Abstract:
An implantable prosthesis for placement in hollow tubular organs is described alongwith an instrument for deploying the said prosthesis. On radial compaction, the prosthesis has a low profile, allowing introduction into the body with a deployment instrument of low calibre. The prosthesis has multiple longitudinal struts to provide longitudinal support. The prosthesis may be provided with helically configured members for circumferential support. The deployment instrument includes a retrievable tool to temporarily secure the prosthesis within the body during the implantation procedure.

Description:
RELATED APPLICATION  
       [0001]     This patent application claims priority from U.S. Provisional Patent Application Ser. No. 60/314,138, filed on Aug. 20, 2001, the entire disclosure of the application being expressly incorporated herein by reference. 
     
    
     TECHNICAL FIELD  
       [0002]     This invention under consideration concerns a prosthetic device and related instrument for non-surgically treating diseases of tubular organs of the human body, and methods for using the using the said prosthesis for the said purpose.  
       BACKGROUND ART  
       [0003]     Over the past two decades, treatment of diseases by the transluminal placement of a prosthesis has garnered increasing attention. In the field of vascular disease, this therapeutic modality now represents the intervention of choice for most occlusive lesions. The satisfactory results obtained with this treatment strategy has encouraged its application for the management of lesions such as aneurysms which are characterized by partial or complete loss of structural integrity rather than hindrance to blood flow. Multiple endoluminal grafts have been described for the purpose, only a few of which have survived the rigours of clinical use. Experience with these prostheses has demonstrated that while they do have therapeutic value, all suffer from a common drawback. They are too bulky to be implanted without creating a surgical vascular access, thereby negating one of the major advantages of the transluminal approach. This characteristic also make them difficult to implant in patients with tortuous blood vessels. Another limitation associated with their use is the inability to treat lesions involving the craniocerebral or visceral branches of the aorta. That all the endoluminal grafts in use have the same disadvantage is not a coincidence because all are based on the same underlying design: a flexible non-porous tube braced by an expandable metallic skeleton.  
         [0004]     Reducing the metallic skeleton to a single, sturdy metallic collar has been proposed as one way to reduce the bulk of a endovascular graft during introduction (PCT International Application WO 97/48350). While this modification certainly makes for a more streamlined device, it does not eliminate the need for surgically creating a vascular access because the introducer catheter required has an outer diameter of approximately 5 mm (15 Fr). Furthermore, clinical experience indicates that the absence of support along the longitudinal axis of the device is likely to increase the risk of complications associated with its use such as migration (Resch T. et. al. J Vasc Intervent Radiol 1999; 10:257-64). Deployment of the tubular component of the prosthesis and its metallic skeleton in sequence offers the possibility of reducing the calibre of the introducer system necessary for deployment. Two implantable devices based on this concept have been described thus far (U.S. Pat. No. 5,776,186, U.S. Pat. No. 6,015,422). However neither can be compacted to the degree necessary for percutaneous implantation.  
         [0005]     Thus there exists a need for a prosthesis for transluminal implantation that has a low enough profile to be introduced into the body by the non-surgical, percutaneous, approach and yet has sufficient longitudinal rigidity to minimise the risk of complications, and sufficient longitudinal flexibility to accommodate geometrical changes that often occur in tubular organs such as the aorta. The prosthesis should preferably not have a metal skeleton with multiple bent struts, which carries with it the risk of the type of structural failure that contributed to the AneuRx endovascular graft being withdrawn from the market (FDA Public Health Notification, Apr. 21, 2001). Likewise the prosthesis should be free of hooks eliminating the chances of severe vascular trauma observed with the Ancure device (FDA Public Health Notification, Apr. 21, 2001). These requirements are fulfilled by the invention under consideration. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     To facilitate understanding, throughout the description, the adjective “leading” identifies the end or edge of an object, such as a prosthesis or device, that precedes the rest of said object, when said object is being introduced into another object such as the human body.  
         [0007]      FIG. 1  is a perspective view of the preferred embodiment of the implantable prosthesis.  
         [0008]      FIG. 2  is a perspective view of the bifurcated embodiment of the implantable prosthesis.  
         [0009]      FIG. 3  is a perspective view of an alternative embodiment of the implantable prosthesis characterized by a trailing end narrower than the rest of the prosthesis.  
         [0010]      FIG. 4  is a perspective view of the bifurcated embodiment of the implantable prosthesis characterized by one distal limb.  
         [0011]      FIG. 5  is a perspective view partly in section of the introducer catheter with the dilator in situ.  
         [0012]      FIG. 6  is a perspective view partly in section of the introducer catheter with the pusher in situ.  
         [0013]      FIG. 7  is a perspective view of the anchor.  
         [0014]      FIG. 8  is a perspective view of an alternative embodiment of the implantable prosthesis characterized by a circumferential slit in the graft.  
         [0015]      FIG. 9  is a perspective view partly see-through view of an alternative embodiment of the implantable prosthesis provided with an internal helical support.  
         [0016]      FIG. 10  is a perspective view partly see-through view of an alternative embodiment of the implantable prosthesis provided with an internal helical support and short supporting struts.  
         [0017]      FIG. 11  is a perspective view partly in section of a loading cartridge containing an the alternative embodiment of the prosthesis provided with an internal helical support.  
         [0018]      FIG. 12  is a longitudinal sectional view of the anchor within a cannula.  
         [0019]      FIG. 13  is a perspective view partly in section of the loading cartridge with the prosthesis and anchor in situ.  
         [0020]      FIG. 14  is a perspective view partly in section of the loading cartridge with the prosthesis and anchor and pusher in situ.  
         [0021]      FIG. 15  is a perspective view of the trailing end of the loading cartridge.  
         [0022]     FIGS.  16  to  21  are longitudinal sectional views illustrating implantation of a prosthesis in an abdominal aorta with an aneurysm according to the invention. 
     
    
     DISCLOSURE OF THE INVENTION  
     DETAILED DESCRIPTION  
       [0023]     The invention is made from biocompatible materials. The materials used to make the components for permanent implantation are in addition characterised by long-term dimensional, structural, and configurational stability under cyclic loading.  
         [0024]      FIG. 1  illustrates the preferred embodiment of the invention. The primary component of the invention is a uni- or multilamellar tube (tubular graft)  1  with circular or elliptical cross-section, made from a flexible polymer. Multiple linear strips or wires (struts)  2  of a flexible metal or metal alloy or a flexible polymer is bonded to the graft  1 , parallel to the longitudinal axis of the graft  1 . The struts  2  may be bonded to the inner or outer surface of the graft  1 , or sandwiched between two adjacent lamellae. The leading and trailing free edges  3 ,  4  of the tube may or may not be parallel to each other, or perpendicular to the longitudinal axis of the tube. The modifications to the graft  1 , described in this may also be incorporated singly or in various combinations in the remaining embodiments of the invention.  
         [0025]     In the second embodiment of the invention, the struts  2  extend beyond the leading edge  3 , or the trailing edge  4  of the graft  1 , or both the leading and the trailing edges.  
         [0026]     The third embodiment of the invention (aorto-biiliac graft)  5   a  has a branched configuration with two peripheral limbs ( 6 ′,  6 ″) as illustrated in  FIG. 2 .  
         [0027]     The fourth embodiment of the invention (aorto-iliac graft)  5   b  has one peripheral limb ( 6 ′) as illustrated in  FIG. 3 .  
         [0028]     The fifth embodiment of the invention (aorto-uniiliac graft)  5   c  has the configuration illustrated in  FIG. 4 .  
         [0029]     The sixth embodiment of the invention (trans-renal aortic graft) is provided with a circumferential slit as illustrated in  FIG. 8 .  
         [0030]     In the seventh embodiment of the invention, the inner surface of the graft  1  is provided with one or more helically configured, reversibly deformable linear members (internal helical support)  2   a  ( FIG. 9 ). The diameter of the helices is equal to or greater than the inner diameter of the graft  1 . Only the leading end of the helical strut  2   a  is attached to the graft  1 , whereby straightening of the helical support will allow radial compaction of the graft. In the eight embodiment of the invention, the struts  2  are made of a resorbable material. In the ninth embodiment of the invention, the struts  2  protrude beyond the leading edge  3  of graft  1  and do not span the length of the graft  1  ( FIG. 10 ). In the tenth embodiment of the invention, one or more helically configured, reversibly deformable linear members are included that are not attached to the graft  1  (external helical support). The diameter of the external helical support is less than or equal to the outer diameter of the graft  1 .  
         [0031]     The delivery system to implant the graft comprises a thin wall catheter  7  (deployment catheter), that accommodates a thick-wall catheter with a tapered tip  8  (dilator) ( FIG. 5 ), or a thick-wall catheter with a blunt tip  9  (pusher) ( FIG. 6 ), and a self-expanding retrievable device (anchor)  10  ( FIG. 7 ). The deployment catheter  7  is fitted with a Touhy-Borst valve  11  carrying a female Luer hub  12 . The lumen of the deployment catheter  7  communicates with the lumen of the female Luer hub  12 , through the Touhy-Borst valve  11 . The anchor  10  consists of a leading linear, resilient member  13  (guide) and a trailing linear, resilient member  14  (shaft), that are connected to each other by multiple, outwardly biased, spirally-oriented resilient members with shape memory  15  (basket), that enclose an ovoid-shaped space ( FIG. 7 ). The basket  15  is radially compressible and its long axis is co-linear and co-planer with the guide  13  and the shaft  14 .  
         [0000]     Use of the Invention  
         [0000]     I. Preparation for Implantation:  
         [0032]     It is anticipated that this step will be performed at the site of manufacture before the device is sterilised.  
         [0033]     The basket is radially compressed and introduced into a cannula  17  ( FIG. 12 ). The graft  1  is tightly rolled around the cannula  17  and a thin-wall polymer tube (loading cartridge)  18  is drawn over the rolled-up graft to prevent it from unravelling ( FIG. 13 ). The cannula  17  is then removed. The pusher is advanced over the shaft  14  of the anchor  10  until its tip abuts the rolled up graft  1  ( FIG. 14 ). A Tuohy-Borst valve is attached to the hub of the dilator  8 . The valve is tightened securing the anchor  10  to the dilator  8 . The trailing end  19  of the loading cartridge  18  is flared and its free edge has two symmetrically placed slits  20 ,  21  extending a short distance along the length of the loading cartridge  18 , creating two flaps  22 , 23  ( FIG. 15 ). By applying traction on the flaps  22 , 23  perpendicular to the longitudinal axis of the loading cartridge  18 , the latter can be split into two separate parts.  
         [0034]     In case of the seventh, eighth, ninth or tenth embodiments of the invention, the internal helical support  2   a  is straightened before the graft  1  is rolled around cannula  17 , such that the trailing end of the internal helical support protrudes from the trailing end of the graft  1  ( FIG. 11 ).  
         [0000]     II. Implantation of Graft:  
         [0035]     The implantation procedure for lesions involving the infrarenal aorta and its bifurcation are described. These represent only examples to illustrate some of the envisaged uses of the invention and do not limit in any way the scope of its application as set forth in this provisional patent application. Furthermore the deployment of a single graft per site is described. Multiple grafts may be coaxially deployed using the same or similar procedure, if warranted by the anticipated circumferential stresses at the site of the lesion.  
         [0000]     A. Prosthesis Without Helical Support:  
         [0000]     (a) Implantation in the Infrarenal Aorta:  
         [0036]     After the anatomy of the lesion has been satisfactorily determined, a guidewire is placed traversing the lesion. The thin-wall catheter  7  carrying its corresponding dilator  8  is introduced coaxially over the guidewire and advanced until it spans the lesion. The dilator  8  is removed. The loading cartridge  18  is introduced into the Luer hub  12  of the thin-wall catheter  7 . The Touhy-Borst valve  11  is opened and axial force applied to the pusher  9  to backload the graft  1  into the thin-wall catheter  7 . Once the entire graft  1  has passed beyond the haemostatic valve, the loading cartridge  18  is split as described above and removed. With the help of the pusher  9 , the graft is advanced to the target site under imaging guidance ( FIG. 16 ). Holding the shaft  14  in place, the thin-wall catheter  7  is withdrawn exposing the leading portion of the graft  1 . The basket  15  expands to its original shape, opening the graft  1 , and apposing it against the luminal surface of the aorta, thereby securing it. The pusher is removed ( FIG. 17 ). With the shaft  14  of the anchor  10  serving as a guide, a stent  24  is deployed in the graft  1  overlapping its trailing edge, using procedures well known to those skilled in the art, reinforcing apposition of the graft  1  to the luminal surface of the aorta ( FIG. 18 ). The anchor is advanced until the basket  15  is beyond the graft  1  ( FIG. 19 ). Another stent  24 ′ is placed overlapping the leading edge  3  of the graft ( FIG. 20 ). The thin-wall catheter  7  is advanced until the basket  15  is captured within the lumen of the catheter  7 . The anchor  10  is withdrawn ( FIG. 21 ).  
         [0000]     (b) Implantation at the Aortic Bifurcation:  
         [0037]     An aorto-biiliac bifurcated graft  5   a  is deployed as described above, ensuring that the entire device lies in the descending aorta. After the first stent is placed in the graft  5   a  central to the peripheral limb, another graft  1  of appropriate size is implanted in the contralateral iliac artery, such that the leading end of the second graft  1  overlaps the trailing end of corresponding limb of the first graft  5   a . The basket  15  in the aorta is advanced out of the graft  5   a , and a stent placed across the leading edge  3  of the graft. The anchor  10  is then removed. Another graft  1  is implanted in the ipsilateral iliac artery overlapping the corresponding peripheral limb of the graft  5   a  in the aorta.  
         [0038]     Another option involves the implantation of two aorto-iliac grafts  5   b . The first graft is deployed ensuring that its peripheral limb lies in the ipsilateral iliac artery. A stent is placed central to the peripheral limb of the graft. Another stent is placed overlapping the trailing edge of the graft in the iliac artery. The thin-wall catheter  7  is advanced until the basket  15  is captured within the lumen of the catheter  7 . The anchor  10  is withdrawn. Via the contralateral femoral artery, another aorto-iliac graft  5   b  is deployed, ensuring that its peripheral limb protrudes from the aorto-iliac graft  5   b  already in situ. A stent is placed central to the peripheral limb of the graft. Another stent is placed overlapping the trailing edge of the aorto-iliac graft. The basket  15  is advanced beyond the leading edges of the two grafts in situ. A stent is placed overlapping the leading edges of the two grafts. Another stent is placed overlapping the luminal free edge of the second aorto-iliac graft  5   b . The thin-wall catheter  7  is advanced until the basket  15  is captured within the lumen of the catheter. The anchor  10  is withdrawn.  
         [0039]     Aorto-biiliac lesions may be alternatively treated by placing two tubular grafts  1  in parallel, with one graft extending into each iliac artery (Sakaguchi S, et. al. Twin-tube endografts for aortic aneurysms: an experimental feasibility study. J Vasc Intervent Radiol 1999; 10:1092-98.)  
         [0000]     B. Prosthesis with Helical Support:  
         [0040]     The implantation procedures described above are used with a few modifications. The pusher is advanced coaxially over both the shaft  14  of anchor  10  and the part of the internal helical support  2   a  protruding from the trailing end of graft  1 . After the basket  15  expands to its original shape, opening the graft  1  and apposing it against the luminal surface of the organ, the pusher is used to advance the trailing end of internal helical support  2   a  into the prosthesis, such that it regains its helical configuration.  
         [0041]     If the eighth or the ninth embodiments of the invention are to be implanted, the external helical support is deployed in the organ before implantation of the prosthesis is performed, such that the graft is sandwiched between the external and the internal helical supports.