Abstract:
A method and device includes advancing an anchor stent assembly and a second stent into a stenosed region of a blood vessel to protect or shield the vessel from possible blockage. The anchor stent assembly may include an anchor stent and a cover made of submucosal tissue (SIS). The cover is delivered in a dried, compressed, condition and is later softened and expanded by exposure to the flow of blood. The second stent may then be advanced within the cover and dilated to press the cover against the stenosed region of the vessel, thus protecting the vessel from emboli formed of stenosis breakage.

Description:
[0001]     The present application claims priority to U.S. Provisional Application No. 60/809,597, filed on May 31, 2006. 
     
    
     BACKGROUND  
       [0002]     The present invention relates generally to devices, methods and systems for vascular treatment. One embodiment of the device includes an anchor stent assembly using submucosal tissue to shield at least a portion of the interior surface of a vessel wall from the flow of blood. The device may ideally prevent emboli from a stenosed region of a vessel from flowing down stream and causing clots or other vascular complications.  
         [0003]     Vascular diseases and disorders are widespread health problems affecting many people. There are many chronic and acute diseases and disorders relating to the vascular system including, for example, thrombosis, embolism, aneurysm, atherosclerosis, arterioscholerosis, infarction and still others.  
         [0004]     Heart attacks and strokes are leading health concerns. Obstruction of blood flow and/or vessel rupture may cause inadequate blood supply to the heart, brain, and other parts or all of the body. Occlusive diseases involving constriction, narrowing or obstruction of a blood vessel often present serious, possibly life-threatening risks. Additionally, complications in vascular treatment(s) may themselves necessitate further treatment. Some such risks include formation of emboli, vessel damage, thrombogenesis, blood loss, hemorrhage, and others. Furthermore, trauma and other injuries may damage the vascular system and often require repair or replacement.  
         [0005]     At present, treatment of vascular disease, damage and disorders suffers from limitations, drawbacks and risks. The invention provides unique treatments and solutions to treatment of the foregoing and other problems.  
       BRIEF SUMMARY  
       [0006]     The endovascular device described below may overcome the aforementioned problems and relates to a medical device, and more particularly, to an endovascular device assembly and method of making the same that shields at least a portion of the interior surface of an organ from emboli and interior breakage.  
         [0007]     One embodiment includes a method for shielding at least a portion of the interior surface of an organ, comprising: introducing a device into an organ, the device including an anchor stent assembly and a second stent; wherein the anchor stent assembly has an anchor stent having a proximal end, a distal end, an exterior surface, and an interior lumen, the exterior surface being at least partially covered with a cover comprised of bioremodelable or bioabsorbable material; the cover being in the form of a rod extending beyond the distal end and having an initial diameter; and wherein the second stent has a proximal end, a distal end, an exterior surface, and an interior lumen. The method further includes positioning the device within a specified region of the organ, the distal end of said second stent being positioned approximately adjacent the proximal end of the anchor stent and exposing the cover to the flow of blood; expanding the anchor stent and the cover within the organ; advancing the second stent through the interior lumen of the anchor stent and an interior surface of the cover; and expanding the second stent.  
         [0008]     The method as described above, wherein the cover is an extracellular matrix.  
         [0009]     The method as described above, wherein the cover is comprised of submucosa dried and crimped into a stiffened rod.  
         [0010]     The method as described above, wherein the specified region of the organ is a blood vessel afflicted with a stenosis.  
         [0011]     The method as described above, wherein the introducing step includes loading the device into a delivery system comprised of an outer sheath and an inner catheter.  
         [0012]     The method as described above, wherein the cover is exposed to the flow of blood when an outer sheath is withdrawn toward the proximal end of the blood vessel.  
         [0013]     The method as described above, wherein the anchor stent is a self expanding stent, and wherein the anchor stent expands when an outer sheath is withdrawn toward said proximal end of said blood vessel to expose said anchor stent.  
         [0014]     The method as described above, wherein the second stent is a self expanding stent, and wherein the second stent is at least partially expanded upon withdraw of an outer sheath.  
         [0015]     The method as described above, wherein the second stent is a self expanding stent, the second stent being at least partially expanded upon withdraw of said outer sheath, and wherein said method further includes post-dilating said second stent with an inflation device.  
         [0016]     The method as described above, wherein the inflation device is a balloon catheter.  
         [0017]     Another embodiment includes a device for shielding at least a portion of the interior surface of an organ, comprising: an anchor stent assembly and a second stent; the anchor stent assembly having an anchor stent with a proximal end, a distal end, an exterior surface, and an interior lumen, the exterior surface being at least partially covered with a cover comprised of bioremodelable or bioabsorbable material; the cover being in the form of a rod extending beyond said distal end and having an initial diameter; and the second stent having a proximal end, a distal end, an exterior surface, and an interior lumen. The distal end of the second stent is positioned approximately adjacent the proximal end of the anchor stent.  
         [0018]     The method as described above, wherein the stiff cover may be softened by exposure to a liquid.  
         [0019]     The method as described above, wherein the liquid is blood.  
         [0020]     The method as described above, wherein the device further includes a delivery system, the delivery system having an outer sheath and an inner catheter.  
         [0021]     The method as described above, wherein the anchor stent assembly and the second stent are disposed between the outer sheath and the inner catheter; the outer sheath being movable relative to the inner catheter.  
         [0022]     The method as described above, wherein the cover is an extracellular matrix.  
         [0023]     The method as described above, wherein the cover is comprised of submucosa dried and crimped into a stiffened rod.  
         [0024]     Yet another embodiment includes a method for shielding at least a portion of the interior surface of an organ, comprising: introducing an anchor stent assembly into said organ, wherein the anchor stent assembly includes an anchor stent having a proximal end, a distal end, an exterior surface, and an interior lumen, said exterior surface being at least partially covered with a cover comprised of bioremodelable or bioabsorbable material, the cover being in the form of a rod extending beyond the distal end and having an initial diameter; positioning the anchor stent assembly within a specified region of said organ; exposing the cover to the flow of blood; expanding the anchor stent within the organ; introducing a second stent into said organ, the second stent having a proximal end, a distal end, an exterior surface, and an interior lumen; advancing the second stent through the interior lumen of the anchor stent and an interior surface of the cover; and expanding the second stent.  
         [0025]     The method as described above, wherein the anchor stent assembly and said second stent are disposed within a single delivery device and said distal end of the second stent is positioned approximately adjacent to the proximal end of the anchor stent.  
         [0026]     The method as described above, wherein the anchor stent assembly and the second stent are disposed within separate delivery devices.  
         [0027]     Another embodiment includes an anchor stent assembly, comprising: an anchor stent having a proximal end, a distal end, an exterior surface, and an interior lumen, the exterior surface being at least partially covered with a cover comprised of bioremodelable or bioabsorbable material, the cover being in the form of a rod extending beyond the distal end and having a first initial diameter less than an expanded diameter of the proximal end, the cover constraining the distal end to a second initial diameter less than the expanded diameter of the proximal end.  
         [0028]     The method as described above, wherein the first initial diameter and the second initial diameter are equal.  
         [0029]     The method as described above, wherein the first initial diameter is less than the second initial diameter.  
         [0030]     The method as described above, wherein the cover is an extracellular matrix.  
         [0031]     The method as described above, wherein the cover is comprised of submucosa dried and crimped into a stiffened rod. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0032]      FIG. 1  is a side view of a stenosed region of a blood vessel;  
         [0033]      FIG. 2  is a side view of one example of an anchor stent and rod-like covering material  
         [0034]      FIG. 3  is a side view of one embodiment of a pre-deployment stent assembly;  
         [0035]      FIG. 4  is a side view of a stenosed region of a blood vessel;  
         [0036]      FIG. 5  is a side view of a stent assembly advanced through a stenosed region of a blood vessel;  
         [0037]      FIG. 6  is a side view of a stent assembly;  
         [0038]      FIG. 7  is a side view of a stent assembly advanced through a stenosed region of a blood vessel;  
         [0039]      FIGS. 8A and 8B  are a series of side views showing a method for using the delivery system;  
         [0040]      FIG. 9  is a side view of a stent assembly advanced through a stenosed region of a blood vessel; and  
         [0041]      FIG. 10  is a side view of a stent assembly advanced through a stenosed region of a blood vessel.  
     
    
     DETAILED DESCRIPTION  
       [0042]     A device and method for protecting and reinforcing blood vessels afflicted with stenosis is shown in  FIGS. 1-10 . The device and method include the use of small intestine submucosa (SIS) or other suitable material. The device and method further include the use of at least two structural stents, supporting the SIS material against a stenosed region.  
         [0043]     With reference to  FIG. 1 , there is shown an illustrative view of a blood vessel  10  which includes an interior surface  12  and a lumen  14 . Blood flow through the vessel  10  is generally in the direction indicated by arrow F and may vary according to physiological conditions.  
         [0044]     Stenosis is a narrowing or constriction of the lumen of the vessel  10  in the region generally indicated at  16 . The narrowing or constriction of the lumen may result in reduced blood flow through the vessel  10  and may increase the risk of thrombosis, embolism, and other complications. While stenosis  16  is illustrated, other diseases, damage, or disorders could be present in region  16 , or in other regions. For example, thrombosis, aneurysm, lodged embolism, necrotic tissue, cut or damaged vessel  10  tissue, perforation, and other lesions, disease, disorders or damage may all be treated by the present invention. For the sake of brevity, treatment of stenosis  16  is illustrated and described with the understanding that treatment of the aforementioned diseases and others is also contemplated and protected.  
         [0045]     With reference to  FIG. 2 , there is shown an anchor stent assembly  20 , including anchor stent  22  having an exterior surface  28  partially covered by a rod-like cover  24 . Reconstituted or naturally-derived collagenous materials can be used for the covering material in the present invention. Such materials that are at least bioresorbable will provide advantage in the present invention, with materials that are bioremodelable and promote cellular invasion and ingrowth providing particular advantage.  
         [0046]     Suitable bioremodelable materials can be provided by collagenous extracellular matrix materials (ECMs) possessing biotropic properties, including in certain forms angiogenic collagenous extracellular matrix materials. For example, suitable collagenous materials include ECMs such as submucosa, renal capsule membrane, dermal collagen, dura mater, pericardium, fascia lata, serosa, peritoneum or basement membrane layers, including liver basement membrane. Suitable submucosa materials for these purposes include, for instance, intestinal submucosa, including small intestinal submucosa, stomach submucosa, urinary bladder submucosa, and uterine submucosa.  
         [0047]     As prepared, the submucosa material and any other ECM used may optionally retain growth factors or other bioactive components native to the source tissue. For example, the submucosa or other ECM may include one or more growth factors such as basic fibroblast growth factor (FGF-2), transforming growth factor beta (TGF-beta), epidermal growth factor (EGF), and/or platelet derived growth factor (PDGF). As well, submucosa or other ECM used in the invention may include other biological materials such as heparin, heparin sulfate, hyaluronic acid, fibronectin and the like. Thus, generally speaking, the submucosa or other ECM material may include a bioactive component that induces, directly or indirectly, a cellular response such as a change in cell morphology, proliferation, growth, protein or gene expression.  
         [0048]     Submucosa or other ECM materials of the present invention can be derived from any suitable organ or other tissue source, usually sources containing connective tissues. The ECM materials processed for use in the invention will typically include abundant collagen, most commonly being constituted at least about 80% by weight collagen on a dry weight basis. Such naturally-derived ECM materials will for the most part include collagen fibers that are non-randomly oriented, for instance occurring as generally uniaxial or multi-axial but regularly oriented fibers. When processed to retain native bioactive factors, the ECM material can retain these factors interspersed as solids between, upon and/or within the collagen fibers. Particularly desirable naturally-derived ECM materials for use in the invention will include significant amounts of such interspersed, non-collagenous solids that are readily ascertainable under light microscopic examination with specific staining. Such non-collagenous solids can constitute a significant percentage of the dry weight of the ECM material in certain inventive embodiments, for example at least about 1%, at least about 3%, and at least about 5% by weight in various embodiments of the invention.  
         [0049]     The submucosa or other ECM material used in the present invention may also exhibit an angiogenic character and thus be effective to induce angiogenesis in a host engrafted with the material. In this regard, angiogenesis is the process through which the body makes new blood vessels to generate increased blood supply to tissues. Thus, angiogenic materials, when contacted with host tissues, promote or encourage the infiltration of new blood vessels. Methods for measuring in vivo angiogenesis in response to biomaterial implantation have recently been developed. For example, one such method uses a subcutaneous implant model to determine the angiogenic character of a material. See, C. Heeschen et al., Nature Medicine 7 (2001), No. 7, 833-839. When combined with a fluorescence microangiography technique, this model can provide both quantitative and qualitative measures of angiogenesis into biomaterials. C. Johnson et al., Circulation Research 94 (2004), No. 2, 262-268.  
         [0050]     Further, in addition or as an alternative to the inclusion of native bioactive components, non-native bioactive components such as those synthetically produced by recombinant technology or other methods, may be incorporated into the submucosa or other ECM tissue. These non-native bioactive components may be naturally-derived or recombinantly produced proteins that correspond to those natively occurring in the ECM tissue, but perhaps of a different species (e.g. human proteins applied to collagenous ECMs from other animals, such as pigs). The non-native bioactive components may also be drug substances. Illustrative drug substances that may be incorporated into and/or onto the ECM materials used in the invention include, for example, antibiotics or thrombus-promoting substances such as blood clotting factors, e.g. thrombin, fibrinogen, and the like. These substances may be applied to the ECM material as a premanufactured step, immediately prior to the procedure (e.g. by soaking the material in a solution containing a suitable antibiotic such as cefazolin), or during or after engraftment of the material in the patient.  
         [0051]     Submucosa or other ECM tissue used in the invention is preferably highly purified, for example, as described in U.S. Pat. No. 6,206,931 to Cook et al. Thus, preferred ECM material will exhibit an endotoxin level of less than about 12 endotoxin units (EU) per gram, more preferably less than about 5 EU per gram, and most preferably less than about 1 EU per gram. As additional preferences, the submucosa or other ECM material may have a bioburden of less than about 1 colony forming units (CFU) per gram, more preferably less than about 0.5 CFU per gram. Fungus levels are desirably similarly low, for example less than about 1 CFU per gram, more preferably less than about 0.5 CFU per gram. Nucleic acid levels are preferably less than about 5 μg/mg, more preferably less than about 2 μg/mg, and virus levels are preferably less than about 50 plaque forming units (PFU) per gram, more preferably less than about 5 PFU per gram. These and additional properties of submucosa or other ECM tissue taught in U.S. Pat. No. 6,206,931 may be characteristic of the submucosa tissue used in the present invention.  
         [0052]     By way of example, this application will refer to SIS as the cover  24 , but other ECM materials are contemplated. SIS may generally be obtained in tubular form and may come in at least one of two forms, vacuum pressed or liotholized. The vacuum pressed SIS is almost translucent in appearance and very rigid. The liotholized SIS is generally freeze dried and much more flexible and pliable than the vacuum pressed variation.  
         [0053]     The SIS cover  24  may be wetted in order to make it flexible and malleable. Once the cover  24  is wetted, it is mounted on an expanded anchor stent  22 . The anchor stent  22  may be any suitable stent, but desirably will be a self expandable stent. Examples of appropriate stents are disclosed in U.S. Pat. No. 4,580,568 to Gianturco, U.S. Pat. No. 5,928,280 to Hansen et al., and U.S. Pat. No. 5,968,088 to Hansen et al., and are incorporated herein by reference. The anchor stent  22  may include an interior surface  26 , an exterior surface  28 , and an inner lumen  30 . As shown in  FIG. 2 , approximately half of the anchor stent  22  may be covered with the SIS cover  24 . For example, a 2 cm stent may have approximately 1 cm of its exterior surface covered with the SIS cover. The length of the anchor stent  22  and of the SIS cover  24  may vary based upon the affliction being treated and the patient&#39;s own body size.  
         [0054]     The expanded anchor stent  22  and cover  24  may then be crimped over a mandrel which can be inserted through the central lumen  30 ,  32  of both the stent  22  and cover  24 . The mandrel around which the stent  22  and the cover are crimped may be as small as 0.014 inches in diameter, but may be larger depending upon the desired size of the resulting partially covered compressed anchor stent  22 . The mandrel may generally be used to provide a center lumen  30 ,  32  within the resulting anchor stent  22  and cover  24 .  
         [0055]     Once the mandrel is inserted into the anchor stent assembly  20 , a crimping machine, or other suitable method, may be used to compress the anchor stent  22  and cover  24 , decreasing the outer diameter of the stent assembly  20 . By crimping the cover  24  around the anchor stent  22 , it is contemplated that the stent  22  and the cover  24  will have a decreased diameter that may be later expanded to their initial size. The crimping process may be carried out in a variety of ways, including manually and mechanically.  
         [0056]     The inner lumen  30 ,  32  of the anchor stent  22  and the cover  24  allow the practitioner to position the assembly  20  on an inner catheter and guidewire of a delivery system (discussed below).  
         [0057]     The SIS cover  24  is dried while in the crimping machine. The resulting material may be stiff and rod-like. This may enable the practitioner to more easily manipulate the cover  24  within the delivery system and the patient&#39;s body. One method of drying the cover  24  is to use a hot air gun; however other methods such as air drying have also been contemplated. After the cover  24  is dried in a compressed state, it will form a resilient rod-like tube, holding the self-expanding anchor stent  22  at a decreased diameter.  
         [0058]     Once assembled, the anchor stent  22  and rod-like cover  24  may be transferred to a delivery device  40 . The transfer may be effectuated by placing the anchor stent assembly  20  in a transfer tube and pushing the assembly  20  into the device  40 . Additionally, it may be possible to take the cover  24  and anchor stent  22  directly from the crimping machine to the delivery device  40 . One advantage of using a transfer tube is that it holds the delivery device  40  and anchor stent assembly  20  in the correct position and helps to position the anchor stent assembly  20  within the delivery device  40 .  
         [0059]     Any suitable delivery device may be used; however, it is desirable that the device include an outer sheath  42  and an inner catheter  44 . One such delivery device is disclosed in U.S. Pat. No. 5,700,253 to Parker, which is incorporated herein by reference.  
         [0060]     The anchor stent assembly  20  is loaded into the delivery device  40  over the inner catheter  44  in a compressed condition. Generally, the assembly  20  may be loaded into the delivery device  40  from the device&#39;s proximal end  46 . This may prevent or lessen the chance that the rod-like SIS cover  24  will be broken during the loading process. However, the assembly  20  could be loaded into the delivery device  40  from either end using known techniques.  
         [0061]     As shown in  FIG. 3 , after the anchor stent assembly  20  is loaded into the delivery device  40  and positioned toward the distal end  48  of the device  40 , a second stent  50  may also loaded into the device  40 , behind the anchor stent assembly  20 . The second stent  50 , like the anchor stent  22 , may generally be a self expandable vascular stent. However, the second stent  50  could also be a balloon expandable vascular stent, or any other structure that is not classified as a stent but capable of being introduced into a blood vessel and which can maintain at least a portion of the SIS cover  24  in a desired position or location.  
         [0062]     The second stent  50  may be loaded into the delivery device  40  similarly to the anchor stent  22 , compressed over the inner catheter  44 . Generally, the outer sheath  42  of the delivery device  40  covers the second stent  50 , the anchor stent assembly  22 , and the cover  24 , preventing premature expansion of the stents.  
         [0063]     The inner catheter  44  may include markers or pushers  52 . The pushers  52  have generally the same outer diameter as the compressed stents  22 ,  50 . The pushers, however, may have an inner diameter that is less than the outer diameter of the tip  58 , preventing the pusher  52  from separating from the inner catheter  44 . In order to effectively launch both stents  22 ,  50  into the desired vessel  10 , the pushers  52  may be located on or around the inner catheter  44 , between the anchor stent  22  and the second stent  50 , as shown in  FIG. 3 . A second set of markers and/or pushers  54  may also be located behind the second stent  50 . One suitable marker would be a radiopaque ring surrounding the inner catheter  44  with an outer diameter large enough to impede the anchor stent  22  and the second stent  50  in their compressed condition, but small enough to pass through the central lumen  30 ,  56  of the stents  22 ,  50  when they are expanded or deployed within the vessel  10 .  
         [0064]     The inner catheter  44  may also include a tip  58 . The tip  58  could be a flexible tip, a guiding tip, a cannula or another tip or tips of differing size, shape, and structure. The tip  58  may generally be made of a soft material, such as polyurethane, and may be attached only to the inner catheter  44 . In another embodiment, the tip  58  may also have part of the SIS cover  24  tucked under, or removably attached to, the tip  58 . This embodiment may lessen the concern that the dried rod-like cover  24  will break upon insertion into the delivery device  40 .  
         [0065]     Referring still to  FIG. 3 , the outer sheath  42  maintains the anchor stent  22  and the second stent  50  in a compressed state in the case of a self-expanding stent, for example. The inner catheter  44 , the anchor stent assembly  22 , the cover  24 , and the second stent  50  may be enclosed within the outer catheter  42 . This allows the practitioner to use both stents  22 ,  50  without performing multiple procedures. In some embodiments more than one subsequent stent may be enclosed within the outer catheter. This may allow the practitioner to treat multiple stenosed regions or regions that vary in length and severity.  
         [0066]     Referring now to  FIG. 4 , one method of introducing the loaded delivery device  40  into the body is to insert a guidewire  60  into the vessel lumen  14  of the patient. The guidewire  60  is positioned within the organ to be treated with its distal end advanced, in the direction indicated by arrow F, through and past the distal end of the stenosed region  16 . Generally, the guidewire  60  may be as small as 0.014 inches in diameter.  
         [0067]     As shown in  FIG. 5 , once the guidewire  60  is positioned within the vessel  10 , the delivery device  40 , including the anchor stent assembly,  22 , the cover  24 , and the second stent  50 , is threaded over the guidewire  60 . The tip  58  of the inner catheter  44 , as well as the distal end of the outer sheath  42 , may include a radiopaque marker used for positioning purposes. In this manner, the tip  58  of the inner catheter  44  can be positioned distally of the stenosed region  16  of the vessel  10  to be treated. The anchor stent  22  and the second stent  50  may also include radiopaque markers at either end. The markers may be in the form of gold rivets on the terminating eyelets of the stent bodies.  
         [0068]     Referring again to  FIG. 5 , the cover  24  may be positioned through the stenosed region  16  of the vessel  10 . The low profile of the crimped, rod-like material allows the cover  24  to cross legions or stenosis  16 , minimizing disturbance to the area. The cover  24  may be long enough to protect the entire length of the stenosis  16  to be treated.  
         [0069]     One example of a deployment method is shown in  FIGS. 6-10 . The proximal end of the delivery device, including the outer sheath  42  and the inner catheter  44 , may be attached to a handle  62 . The handle  62  is generally located outside of the patient&#39;s body and allows the sheath  42  and the inner catheter  44  to be moved independently of, or relative to, one another.  
         [0070]     In one embodiment, a tube-like structure  64  may be attached to the proximal end of the sheath  42 , allowing the user to withdraw the outer sheath  42  in the direction of arrow A. In addition, the inner catheter  44  may be attached to a back bushing  66  and may be disposed through the tube-like structure  64 . The user may be able to hold the inner catheter  44  in place, while the tube-like structure  64  pulls the outer sheath  42  in the direction of arrow A. Alternatively, the inner catheter  44  may be moved in the direction of arrow B by moving the inner catheter  44  in and out of the tube  64 , holding the back bushing  66  for support.  
         [0071]     In  FIG. 5 , the loaded delivery device  40  has been moved into the deployment position. Once the loaded delivery device  40  is in place, using the handle  62  ( FIG. 6 ), the user may begin to withdraw the outer sheath  42  relative to the anchor stent assembly  22  and the second stent  50 , in the direction of arrow A. Other deployment techniques and devices are also contemplated.  
         [0072]     Regardless of which deployment mode is used, as shown in  FIG. 7 , when the outer sheath  42  is withdrawn in the direction of arrow A, the cover  24  and the anchor stent  22  are exposed to the flow of blood. The proximal end  68  of the anchor stent  22  may expand as it exits the outer sheath  42 . As the flow of blood softens the rod-like cover  24 , the hemostatic pressure of the blood flow and the expanding anchor stent  22  may cause the cover  24  to expand with the anchor stent  22  and against the stenosed region  16  of the vessel  10 . The cover  24  can conform to the shape of the interior of the vessel  10  as well as to the irregularities presented by the stenosis  16 . The cover  24  may be temporarily held against the distal end of the stenosed region  16  by the vessel&#39;s natural hemostatic pressure. Hemostatic pressure may be present within the cover  24  due to the flow of blood therethrough, but in the case of trauma or patient and treatment conditions, for example, wide variation in pressure may exist. Blood flow generally enters the cover  24  through the proximal end and is routed through the inner lumen of the cover and out of the distal end, in the direction indicated by arrow F. Thus, blood flow is isolated from the stenosis  16 .  
         [0073]     After the anchor stent  22  has been deployed, the practitioner will ideally wait about one minute when this procedure is performed on a patient with good blood flow through the stenosed region. The time allotted for the cover  24  to soften may vary from about 30 seconds to about 2 minutes, depending on the patient and the blood pressure through the region.  
         [0074]     When the loaded delivery device  40  is inserted into the stenosed region  16  of the blood vessel  10 , it may temporarily cut off blood flow through the vessel  10 . (See  FIG. 5 ). Therefore, holes or slits  70  may be cut or put in the outer sheath  42  so that the blood can flow through the outer sheath  42 , as shown in  FIGS. 8   a  and  8   b.    
         [0075]     With reference to  FIG. 9 , there is illustrated deployment of the second stent  50 . In  FIG. 9 , the guidewire  60  has been advanced in the direction indicated by arrow C, which is effective to move the tip  58  of the inner catheter  44  in the same direction. The result of this movement is to position the second stent  50  within the stenosed region  16 , with the proximal end  72  of the second stent  50  generally overlapping with the distal end  74  of the anchor stent  22 . The positions of the ends of the stents may generally be obtained by using radiopaque markers disposed at either end. The second stent  50  may generally extend the length of the stenosed region  16  and may or may not extend past the distal end of the cover  24 .  
         [0076]     Once the second stent  50  has been advanced through the stenosis  16 , the outer sheath  42  may again be withdrawn in the direction of arrow A, thus exposing the second stent  50  to the inner surface of the cover  24 . Again, the self expanding second stent  50  expands as it exits the sheath  42 . The delivery device, including the outer sheath  42  and inner catheter  44 , may then be removed from the patient&#39;s body. As shown in  FIG. 10 , upon removal of the delivery device, a post-dilation balloon catheter  76  may then be inserted into the stenosed region  16  to fully expand the second stent  50 , the cover, and the anchor stent against the vessel wall. This expansion exerts force on the stenosis  16  which may cause it to break down. This treatment and others can produce emboli  78  which are fragments of the stenosis  16 . The cover  24  protects the emboli  78  from blood flow and may prevent them from entering the blood stream. Generally, the practitioner will sequentially dilate the balloon, expanding the balloon gradually to fully open the stenosed region, beginning at the distal end of the vessel  10 .  
         [0077]     In another embodiment, the second stent  50  may be introduced separately from the anchor stent assembly  20 . In this embodiment, the anchor stent assembly  20  may be loaded into the delivery device  40 , as described above. The anchor stent assembly may be inserted in to the vessel  10  and deployed, as described above. The assembly  20  may be deployed within the vessel  10  by positioning the cover  24  through the stenosed region  16  of the vessel  10  and the outer sheath  42  is withdrawn, relative to the anchor stent assembly. The cover  24  and the anchor stent  22  are exposed to the flow of blood and the cover is softened. At this point, the delivery device  40  may be withdrawn from the vessel  10 , leaving the anchor stent assembly  20  deployed within the stenosed region. The second stent  50  may then be deployed within the vessel by known techniques.  
         [0078]     It is intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention.