Abstract:
Methods and apparatus for delivering prostheses to body lumens, such as stents and grafts to blood vessels, utilize a delivery device which carries one or more linearized elements. The linearized elements assume non-linear configurations, particularly helical configurations, when advanced and released from the delivery device. By selectively controlling the length and/or number of elements delivered from the delivery device, extended and disseminated disease within the body lumens may be effectively treated.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
   The present application is a non-provisional of U.S. patent application Ser. No. 60/336,767 , filed Dec. 3, 2001, the full disclosure of which is incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention. 
   The present invention relates generally to medical devices and methods. More particularly, the present invention relates to apparatus and methods for independently delivering a plurality of luminal prostheses within a body lumen, such as a blood vessel. 
   Coronary artery disease is the leading cause of death and morbidity in the United States and Western society. In particular, atherosclerosis in the coronary arteries can cause myocardial infarction, commonly referred to as a heart attack, which can be immediately fatal or even if survived, cause damage to the heart which can incapacitate the patient. 
   While coronary artery bypass surgery can be an effective treatment for stenosed arteries resulting from atherosclerosis or other causes, it is a highly invasive, costly procedure, which typically requires substantial hospital and recovery time. Percutaneous transluminal coronary angioplasty, commonly referred to as balloon angioplasty, is less invasive, less traumatic, and significantly less expensive than bypass surgery. Heretofore, however, balloon angioplasty has not been considered as effective a treatment as bypass surgery. The effectiveness of balloon angioplasty, however, has improved significantly with the introduction of stenting, which involves the placement of a scaffold structure within the artery which has been treated by balloon angioplasty. The stent inhibits abrupt reclosure of the artery and has some benefit in inhibiting subsequent restenosis resulting from hyperplasia. Recently, experimental trials have demonstrated that coating stents with anti-proliferative drugs, such as paclitaxel, can significantly reduce the occurrence of hyperplasia in angioplasty treated coronary arteries which have been stented with the coated stents. 
   While the combination of balloon angioplasty with drug-coated stents holds great promise, significant challenges still remain. Of particular interest to the present invention, the treatment of extended or disseminated disease within an artery remains problematic. Most stents have a fixed length, typically in the range from 10 mm to 30 mm, and the placement of multiple stents to treat disease over a longer length requires the successive use of multiple balloon stent delivery catheters. Moreover, it can be difficult to stent an angioplasty-treated region of a blood vessel with the optimum stent length. 
   For these reasons, it would be desirable to provide improved stents, stent delivery systems, stenting methods, and the like, for the treatment of patients having coronary artery disease, as well as other occlusive diseases of the vasculature. In particular, it would be desirable to provide stents, delivery systems, and methods for the treatment of disseminated and variable length stenotic regions within the vasculature. For example, it would be desirable to provide methods which permit a physician to optimize the length of the treated vessel which is stented according to the nature of the disease, either by adjusting the stent length in situ or by placing multiple stents of the same or different lengths over the treatment region. At least some of these objectives will be met by the inventions described hereinafter. 
   2. Description of the Background Art. 
   U.S. Pat. No. 6,190,402B1, describes a self-forming vascular implant. U.S. Pat. No. 6,258,117, describes a multiple section stent structure; and U.S. Pat. No. 5,895,398, describes a clot retrieval device having a deployable helical clot snare. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention provides for improved methods, apparatus, and systems for delivering prostheses to body lumens, particularly stents and grafts to blood vessels in the arterial and venous vasculature. The prostheses comprise scaffold structures formed from linearized elements, typically metal wires having a round diameter, but also including ribbons, multifilar cables, braided structures, composite structures, wires having non-circular cross-sections, and the like. By “linearized element,” it is meant that the structural component will be capable of assuming a linearized configuration while the scaffold is being delivered. Most simply, the linearized element will have a non-linear configuration when unconstrained and will assume the linearized configuration when subjected to radial or axial constraint. In such instances, the linearized element will be formed so that it has a “memory” of the non-linear configuration but can be linearized by applying compressive or axial stress. In the exemplary embodiment, the linearized element has a helical memory. When constrained within the lumen of a delivery device, the linearized element assumes a generally straight configuration. When advanced outwardly from the constrained lumen, however, the linearized element returns to its helical configuration. A number of metals will have efficient elasticity to be able to shift between the linearized and non-linear configurations. Some of the metals include spring stainless steels, such as MP35N, Elgiloy, as well as superelastic alloys, such as nickel-titanium alloys, e.g. Nitinol™ alloy. 
   While the presently preferred linearized element will be formed from an elastic metal, one skilled in the art will appreciate that a variety of other metal and non-metal materials could be used to form such elements. For example, the elements could be formed from malleable metals, such as malleable stainless steel alloys, where the linearized element is then deformed into the non-linear configuration as it is advanced from the delivery device, e.g., by passing the linearized element over a shaping mandrel in the delivery device. Alternatively, the linearized element could be formed from a heat memory alloy, where the element is heated in situ after deployment in order to effect the change in shape from linear to non-linear. In addition, resilient and malleable polymeric and other non-metal materials might find use. These technologies, as well as others, for changing the shape of metal and non-metal structures within body lumens, are well described in the technical and medical literature. 
   The linearized elements of the present invention will be capable of assuming a variety of non-linear configurations. While helical non-linear configurations are presently preferred, it will be appreciated that serpentine, zigzag and other irregular configurations would also be suitable for at least some of the intended purposes of the present invention. Moreover, while it will generally be preferred to form the linearized elements from wire, most usually wire having a circular cross-section, it will also be possible to form the linearized elements from ribbons, flat sheets of material, and other conventional techniques. For example, serpentine or zigzag non-linearized elements could be formed from flat sheets of appropriate metal, e.g. by laser cutting, chemical etching, or the like. For example, a flat sheet could be configured to assume a desired tubular geometry. 
   Methods according to the present invention for delivering prostheses to a body lumen comprise introducing a delivery device to an interior of the body lumen, typically the lumen of a blood vessel, where the device carries the linearized element, as discussed above. The element is deployed by advancing the element relative to the delivery device within the interior of the body lumen so that the element assumes its non-linear configuration across the surface region of the interior as the element is advanced. The element is then released from the delivery device after it has assumed its non-linear configuration. Release may be effected by selectively severing the element after a desired length of the element has been reached. Alternatively, the delivery device may carry a plurality of linearized elements, each having a desired length so that each individual element is released after its entire length has been advanced from the delivery device. 
   Advancing the linearized element relative to the delivery device may comprise drawing the delivery device proximally relative to the body lumen while pushing the linearized element from the delivery device, typically using an internal pusher element. In such instances, the pusher rod will usually be held in a generally stationary relationship to the body lumen, while the delivery device is retracted proximally relative to both the body lumen and the pusher rod. In this way, the linearized element will deploy within the body lumen, while assuming its nonlinear configuration, with little or no relative movement relative to the luminal wall. This is desirable since any movement of the linearized element against the luminal wall may cause injury, particularly in arteries and other blood vessels. 
   In order to even further reduce movement of the deploying linearized element against the vessel wall, and thus reducing the risk of trauma to the vessel wall, it will often be desirable to control the deployment to offset the foreshortening of the linearized element as it is deployed. It will be appreciated that when a linearized element assumes a non-linear configuration, such as a helical configuration, the absolute length of the element will shorten. In the case of helical elements, the shortening will be quite significant, typically from 80 percent to 99 percent, depending on the pitch of the helix which is released. In order to minimize motion of the element against the vessel wall as it is deployed, it is therefore desirable to move the delivery device approximately at a rate substantially equal to the axial progress of the deployed helix within the body lumen (which will be much less than the absolute length of the linearized element which is being expelled). Thus, the pusher rod will be moving in a distal direction which is more rapid than the proximal withdrawal of the delivery device. Moreover, it will be further desirable to rotate the delivery device so that the deploying “helical” element is not caused to rotate within the vessel. Thus, three separate parameters of the deployment will need to be controlled to minimize the relative motion of the helical element against the blood vessel wall. First, the delivery device will be withdrawn proximally at a rate equal to the axial rate of deployment of the helix within the blood vessel. Second, the pusher rod will be distally advanced at a rate equal to the linear deployment rate of the helix within the deployment device. Finally, rotation of the delivery device will be controlled to counteract any tendency of the delivery device to rotate the helix as it is being deployed. All three of these deployment parameters may be manually controlled by the physician by observing the deployment under fluoroscopic imaging. Alternatively, programmable systems may be provided to automatically deploy and control the element deployment. 
   In a specific aspect of the method of the present invention, the pitch of the helical element may be controlled by adjusting the rate of drawing the delivery device proximally and/or advancing the linearized element from the delivery device. While the helical configuration of the linearized device will usually have a preferred or natural pitch, the actual pitch within the blood vessel or the body lumen may be controlled to a certain degree by adjusting its rate of advancement and the withdrawal rate of the delivery device to adjust the pitch. Usually, the delivery device will be rotated in order to further control the release geometry of the linearized element. 
   In other specific aspects of the method of the present invention, the prostheses are selectively deployed to traverse desired lengths of the vasculature or other body lumen. The covered length can be controlled in either or both of two ways. First, when the delivery device has the ability to sever the linearized element, the treating physician can control the length of prostheses by simply starting at a first target location, deploying the prostheses as described above (optionally with control of pitch in a helical prostheses), and severing the prostheses from the delivery device when a desired end location has been reached. 
   Additionally, the length of the vessel to be treated may be controlled by delivering multiple helical or other prostheses at selected and distributed portions of the luminal wall. Again, the treating physician will choose a beginning point within the body lumen and then deliver a prostheses over a selected length of the body lumen from that point. One, two, three, four or more additional segments of the prostheses may then be deployed. 
   Thus, the methods and apparatus of the present invention can be used to treat both short and long diseased segments within the vasculature and other body lumens. Usually, the treated regions will have a length of at least 10 mm and may have a length up to 60 mm and in some instances 100 mm or longer. Typically, when using only a single deployed prostheses, the treated lengths will be from 10 mm to 50 mm, usually from 10 mm to 30 mm. When using multiple prostheses, the lengths may be much greater, typically from 20 mm to 100 mm, more often from 20 mm to 60 mm. 
   As a further option, the linearized elements of the present invention may be coated, loaded, or otherwise coupled to or with an active substance intended to enhance the selected therapy. Linearized elements intended for treating blood vessels and other body lumens may be coated with substances intended to inhibit cellular proliferation, inflammation, or other conditions. Exemplary active substances include anti-neoplastic drugs such as paclitaxel, methotrexate, and batimastal; antibiotics such as doxycycline, tetracycline, rapamycin, and actinomycin; immunosuppressants such as dexamethosone, methyl prednisolone, nitric oxide sources such as nitroprussides; estrogen; estradiols; and the like. 
   The present invention further comprises catheters and other apparatus for delivering helical prostheses. The catheters comprise a catheter body having a proximal end, a distal end, and at least one lumen through at least a portion thereof. A linearized element is disposed in the lumen, and the mechanism for advancing and releasing at least one length of the linearized element from the lumen is provided. As described above, the linearized elements will assume a non-linear configuration when advanced and released from the catheter body. Usually, the advancing and releasing mechanism will comprise a severing mechanism to selectively cut the linearized element after a desired length has been released. Alternatively, the catheter may carry a plurality of linearized elements which are divided or cut into discrete lengths prior to deployment. Thus, the discrete lengths may be released after they are fully advanced from the lumen of the catheter body. In the latter case, the catheter body may carry from two to twenty discrete elements, typically from three to ten discrete elements. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a catheter capable of delivering helical elements constructed in accordance with the principles of the present invention. 
       FIGS. 1A and 1B  illustrate alternatively non-linearized element geometries according to the present invention. 
       FIG. 2  is a detailed view of the distal end of the catheter of  FIG. 1 , shown in section. 
       FIG. 3  is an alternative view of the distal end of the catheter of  FIG. 1 , shown in section. 
       FIG. 4  is a second alternative view of the distal end of the catheter of  FIG. 1 , shown in section. 
       FIGS. 5A-5E  illustrate use of the catheter of  FIG. 1  for delivering multiple, helical prostheses at distributed points in the blood vessel. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 1 , a delivery device comprising a catheter  10  includes a catheter body  12  having a proximal end  14  and a distal end  16 . The catheter will include at least one lumen  18  ( FIG. 2 ) extending over at least a portion thereof, and will further include a proximal hub  20  attached to the proximal end  14 . Hub  14  will include a mechanism for advancing a linearized element  26  from the lumen  18 , such as a thumb slide  30 . In the exemplary embodiment, the thumb slide will be attached to a push rod  32  which extends through the lumen  18  and engages the linearized element(s)  40  to be advanced from the catheter. As shown in  FIG. 1 , the linearized element  40  assumes a helical non-linear configuration as it is advanced from the lumen  18  of the catheter body  12 . 
   Referring now to  FIG. 1A , an alternative linearized element  42  is illustrated which will assume a serpentine non-linear configuration when advanced from the catheter or other delivery device.  FIG. 1A  shows the serpentine structure in its flattened or “rolled-out” configuration. It will be appreciated that the scaffold provided by the serpentine structure will be rolled into a generally tubular configuration, as indicated by the arrows in  FIG. 1A . When linearized, the element  42  will still assume a generally straight configuration, as shown in  FIG. 2 . A second alternative non-linear geometry comprises the zigzag pattern shown in  FIG. 1B . Again,  FIG. 1B  illustrates this pattern in its flattened or rolled-out configuration. The actual device would be rolled as indicated by the arrows into a generally tubular configuration to serve as a scaffold structure in the present invention. 
   As illustrated in  FIG. 2 , a single linearized element  40  is pushed by the pusher rod  32  to assume its helical or rather non-linear configuration when fully released from the catheter body  12 . Since the linearized element  40  and the pusher rod  42  are not connected, there is no need to provide a severing or other release mechanism in the embodiment of  FIG. 2 . 
     FIG. 3 , in contrast, shows a linearized element  46  having an indeterminate length. That is, the linearized element  46  will be sufficiently long so that it may be divided into two, three, four, or an even larger number of discrete non-linearized elements upon release from the catheter body  12 . In order to effect such release, a severing device  50 , such as an actuable blade, electrochemical, or other severing mechanism, is provided at the distal end of the delivery device. In this way, once a non-linear structure having a sufficient length has been delivered, the transition point between the linearized element and the non-linearized element will be severed using the device  50 . Additional non-linear scaffold devices may then be delivered using the same catheter over regions spaced apart within the vasculature or other body lumens. 
   Referring now to  FIG. 4 , a third alternative advancement and release mechanism is illustrated. The embodiment of  FIG. 4  is similar to that of  FIG. 2 , except that a plurality of discrete linearized elements  48   a ,  48   b , and  48   c , are carried within lumen  18  and advanced using pusher rod  32 . It will be appreciated that since these linearized elements  48   a - 48   c  are separate, and unconnected, they may be released sequentially by advancing the pusher rod (and optionally retracting and/or rotating the catheter body  12 ) to deliver each non-linearized element. There is no need to provide for a severing mechanism as with the embodiment of  FIG. 3 . While three discrete linearized elements  48   a - 48   c  are illustrated, it will be appreciated that anywhere from two to 10 linearized elements, or more, could be accommodated using the approach of  FIG. 4 . 
   Referring now to  FIGS. 5A-5C , use of the delivery catheter  10  of  FIG. 3  or  FIG. 4  will be illustrated. Catheter  10  is initially delivered so that its distal end  16  lies past a first target region TR 1 , as shown in  FIG. 5A . The catheter  10  may be introduced over a guide wire GW. The catheter may be an over-the-wire design. In some instances, however, it will be preferable to provide a rapid exchange design having a side guide wire port  60  spaced a short distance from its distal end, as shown in  FIG. 2 . In this way, the catheter may be introduced by withdrawing the pusher rod  32  and linearized element proximally so that they lie behind the side guide wire  60 . The catheter may then be introduced over the conventional guide wire GW without the need to completely remove and/or exchange the pusher rod and linearized element assembly with the guide wire. Of course, for catheters having larger diameters, it would be possible to provide a separate guide wire lumen extending the entire length of the catheter for an over-the-wire introduction. 
   Once the catheter  10  is in place, the pusher rod  32  will be advanced so that the first non-linearized element  48  is advanced from the distal end  16 , as illustrated in  FIG. 5B . The pusher rod is pushed in the direction of the arrow and a leading end of the element  48   c  engages the luminal wall of the blood vessel BV. 
   After the element  48   c  engages the luminal wall, it is desirable to begin retracting the catheter body in the direction of arrow  70  while advancing the pusher rod  32  in the direction of arrow  72  while preferably rotating the catheter body to counteract the relative rotation of the element  48   c . The catheter body is thus rotated in the direction of arrow  74 . By appropriately controlling each of these three motions, the coil will deploy helically with minimal motion relative to the luminal wall. 
   The first prostheses  48   a  will be completely delivered when it is advanced fully from the distal end  16  of catheter  10 , as illustrated in  FIG. 5D . The catheter  10  may continue to be withdrawn through the vasculature or other body lumen until a second region is reached where it is desired to deliver the second element  48   b . The steps of delivering the second linearized element  48   b  from the catheter are analogous to those described in  FIGS. 5A-5C  for the first element  48   a . A complete deployment of the first linearized element  48   a  into its helical configuration and the second linearized element  48   b  into its helical configuration are illustrated in  FIG. 5E . 
   It will be appreciated that the lengths, pitches, adjacent spacings, and the like, of the helical and other elements deployed according to the methods of the present invention can be controlled at the discretion of the treating physician. Thus, the methods and apparatus of the present invention provide useful flexibility for the treating physician to treat extended and disseminated disease in the vasculature and other body lumens. 
   Although the foregoing invention has been described in some detail by way of illustration and example, for purposes of clarity of understanding, it will be obvious that certain changes and modifications may be practiced within the scope of the appended claims.