Patent Document

[0001]     This application claims priority from provisional application 60/646,078 filed Jan. 21, 2005, which is hereby incorporated by reference herein in its entirety. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This invention relates broadly to implantable heart valves. More particularly, this invention relates to stent-valves that employ a stent for fixation of the valve.  
         [0004]     2. State of the Art  
         [0005]     Heart valve disease typically originates from rheumatic fever, endocarditis, and congenital birth defects. It is manifested in the form of valvular stenosis (defective opening) or insufficiency (defective closing). When symptoms become intolerable for normal lifestyle, the normal treatment procedure involves replacement with an artificial device.  
         [0006]     According to the American Heart Association, in 1998 alone 89,000 valve replacement surgeries were performed in the United States (10,000 more than in 1996). In that same year, 18,520 people died directly from valve-related disease, while up to 38,000 deaths had valvular disease listed as a contributing factor.  
         [0007]     Heart valve prostheses have been used successfully since 1960 and generally result in improvement in the longevity and symptomatology of patients with valvular heart disease. However, NIH&#39;s Working Group on Heart Valves reports that 10-year mortality rates still range from 40-55%, and that improvements in valve design are required to minimize thrombotic potential and structural degradation and to improve morbidity and mortality outcomes.  
         [0008]     A large factor that contributes to the morbidity and mortality of patients undergoing heart valve replacement is the long length of time required on cardiopulmonary bypass as well as under general anesthesia. A heart valve that can be placed using minimally invasive techniques that reduces the amount of anesthesia and time on cardiopulmonary bypass will reduce the morbidity and mortality of the procedure.  
         [0009]     Heart valve prostheses can be divided into three groups. The first group are mechanical valves, which effect unidirectional blood flow through mechanical closure of a ball in a cage or with tilting or pivoting (caged) discs. The second group are bioprosthetic valves which are flexible tri-leaflet, including (i) aortic valves harvested from pigs, (ii) valves fabricated from cow pericardial tissue, and mounted on a prosthetic stent, and (iii) valves harvested from cryo-preserved cadavers. The third group are polymer-based tri-leaflet valves.  
         [0010]     Mechanical heart valve prostheses exhibit excellent durability, but hemolysis and thrombotic reactions are still significant disadvantages. In order to decrease the risk of thrombotic complications patients require permanent anticoagulant therapy. Thromboembolism, tissue overgrowth, red cell destruction and endothelial damage have been implicated with the fluid dynamics associated with the various prosthetic heart valves.  
         [0011]     Bioprostheses have advantages in hemodynamic properties in that they produce the central flow characteristic to natural valves. Unfortunately, the tissue bioprostheses clinically used at present also have major disadvantages, such as relatively large pressure gradients compared to some of the mechanical valves (especially in the smaller sizes), jet-like flow through the leaflets, material fatigue and wear of valve leaflets, and calcification of valve leaflets (Chandran et al., 1989).  
         [0012]     Polymer-based tri-leaflet valves are fabricated from biochemically inert synthetic polymers. The intent of these valves is to overcome the problem of material fatigue while maintaining the natural valve flow and functional characteristics. Clinical and commercial success of these valves has not yet been attained mainly because of material degradation and design limitations.  
       SUMMARY OF THE INVENTION  
       [0013]     It is therefore an object of the invention to provide a heart valve device that provides for natural valve flow and functional characteristics with minimal material degradation.  
         [0014]     It is another object of the invention to provide such a heart valve device that is efficiently and effectively fixated within the heart.  
         [0015]     It is a further object of the invention to provide such a heart valve device with minimal and hemolysis and thrombotic reactions.  
         [0016]     In accord with these objects, a stent-valve device is provided that includes a non-collapsible valve component and a stent component having a first ring connected to a second ring. The first ring has a characteristic first diameter and a valve support for supporting the valve component. The second ring is contractible and expandable between a second diameter less than a third diameter. The second diameter is less than the first diameter and the third diameter is greater than the first diameter. The stent component is preferably realized from at least one shape memory metal. The non-collapsible valve component preferably comprises a substantially rigid annular base and a plurality of flexible leaflets that extend from its base. The non-collapsible valve component may be a mechanical valve prosthesis, a bio-prosthesis (such as a non-collapsible porcine valve) or a polymer-based prosthesis.  
         [0017]     According to one embodiment, the first ring of the stent component includes a plurality of elements that extend downward to feet that project radially inward. The valve component rests on the feet for support. A seal is preferably disposed about the first ring.  
         [0018]     According to another embodiment, a plurality of suspension elements connect the first ring to the second ring to thereby allow the first ring to hang below the second ring in use.  
         [0019]     According to a preferred embodiment, the second ring comprises a band of hexagonal elements having upper and lower apices that extend radially outward in a manner that fixates the stent-valve device in place against an inner wall of a blood vessel.  
         [0020]     In another aspect of the invention, a deployment catheter is provided for effectively deploying the stent-valve device(s) described herein. The deployment catheter includes a first housing that is adapted to store the second ring in its contracted state, and a first body member adapted to move the first housing axially to deploy the second ring from the first housing. A restrictor member is operably disposed adjacent the second ring. The restrictor member is adapted to limit axial movement of the second ring while the first body member is moved axially to deploy the second ring. A second body member, preferably concentric over the first body member, is manipulated to effectuate axial movement of the first housing relative to the restrictor member.  
         [0021]     According to one embodiment, the deployment catheter includes a second housing that is adapted to extend through the valve component (e.g., through the flexible leaflets and base of the valve component). The second housing is retracted therefrom after deploying the second ring. Preferably, a third body member is provided, which is concentric over the first and second body members, to allow for axial movement of the second housing relative to the restrictor member and the first housing.  
         [0022]     Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]      FIG. 1  is an isometric view of the stent component of an exemplary stent-valve device in accordance with the present invention.  
         [0024]      FIG. 2  is an isometric view of valve component of an exemplary stent-valve device in accordance with the present invention.  
         [0025]      FIG. 3  is an isometric view of an exemplary stent-valve device in accordance with the present invention, wherein the valve component of  FIG. 2  is placed within the stent component of  FIG. 1 .  
         [0026]      FIG. 4  illustrates an exemplary stent valve device with a seal operably disposed around the lower securing ring with the upper fixation ring compressed radially inward into a compressed state which is suitable for loading into the upper nose of a deployment catheter as shown in  FIGS. 5-10 .  
         [0027]      FIGS. 5-9  are cross section views of the operations of an exemplary deployment catheter for deploying and fixating the stent-valve device of  FIG. 3  to its intended deployment site where it is secured to the inner wall of a blood vessel.  
         [0028]      FIG. 10  is an isometric view of the deployment catheter of  FIGS. 5-9 .  
         [0029]      FIG. 11  is a pictorial illustration of the heart showing the stent-valve device of  FIG. 3  positioned in the ascending aorta upstream from left ventricle.  
         [0030]      FIGS. 12-14  are cross section views of the operations of another deployment catheter for deploying and fixating the stent-valve device of  FIG. 3  to its intended deployment site where it is secured to the inner wall of a blood vessel.  
         [0031]      FIG. 15  is an isometric view of an alternate stent component for a stent-valve device in accordance with the present invention.  
         [0032]      FIG. 16  is an isometric view of a stent-valve device in accordance with the present invention, wherein the valve component of  FIG. 2  is placed within the stent component of  FIG. 15  with a seal operably disposed around the suspenders of the stent and the valve component supported there. 
     
    
     DETAILED DESCRIPTION  
       [0033]     Turning now to  FIG. 1 , there is shown the stent component  1  of a stent-valve in accordance with the present invention. The stent  1  is typically made from a laser machined shape memory metal such as nitinol or Elgiloy or any other medical grade metal suitable for stents, stent-grafts and the like. Further, the stent component can be made using wire forms with and without welding. The stent  1  consists of a proximal end  2  opposite a distal end  3 . The distal end  3  contains a band of hexagonal shaped elements with adjacent elements sharing a common side. This band of hexagonal elements is herein called a fixation ring  4 . The fixation ring  4  can also be comprised of diamond shaped or zig-zag shaped elements, etc. Each hexagonal element  3   a  is formed in a geometry such that both the upper apices  5  and the lower apices  6  extend radially outward from the central portion of the fixation ring  4  as best shown in  FIGS. 1 and 3 . The purpose of the angle of the apices  5  and  6 , as will later be demonstrated, is to contact the inner wall of a blood vessel in order to prevent the stent from moving distally (or proximally) in the blood vessel; in other words, such apices fixates the stent in place against the inner wall of the blood vessel.  
         [0034]     A plurality (preferably, at least three) suspenders or connectors  7  hang from the fixation ring  4  and attach the fixation ring  4  to a lower securing ring  8 . The securing ring  8  preferably comprises a band of zig-zag elements  9  (although this ring  8  can also include diamond shaped or hexagonal shaped elements, etc.). The lower part of the securing ring  8  is comprised of elements  10  that project generally downward to feet  11  that project radially inward. The securing ring  8  is suspended in place by the fixation ring  4 .  
         [0035]      FIG. 2  illustrates an exemplary non-collapsible prosthetic heart valve  20  for use in conjunction with the present invention. The valve  20  includes a substantially rigid annular base  21  with three flexible leaflets  22   a ,  22   b ,  22   c  attached along its upper surface  23 . The base  21  and leaflets  22   a ,  22   b ,  22   c  may be formed from a biochemically inert polymeric material. Alternatively, the rigid base may be formed from a metal, such as titanium, stainless steel, nitonol, etc. It will be appreciated by those skilled in the art that fluid flowing in the direction of arrow  24  will displace the leaflet  22   a ,  22   b ,  22   c  axially and move through a central gap formed by the axial displacement of the leaflets  22   a ,  22   b ,  22   c ; while fluid traveling in the opposite direction of arrow  24  will cause the leaflets  22   a ,  22   b ,  22   c  to close by opposing each other and thus block the flow of fluid in this opposite direction. Any other non-collapsible prosthetic heart valve may be used, including, but not limited to, mechanical valves (e.g., tilting disk), non-collapsible bioprosthetic valves and other non-collapsible polymer-based prosthetic valves.  
         [0036]      FIG. 3  shows the valve  20  placed in the stent  1  with the base  21  of the valve resting on the feet  11  of the stent. It will be appreciated by those skilled in the art that the valve  20  can be sutured, glued to, mechanically attached, force fit, locked into or otherwise rigidly attached to the securing ring  8  of the stent  1 . It can further be appreciated that the securing ring  8  may be heat treated at a very small diameter and expanded such that valve  20  fits into the securing ring stent such that inward forces of the expanded securing ring hold the valve  20  in place. It should be noted that this is the reverse of a typical stent design that relies on outward forces to hold it in place. It can also be appreciated by those skilled in the art that the feet  11  can be designed as a harness or the like to capture the valve  20  which will enable easy assembly of the stent-valve in the operating room.  
         [0037]     As shown in  FIG. 4 , a seal  40  is preferably disposed around the securing ring  8 . The seal may be an annulus of foam, a multiplicity of strands, a rolled sewing cuff, or the like. The seal  40  prevents blood from leaking around the device once it is fixated. In addition, the seal  40  can be made porous to allow tissue ingrowth and facilitate permanent fixation of the device. Further, for certain applications, such as for aortic valve replacement as discussed below, the seal  40  can also take the form of an annular wedge such that a wide potion of the wedge remains in the ventricle, while the remaining portion of the wedge lies in the aorta, much like a cork in a bottle.  
         [0038]     In another aspect of the present invention, the stent valve device described above is loaded into and deployed from a deployment catheter as shown in  FIGS. 4-10 . After the valve  20  is secured in place to the securing ring  8  and the seal  40  disposed around the securing ring  8 , the fixation ring  4  is compressed radially inwards as shown in  FIG. 4 . A catheter  50  is provided with an upper nose cone  51  rigidly secured to an inner-body  60  as shown in  FIG. 5 . The inner-body  60  can be hollow to accommodate a guide wire, endoscope, fiber optics, fluid passage way, and the like. The inner-body  60  extends the entire length of the catheter where it can terminate with a hub with a luer or the like (not shown). The nose cone  51  holds the fixation ring  4  in its compressed state while the catheter is guided through the vasculature to the deployment site.  
         [0039]     A restrictor  61  is rigidly secured to a mid-body  62 . The mid-body  62  is concentric over the inner-body  60  and can be attached to a grip or the like (not shown) to enable holding in place during deployment. The restrictor  61  is disposed distally adjacent the fixation ring  4  and prevents the fixation ring from moving distally when the nose cone  51  is moved forward to enable deployment of the stent-valve device.  
         [0040]     The deployment catheter  50  also includes a second inverse or lower cone  53  securely attached to an outer-body  64 . The outer-body  64  is concentric over the mid-body  62  and can be attached to a grip or the like (not shown) to enable holding in place during deployment. The second cone  53  is inserted through the valve  20  (e.g., through the flexible leaflets and base the valve) where it nests or otherwise mates concentrically with the upper nose cone  51  as best shown in  FIGS. 5 and 10 .  
         [0041]     The proximal end of the upper nose cone  51  includes cutouts  65  through which pass the suspenders  7  of the stent as the stent is fixation ring  4  is held in its compressed state under the upper nose cone  51  as best shown in  FIGS. 5 and 10 .  
         [0042]     The stent-valve is deployed as shown in  FIGS. 6-9 . The catheter  50  (and the stent-valve housed therein as shown in  FIGS. 5 and 10 ) is introduced into the deployment area preferably by an intercostal penetration methodology. The catheter is then positioned in place at the deployment site ( FIG. 6 ). While the restrictor  61  is held in place by securing the mid-body  62 , the upper nose cone  51  is advanced forward thereby allowing the fixation ring  4  to deploy ( FIG. 7 ). The outward radial force produced by the fixation ring  4  combined with the angled orientation of the apices of the fixation ring  4  securely attach the fixation ring  4  to the vessel wall  70 . The suspenders  7  and securing ring  8  with feet  11  hold the valve  20  in place and the seal  40  prevents fluid from flowing around the valve  20 . After the fixation ring  4  is deployed, the entire catheter assembly is retracted through the valve  20  by pulling the bodies  60 ,  62 ,  64  rearward ( FIGS. 8 and 9 ) and out of the body.  
         [0043]     The lower cone  53  is shaped to mate with the upper nose cone and thereby protect the leaflets of the valve  20  from damage when the assembly is retracted back through the leaflets after deployment.  FIG. 9  shows the stent-valve assembly deployed and secured to the vessel wall  70  at the deployment site.  FIG. 10  illustrates the stent-valve assembly loaded into the deployment catheter  50  prior to introduction into the body.  
         [0044]      FIG. 11  illustrates the deployment and fixation of the stent-valve assembly of the present invention in the ascending aorta  72 . It can be located at or near the original location of a removed aortic valve or it can be inserted through an old aortic valve where it essentially pushes the leaflets of the old aortic valve aside. It is placed in the ascending aorta  72  just distal to the left ventricle  83  with the upper fixation ring  4  located distal to the coronary arteries  71   a ,  71   b  and the lower securing ring  8  placed proximal to the coronary arteries  71   a ,  71   b  and above the ventricle. The suspenders  7  of the stent are rotated/located so as not to interfere with blood flow to the coronary arteries  71   a ,  71   b . The deployment catheter  50  is inserted below the deployment site through the wall of the left ventricle  83  by cutting a slit in the left ventricle at site  80  which is thereafter repaired. Alternate entrance sites within the left ventricle  83  may be used. The left atrium  82  and left ventricle  83  are shown as landmarks within the heart for simplicity of description.  
         [0045]     Alternatively, the stent-valve assembly can be deployed from above the deployment site (e.g., from the aorta where a slit can be made, for example, at site  81  as shown in  FIG. 11 ). In this alternative embodiment, the fixation ring  4  is disposed proximal relative to the securing ring  8 . A deployment catheter  50 ′ as shown in  FIGS. 12-14  can be used to deploy the stent-valve at the intended deployment site. The catheter  50 ′ includes an outer cannula  101  whose distal end  103  holds the fixation ring  4  in its compressed state as shown in  FIG. 12 . An inner push rod  105  is disposed within the outer cannula  101  with its distal end  107  disposed adjacent the fixation ring  4 . The inner push rod  105  can be hollow to accommodate a guide wire, endoscope, fiber optics, fluid passage way, and the like. The outer cannula  101  is retracted back (with the push rod  105  held in place axially) to allow for deployment and fixation of the fixation ring  4  and the valve  20  secured thereto as shown in  FIG. 13 . The catheter  50 ′ is retracted further ( FIG. 14 ) and out of the body.  
         [0046]     Turning now to  FIG. 15 , there is shown an alternate stent component  1 ′ for a stent-valve in accordance with the present invention. The stent  1 ′ is typically made from a laser machined shape memory metal or wire forms as described above. The stent  1 ′ contains a band of hexagonal shaped elements with adjacent elements sharing a common side, referred to as a fixation ring  4 ′. The fixation ring  4 ′ can also be comprised of diamond shaped or zig-zag shaped elements, etc. Each hexagonal element  3   a ′ is formed in a geometry such that both the upper apices  5 ′ and the lower apices  6 ′ extend radially outward from the central portion of the fixation ring  4 ′. Small barbs  13 ,  15  project from the apices  5 ′ and  6 ′, respectively, as shown. The purpose of the angle of the apices  5 ′,  6 ′ and the barbs  13 ,  15  is to contact the inner wall of a blood vessel in order to prevent the stent  1 ′from moving distally (or proximally) in the blood vessel; in other words, such apices and barbs aid in fixating the stent in place against the inner wall of the blood vessel.  
         [0047]     A plurality (preferably, at least three) elements  10 ′ project generally downward (preferably from the bottom apices  6 ′ of the ring  4 ′) to feet  11 ′. The feet  11 ′ project radially inward and then upward as shown in  FIG. 15 . The feet  11 ′ support the non-collapsible valve element  20  as shown in  FIG. 16 . A seal  40 ′ is preferably disposed around the elements  10 ′ and the base of the valve element  20 . The seal  40 ′ may be an annulus of foam, a multiplicity of strands, a rolled sewing cuff, or the like. The seal  40 ′ prevents blood from leaking around the valve element  20  once it is fixated. In addition, the seal  40 ′ can be made porous to allow tissue ingrowth and facilitate permanent fixation of the device. Further, for certain applications, such as for aortic valve replacement as discussed herein, the seal  40 ′ can also take the form of an annular wedge such that a wide potion of the wedge remains in the ventricle, while the remaining portion of the wedge lies in the aorta, much like a cork in a bottle.  
         [0048]     The stent-valve device of  FIG. 16  is preferably loaded into and deployed from a deployment catheter in a manner similar to that described above with respect to  FIGS. 4-14 . After the valve  20  is supported by the feet  11 ′, the fixation ring  4 ′ is compressed radially inwards (in a manner similar that shown in  FIG. 4 ) and loaded into the catheter (e.g., into the nose cone  51  ( FIG. 5 ) or in the outer cannula ( FIG. 12 )). The catheter is introduced into the body and located adjacent the intended deployment site. The catheter is manipulated to the deploy the fixation ring  4 ′ from the distal end of the catheter, where it expands and contacts the vessel wall for fixation of the ring  4 ′ and the valve  20  secured thereto. The catheter is then retracted out of the body. The apices and barbs of the fixation ring  4 ′ aid in fixating the stent-valve device  1 ′ in place against the inner wall of the blood vessel.  
         [0049]     Advantageously, the prosthetic stent-valve devices described herein and the associated deployment mechanisms and surgical methods are minimally invasive and thus eliminate the multitude of sutures that are traditionally used to implant a heart valve. It also avoids total severing and re-suturing of the aorta which is standard practice for deploying prosthetic valves. By eliminating these complex procedures, the implantation time can be reduced significantly.  
         [0050]     Although the above stent device is described as holding and deploying a non-collapsible prosthetic valve, it can be appreciated by those skilled in the art that the prosthetic valve, if designed to be compressed, can be made flexible and be compressed down and introduced through a small catheter. It is further appreciated by those skilled in the art that this device can be introduced percutaneously through a small hole in the iliac or femoral artery in the groin.  
         [0051]     There have been described and illustrated herein several embodiments of a stent-valve assembly and a deployment catheter and surgical methods for use therewith. While particular embodiments of the invention have been described, it is not intended that the invention be limited thereto, as it is intended that the invention be as broad in scope as the art will allow and that the specification be read likewise. Thus, while particular geometries and configurations of the stent component have been disclosed, it will be appreciated that other geometries and configurations can be used as well. For example, the self-expanding fixation ring of the stent may be replaced by a fixation ring that is expanded through the use of an expandable balloon disposed inside the fixation ring. In addition, while particular configurations of the deployment catheter component have been disclosed, it will be understood that alternative configurations of the deployment catheter can be used. For example, instead of (or in conjunction with) a catheter housing or sheath that restrains the fixation ring, a suture can be used for this purpose. Once the fixation ring is located, the suture can be cut (or possibly pulled through) to release the fixation ring where it expands and fixates the stent-valve assembly in place. Such suture tension may be worthwhile as it keeps the valve from jumping which may happen when pushed from a catheter (commonly referred to as the “water melon seed” effect). Also, while particular applications have been disclosed for replacement of the aortic valve of the left ventricle of the heart, it can be readily adapted for use in the replacement of other heart valves (e.g., pulmonary valve). It will therefore be appreciated by those skilled in the art that yet other modifications could be made to the provided invention without deviating from its spirit and scope as claimed.

Technology Category: 1