Abstract:
A method of minimally invasively replacing a cardiac valve of a patient including inserting a delivery catheter intraluminally, inserting a valve resecting instrument intraluminally through the delivery catheter to a position adjacent the cardiac valve of a patient, manipulating the valve resecting instrument to resect the cardiac valve, removing the resected valve through the delivery catheter, and providing a delivery instrument having a replacement valve contained therein. The delivery instrument is advanced into the delivery catheter and intraluminally so that a distal end portion of the instrument is adjacent an annulus of a patient, and a first portion of the valve is exposed from the delivery instrument to position it on a first side of the annulus, and thereafter a second portion of the valve is exposed to position it on a second side of the annulus.

Description:
This application is a continuation of U.S. application Ser. No. 12/880,456, filed Sep. 13, 2010, now U.S. Pat. No. 8,167,935, which is a continuation of U.S. application Ser. No. 12/288,620, filed on Oct. 22, 2008, now U.S. Pat. No. 7,803,184, which is a continuation of U.S. application Ser. No. 11/222,570, filed Sep. 9, 2005, now U.S. Pat. No. 7,445,632, which is a continuation of U.S. application Ser. No. 10/429,536, filed on May 5, 2003, now U.S. Pat No. 6,974,476, which is a continuation of PCT application no. PCT/US01/43879, filed Nov. 14, 2001 which claims priority from Provisional application No. 60/252,187, filed Nov. 21, 2000. The entire contents of each of these applications are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Technical Field 
     This application relates to a prosthetic valve and more particularly to a prosthetic valve for minimally invasive replacement of a patient&#39;s cardiac valve. 
     2. Background of Related Art 
     The aortic and mitral valves are heart valves that open and close automatically in response to the pumping of the heart to control blood flow. The aortic valve is open during ventricular systole, when the heart is in contraction and blood is surged through the aorta and pulmonary artery, and is closed during diastole, when the heart is in relaxation, dilates and the cavity fills with blood. The aortic valve is positioned between the left ventricle and ascending aorta and functions to prevent back flow into the ventricle. The mitral or bicuspid valve closes the orifice between the left atrium and the left ventricle to prevent back flow into the atrium. 
     If the aortic valve doesn&#39;t close properly after the heart pumps the blood through the valve into the aorta, blood will leak back into the heart. This oxygenated back flow of blood causes the heart to work harder and faster, thereby initially causing chest pain, fatigue, and reduced blood output from the heart, which over time can result in cardiomyopathy. Additionally, when the aortic valve is defective for a period of time, it oftentimes leads to mitral valve damage because the retrograde inflow of blood applies pressure against the mitral valve, preventing it from closing properly. 
     There are a variety of causes of heart valve malfunction, many resulting from infections or diseases such as congenital heart disease, calcification related to athrosclerosis, and fibrosis. Generally, there are two types of damaged valves: stenotic valve in which the valve does not open fully thereby limiting forward blood flow; and regurgitant valves in which the valve does not close properly thereby permitting back flow. In either instance, valve malfunction can leads to cardiomyopathy which is a disease of the heart muscle which if left untreated can lead to heart failure and death or post stenotic dilatation of the aorta which can lead to aneurysm. 
     If a defective heart valve cannot be surgically repaired, it may need to be removed and replaced with a replacement valve. Currently, the surgical technique for valve replacement is open heart surgery. This open surgery is quite traumatic because it requires a full sternotomy, namely cracking the patient&#39;s ribs and creating a chest incision extending almost along the entire length of the chest. This incision can be as long as 10-12 inches. Additionally, to perform the valve surgery, the patient&#39;s heart is stopped with cardioplegia and the patient is placed on a heart lung machine requiring withdrawing the blood from the venous side of the patient through blood flow tubes, transporting the blood to the heart lung machine for oxygenation, and delivering the oxygenated blood to the arterial side of the patient&#39;s body through blood inflow tubes. The problems and risks inherent with the heart lung machine are well documented. These include the risk of infection, trauma to the body as a result of the blood exchange, and the risk of brain damage or stroke. It is also been found that patients who undergo open heart surgery may suffer from permanent neurological lapses. Additionally, in stopping the heart and utilizing the heart lung machine, the aorta must be cross clamped to cut off the blood flow. This cross clamping can dislodge plaque inside the vessel, potentially sending it through the bloodstream to the brain and causing stroke. Moreover, open heart surgery, being a highly invasive procedure, requires a long patient recovery time. The long patient recovery time, the use of the heart lung machine, and the requirement for additional hospital staff, e.g. machine technicians, all add to the costs of the surgical procedure. 
     Recognition of the disadvantages and risks of open heart surgery has recently led to attempts at minimally invasive approaches. For example, smaller chest incisions, such as partial sternotomies or creating a “window” between adjacent ribs, are now being utilized in some instances to access the aorta for performing certain heart bypass procedures. However, these approaches still require cracking and/or retracting ribs and are surgically difficult not only due to the limited access and maneuverability of the instrumentation, but due to limited visibility. Additionally, the heart may need to be manipulated to provide proper access, potentially causing additional trauma. For these reasons, such minimally invasive approaches have found only limited applications in bypass procedures and to the inventors&#39; knowledge have not been successfully used for aortic valve replacement surgery. 
     U.S. Pat. No. 5,571,215 discloses another approach to avoiding the aforementioned problems and risks associated with a full sternotomy, i.e. open heart surgery. In the &#39;215 patent, a percutaneous endoscopic method for valve installation is disclosed. Basically a series of cannulas or trocars are inserted percutaneously, along with an endoscopic viewing device, and the valve replacement is performed through these small tubes with visualization on a remote video screen. To the inventors&#39; knowledge, this form of endoscopic surgery is not currently being utilized, most likely because 1) access is limited; 2) the ability to manipulate the tissue and valve through small tubes is difficult; 3) visibility is limited; 4) and the small instrumentation needed for the procedure is limited. The problem with this endoscopic approach is compounded by the fact that the valve is sutured to the valve annulus. As can be appreciated, manipulating a suturing instrument through small tubes, with limited maneuverability and restricted visibility is quite difficult. Additionally, as with suturing in open procedures, the success of the suturing and knot tying can oftentimes be dependent on the particular skills of the surgeon. This method also requires opening the aorta, and ensuring proper closure after the surgery. 
     Therefore, to date, no surgical method is effective in avoiding the aforementioned disadvantages of open heart valve surgery. Thus, it would be advantageous to provide a minimally invasive method to insert and implant a heart valve, therefore avoiding the problems and risks associated with open surgery. It would also be advantageous to provide a replacement valve that can more easily be secured to the valve annulus without requiring the difficult, skill dependent and time consuming suturing and knot tying of the replacement valve. 
     SUMMARY 
     The present invention overcomes the disadvantages and deficiencies of the prior valves and valve insertion methods. The present invention provides a valve configured for insertion on the proximal and distal sides of a heart valve annulus to replace the heart valve of a patient. The valve comprises a first substantially annular portion adapted to be positioned on a proximal side of the annulus and a second substantially annular portion adapted to be positioned on a distal side of the annulus, wherein at least one of the first and second substantially annular portions is movable towards the other portion to a clamped position to clamp around the annulus. The second substantially annular portion has a flow restricting portion extending therefrom and is movable between a first position to permit the flow of blood and a second position to restrict the flow of blood. 
     The first and second portions are preferably comprised of shape memory alloy. In one embodiment, the valve has a suture joining the first and second substantially annular portions to draw them into closer proximity and a cinch member securing the suture to maintain the first and second portions in the clamped position. In another embodiment, the first and second portions are formed from a unitary wire and are connected by a wire segment which biases the first and second portions toward the clamped position. In this embodiment, the first substantially annular portion preferably underlies a first arcuate portion and a second arcuate portion preferably underlies the second substantially annular portion to form a coiled wire of multiple overlapping segments. 
     Various embodiments of flow restricting portions are provided. In one embodiment, the flow restricting portion comprises a plurality of leaflets extending circumferentially around the second portion in a direction away from the first portion and are foldable inwardly towards a convergence region at the midpoint of the second portion so the convergence region is concentric with the second portion to restrict blood flow. In another embodiment, the leaflets are foldable inwardly towards a convergence region offset from a midpoint of the second portion so the convergence region is eccentric with the second portion to restrict blood flow. The flow restricting portion may further include a membrane joining adjacent leaflets to cooperate with the leaflets to restrict blood flow when the leaflets are in the closed position. 
     A replacement cardiac valve implantation system is also provided comprising a valve and a delivery member. The valve comprises a wire element having a first ring-like portion and a second ring-like portion positioned over the first ring like portion. At least the first ring like portion is movable towards and away from the second ring-like portion and is biased towards the second ring like portion. The delivery member introduces the wire element into a patient&#39;s body, such that the first ring-like portion is placed on a first side of the annulus and the second ring-like portion is placed on a second side of the annulus, the bias of the portions forcing the first ring-like portion in closer proximity to the second ring-like portion to secure the valve in a clamped position around the annulus. The first and second ring-like portions are preferably joined by an arcuate wire segment extending therebetween which biases the first and second ring-like portions to a clamped position. 
     A method of installing a valve to replace a heart valve of a patient is also provided comprising: 
     positioning a valve in a first configuration inside a first catheter; 
     inserting the first catheter through the femoral artery; 
     advancing the first catheter around the aortic arch so that a distal end portion of the first catheter is adjacent an annulus of a patient; 
     ejecting a first portion of the valve from the first catheter to position it on a first side of the annulus; and 
     ejecting a second portion of the valve from the first catheter on a second side of the annulus allowing the first and second portions of the valve to clamp around both sides of the annulus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiment(s) of the present invention are described herein with reference to the drawings wherein: 
         FIG. 1A  is an isometric view showing the delivery catheter being inserted percutaneously though the left femoral artery to access the aortic valve annulus; 
         FIG. 1B  is an enlarged perspective view of the proximal portion of the delivery catheter shown inserted into a conventional sheath; 
         FIG. 2A  is a broken view of a percutaneously inserted valve resector shown extending through the delivery catheter and around the aortic arch to minimally invasively resect the aortic valve, and further showing the resected tissue being suctioned from the delivery catheter; 
         FIG. 2B  illustrates the resector of  FIG. 2A  withdrawn into the delivery catheter, proximal of the slit valve, with the resected tissue being suctioned through the catheter; 
         FIG. 3  is a broken view of a percutaneously inserted rongeur shown extending around the aortic arch and protruding through the delivery catheter to minimally invasively resect the aortic valve; 
         FIG. 4  is a perspective view of the rongeur of  FIG. 3  with a portion of the delivery catheter removed to show the resected tissue being suctioned through the rongeur; 
         FIG. 5  is a perspective view of the valve annulus of the patient; 
         FIG. 6-9  illustrate the steps of insertion of the valve of a first embodiment of the present invention wherein 
         FIG. 6  is a perspective view showing the partial ejection of the first wire element from the delivery catheter to a position on the proximal side of the annulus; 
         FIG. 7A  is a perspective view showing the first wire element further ejected from the catheter for deployment on the proximal side of the annulus to form a first or proximal ring; 
         FIG. 7B  is a perspective view showing the first ring fully ejected from the valve retaining catheter (the delivery catheter removed for clarity) and with the catheter sectioned to illustrate the positioning of the second wire element and suture cinch mechanisms therewithin; 
         FIG. 8  is perspective view showing full deployment of the first and second wire elements to form the first and second rings positioned on the proximal and distal sides of the annulus, respectively, and showing a first embodiment of the valve leaflets in the open position (with several of the leaflets removed for clarity); 
         FIG. 9  is a perspective view of the delivery catheter and a sectional view of the first and second rings fully deployed and the suture being tightened to clamp the rings on the annulus; 
         FIG. 10A  is a partial cross-sectional view illustrating the valve of  FIGS. 6-9  in the clamped position around the annulus with the cinch mechanism in the locking position; 
         FIG. 10B  is a perspective view of the valve of  FIGS. 6-9  in the clamped position with the leaflets in the open position to allow blood flow in the direction of the arrow; 
         FIG. 10C  is a perspective view of the valve of  FIGS. 6-9  in its clamped position with the leaflets in the closed position to stanch blood flow; 
         FIG. 11A  is a perspective view of the cinch mechanism of  FIG. 10A  for retaining the suture with part of the housing removed for clarity; 
         FIG. 11B  is a perspective view showing the cinch mechanism of  FIG. 11A  attached to a top surface of the distal ring; 
         FIG. 12A  is a perspective view of a second embodiment of the valve of the present invention; 
         FIG. 12B  is a perspective view showing initial deployment of the valve of  FIG. 12A  from a delivery catheter to form a first (proximal) ring; 
         FIG. 13  is a perspective view showing the valve of  FIG. 12  clamped on the annulus with a second embodiment of the leaflets in the open position to allow blood flow; 
         FIG. 14  is a perspective view showing the valve of  FIG. 13  clamped on the annulus with the leaflets in the closed position to stanch blood flow; 
         FIG. 15  is a side view of a third embodiment of the valve leaflets in a closed position shown having a curved overlapping configuration; 
         FIG. 16  is a top view of the valve of  FIG. 15  showing the overlapping leaflets in a closed configuration, concentric with the ring, to restrict blood flow; 
         FIG. 17  is a side perspective view of the valve leaflets of  FIG. 15  in the open position showing the membrane joining adjacent leaflets; 
         FIG. 18  is a perspective view showing the valve of  FIG. 12 , with the leaflet configuration of  FIGS. 15-17 , in the closed position and clamped on the annulus; 
         FIG. 19  is a side view of the valve of  FIGS. 6-9 , with the leaflet configuration of  FIGS. 15-17 , shown clamped on the annulus and in the open configuration, with only a few of the leaflets shown for clarity; 
         FIG. 20  is a bottom view of a fourth embodiment of the valve leaflets of the present invention; 
         FIG. 21  is a top view of the valve leaflets of  FIG. 20  shown in a closed position eccentric with the second (distal) ring; 
         FIG. 22  is a side view of the valve of  FIG. 20  showing the eccentric leaflets in the closed position; 
         FIG. 23  is a perspective view of a fifth embodiment of the valve leaflets of the present invention, having a membrane joining adjacent leaflets, shown in the closed position; 
         FIG. 24  is a side view of the valve of  FIG. 23  shown in the closed position; 
         FIG. 25  is a top view of the valve of  FIG. 23  shown in the closed position; 
         FIG. 26  is a cross sectional view taken along lines  26 - 26  of  FIG. 23  showing the varying thickness of the valve leaflets and membrane; 
         FIG. 27  is a perspective view of a sixth embodiment of the valve leaflets of the present invention shown in the open position to allow blood flow; 
         FIG. 28  is a top view of the valve of  FIG. 27  showing the leaflets in the closed position to restrict blood flow; 
         FIG. 29  is a cross-sectional view taken along lines  29 - 29  of  FIG. 27  showing the leaflets threaded onto the second (distal) ring; 
         FIG. 30  is a cross-sectional view of an alternate way to attach the leaflets showing the leaflets attached to the upper surface of the second ring; 
         FIG. 31  is a perspective view of an alternate approach to inserting the valve of the present invention; and 
         FIG. 32  is a perspective view of another alternate approach to inserting the valve of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring now in detail to the drawings where like reference numerals identify similar or like components throughout the several views,  FIGS. 6-10  illustrate a first embodiment of the heart valve of the present invention and  FIGS. 12-14  illustrate a second embodiment of the heart valve of the present invention, each valve configured and dimensioned for minimally invasive insertion and implantation in a patient&#39;s body. Various leaflet embodiments for use with either valve are disclosed in  FIGS. 15-30  and described in detail below. 
     The valve of the present invention, designed to replace the patient&#39;s aortic valve, is contained within a valve retaining catheter and inserted through a delivery catheter  70  as shown in  FIGS. 1A and 1B . Delivery catheter  70  is retained within a conventional sheath  101  having a side arm or tube  109  for flushing the surgical site. Sheath  101  has a slit valve  103  to seal around the delivery catheter  70  when inserted therethrough. Delivery catheter is inserted through the femoral artery “a” in the patient&#39;s leg, directed through the aortic arch “b” and into the left ventricle “c” of the patient. The valve is then deployed around the annulus, (a naturally formed tissue collar) in the manner described below to thereby form a replacement prosthetic valve to provide the function of the aortic valve. It should be understood that although the various embodiments of valves of the present invention are described below for replacement of the aortic valve, the valves of the present invention could also be used to replace other valves such as the mitral valve. 
     The valve of the present invention, as can be appreciated, is inserted intraluminally (or percutaneously through the femoral artery) so the aorta does not need to be penetrated to provide access to the annulus. To complement the intraluminal implantation of the valve, instrumentation is provided to resect the natural valve of the patient intraluminally. Thus, by providing a percutaneous valve resector, an entire percutaneous system is provided since the resection of the natural valve as well as insertion and implantation of the replacement valve can be achieved percutaneously, e.g. through a small incision into the femoral artery in the patient&#39;s leg. The intraluminal insertion avoids a sternotomy or partial sternotomy and its associated risks and disadvantages discussed above.  FIGS. 2-5  illustrate two examples of instrumentation to percutaneously (intraluminally) remove the defective aortic valve. 
     Turning first to  FIGS. 2A and 2B , a first embodiment of a valve resecting instrument is designated by reference numeral  50 . Resecting instrument  50  is inserted through delivery catheter  70 . Delivery catheter  70  is inserted through a small incision in the patient&#39;s leg to access the femoral artery (not shown), retained within sheath  101  (see  FIG. 1 ), and advanced through the femoral artery and around the aortic arch “b” to access the patient&#39;s defective valve. Delivery catheter  70  has slit valves  72 ,  74  on its proximal and distal ends  76 , 78 , respectively, to maintain a fluid seal when surgical instruments are inserted into the lumen  77  of the delivery catheter  70 . Thus, blood and debris are prevented from entering into the lumen  77  except for removal of resected valve tissue as described below. Delivery catheter  70  has a side tube or arm  79  connected to a suction source to remove the resected valve tissue. 
     Resecting instrument  50  has a flexible outer tube  58 , a pair of resecting jaws  56  extending from a distal end  55  of the outer tube  58 , and a jaw manipulator such as a wire (not shown) mechanically connected to the jaws  56  to manipulate the jaws  56  between open and closed positions to resect the valve. Resecting jaws  56  of resecting instrument  50  are controlled from a proximal end of outer tube  58 , which extends proximally of slit valve  72  to provide access to the surgeon outside the patient&#39;s body. Thus, the wire or controller is manipulated from outside the body to resect the valve. The resected valve tissue is suctioned through the slit valve  74  (the negative pressure opening the valve  74 ) and through delivery catheter lumen  77 , in the space between inner wall  73  of delivery catheter  70  and outer wall  53  of resecting instrument  50 , as shown in  FIG. 2B . Alternatively, a separate suctioning instrument can be placed alongside the resecting instrument  50  within the delivery catheter  70 . The pressure of the blood from the aorta can aid in pushing the debris out through the valve  74 . 
     An alternate embodiment of the valve resector is shown in  FIGS. 3 and 4 . A flexible rongeur  60  is depicted having a central lumen  62  to suction the resected pieces of the valve therethrough.  FIG. 4  illustrates a distal end portion  64  of the rongeur  60 , with a portion of delivery catheter  70  removed, to show the tissue being removed through the lumen  62 . The rongeur  60  is inserted through the delivery catheter  70  in the same manner as the aforedescribed resecting instrument  50 . To resect tissue, the tissue is placed between end plate  64  and cutter  66 . Plate  64  is retracted in the direction of the arrow, or alternately the cutter  66  is advanced toward the plate  64 , thereby forcing the tissue against cutter  66  for resecting the valve. The resected tissue is suctioned through lumen  62 . 
       FIG. 5  illustrates the patient&#39;s anatomy with the aortic valve removed to enable implantation of a replacement valve. The annulus is designated by letter “n” and due to its annular collar like configuration, provides a natural mount or clamping surface for the valve of the present invention which will become apparent from the discussion below. 
     Turning now to the first embodiment of the valve illustrated in  FIGS. 6-9 , and referring first to  FIG. 8 , the valve  10  includes a first wire forming a first or proximal ring  14  and a second separate wire forming a second or distal ring  12 . The first and second wire rings  14 ,  12  are joined by a series of sutures  24 . Although three sutures  24  are shown, additional or fewer sutures can be utilized. The wire can alternatively be composed of a unitary element so that the proximal and distal rings form a unitary piece joined by a wire portion therebetween. The wire can be made of stainless steel, but is preferably composed of shape memory material such as Nitinol (nickel-titanium alloy). Shape memory alloy enables the wires to be retained inside the valve retaining catheter  11  in an elongated position, extending along the longitudinal axis of the catheter  11  as shown in  FIG. 7B , and return to a preconfigured, memorized configuration when deployed from the catheter. Consequently, the proximal and distal rings can be positioned in the catheter, one behind the other or even adjacent each other in a substantially straight position, thereby allowing a small diameter delivery catheter to be utilized. This is best illustrated in  FIG. 7B  which illustrates the distal ring  14  deployed from the valve retaining catheter  11  but the proximal ring  12  still retained in its straightened configuration inside the catheter  11 . Note that both the distal and proximal wire rings  14   12  have atraumatic tips, such as a ball tip  17 ,  19 , respectively, at their exposed ends. 
     A pusher (not shown) ejects the first or proximal wire ring  14  by contact with a proximal end, enabling it to return to its substantially annular configuration. After ejection of the first ring  14 , either the same pusher, or a separate pusher proximal to or alongside the first pusher, ejects the distal wire ring  12  by advancing it from its proximal end, allowing it also to return to its substantially annular configuration. The sutures  24  which wrap around and hold the rings together, are ejected as the rings  12 ,  14  are ejected. 
     Three sutures  24  are provided, preferably about 120 degrees apart as shown. Each suture is wrapped around the rings  12  and  14  as best shown in  FIGS. 7B ,  9  and  11 B, and are tensioned to draw the rings  12  and  14  toward each other. A cinch mechanism  26  comprising a housing  27  and pivotable locking element  28  (see  FIG. 11A ) is provided for each suture. Housing  27  has a convex surface  25  to conform to an outer surface of the distal ring  12  to enable it to rest atop ring  12  and is preferably welded or adhesively attached thereto. Alternatively, housing  27  can be provided with a longitudinally extending opening to receive the distal wire therethrough. 
     One end  24   a  of each suture  24  is secured within slot  21  and the other end  24   b  is retained between locking element  28  and inner wall surface  23 . End  24   b , prior to being cut, extends beyond the length of the catheter, exiting through the proximal end. The suture is tensioned by pulling from its proximal end, thereby moving the two rings  12 ,  14  towards each other into locking engagement. Locking element  28 , spring biased as shown, prevents movement of the suture in a distal direction to maintain the suture and respective rings in a clamped (locked) position. 
     A series of leaflets or petals  30  extend upwardly from the distal ring  12  along the entire circumference as seen in  FIGS. 8 and 10B . (Only some of the leaflets are shown in  FIG. 8  for clarity.) Leaflets  30  are preferably attached to distal ring  12  by welding or adhesives; however, other methods of attachment as known in the art can also be utilized. Leaflets  30  are movable from an open position as shown in  FIG. 10B  to allow blood flow from the heart to the aorta to a closed position shown in  FIG. 10C , where their end portions are curved and converge to a closed position to prevent blood flow. The point of convergence as shown is aligned with a center region of the rings  12 ,  14 . 
     The steps of deploying and securing the valve  10  will now be described. First, the delivery catheter  70  is inserted through a conventional sheath, over a conventional guidewire (not shown) through the femoral artery, around the aortic arch, and down to the aortic valve area adjacent the valve annulus (the aortic valve having already been removed). As shown in  FIG. 6  the distal end  76  of the delivery catheter  70  is placed slightly past of the valve annulus, i.e. on the “inner” side of the annulus, also referred to herein as the proximal side of the annulus, relative to the heart. The guidewire is then removed. Valve retaining catheter or valve sheath  11 , with the aortic valve  10  contained therein in an elongated orientation, with the leaflets folded, is inserted through the delivery catheter  70  and likewise advanced through the femoral artery, around the aortic arch to adjacent the valve annulus. 
     The first wire element, which will form the first or proximal (inner) ring  14 , is initially advanced from the valve retaining catheter  11  and through the slit valve  74  of the delivery catheter  70  to the position of  FIG. 6 , ensuring it is on the proximal side of the annulus “n”, relative to the heart.  FIG. 7A  illustrates further advancement of the first wire element to enable it to return to its memorized configuration to form proximal annular ring  14  (see also  FIG. 7B ). After deployment of the ring  14 , the second wire element is ejected from valve retaining catheter  11  through slit valve  74  of delivery catheter  70 , allowing it to return from its straightened configuration within the valve retaining catheter  11  to its memorized configuration, shaped to form an annular second ring  12  on the distal (outer) side of the annulus, as shown in  FIG. 8 . The sutures are wrapped around the rings  12  and  14  as shown, with housing  27  of cinch mechanism  26  attached to the second ring  12  so the sutures are ejected with the rings  12 ,  14 . 
     Once the wire elements are fully deployed and the positioning of the first and second rings  14 ,  12  on respective sides of the annulus is confirmed by visualization techniques such as ultrasound, the rings  14 ,  12  are pulled together by tensioning the suture  24 . The surgeon manually pulls on the proximal end of each suture which extends proximally of the delivery catheter  70  and valve retaining catheter  11  outside the body. The two rings  12 ,  14  are thus pulled tightly together to clamp around the annulus with the cinch mechanism  26  ensuring that the suture is secured to lock the rings in this clamped position. The excess suture is cut at proximal end  24   b  and the valve retaining catheter  11  and delivery catheter  70  are withdrawn, leaving the valve  10  secured around the annulus. As noted above, although described for aortic valve replacement, the valve  10  described herein can be used to replace other valves such as the mitral valve. It should also be noted in  FIG. 9 , the cinch mechanism  26 ′ is shown spaced from the distal ring  12 , it being contemplated that the cinch mechanism can alternatively be slid into engagement with the distal ring  12  by a pusher (not shown), and attached thereto by conventional means such as a snap fit. 
     An alternate (second) embodiment of the valve of the present invention is illustrated in  FIGS. 12-14  and designated generally by reference numeral  40 . Valve  40  includes a coiled wire element preferable of unitary construction which forms a first or proximal (inner) ring  42  and a second or distal (outer) ring  44 . The rings  42  and  44  are joined by an arcuate wire segment  45  which also functions to bias the rings  42  and  44  toward each other as discussed below. 
     As shown, the first ring  42  has a 360 degree segment  46  which extends into overlying partially annular or arcuate segment  48 , preferably ranging from about 90 to about 180 degrees. Second ring  44  likewise has a 360 degree segment  47  extending into underlying partially annular or arcuate segment  49 , preferably ranging from about 90 to about 180 degrees. Thus, in the illustrated embodiment each ring  42 ,  44  can be considered to circumscribe at least about a 450 degree segment forming a coiled wire of multiple overlapping segments. Arcuate segment  48  transitions into arcuate segment  49  in the transition area defined by wire segment  45  extending at an angle to the parallel planes defined by each of the rings  42 ,  44 . 
     A series of substantially triangular leaflets  50  extend from the second ring  44 , preferably attached thereto by adhesive, although other means of attachment are also contemplated. When in the closed position of  FIG. 14 , leaflets  50  converge at a concentric point  52 , aligned with the midpoint of rings  42 ,  44  to close off blood flow. As in the valve of the first embodiment, the rings  42 ,  44  are placed on opposing sides of the annulus, i.e. on proximal and distal sides of the annulus relative to the heart. The bias of wire segment  45  forces the rings  42 ,  44  together to clamp against the annulus. 
     The wire element is preferably composed of a shape memory material, such as Nitinol, having the memorized configuration of  FIG. 12A . Thus, the wire element is contained in the valve retaining catheter or valve sheath  13  in a longitudinally straightened position, with the leaflets folded, to reduce the profile for insertion. In use, delivery catheter  70  is inserted into a conventional sheath (e.g. sheath  101  of  FIG. 1A ) and advanced over a guidewire through the femoral artery as described above with the distal end of the delivery catheter  70  placed on the “inner” or proximal side of the annulus. Next, valve retaining catheter  13  with the wire element contained therein is inserted through the slit valve  72  of the delivery catheter  70  and advanced around the aortic arch to terminate adjacent the distal end of delivery catheter  70 . A pusher element pushes the wire element distally outside the valve retaining catheter  13  and delivery catheter  70 .  FIG. 12B  illustrates wire element initially advanced. (Note that  FIG. 12B  shows the leaflets  50  in the unfolded condition for clarity, it being understood that the leaflets would be folded or compressed within the valve retaining catheter  13  to reduce the profile). 
     When the wire element is deployed, the first ring segment reverts from it straightened configuration inside the valve retaining catheter  13  to the memory configuration of  FIG. 12B , thus forming a first (proximal) ring  42  with an overlying segment  48 . Once the position of the proximal ring  42  is confirmed using applicable visualization techniques, the wire element is further deployed, allowing the second wire to return to its memory configuration to form a second or distal ring  44  with underlying segment  49 . The rings  42 ,  44  are then forced together by wire segment  45  to the position of  FIG. 14 , with the rings  42 , 44  clamped on opposing sides of the annulus. Thus, sutureless attachment to the annulus is achieved. 
       FIG. 14  illustrates the valve leaflets  50  in the closed position, where they converge at their tips during diastole. Their systolic or open position is illustrated in  FIG. 13 . It should be appreciated that the rounded edge, curved leaflets of the embodiment of  FIG. 8  could alternatively be used with the valve of the second embodiment of  FIG. 12-14 . 
     Various alternate embodiments of valve leaflets are disclosed in  FIG. 15-30  and will now be described. The leaflets need to accommodate two competing requirements: long term stability to handle repeated opening and closing without inverting or undesirably contacting the vessel wall and flexibility for unimpeded opening and closing to simulate natural valve function. The embodiments described below are intended to strike a balance between these two requirements. It should be understood that these leaflet configurations could be used with either of the two valve embodiments  10 ,  40  described above. Additionally the leaflets can be attached to the surface of the distal ring by welding, adhesive, insert molding or other means. Alternatively, the distal ring can extend directly through the leaflets to secure the leaflets to the ring. 
     Turning first to  FIGS. 15-18 , in this embodiment, leaflets  80 , having rounded edges  81 , are connected by a membrane  82  of sheet material. The membrane  82  will add to the stability of the leaflets by reducing the likelihood of inversion or “floppy valve” and may minimize post stenotic valve fibrillation or beating/trauma against the aortic wall. The leaflets  80 , when closed, converge in a partially overlapping fashion to a midpoint “M” concentric with the distal and proximal rings, i.e. aligned with the centerline of the rings. The curved or spiral-like overlapping configuration will also add to the stability of the leaflets and reduce the likelihood of leakage.  FIG. 18  illustrates the leaflets  80  utilized with the embodiment of  FIGS. 12-14  and  FIG. 19  illustrates the leaflets  80  utilized with the embodiment of  FIGS. 6-10 . 
     In the embodiment of  FIG. 20-22 , the leaflets  90  are curved and also have a membrane  92  joining adjacent leaflets. However, the leaflets  90 , when closed into their curved partially overlapping configuration converge to a point “E” eccentric with respect to the distal and proximal rings. Thus, the convergence point “E” of the leaflets  90  is offset with respect to the centerline of the rings. This offset will direct blood flow toward the side of the vessel rather than in the center of the vessel as in the concentric leaflets of  FIGS. 15-17 . 
       FIGS. 23-25  illustrate another embodiment of leaflets of the present invention. Leaflets  100  are connected by a membrane  102  to increase the stability of the leaflets. The membrane  102  joins adjacent leaflets, however, alternatively, the membrane can extend around the entire periphery of the leaflets, functioning to further prevent leakage when the valve is closed. As shown in the cross sectional view of  FIG. 26 , the leaflets  100  have a thickness greater than the thickness of the membrane  102 . This will increase stability towards the base of the leaflets, i.e. closer to the distal ring  44 , while increasing flexibility towards the top or outer portion of the leaflets. In the closed position, the leaflets  11  converge at point “F”, aligned with the center point of the rings. 
     The foregoing membranes can be composed of polyethylene, PTFE, or other suitable materials. Additionally, flexible metallic struts, made from materials such as Nitinol, can also be embedded in the membrane  82  to provide additional support. 
     A porcine or tricuspid valve is illustrated in  FIGS. 27-30 . This valve configuration more closely resembles the natural valve of the patient. In this embodiment, the tricuspid valve  110  having three leaflets  112  can be connected to the top of distal ring  44  as shown in  FIG. 29 . 
       FIG. 30  illustrates an alternative way to attach the leaflet. In this version, the ring  44  extends directly through the leaflets  200 , e.g. the leaflets are threaded onto the wire ring. 
     Alternate Approaches 
     As discussed above, the valves of the present invention are designed for percutaneous (intraluminal) insertion through the femoral artery. However, the inventors have realized that some surgeons might prefer either a full or partial sternotomy before transitioning to a minimally invasive approach. Some surgeons may also prefer the “window” approach which involves an incision between, and retraction of, the ribs of a patient. The valves of the present invention provide an advantage even if performing a sternotomy or “window” approach since they avoid the time consuming and complicated steps of suturing the valve to the annulus.  FIG. 31  illustrates how either valve of the present invention can be inserted through the aorta, in an open or more invasive surgical procedure. A portion of the aortic wall would be dissected as shown, and a delivery catheter  200  containing a valve retaining catheter  210  would be inserted therethrough. The valve  10  or  40  would be deployed from the valve retaining catheter  210  in the manner described above, and clamp against the annulus to provide sutureless attachment to the annulus as described above. 
     Although the endoscopic approach has not been clinically accepted for reasons suggested above, in the event this approach becomes accepted, the valve  10  and  40  of the present invention would provide an advantage because of their sutureless attachment to the annulus.  FIG. 32  illustrates such insertion of the valve through an endoscope  300  in a thoracoscopic approach to valve replacement. 
     While the above description contains many specifics, those specifics should not be construed as limitations on the scope of the disclosure, but merely as exemplifications of preferred embodiments thereof. Those skilled in the art will envision many other possible variations that are within the scope and spirit of the disclosure as defined by the claims appended hereto.