delivery system and constrained in the sheath, to prevent the elastic nature of the self-expanding stent from causing it to expand prematurely. Once in position at the interventional procedure site, the sheath is retracted, enabling the stent to expand and deploy. However, there are problems associated with the retraction of the sheath for enabling deployment of the self-expanding stent. When the sheath is retracted during stent deployment, axial forces are generated in the stent when one end of the stent is fully open and the other end is still constrained. The stent is biased to slip out from under the sheath and finish deploying. An abrupt shortening that occurs as the stent deploys also generates axial forces. These axial forces can cause the stent to move in the distal direction during deployment and not properly cover the lesion as desired. 
     What has been needed is a reliable system and method for delivering an interventional device for treating stenosis in blood vessels which improve the accuracy of stent deployment over the lesion to be treated, while preventing axial movement of the stent during retracting of the sheath from extending thereabout. The system and method should be capable of enabling the stent to expand, while precisely placing the stent over the lesion to be treated. The system and method should be relatively easy for a physician to use. Moreover, such a system should be relatively easy to deploy and remove from the patient&#39;s vasculature. The inventions disclosed herein satisfy these and other needs. 
     SUMMARY OF INVENTION 
     The present invention provides a system and method for treating an entire affected area in a blood vessel during the performance of a therapeutic interventional procedure, such as a balloon angioplasty or stenting procedure, while preventing adverse effects to surrounding tissue. The present invention is particularly useful when performing an interventional procedure in vital arteries, such as the carotid arteries, including the main blood vessels leading to the brain or other vital organs. As a result, the present invention provides the physician with a higher degree of confidence that an entire lesion will be treated, and that healthy tissue will not be adversely affected by the stenting procedure. 
     The present invention enables an interventional procedure to be performed in a blood vessel at the site of a lesion at an interventional procedure site, such that axial movement of a stent is prevented during retraction of a sheath extending thereabout, and the stent is accurately deployed at the interventional procedure site to treat the lesion. 
     In the present invention, the system includes a catheter for positioning in a blood vessel at an interventional procedure site, an interventional device located at a distal end portion of the catheter for expanding and deploying in the blood vessel at the interventional procedure site, an extendable member adapted to be extendable about the interventional device and retractable relative thereto, and a movement preventing element for preventing axial movement of the interventional instrument during retraction of the extendable member. 
     In an embodiment of the present invention, the system includes a catheter, including an elongated shaft having a distal end portion adapted to be positioned in a blood vessel at an interventional procedure site, and a support region proximate the distal end of the elongated shaft. An interventional instrument is adapted to move between a collapsed and expanded position in the blood vessel at the interventional procedure site, and to be supported on the support region of the elongated shaft. An extendable member is adapted to be extendable about the interventional instrument for delivery of the interventional instrument to the interventional procedure site, and to be retractable from extending about the interventional instrument for enabling the interventional instrument to expand at the interventional procedure site. A movement preventing element, for preventing axial movement of the interventional instrument in the support region of the catheter elongated shaft, during retraction of the extendable member from extending about the interventional instrument, enables deployment of the interventional instrument. 
     In another embodiment of the present invention, the system includes a catheter, including an elongated shaft having a distal end portion adapted to be positioned in a blood vessel at an interventional procedure site, and a support region proximate the distal end of the elongated shaft. An interventional instrument is adapted to move between a collapsed and expanded position in the blood vessel at the interventional procedure site, and to be supported on the support region of the elongated shaft, which interventional instrument includes a distal portion and a proximal portion. A movement preventing element, for preventing axial movement of the interventional instrument in the support region of the catheter elongated shaft, includes a distal element, adapted to be extendable about the distal portion of the interventional instrument, and a proximal element, adapted to be extendable about the proximal portion of the interventional instrument. The distal element and the proximal element are adapted to be extendable about the interventional instrument for delivery of the interventional instrument to the interventional procedure site, and to be retractable from extending about the interventional instrument for enabling the interventional instrument to expand at the interventional procedure site. The movement preventing element is further adapted to prevent axial movement of the interventional instrument during retraction of the distal element and the proximal element. 
    
    
     Other features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the invention, when taken in conjunction with the accompanying exemplary drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational view, partially in section, depicting the system of the present invention disposed within the internal carotid artery of a patient, including a catheter, an extendable member in extended condition, an interventional instrument in unexpanded condition, and a first embodiment of a movement preventing element. 
     FIG. 2 is an elevational view, partially in section, similar to that shown in FIG. 1, depicting the system of the present invention, wherein the extendable member is retracted, and the interventional instrument is in expanded condition. 
     FIG. 3 is an elevational view, partially in section, depicting the system of the present invention, including a catheter, an extendable member in extended condition, an interventional instrument in unexpanded condition, and a second embodiment of a movement preventing element. 
     FIG. 4 is an elevational view, partially in section, similar to that shown in FIG. 3, depicting the system of the present invention, wherein the extendable member is retracted, and the interventional instrument is in expanded condition. 
     FIG. 5 is an elevational view, partially in section, depicting the system of the present invention, including a catheter, an interventional instrument in unexpanded condition, and a third embodiment of a movement preventing element including a pair of extendable members in unextended condition. 
     FIG. 6 is an elevational view, partly in section, similar to that shown in FIG. 5, depicting the system of the present invention, wherein the pair of extendable members are in retracted condition, and the interventional instrument is in expanded condition. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is directed to an improved system and method for efficiently and effectively enabling a therapeutic interventional procedure to be performed in a blood vessel at an interventional procedure site which is the site of a lesion. It is adapted to enable the delivery of a self-expandable interventional instrument to the interventional procedure site, and to enable expansion of the self-expandable interventional instrument at the interventional procedure site. It is further adapted to enable an extendable member to extend about the self-expandable interventional instrument for enabling delivery thereof to the interventional procedure site, and to enable retraction of the extendable member to enable the self-expandable interventional instrument to expand at the location of the stenosis at the interventional procedure site. It is also adapted to prevent axial movement of the self-expandable interventional instrument during retraction of the extendable member from extending thereabout for enabling deployment thereof. The embodiments of the improved system and method are illustrated and described herein by way of example only and not by way of limitation. While the present invention is described in detail as applied to the carotid arteries of the patient, those skilled in the art will appreciate that it can also be used in other body lumens as well, such as the coronary arteries, non-coronary arteries, renal arteries, saphenous veins and other peripheral arteries. 
     Referring now to the drawings, wherein like reference numerals denote like or corresponding parts throughout the drawing figures, and particularly to FIGS. 1-6, a system  10  is provided for enabling an interventional procedure to be performed in a blood vessel  12  at an area of treatment  14 . The system  10  includes a catheter  16  adapted to enable the interventional procedure to be performed. As shown in FIGS. 1-6, the system  10  may be positioned on the catheter  16 , and may be placed within the carotid artery  18  or other blood vessel of the patient on the catheter  16  and may be guided into position by a guide wire. The carotid artery  18  may have the area of treatment  14 , which may comprise the interventional procedure site, wherein atherosclerotic plaque  20  may have built up against the inside wall  22 , which decreases the diameter of the carotid artery  18 . As a result, blood flow may be diminished through this area. The catheter  16  may include an elongated shaft  24  having a distal end  26  and a proximal end  28 , and a support region  30  proximate the distal end  26  of the elongated shaft  24 . The support region  30  includes a distal end  32  and a proximal end  34 . 
     The therapeutic interventional procedure may comprise implanting an interventional instrument  36  at the interventional procedure site  14 , to compress the build-up of plaque  20  of the stenosis against the inside wall  22 , to increase the diameter of the occluded area  14  of the artery  18 , and to help restore sufficient flow of blood to the downstream vessels leading to the brain. The interventional instrument  36  not only helps increase the diameter of the occluded area, but may help prevent restenosis in the area of treatment  14 . The interventional instrument  36  is adapted to be supported on the support region  30  of the catheter  16 , and to be expanded and deployed at the interventional procedure site  14 . It includes an unexpanded axial dimension constituting the unexpanded length thereof, and is adapted to be expandable in a direction generally transverse to the axial dimension thereof. The interventional instrument  36  may comprise for example a self-expandable stent, the elastic nature of which enables self-expansion thereof absent constraint. The self-expandable stent  36  includes a distal end  38  and a proximal end  40 , and includes a plurality of struts  42 , each of which includes a distal end  44  and a proximal end  46 . 
     An extendable member  48  is adapted to be extendable about the self-expandable stent  36  for delivery of the self-expandable stent  36  to the interventional procedure site  14 . It is further adapted to be retractable from extending about the self-expandable stent  36  for enabling the self-expandable stent  36  to expand at the interventions procedure site  14 . The extendable member  48  may comprise a sheath. 
     A movement preventing element  50  is adapted to prevent axial movement of the self-expandable stent  36  in the support region  30  of the catheter elongated shaft  24 , during retraction of the extendable member  48  from extending about the self-expandable stent  36 , for enabling deployment of the self-expandable stent  36  at the location of the stenosis at the interventional procedure site  14 . The movement preventing element  50  may be adapted to prevent distal axial movement of the self-expandable stent  36 . 
     In the embodiment of the invention illustrated in FIGS. 1-2, the movement preventing element  50  comprises portions  52  projecting from the support region  30  of the elongated shaft  24 , so as to project distal to the struts  42  of the self-expandable stent  36  and prevent distal axial movement thereof The projecting portions  52  may comprise for example bumps, ridges, knobs or hooks. In the embodiment of the invention shown in FIGS. 3-4, the movement preventing element  50  comprises a pair of spring anchors, each of which includes a proximal end  54  and a distal end  56  therein. Each spring anchor  50  is adapted to be secured to the proximal end  34  of the support region  30  of the elongated shaft  24 . The distal end  56  of each spring anchor  50  includes a portion  58  projecting therefrom distal to a strut  42  of the self-expandable stent  36 . The projecting portion  58  may comprise a bump or a hook. Each spring anchor  50  is adapted to expand with and restrain the strut  42  to prevent distal axial movement of the self-expandable stent  36  during deployment thereof. The sheath  48  is further adapted to be advanced over the support region  30  of the elongated shaft  24  to recover the spring anchors  50  after deployment of the self-expanding stent  36 . 
     In the embodiment of the invention seen in FIGS. 5-6, the movement preventing element  50  comprises a distal sheath  60 , adapted to be extendable about and retractable from extending about the distal end  38  of the self-expandable stent  36 , and a proximal sheath  62 , adapted to be extendable about and retractable from extending about the proximal end  40  of the self-expandable stent  36 , so as to provide a mid-stent articulation point, and prevent axial movement of the self-expandable stent  36 . The middle-outward deployment is adapted to reduce jumping of the stent  36 , since axial forces generated would be equal and opposite, counteracting each other and reducing any tendency of the stent  36  to shift. The system  10  further includes an element  64  for enabling the distal sheath  60  to be retracted from extending about the distal end  38  of the self-expandable stent  36 , and an element for enabling the proximal sheath  62  to be retracted from extending about the proximal end  40  of the self-expandable stent  36 . The distal sheath retraction-enabling element  64  and the proximal sheath retraction-enabling element are preferably adapted to enable retracting movements at substantially equal rates of the distal sheath  60  and the proximal sheath  62 . The self-expandable stent  36 , further includes a medial portion  66 . The distal sheath  60  includes a distal end  68 , and the distal sheath retracting-enabling element  64  is adapted to be connected to the distal end  68  of the distal sheath  60 , and to be controlled from the proximal end  28  of the elongated shaft  24 . The distal sheath retraction-enabling element  64  may comprise for example a mandrel or hypo tube, or a cylindrical or tubular member extending under the self-expandable stent  36  and connected to the distal end  68  of the distal sheath  60 . 
     In use, as illustrated in FIGS. 1-6, the system  10  may be positioned in the patient&#39;s vasculature utilizing any one of a number of different methods. In one preferred method of positioning, the catheter elongated shaft support region  30 , the stent  36  supported thereon, and the sheath  48  extending thereabout, may be placed in the blood vessel  12  by utilizing the catheter  16  and the sheath  48 , which are inserted into the patient&#39;s vasculature and manipulated by the physician to the area of treatment  14  so as to cross the stenosis in the blood vessel  12 . The sheath  48  may then be retracted from extending about the stent  36 , so as to enable the stent  36  to expand at the interventional procedure site  14 . As the sheath  48  is retracted, the movement preventing element  50  in the catheter elongated shaft support portion  30  is adapted to prevent axial movement and expansion of the stent  36  during retraction of the sheath  48 , so as to enable deployment of the stent  36  at the location of the stenosis at the interventional procedure site  14  upon retraction of the sheath  48 . 
     In the embodiment of the invention illustrated in FIGS. 1-2, the projecting portions  52  in the catheter elongated shaft support region  30  prevent distal axial movement of the stent  36  during retraction of the sheath  48  in the proximal direction. In the embodiment of the invention shown in FIGS. 3-4, the projecting portion  52  at the proximal end  54  of the spring  50  prevents a distal axial movement of the stent  36  during retraction of the sheath  48  in the proximal direction. In the embodiment of the invention seen in FIGS. 5-6, the retraction of the distal sheath  60  in the distal direction and the retraction of the proximal sheath  62  in the proximal direction, from the medial portion  64  of the stent  36  outwardly towards the distal end  38  and the proximal end  40  of the stent  36 , prevent expansion of the stent  36  during retraction of the distal sheath  60  in the distal direction and the retraction of the proximal sheath  62  in the proximal direction. 
     It should be appreciated that the particular embodiments of the movement preventing element  50  are capable of being positioned in the blood vessel  12 . However, other forms of the movement preventing element  50  may be utilized with the present invention without departing from the spirit and scope of the invention. For example, the movement preventing element  50  may further be comprised of other forms of material. Additionally, while the movement preventing element  50  is shown as in various shapes in the embodiments herein, it can be formed in any one of a number of different shapes depending upon the construction desired. Also, the portions  52  of the movement preventing element  50  which project from the support region  30  of the catheter elongated shaft  24 , as shown in FIGS. 1-2, which may comprise bumps, ridges, knobs, or hooks, for example may be comprised of a separate metallic or polymer piece adapted to be attached to the support region  30 , or may be formed in the support region  30  by heat-processing thereof Further, the spring anchor of the movement enabling element  50 , as shown in FIGS. 3-4, for example may be comprised of a material sufficiently elastic to expand with the stent  36 , and to be safely recoverable, such as steel, nitinol, or polymer. The portion  58  of the spring anchor  50  may be comprised for example of material different from the material of the spring anchor  50 , and may be attached to the distal end  56  of the spring anchor  50 . The distal sheath  60  and the proximal sheath  62  as seen in FIGS. 5-6, may each for example be comprised of a material different from the other, adapted to provide enhanced delivery properties, wherein the distal sheath  60  may be softer or may include an atraumatic tip. 
     Further, the various components may be joined by suitable adhesives such as acrylonitrile based adhesives or cyanoacrylate based adhesives. Heat shrinking or heat bonding may also be employed where appropriate. Plastic-to-plastic or plastic-to-metal joints can be effected by a suitable acrylonitrile or cyanoacrylate adhesive. Variations can be made in the composition of the materials to vary properties as needed. 
     In view of the foregoing, it is apparent that the system and method of the present invention enhances substantially the effectiveness of performing interventional procedures by preventing axial movement of the self-expandable stent during retraction of the extendable member, to enable the self-expandable stent to expand at the location of the stenosis at the interventional procedure site. Further modifications and improvements may additionally be made to the system and method disclosed herein without the departing from the scope of the invention. Accordingly, it is not intended that the invention be limited, except as by the appended claims.