Abstract:
A method and apparatus for a securement device useful for the treatment of aneurysms includes a hub and, in one aspect, a plurality of arms or spikes in a star pattern extendable therefrom and into engagement with a blood vessel wall. The securement device may be deployed to anchor a secondary device, such as an exclusion device for example a stent graft, in position in a flow lumen and thereby prevent the migration of the exclusion device in the flow lumen. The arms may be positioned to penetrate through the exclusion device and thence into the flow lumen wall to provide such securement.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     Embodiments of the present invention generally relate to the field of the treatment of body lumens, more particularly to the field of the treatment of blood vessels, and more particularly to the treatment of blood vessel aneurysms with intraluminal devices such as stents, lined stents such as stent grafts, and the use of a securement device therewith to secure the intraluminal device in an intended position within the blood vessel.  
         [0003]     2. Description of the Related Art  
         [0004]     Aneurysm, i.e., the enlargement of a blood vessel at a specific location therein to the point where rupture of the blood vessel is imminent, has been treated in the past by surgical intervention techniques, whereby the affected portion of the blood vessel is removed, or bypassed, so that a synthetic graft replaces the flow lumen. This treatment regimen is highly invasive for the patient undergoing it, and typically requires a multiple day post-operative hospital stay, as well as several months of recovery time until the patient has fully recovered from the surgery. Additionally, some patients may not be capable of undergoing such a procedure.  
         [0005]     To address the limitations imposed by surgical intervention to replace the aneurysmal blood vessel region with an artificial graft, a technique has been developed by which the aneurysmal blood vessel site is treated by placing what is known in the art as a stent graft, within the blood vessel in a position by which the tubular body of the stent graft spans the interior of the weakened area of the blood vessel wall. The stent graft, properly positioned, allows blood to flow through the hollow tubular interior, thereof, and also prevents blood, under systemic pressure, from reaching the weakened blood vessel wall at the aneurysmal site. The stent graft includes a graft portion provided to channel blood passage therethrough, and a stent portion, which supports the graft portion to maintain it in a hollow tubular configuration and press the graft portion against the blood vessel wall at locations remote from the aneurysmal site to seal off the aneurysm from further blood flow. Despite the intended expansion and sealing capability of the stent graft to the blood vessel wall, it is still possible, on occasion, for the stent graft to become dislodged or improperly sealed against the blood vessel wall. In such a case, fresh blood will reach the weakened aneurysmal wall location, creating a renewed risk that the blood vessel may rupture. Furthermore, if the stent graft is inadequately engaged against the blood vessel wall, such that the seal with healthy tissue is lost, it may migrate. In a graft having fenestrations, the wall of the stent graft around the fenestration could slip to become positioned over (obstruct) a branch artery, such as the renal arteries inducing renal blood starvation and potential renal failure.  
         [0006]     It is known, in the art, to provide anchoring of the stent graft to the blood vessel wall by the provision of individual hooks connected to stents at multiple discrete locations about the circumference of the stent graft. These individual securement devices are deployed using a catheter or tube protecting the hook ends. The end of the catheter is tracked through a blood vessel to the securement location and when in position the hooks are extended through the wall of the stent graft and into the wall of the blood vessel. This process is both cumbersome and time consuming. In particular, the known securement devices which provide individual hooks are manipulated into place and located against the stent graft to pierce the stent graft and then enter the blood vessel wall. Deployment hooks or hooks attached to stents can require intricate twisting and pulling motions by the surgeon on the end of a wire or tube external to the body. This complex procedure is typically repeated to provide stents with hooks or hooks alone at several locations about the inner circumference or near the ends of the stent graft. Additionally, the placement of such hooks can distort the stent graft, as hook placement through the stent graft may be angled and therefore not, circumferentially, match the subsequent placement of the hook in the blood vessel wall. This can create a distortion about the circumference of the stent graft, thereby reducing the sealing capability of the stent graft allowing the leakage of blood into the aneurysmal location. Additionally, such hooks are used to anchor other intraluminal devices, such as those intended for in situ therapeutic materials delivery to the blood vessel site.  
         [0007]     Therefore, there exists a need in the art for a stent graft securement system, which is easily deployable and results in securement of the stent graft to the blood vessel wall without circumferential distortion, with rapid deployment capability and verifiable positioning.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention generally concerns methods and apparatus for the placement and securement of intraluminal devices, such as a stent graft, in a body flow lumen location with minimal risk of endoleak and minimal risk of migration of the device from the intended location to an additional location in the lumen. In one embodiment, the invention includes an intraluminal exclusion device (exclusion device), such as a stent graft, having an outer cylinder-like wall which is located to span the location of a luminal risk factor, such as an aneurysm, and a securement device deployable to extend through the stent graft wall and into the blood vessel wall, to secure the stent graft to the blood vessel wall. The securement device may be placed in the body flow lumen at the time of intraluminal exclusion device placement or at some time thereafter where risk of intraluminal exclusion device migration becomes apparent. Additionally, the securement device may be used in conjunction with a device or material other than an intraluminal exclusion device, such as a device intended for the time release of therapeutic agents to the aneurysmal site, or may include such a delivery device formed therewith.  
         [0009]     In a further embodiment, the securement device is provided, and includes at least one anchor portion extending from a main body portion. The anchor portion extends through the intraluminal exclusion device wall and into the flow lumen wall there adjacent. The securement device, in one embodiment, includes at least three anchor portions extending from a main body portion, where at least one of the anchor portions has a tip that is configured to pierce the intraluminal exclusion device and flow lumen wall with a limiter extending therefrom that is configured to bear against the inner surface of the intraluminal exclusion device and thereby limiting the penetration depth of the anchor into the blood vessel wall. In a still further embodiment, the securement device deploys without the need for extensive manipulation of a catheter or tube. Instead, upon release from the tube or catheter at the deployment location, the anchor portion of the securement device is deployed adjacent to its final anchoring position, i.e., adjacent the blood vessel wall, simply upon release thereof from the catheter or tube. Alternatively, the anchor portion of the securement device may be deployed through the simple inflation of a balloon. Thus, the securement device may be deployed without the need for excessive twisting and manipulation of a catheter or tube from a position remote from the securement device deployment position. Once the securement device is deployed and position, in one embodiment, it is anchored into the blood vessel wall by the simple act of pulling on a wire detachably connected therewith.  
         [0010]     In a method of deploying the anchoring device, a catheter or tube capable of intravenous deployment is provided, and the securement device is located therein for deployment through a flow lumen, such as a leg artery, and thence to the intended position of securement of the intraluminal exclusion device. The tube includes an inner push rod capable of holding the securement device and moving it with respect to the flow lumen, as well as being releasable from the securement device once positioned in the flow lumen. Once the tip of the catheter or tube is positioned adjacent a deployment location, the securement device is deployed therefrom by maintaining the push rod stationary while the tube is withdrawn slightly from the deployment location, thereby pulling the tube past the securement device thereby locating the securement device in position in the flow lumen. The push rod is then pulled, to engage the tip of the securement device into the body flow lumen, after first piercing the exclusion device where the securement device is deployed in conjunction with an exclusion device. In one embodiment, the push rod includes one or more fluid passages therethrough, and a first balloon is positioned thereon at a location where the push rod extends through the securement device, and such balloon is inflatable to hold the securement device on the push rod while the securement device is still positioned within the tube or catheter. The tube or catheter is then further withdrawn, while holding the push rod stationary, to deploy the securement device out the end of the tube, whereby the anchor portions of the securement device are then extended into a position such that the tips thereof are engaged against the inner wall of the exclusion device. In one aspect, this is provided by configuring the securement device of a shape memory material, such that when the securement device is released from the tube, the anchor portions expand of their own accord into a shape to position the tips against the interior wall portion of the exclusion device about the inner circumference thereof. Alternatively, a second balloon may be provided on the push rod adjacent the anchor portions to urge the anchor portions outwardly to engage against the inner wall portion of the exclusion device. Thence, once the anchor portions are positioned with the tips against the inner wall of the exclusion device, the push rod extending through the securement device is retracted with respect to the tube or body, causing the first and second balloons to engage against the securement device and thereby move the securement device to cause the tips to pierce the wall of the exclusion device and the blood vessel wall, thereby securing the exclusion device in position. The first balloon is then deflated, (as is the second balloon, where used) thereby allowing the push rod, with the deflated balloon thereon, to be withdrawn through the securement device, leaving the securement device in position in the blood vessel wall. The catheter or tube, along with the push rod, is then retracted from the leg artery and the artery and entry cut in the leg are sutured shut.  
         [0011]     The placement of the securement device may occur simultaneously with, or immediately after, placement of the exclusion device, or at a later time where risk of migration of the exclusion device is indicated. Additionally, the securement device may be deployed independently of an exclusion device, such that the securement device may secure an additional or different intraluminal device therein, or, may include such a device as an integral part thereof. In such a case, the tips of the securement device will, in one embodiment, directly pierce the blood vessel wall without first passing through an intermediate member such as an exclusion device.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings.  
         [0013]      FIG. 1  is a schematic cross sectional view of a aneurysmal human ascending aorta, showing an exclusion device, in this embodiment, a stent graft, deployed therein;  
         [0014]      FIG. 2  is a schematic cross sectional view, showing an aneurysmal thoracic aorta and an exclusion device, specifically a stent graft, deployed across the aneurysmal portion of the aorta;  
         [0015]      FIG. 3  is a further sectional view of the aneurysmal aorta and stent graft of  FIG. 1 , having a securement device deployed therein;  
         [0016]      FIG. 3   a  is a top, plan view of the securement device deployed in  FIG. 3 ;  
         [0017]      FIG. 3   b  is a sectional view of the securement device of  FIG. 3   a  taken at  3   b - 3   b;    
         [0018]      FIG. 4  is a plan view of the preform of the attachment device of the present invention;  
         [0019]      FIG. 5  is a side view of the preform of the attachment device of  FIG. 4  having been cooled in a cooling media and bent to be positioned within an intraluminal delivery tube;  
         [0020]      FIG. 6  is a partial view, partially cutaway, of a delivery tube and securement device ready to deploy the securement device in a flow lumen;  
         [0021]      FIG. 7  is a view, in partial cutaway, of the lower aorta having a stent graft deployed therein, with the end of the tube  70  of  FIG. 6  disposed adjacent the blood flow entry end of the stent graft for deployment of the securement device;  
         [0022]      FIG. 8  is a further view of the stent graft and aorta of  FIG. 7 , showing the securement device being deployed;  
         [0023]      FIG. 9  is a further view of the stent graft and aorta of  FIG. 8 , showing the securement device deployed from the tube but not yet secured in place;  
         [0024]      FIG. 10  is a further view of the stent graft and aorta of  FIG. 9 , showing the securement device deployed in the aorta and securing the stent graft to the aorta wall; and  
         [0025]      FIG. 11  is a further view of the stent graft and aorta, with the stent graft shown in partial cutaway, showing the tube being retracted from the deployment position. 
     
    
     DETAILED DESCRIPTION  
       [0026]     Referring initially to  FIG. 1 , there is shown an intravascular repair vehicle, specifically a stent graft  10 , positioned in a blood vessel, in this embodiment, the descending abdominal aorta  12 , and spanning, within the aorta  12 , an aneurysmal portion  14  of the aorta  12 . The aneurysmal portion  14  is formed of a bulging of the aorta wall  16 , in a location where the strength and resiliency of the aorta wall  16  is weakened. As a result, an aneurysmal sac  18  is formed of distended vessel wall tissue. The stent graft  10  is positioned spanning the sac  18  and thereby both provides a secure passageway for blood flow through the aorta  12  and seals off the aneurysmal portion  14  of the aorta  12  from contact with further blood flow through the aorta  12 . The stent graft  10  further includes a graft portion  20 , which is configured from a biocompatible fabric, and which is sewn or otherwise attached to stent portion  22 , which is shown as a plurality of wires  24  interleaved into a mesh  26  pattern (though any number of stent graft structures are well known in the art). The wires are preferably made from a shape memory material, such as nitinol, which may be cooled, in the desired shape, in liquid nitrogen or otherwise and when cold compressed or rolled into a shape which will fit within a delivery tube such as a catheter, and inserted therein cold. Once deployed from the catheter at room or body temperature, the wires regain the shape they had when originally cooled. The upper, or blood entry end  28  of the stent graft is positioned such that the renal arteries  30 ,  30 ′ are not occluded, i.e., below or downstream thereof. The lower or blood exit end  32  of the stent graft  10  is bifurcated into two branches  34 ,  36 , each branch deployed to extend into and secure against the iliac branch arteries extending downstream from the aneurysm. The main body portion  35  of the stent graft  10  forms the upper end thereof, while branch  34  is preferably integrally formed with body portion  35 , and branch  36  is provided as a separate element which is combined, in situ in the patient, to form the bifurcated stent graft.  
         [0027]     Blood flowing through the stent graft  10  is not continuous in pressure or flow, and in fact the pressure can fluctuate substantially, causing expansion and contraction of the stent graft, as well as axial, i.e., along the flow direction of the blood, forces on the stent graft  10 . It has been found that these forces can be sufficient to disengage the stent graft ends from the blood vessel wall, such that the stent graft  10  can migrate upwardly (against blood flow direction) and block the renal arteries  30 ,  30 ′, as shown by the dashed outline  28 ′ of the upper end  28  of the stent graft shown in  FIG. 1 . Alternatively, the upper end of the stent graft may become compressed or crumpled, leading to graft/blood vessel seal failure at the entry end  28  of the stent graft  10 , allowing fresh blood to enter the excluded aneurysmal sac  16 , which may lead to aneurysm growth and eventual rupture.  
         [0028]     Referring now to  FIG. 2 , there is shown a stent graft  100 , which is located to span a thoracic aneurysm  102 . In this embodiment, stent graft  100  must be positioned such that blood flow to the branch arteries  101  in the top of the aortic arch is not blocked. Stent graft  100 , like stent graft  10 , includes a graft portion  104  and a stent portion  106 , the graft portion providing a barrier to blood flow to the aneurysmal sac  108  of the thoracic aneurysm  102 , and stent portion  106  providing support thereof to form the graft in a hollow tubular form and cause sealing thereof against the thoracic wall.  
         [0029]     Referring now to  FIGS. 3, 3   a  and  3   b , there is shown the placement of the stent graft  10  in an aorta  12  to span an aneurysmal portion  14  therein and a securement device  40  deployed therewith to secure the stent graft, at the blood entry end  28  thereof to the aortal wall  16 . Securement device  40 , in this embodiment, includes a hub  42 , from which a plurality, in this embodiment three, legs  44  extend in an equally spaced relationship about hub  40 . Each of the legs  44  terminate in a spike portion  46 , having a sharp tip  48  and a stop element  50  deployed thereon inwardly of the tip  48  of the spike portion  46 . As also shown in  FIG. 3 , the tip  48  of each of the spike portion  46  extends through the graft portion  20  of stent graft  10  and through, or alternatively into, aorta wall  16 . Additionally, hub  44  includes an aperture  52  extending therethrough, preferably at the center of the hub  42 . Additionally, the angle  54  prescribed between adjacent legs is preferably less than 180 degrees. Thus, when properly deployed, the hub  42  of the securement device  40  is positioned slightly upstream, from a blood flow perspective, of the location of the spike portions  46  as they engage the stent graft  10 . Thus, blood flowing against the securement device directs force, as shown by arrow F in  FIGS. 3 and 3   b , in a direction to increase the loading of the spike portions  46  against the stent graft  10 , and thereby further increase the ability of the securement device  40  to be maintained in position with the stent graft  10  without the need to otherwise secure the securement device to the stent graft  10 , such as by sewing, adhesives, etc. This enables separate delivery of the securement device  40  to the aneurysmal location, as well as relatively simple deployment thereof.  
         [0030]     Referring to  FIG. 4 , there is shown in schematic form the sequence of operations to form the securement device  40 . Beginning, with a sheet of shape memory material, such as nitinol, a generally star shaped perform  56  is cut, punched, or otherwise formed therefrom, having a hub  42  with an aperture  52  therethrough, and a plurality, in this embodiment three, legs  44  extending from hub  44  and evenly spaced, at approximately 120 degree separation, from one another, about the periphery of hub  42 . Legs  44 , when formed, preferably integrally include spike portion  46  and stop elements  50  integrally formed therewith. The preform, when cut, etc., from the sheet of material, will be generally planar, i.e., the hub  42  and each of legs  44  lie in the same plane. Thus, to provide the shape of the securement device  40  as shown in  FIG. 3 , each of the legs  44  is bent, with respect to the hub  42 , at the immediate location of the extension of the legs  44  from the hub, and each leg  44  is bent in the same direction to the same extent, to provide the structure of the preform as shown in  FIG. 3 . This configuration and alignment of the legs  44  to the hub  42  is selected to ensure that when the securement device of this same configuration is deployed, the ends of the three legs, i.e., the tips  48  of each of the legs  44  contact the inner wall of the stent graft  10  such that a slight tugging of the securement device in a blood flow direction, or downstream of the deployment location, will cause the tips  48  to pierce the graft portion  24  of the stent graft and further extend into the blood vessel, or aorta, wall  16 , as will be further described herein.  
         [0031]     Once the preform  56  is shaped to the desired securement device shape, the preform is cooled in liquid nitrogen to a temperature on the order of minus 196 degrees Celsius, and the preform is further bent, such as by continuing to bend the legs about the location of their extension from the hub  42 , such that an elongated shape having the hub  42  forming one end thereof and the bringing together of the three tips  48  forms the other end thereof, as shown in  FIG. 5 . A gap  60  remains between the adjacent, closely spaced tips  48 . The preform is now in a sufficiently collapsed state such that it may fit into a catheter or tube for intraluminal delivery to an aneurysmal site. It should be appreciated that the preform, when heated back to room temperature or a temperature sufficiently above that of liquid nitrogen, will regain the shape shown in  FIG. 4C . The wall of the tube within which the preform is placed prevents this reformation of shape until the securement device  40  is deployed therefrom.  
         [0032]     Referring now to  FIG. 6 , the deployment vehicle  62  for delivering the securement device  40  to the deployment location, and for deployment of the securement device, is shown. Specifically, deployment vehicle  62  includes a hollow push rod  64 , extending through the aperture  52  in hub  42 . Push rod  64  terminates, adjacent the hub  42 , and has an inflatable balloon  66  of the type used for balloon catheterization thereon in a deflated state. Additionally, a second balloon  68  may be provided on push rod  64  and positioned within the envelope of the gap  60  of the folded legs  44  of the securement device  40 , and fed from a second fluid channel in the push rod  64 . Push rod  64  also includes, on its outer surface thereof intermediate of the two balloon locations, a raised ridge (not shown) of greater diameter than aperture  52  such that push rod  64  engages against the hub  42  when pushed in a first direction, but is free to move within aperture  52  in the opposed direction. Securement device  40 , along with balloons  66 ,  68  and push rod  64 , are provided in an intraluminal catheter or delivery tube  70 , which is sufficiently long to be inserted in a leg artery and fed up the artery to be located at the aneurysmal location of an aorta or other blood vessel. Likewise, push rod  64  is sufficiently longer than delivery tube  70 , such that the end of push rod  64  may be manipulated, with respect to delivery tube  70  by the hand of a surgeon or operator, and holes for providing fluids under pressure to the separate feed conduits of push rod  64  are accessible.  
         [0033]     Referring now to FIGS.  7  to  12 , there is shown a paradigm for deployment of the stent graft securement device as shown in  FIG. 3 . In this embodiment, the delivery tube  70  is entered into an incision (not shown) in the leg of a patient, and thence through an incision in the artery therein (not shown), and the end  71  of delivery tube  70  received within the artery, having the securement device  40  therein (not shown in  FIG. 7 ), is pushed up the artery until it is positioned adjacent blood entry end  28  of stent graft  10  as shown in  FIG. 7 . The position of the stent graft  10  in the aorta  12 , as well as the position of the end  71  of the delivery tube  70 , may be readily determined by the presence of radiopaque markers (not shown) thereon through the use fluoroscopy, as is well known in the art. Once the delivery tube  70  is in the proper position with respect to blood entry end  28  of the stent graft  10 , the surgeon or operator of the delivery device begins withdrawing the delivery tube  70  from the incision thereby pulling the end  71  downwardly through the stent graft  10 , in the direction of arrow S in  FIG. 8 , while holding push rod  64  stationary and inflating first balloon  66 , whereby the balloon  66  is now inflated and blocks migration of the securement device off of the tube  70 . As delivery tube  70  is further retracted, the tips  480   f  the legs  44  of the securement device  40  are no longer constrained in motion, and they swing out, as shown in  FIG. 8 , and continue to swing out until they engage against the graft portion  24  of the stent graft  10  along the inner circumferential (cylindrical) face of the stent graft as shown in  FIG. 9 . If necessary, such as where the securement device is manufactured of a non-shape memory material, the second balloon  68  is inflated, thereby expanding the lags  44  outwardly a the tips  48  about their intersection with hub  42 , to secure tips  48  against the inner face of the graft portion of the stent graft.  
         [0034]     The first balloon  66 , provides maintenance of the securement device  40  on the tube  70  during deployment, and also tends to center the tube  70 , and thus the securement device  40 , within the blood flow entry end  28  of the stent graft  10 . Once the securement device  40  is expanded to cause tips  48  thereof the contact the stent graft, then the push rod  64  is moved in a direction to retract it from the incision, causing movement of the securement device  40  in the direction of arrow  90 , but only a very small distance sufficient to cause the tips  48  to piece the graft portion  24  of stent graft  10  and aorta wall  16 , thereby securing the stent graft  10  in place within the aorta  12  as shown in  FIG. 10 . The stops  50  on legs  44  prevent excessive penetration of the tips  48  into or through the aorta wall  16 , as they bear against the inner surface of the graft portion  24 , thus defining the total penetration depth of the tips into the graft and aorta wall  16  as the distance from stop  50  lower or outermost surface to the end of the tip  48 . Thus, damage to adjacent organs, which could otherwise occur if tips penetrated them, can be prevented.  
         [0035]     Once the securement device is deployed and tips  48  are in securing engagement through the stent graft  10  and in or through aorta wall  16 , the push rod  64 , as well as delivery tube  70 , need be removed from the blood vessel and aorta  12 . As shown in  FIG. 11 , balloons  66 ,  68  are deflated, such that the push rod  64  may now be pulled through the aperture  52 , being prevented previously from doing so by the presence of balloon  66  on the distal end of push rod  64 . Thus, as is shown in FIG.  11 , the tube  70  and balloon  66  are pulled through aperture  52 , leaving securement device  40  anchored in place. Push rod  64  and delivery tube  70  are then withdrawn from the artery and the incisions are sutured shut.  
         [0036]     Although the deployment of the securement device  40  has been discussed herein in detail in terms of securing an excluding device, such as a stent graft, located at an ascending aorta  12  location, it is likewise applicable to securing a stent graft at a thoracic aneurysm site. Further, although the securement device had been described herein in terms of specific configurations, and as deployed separately from the deployment of the stent graft, the securement device structure may be modified, and the securement device may be deployed in conjunction with stent graft deployment. Additionally, although the securement device has been described herein in terms of securing a specific device, specifically an excluding device such as a stent graft, it may equally be useful to deploy pharmaceutical type release agents, monitoring devices, or other device for which it would be useful to be secured in a blood vessel location.  
         [0037]     The foregoing embodiments of the invention provide anchoring of an intraluminal device with minimal invasiveness to the patient, and with the capability to extend in the flow region of the flow lumen/blood vessel to use the force created by blood flow to further anchor the securement device, while enabling substantial blood flow therethrough. The securement device  40  may be provided during stent graft deployment, the mechanisms of stent graft deployment being well known in the art.  
         [0038]     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof.