Abstract:
Methods and systems for delivering and deploying a prosthetic heart valve include a deployment mechanism coupled to the prosthetic heart valve, the deployment mechanism having a longitudinal shaft that when rotated in a first direction, expands the prosthetic heart valve from a contracted state to an expanded state, and optionally, when rotated in a second direction opposite the first direction, re-contracts the prosthetic valve from the expanded state. Embodiments of the deployment mechanism include a pinion gear that engages a gear track on the prosthetic heart valve.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 13/350,730, filed Jan. 13, 2012, now U.S. Pat. No. 9,452,046, which is a continuation of U.S. application Ser. No. 12/488,480, filed Jun. 19, 2009, now U.S. Pat. No. 8,740,975, which is a continuation for of U.S. application Ser. No. 09/951,701, filed Sep. 13, 2001, now U.S. Pat. No. 7,556,646, the disclosures all of which are incorporated by reference in their entireties. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to medical devices and particularly to methods and devices for deploying expandable heart valve prostheses especially for use in minimally-invasive surgeries. 
     BACKGROUND OF THE INVENTION 
     Prosthetic heart valves are used to replace damaged or diseased heart valves. In vertebrate animals, the heart is a hollow muscular organ having four pumping chambers: the left and right atria and the left and right ventricles, each provided with its own one-way valve. The natural heart valves are identified as the aortic, mitral (or bicuspid), tricuspid and pulmonary valves. Prosthetic heart valves can be used to replace any of these naturally occurring valves. 
     Where replacement of a heart valve is indicated, the dysfunctional valve is typically cut out and replaced with either a mechanical valve or a tissue valve. Tissue valves are often preferred over mechanical valves because they typically do not require long-term treatment with anticoagulants. The most common tissue valves are constructed with whole porcine (pig) valves, or with separate leaflets cut from bovine (cow) pericardium. Although so-called stentless valves, comprising a section of porcine aorta along with the valve, are available, the most widely used valves include some form of stent or synthetic leaflet support. Typically, a wireform having alternating arcuate cusps and upstanding commissures supports the leaflets within the valve, in combination with an annular stent and a sewing ring. The alternating cusps and commissures mimic the natural contour of leaflet attachment. 
     A conventional heart valve replacement surgery involves accessing the heart in the patient&#39;s thoracic cavity through a longitudinal incision in the chest. For example, a median sternotomy requires cutting through the sternum and forcing the two opposing halves of the rib cage to be spread apart, allowing access to the thoracic cavity and heart within. The patient is then placed on cardiopulmonary bypass which involves stopping the heart to permit access to the internal chambers. Such open heart surgery is particularly invasive and involves a lengthy and difficult recovery period. 
     Recently, a great amount of research has been done to reduce the trauma and risk associated with conventional open heart valve replacement surgery. In particular, the field of minimally invasive surgery (MIS) has exploded since the early to mid-1990&#39;s, with devices now being available to enable valve replacements without opening the chest cavity. MIS heart valve replacement surgery still typically requires bypass, but the excision of the native valve and implantation of the prosthetic valve are accomplished via elongated tubes (catheters or cannulas), with the help of endoscopes and other such visualization techniques. Some examples of recent MIS heart valves are shown in U.S. Pat. No. 5,411,552 to Anderson, et al., U.S. Pat. No. 5,980,570 to Simpson, U.S. Pat. No. 5,984,959 to Robertson, et al., PCT Publication No. 00/047139 to Garrison, et al., and PCT Publication No. WO 99/334142 to Vesely. 
     The typical MIS valve of the prior art includes a directly radially expanding stent that is initially compressed for delivery through a cannula, and is then expanded at the site of implantation after removing the constraint of the cannula. The expansion is accomplished using an internal balloon catheter around which the stent is compressed. 
     Despite various delivery systems for conventional MIS valves, there remains a need for a delivery system that more reliably controls the expansion of new MIS valves. 
     SUMMARY OF THE INVENTION 
     In accordance with a preferred embodiment, the present invention provides a system for delivering and deploying an expandable prosthetic heart valve, comprising a catheter shaft having a proximal end and a distal end and a lumen therethrough extending along an axis. The heart valve deployment mechanism extends axially from the distal end of the catheter shaft, and includes spaced apart proximal and distal deployment members. An actuating shaft extends through the lumen of the catheter shaft and operates to actuate at least one of the proximal and distal deployment members. The deployment members may be radially movable and comprise fingers each pivoted at one end thereof to the deployment mechanism. There are desirably at least two proximal deployment fingers and at least two distal deployment fingers, wherein the deployment fingers are axially movable. The deployment members may be radially movable and there are two of the actuating shafts. A first actuating shaft operates to radially displace the proximal deployment members and a second actuating shaft operates to radially displace the distal deployment members, wherein the first and second actuating shafts are concentrically disposed to slide with respect one another. 
     In one embodiment the deployment mechanism comprises a proximal collet with respect to which the proximal deployment members pivot, and a distal collet with respect to which the distal deployment members pivot, wherein the proximal collet and distal collet are relatively axially movable. A first actuating shaft extends within a cavity in the proximal collet and a first driver attaches thereto that acts upon the proximal deployment members to pivot them with respect to the proximal collet. A second actuating shaft extends through the first actuating shaft and into a cavity in the distal collet and a second driver attaches thereto that acts upon the distal deployment members to pivot them with respect to the distal collet. 
     There are various ways to actuate the deployment members. First, each deployment member may pivot about a point that is fixed with respect to the associate collet and includes structure that engages cooperating structure on the associated driver, wherein axial movement of the driver rotates the structure about the pivot point, thus rotating the deployment member. Alternatively, each deployment member has a pin fixed with respect thereto that is received within a corresponding slot in the associated driver, and each collet includes a plurality of pins fixed with respect thereto that are received within corresponding slots in the associated deployment members. In the alternative configuration, axial movement of the driver displaces the pins fixed with respect to the deployment members and causes the deployment members to pivot outward due to a camming action of the deployment member slots over the collet pins. 
     In a still further embodiment, each deployment member may comprise a pad that is coupled to a respective proximal and distal end cap disposed along the catheter shaft, the pads being radially displaceable with respect to the associated end cap, wherein the proximal and distal end caps are axially movable with respect to each other. There may be two of the actuating shafts, each shaft controlling a plurality of flexible tongs having column strength that extend between one of the end caps and attach to the associated pads, wherein axial movement of each shaft shortens or lengthens the radial extent of the flexible tongs controlled thereby so as to radially displace the attached pads. 
     Still further, each deployment member may comprise a gear that engages a gear track on the heart valve. 
     The system preferably includes a stabilization balloon on the catheter shaft proximal to the deployment mechanism and sized to expand and contact a surrounding vessel adjacent the site of implantation. The stabilization balloon may be shaped so as to permit blood flow past it in its expanded configuration, such as with multiple outwardly extending lobes. 
     The heart valve deployment mechanism may be a modular unit coupled to the distal ends of the catheter shaft and actuating shaft. 
     In another aspect of the invention, a system for delivering and deploying a self-expandable prosthetic heart valve to a site of implantation is provided. The system comprises a catheter for advancing the heart valve in a contracted configuration to the site of implantation; means on the catheter for permitting the heart valve to self-expand from its contracted configuration to an initial expanded configuration in contact with the surrounding site of implantation; and means for regulating the rate of self-expansion of the heart valve. The system may also include means for expanding the heart valve from its initial expanded configuration to a final expanded configuration, such as a balloon. Alternatively, the means for expanding the heart valve from its initial expanded configuration to a final expanded configuration may be the same as the means for regulating the rate of self-expansion of the heart valve. 
     The means for expanding the heart valve from its initial expanded configuration to its final expanded configuration and the means for regulating the rate of self-expansion of the heart valve may comprise a gear mechanism that engages both the distal and proximal ends of the heart valve. If the heart valve is of the rolled type having multiple wound layers, the gear mechanism may have a gear shaft that engages an inner layer of the spirally wound heart valve and a retaining bar that engages an outer layer of the spirally wound heart valve, wherein the distance between the gear shaft and retaining bar is adjustable. 
     Another aspect of the invention is a system for delivering and deploying an expandable prosthetic heart valve to a site of implantation, comprising a catheter for advancing the heart valve in a contracted configuration to the site of implantation, and a stabilization device provided on the catheter sized to expand and contact a surrounding vessel adjacent the site of implantation. The system also has means on the catheter distal to the stabilization device for expanding the heart valve from its contracted configuration to an initial expanded configuration in contact with the surrounding site of implantation. The stabilization device may be a balloon shaped so as to permit blood flow past it in its expanded configuration, such as for example with multiple outwardly extending lobes. 
     A method for delivering and deploying a self-expandable prosthetic heart valve to a site of implantation is also provided by the present invention. The method comprises: 
     advancing the heart valve in a contracted configuration to the site of implantation; 
     permitting the heart valve to self-expand from its contracted configuration to an initial expanded configuration in contact with the surrounding site of implantation; and 
     regulating the rate of self-expansion of the heart valve. 
     In the preferred method, the step of advancing the heart valve in a contracted configuration to the site of implantation comprises providing a heart valve deployment mechanism that in one operating mode maintains the heart valve in the contracted configuration, and in another operating mode regulates the rate of self-expansion of the heart valve. The heart valve deployment mechanism may have a plurality of proximal deployment members that engage a proximal end of the valve, and a plurality of distal deployment members that engage a distal end of the valve, and wherein coordinated radial movement of the proximal and distal deployment members regulates the rate of self-expansion of the heart valve. Alternatively, the heart valve deployment mechanism includes a gear shaft having a plurality of gear teeth that engage a gear track provided on the heart valve, wherein the rate of self-expansion of the heart valve is regulated by regulating the rotational speed of the gear shaft. 
     The preferred method further includes expanding the heart valve from its initial expanded configuration to a final expanded configuration. Also, a catheter-based valve deployment mechanism may be provided having deployment members that both regulate the rate of self-expansion of the heart valve and expand the heart valve from its initial expanded configuration to its final expanded configuration. Alternatively, a catheter-based valve deployment mechanism may be provided having deployment members that regulate the rate of self-expansion of the heart valve, and an inflation balloon expands the heart valve from its initial expanded configuration to its final expanded configuration. In the latter case, the valve inflation balloon is separate from the deployment mechanism and is introduced into the valve after at least a partial expansion thereof. The method further desirably includes stabilizing the heart valve in its contracted configuration adjacent the site of implantation prior to permitting the heart valve to self-expand. The step of stabilizing the heart valve may involve inflating a stabilization balloon, and also permitting blood flow past the inflated stabilization balloon. 
     A further understanding of the nature and advantages of the invention will become apparent by reference to the remaining portions of the specification and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevational view of an exemplary expandable heart valve delivery and deployment system of the present invention with a catheter shaft shown broken so as to illustrate the main components thereof; 
         FIG. 2  is a perspective view of the distal end of the delivery system of  FIG. 1  showing a heart valve in its expanded configuration; 
         FIG. 3A  is a longitudinal sectional view through a portion of the distal end of the delivery and deployment system of  FIG. 1  illustrating part of a mechanism for controlling the expansion of a heart valve, which is shown in its contracted configuration; 
         FIG. 3B  is a longitudinal sectional view as in  FIG. 3A  showing the heart valve expanded; 
         FIG. 4  is a perspective view of the distal end of an alternative heart valve delivery and deployment system of the present invention showing a heart valve in its contracted configuration; 
         FIG. 5A  is a perspective view of the delivery and deployment system of  FIG. 4  showing the heart valve in its expanded configuration and an inflated stabilization balloon; 
         FIG. 5B  is a perspective view as in  FIG. 5A  illustrating a final step of deployment of the heart valve; 
         FIG. 6A  is an enlarged elevational view of a portion of the distal end of the delivery and deployment system of  FIG. 4 ; 
         FIG. 6B  is an enlarged longitudinal sectional view of the portion of the distal end of the delivery and deployment system seen in  FIG. 6A ; 
         FIGS. 7A-7F  are perspective views showing a number of steps in the delivery and deployment of an expandable heart valve using the system of  FIG. 4 ; 
         FIG. 8  is a perspective view of the distal end of a second alternative delivery and deployment system of the present invention showing a heart valve in its expanded configuration; 
         FIG. 9  is a perspective view of the distal end of the second alternative delivery and deployment system shown as in  FIG. 8  without the heart valve; 
         FIG. 10  is a perspective view of the distal end of the delivery and deployment system of  FIG. 8  shown in a mode of operation that expands the heart valve outward into a locked position; 
         FIG. 10A  is an enlarged sectional view of a portion of the distal end of the second alternative delivery and deployment system as taken along line  10 A- 10 A of  FIG. 10 ; 
         FIGS. 11A-11F  are perspective views showing a number of steps in the delivery and deployment of an expandable heart valve using the system of  FIG. 8 ; 
         FIG. 12  is a perspective view of the distal end of a third alternative delivery and deployment system of the present invention that utilizes a gearing mechanism and showing a heart valve in its expanded configuration; 
         FIG. 12A  is an enlarged sectional view of a portion of the distal end of the third alternative delivery and deployment system as taken along line  12 A- 12 A of  FIG. 12 ; 
         FIG. 13  is an enlarged perspective view of a portion of the delivery and deployment system of  FIG. 12  shown without the heart valve; and 
         FIG. 14  is a plan view of a stent of an expandable heart valve of the present invention for use with the third alternative delivery and deployment system as seen in  FIG. 12 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention discloses a number of expandable heart valves for implantation in a host annulus, or host tissue adjacent the annulus. The valves may be implanted in any of the four valve positions within the heart, but are more likely to be used in replacing the aortic or mitral valves because of the more frequent need for such surgery in these positions. The patient may be placed on cardiopulmonary bypass or not, depending on the needs of the patient. 
     A number of expandable prosthetic heart valves are disclosed in co-pending U.S. application Ser. No. 09/815,521 that are initially rolled into a tight spiral to be passed through a catheter or other tube and then unfurled or unrolled at the implantation site, typically a valve annulus. These will be denoted “rolled heart valves” and comprise one- or two-piece sheet-like stent bodies with a plurality of leaflet-forming membranes incorporated therein. Various materials are suitable for the stent body, although certain nickel-titanium alloys are preferred for their super-elasticity and biocompatibility. Likewise, various materials may be used as the membranes, including biological tissue such as bovine pericardium or synthetic materials. It should also be noted that specific stent body configurations disclosed herein or in U.S. application Ser. No. 09/815,521 are not to be considered limiting, and various construction details may be modified within the scope of the invention. For example, the number and configuration of lockout tabs (to be described below) may be varied. 
     As a general introduction, the heart valves in a first, spirally-wound or contracted configuration are delivered through a tube such as a percutaneously-placed catheter or shorter chest cannula and expelled from the end of the tube in the approximate implantation location. The heart valve is then expanded into a second, unwound or expanded configuration that engages the native host tissue, such as the target valve annulus. Depending on the native valve being replaced, the prosthetic heart valve may have varying axial lengths. For example, in the aortic position, an outflow portion of the valve may extend upward into and even flare out and contact the aorta to better stabilize the commissure regions of the valve. In other words, the particular design of the valve may depend on the target valve location. 
     The present invention is particularly adapted for delivering and deploying self-expandable rolled heart valves, although those of skill in the art will recognize that certain embodiments may be adapted for deploying plastically deformable rolled heart valves. Self-expandable stents in general are known, typically constructed of a tubular metal lattice that has a normal, relaxed diameter and is compressed for insertion into a vein or artery. Upon expulsion from the end of a catheter, the tubular metal lattice expands to its original larger diameter in contact with the vessel wall. It is important to note that there is no regulation of the self-expansion of the stent, as the tube reliably assumes its larger shape. 
     A number of embodiments of the present invention will now be described with reference to the attached drawings. It should be understood that the various elements of any one particular embodiment may be utilized in one or more of the other embodiments, and thus combinations thereof are within the scope of the appended claims. 
       FIG. 1  illustrates an exemplary system  20  for delivering and deploying an expandable heart valve. The main elements of the system  20  include a proximal operating handle  22 , a catheter shaft  24  extending distally from the handle and shown broken to fit on the page, a heart valve deployment mechanism  26 , and a guidewire  28  typically extending entirely through the system. The expandable heart valve  30  is seen held in a contracted configuration between a distal collet body  32  and a proximal collet body  34  of the deployment mechanism  26 . The system may further include a stabilization balloon  36  provided on the catheter shaft  24  just proximal the deployment mechanism  26 . 
     Prior to describing the exemplary deployment mechanism  26 , and alternative mechanisms, in greater detail, an overview of the techniques for using the system  20  is appropriate. For this discussion, it will be assumed that the heart valve  30  will be implanted in the aortic position. 
     Prior to introduction of the distal end of the system  20  into the patient, the expandable heart valve  30  is selected based on a measurement of the aortic annulus. Various sizing methodology are available, a discussion of which is outside the scope of the present invention. The selected heart valve  30  may be initially wound into a tight spiral in its storage container, or it may be stored expanded and then wound into its contracted configuration just prior to use. For this purpose, co-pending U.S. application Ser. No. 09/945,392, entitled Container and Method for Storing and Delivering Minimally-Invasive Heart Valves, filed Aug. 30, 2001, now U.S. Pat. No. 6,723,122, which is expressly incorporated herein, may be used. That application discloses a system for storing and then automatically converting an expandable valve into its contracted shape while still in the storage container. Additionally, the valve  30  may be stored along with the deployment mechanism  26  as a modular unit. In that case, the deployment mechanism  26  and valve  30  may be snapped onto or otherwise coupled with the distal end of the catheter shaft  24 . This enables one operating handle  22  and catheter shaft  24  to be used with a number of different valve/deployment mechanism units. After those of skill in the art have an understanding of the various control or actuation shafts/cables described herein, the coupling structure should be relatively straightforward, and thus a detailed explanation will not be provided. 
     The guidewire  28  is first inserted into a peripheral artery, such as the femoral or carotid, using known techniques, and advanced through the ascending aorta into the left ventricle. The catheter shaft  24  with the deployment mechanism  26  on its leading or distal end is then passed over the guidewire  28 , possibly with the assistance of an intermediate sized obturator, and into the peripheral vessel via the well-known Seldinger method. The operator then advances and positions the deployment mechanism  26  in proximity to the implantation site, in this case the aortic annulus, using visualization devices such as radiopaque markers on the deployment mechanism  26  or heart valve  30 , or an endoscope. Advancement of the deployment mechanism  26  involves simply pushing the entire catheter shaft  24  along the guidewire  28  using the handle  22 . Once the valve  30  is properly positioned, the operator expands the stabilization balloon  36  into contact with the surrounding aorta. In this manner, the heart valve  30  is both axially and radially anchored with respect to the surrounding annulus to facilitate proper engagement therewith. The stabilization balloon  36  may be shaped to permit blood flow in its expanded configuration for beating heart surgeries. 
     Expansion of the heart valve  30  may be accomplished in various ways, as will be described in greater detail below. Operation of the deployment mechanism  26  involves manipulation of cables, shaft, or other elongated devices passing from the operating handle  22  through the catheter shaft  24 . These elongated devices may be utilized to transfer axial (push/pull) forces or rotational torque initiated in the handle  22  to various elements of the deployment mechanism  26 . The present application will not focus on specific mechanisms in the handle  22  for initiating the forces on the cables or shafts passing through the catheter shaft  24 , as numerous such apparatuses are known in the art. 
     Now with reference to  FIG. 2 , the distal end of the delivery and deployment system  20  is illustrated with the deployment mechanism  26  holding the generally tubular heart valve  30 . The heart valve  30  is shown in an expanded configuration with a portion cut away to illustrate a lockout balloon  40  therewithin. The heart valve  30  has a rolled configuration and includes a generally sheet-like stent body  42  that unwinds from a tight spiral into an expanded tube having a distal end  44   a  and a proximal end  44   b . A plurality of distal deployment members or fingers  46  extending proximally from the distal collet body  32  engage the valve body distal end  44   a , while a plurality of proximal deployment fingers  48  extending distal from the proximal collet body  34  engage the valve body proximal end  44   b . It should be noted that various features of the heart valve  30 , such as the valve leaflets, are not illustrated for clarity. 
     The inflated stabilization balloon  36  is shown having generally a disk-shape, although other shapes are contemplated, such as a lobed-shape to permit blood flow, as will be described below. A cross-section of the catheter shaft  24  illustrates a plurality of outer lumens  50  surrounding a central lumen  52 . The lumens  50  may be used for inflating the balloon  36 ,  40 , or for passing fluid or the devices therethrough. The central lumen  52  is typically used for passage of the cables or shafts for operating the deployment mechanism  26 . 
       FIGS. 3A and 3B  illustrate in cross-section the details of the distal end of the deployment mechanism  26 , and specifically the distal collet body  32 .  FIG. 3A  shows the heart valve body  42  in its contracted configuration with multiple spirally wound layers  60   a - 60   e , while  FIG. 3B  shows the valve body  42  in its expanded configuration having only one layer  62 . The distal deployment fingers  46  each possesses a flexible claw  64  that directly engages the outer layer  60   a  of the valve body  42 . The flexible claw  64  has an initial curved set indicated in dashed line that applies a radially inward spring force to the valve body  42 . When in the position of  FIG. 3A , the claw  64  flexes outward into a generally linear configuration, and helps prevent damage to the valve body by the fingers  46 ,  48 . At least two of the fingers  46 ,  48  on each end, and preferably three or more, retain the valve body  42  in its spirally wound or contracted configuration during delivery through the vascular system to the site of implantation. It should be noted also that the distal collet body  32  has a rounded, generally bullet-shaped nose  66  that facilitates introduction into and passage through the vascular system. 
     As seen in  FIG. 3A , each of the fingers  46  initially resides within an axial channel  70  formed in the collet body  32  and pivots outward in a radial plane in the direction of arrow  72  about a collet pin  74  fixed in the collet body across the channel. In the radially inward configuration of  FIG. 3A , the fingers  46  are recessed within the channels  70  to present a low introduction profile for the deployment mechanism  26 . Each of the fingers  46  includes a lever  76  that engages a depression  78  within a distal driver  80 . The driver  80  reciprocates axially within a cavity  82  formed within the distal collet body  32 , as indicated by the double-headed movement arrow  84 . From the position shown, proximal movement of the driver  80  with respect to the collet body  32  acts on the lever  76  to pivot the finger  46  outward in the direction of arrow  72 . The lever  76  is shown rounded so as to easily slide within the similarly shaped though concave depression  78 . Of course, other arrangements for coupling axial movement of the distal driver  80  to rotational movement of the finger  46  are possible. 
     A distal driver shaft  90  extends over the guidewire  28  to be fixed within a bore of the distal driver  80 . Likewise, the distal collet shaft  92  is concentrically disposed about the distal driver shaft  90  and is fixed within a bore of the distal collet body  32 . All these elements are thus coaxial about the guide wire  28 . Axial movement of the shafts  90 ,  92  causes axial movement of the driver  80  and collet body  32 , respectively. Collet movement is indicated by the double-headed arrow  94 . In the initial delivery configuration of  FIG. 3A , the collet body  32  is positioned distally from the distal end  44   a  of the valve body  42 . 
     In operation of the deployment mechanism  26  of  FIG. 2 , as best seen in  FIG. 3B , the distal driver  80  is displaced within the cavity  82  by relative movement of the distal driver shaft  90  and distal collet shaft  92 , and interaction between the lever  76  and depression  78  causes outward pivoting motion of the finger  46 . Because the valve body  42  is annealed into its expanded configuration, outward pivoting of the fingers  46  permits expansion thereof. 
     Therefore, the valve body  42  converts from its spirally wound configuration with multiple spirally-wound layers  60   a ,  60   e  as seen in  FIG. 3A , to the expanded configuration of  FIG. 3B  having the single layer  62 . During this expansion, contact between the flexible claws  64  and the outer layer  60   a  of the valve body  42  is maintained by controlling the relative movement between the distal driver  80  and the distal collet body  32 . This contact between the claws  64  and valve body  42  regulates the speed or rate of expansion of the valve body, thus preventing any mis-alignment problems. That is, because of the provision of both the distal collet body  32  and proximal collet body  34 , and associated fingers  46  and  48 , the rate of expansion of both the distal end  44   a  and proximal end  44   b  of the valve body  42  can be equilibrated. Because both ends of the valve body  42  expand at the same rate, the valve forms a tube father than potentially expanding into a partial cone shape. 
     It is important to note that during transition of the valve body  42  from its contracted to its expanded configuration, the distal collet body  32  moves in a proximal direction with respect to the valve body  42  as indicated by the movement arrow  96 . The reader will note the different relative positions of the proximal end of the collet body  32  with respect to the distal end  44   a  of the valve body  42  in  FIGS. 3A and 3B . This collet body  32  movement results from relative movement of the distal collet shaft  92  with respect to the valve body  42 , which body position is determined by the position of the proximal fingers  48 , or by a supplemental shaft (not shown) coupled to the operating handle  22 . Because of the proximal collet body  32  movement with respect to the valve body  42 , the flexible claws  64  maintain the same axial position with respect to the valve body  42  during outward pivoting of the fingers  46 . That is, outward pivoting of the fingers  46  causes both radially outward and distal axial movement of the claws  64  with respect to collet pin  74 , and the axial component of movement must be accommodated by movement of the collet body  32  or else the claws  64  would disengage the valve body  42 . The distal collet body  32  includes a frusto-conical proximal end  98  that facilitates displacement of the collet body into the partially unwound valve body  42 , and prevents binding therebetween. 
     The valve body  42  expands outward under regulation of the fingers  46 ,  48  until it contacts the surrounding host tissue. The valve body  42  has an annealed shape such that its relaxed configuration is open, with its inner and outer side edges being spaced apart. As such, the valve body  42  will continue to expand until it contacts the surrounding tissue, as long as the final tubular size of the valve is larger than the site of implantation. Therefore, proper sizing of the valve is extremely important. 
     Once the valve body  42  contacts the surrounding tissue, it has reached its initial expanded state. At this stage, the deployment fingers  46 ,  48  remain outwardly pivoted but are moved apart by relative axial movement of the collet bodies  32 ,  34  away from each other so as to disengage the claws  64  from the distal and proximal ends  44   a ,  44   b  of the valve body  42 . Once disengaged from the valve, the fingers  46 ,  48  may be retracted into their respective channels  70 . Subsequently, inflation of the lockout balloon  40  ( FIG. 2 ) further expands the valve body  42  into more secure engagement with the surrounding tissue until lockout features on the valve body engage and secure the valve body in its final expanded configuration. These lockout features are fully described in co-pending U.S. application Ser. No. 09/815,521, which disclosure is hereby expressly incorporated by reference. 
     The lockout balloon  40  resides initially in the catheter shaft  24  or even outside of the body during the first phase of expansion of the valve body  42 . Because the valve body  42  advances through the vasculature in a relatively tight spiral so as to minimize its radial profile for minimally invasive surgeries, the lockout balloon  40  is preferably not positioned in the middle thereof. Of course, this constraint is necessary only when the insertion space is limited, and if the surgery is open heart or otherwise not so space-limited then the balloon  40  may indeed be initially positioned inside and delivered along with the valve. In the preferred minimally invasive deployment, however, the balloon must be introduced within the valve body  42  after at least a partial expansion or unwinding thereof. Typically, the valve body  42  expands into its initial expanded configuration in contact with the surrounding tissue before the lockout balloon  40  advances into its position as seen in  FIG. 2 , although the balloon may be advanced into the valve as soon as a sufficient space in the middle of the valve opens up. 
     The lockout balloon  40  preferably has a shape with enlarged ends and a connecting middle portion, much like a dumbbell. In this manner, the balloon acts on the proximal and distal ends of the valve body  42 , without contacting a middle portion where the leaflets of the valve are located. Of course, other arrangements of balloon are possible, as are multiple lockout balloons. 
     After the valve body  42  is fully implanted, the lockout balloon  40  is deflated and the catheter shaft  24  withdrawn from the body along the guide wire  28 . The proximal collet body  34  also has a bullet-shaped proximal end to facilitate this removal through the vasculature. 
       FIGS. 4-6B  illustrate the distal end of an alternative expandable heart valve delivery and deployment system  100  of the present invention that is in many ways similar to the first-described embodiment of  FIGS. 1-3B . Namely, as seen in  FIG. 4 , the system  100  includes a deployment mechanism  102  having a distal collet  104  with a plurality of deployment members or fingers  106 , and a proximal collet  108  having a plurality of deployment members or fingers  110 . The deployment fingers  106 ,  110  engage respective ends of a self-expandable heart valve  112 , which is shown in its contracted configuration. As in the earlier embodiment, the deployment fingers  106 ,  110  enable regulated self-expansion of the heart valve  112  to ensure the valve expands to the correct tubular shape. Although there are a number of constructional differences between the two embodiments, the main functional difference pertains to the manner in which flexible claws  114 ,  116  of the deployment fingers  106 ,  110  are maintained in particular axial locations with respect to the distal and proximal ends  118   a ,  118   b , respectively, of the valve  112 . In the first-described embodiment, the collets  32 ,  34  were axially displaced along with the drivers  80 , thus necessitating axial movement and coordination of four different shafts, while in the embodiment of  FIGS. 4-6B  movement of only two shafts are needed. This modification will become clear below. 
       FIG. 4  illustrates a stabilization balloon  120  in its folded or deflated configuration just proximal to proximal collet  108 .  FIG. 5A  shows the stabilization balloon  120  inflated and assuming a four-lobed star shape. The entire distal end of the system  100  is positioned at the distal end of a catheter shaft  122  and travels over a guide wire  124 . The stabilization balloon  120  is sized to expand and contact a surrounding vessel adjacent the site of implantation, such as the ascending aorta. The star shape of the stabilization balloon  120  permits blood flow in the expanded configuration of the balloon for beating heart surgeries, though of course other balloon shapes could be used. Furthermore, devices other than a balloon for stabilizing the distal end of the system  100  may be utilized. For example, a mechanical expanding structure having struts or a wire matrix may work equally as well as a balloon and also permit blood flow therethrough. Therefore, the term stabilization device refers to all of the above variants. 
       FIG. 5A  also illustrates the heart valve  112  in its initial expanded configuration such that a plurality of leaflet mounting windows  126  are visible. In this case, the leaflets are not shown for clarity so as to expose a distal collet shaft  128  extending through the middle of the valve between the proximal and distal collets  104 ,  108 . The heart valve  112  is permitted to expand into the shape shown in  FIG. 5A  by outward pivoting of the respective flexible claws  114 ,  116  of the deployment fingers  106 ,  110 . This pivoting occurs by proximal movement of a distal driver  130  with respect to the distal collet  104 , and distal movement of a proximal driver  132  with respect to the proximal collet  104 . The change in the relative positions of the drivers  130 ,  132  and collets  104 ,  108  may be seen by comparison of  FIG. 4  and  FIG. 5A . 
       FIG. 5B  shows the deployment mechanism  102  during a valve deployment phase that converts the valve  112  from its initial expanded configuration to a final expanded or locked out configuration. The deployment fingers  106 ,  110  have been displaced so that they reside within the tubular valve  112  and are then in a position to be once again pivoted outward, as indicated by the arrows  134 , into contact with the valve. In this case, therefore, a separate lockout balloon within the valve  112 , such as balloon  40  in  FIG. 1 , may not be necessary, unless the additional expansion force is required. A full sequence of operation of the deployment system  100  will be described below with respect to  FIGS. 7A-7F  after an exemplary construction of the system is explained. 
       FIGS. 6A and 6B  illustrate, in elevational and sectional views, respectively, the proximal end of the deployment system  102  with the fingers  110  pivoted open to an intermediate position during the stage of self-expansion of the valve  112  from its contracted configuration to its initial expanded configuration. The flexible claws  116  are shown in contact with the exterior of the valve body  112 , with their curved set shown in phantom. The direction of movement of the fingers  110  is indicated in both views by the movement arrow  136 . 
     With specific reference to  FIG. 6B , the collet  108  includes a central through bore (not numbered) that slidingly receives the distal collet shaft  128 . The distal collet shaft  128 , in turn, slidingly receives a distal driver shaft  140 , which directly travels over the guidewire  124 . Each of the deployment fingers  110  resides within an axial collet channel  144  that extends from the distal end of the collet  108  into proximity with a cavity  146  located on the proximal end. The proximal driver  132  reciprocates within the cavity  146  and includes a through bore (not numbered) that slides over a tubular boss  148  extending proximally from the collet  108 . The driver  132  includes a proximal tubular flange  150  that closely receives and is fixed with respect to a proximal driver shaft  152 . A proximal collet shaft  154  mounts to the exterior of the tubular boss  148  of the collet  108 , and is adapted to slide within the proximal driver shaft  152 . By virtue of the four shafts  128 ,  140 ,  152 , and  154 , the collets  104 ,  108  and drivers  130 ,  132  may be axially displaced with respect to one another. 
     The proximal collet  108  carries a plurality of collet pins  116  that are fixed across an approximate midpoint of each of the collet channels  144  and are received within curved finger cam slots  162 . As mentioned previously, two, and preferably three fingers  110  are required for reliable regulation of the self expansion of the valve  112 , and there are an equivalent number of collet channels  144  and pins  160 . The finger cam slots  162  are disposed in the middle of each finger  110 , and the finger also carries a pin  166  fixed to its proximal end. As seen best in  FIG. 6A , each finger pin  166  travels along a curvilinear collet cam slot  168 . The finger pins  166  are each also constrained by a linear driver travel slot  170  that is best seen in  FIG. 6B . With reference again to  FIG. 6A  each finger  110  includes a flange portion  172  that is received in a driver channel  174  formed between bifurcated walls  176  of the proximal driver  132 . The driver travel slot  170  is thus formed in both walls  176 . 
     Movement of the various components of the proximal end of the deployment mechanism  102  is depicted in  FIG. 6B . The outward pivoting motion of the finger  110  is indicated by arrow  136 . The outward finger movement is accomplished by distal movement of the finger  110  with respect to the collet pin  160  which travels from the upper right end of the finger cam slot  162  to the lower left end. Because the collet pin  160  is fixed with respect to the collet  108 , the finger  110  moves outward by the caroming action of the pin  160  within the slot  162 . Distal movement of the finger  110  is caused by movement in the distal direction of the driver  132  with respect to the collet  108 , as indicated by arrow  180 , due to the engagement between the driver travel slot  170  and the finger pin  166 . As the finger pin  166  moves in the distal direction, it travels along the curvilinear collet cam slot  168 . The linear driver travel slot  170  accommodates radially inward movement of the finger pin  166  in this regard. 
     The shapes of the finger cam slot  162  and collet cam slot  168  are designed such that the claw  116  at the distal end of the finger  110  moves radially outward but remains in the same axial position. Furthermore, this movement of the finger  110  is accomplished by maintaining the proximal collet  108  in a fixed relationship with respect to the valve body  112 , while only displacing the proximal driver  132  in a distal direction, indicated by arrow  180 . As such, only the proximal driver cable  152  need be displaced. In the same manner, only the distal driver shaft  140  need be displaced with respect to the distal collet shaft  128  to actuate the distal deployment fingers  106  ( FIG. 4 ). Indeed, the distal and proximal collets  104 ,  108  remain stationary with respect to the valve  112  while the distal and proximal drivers  130 ,  132  are displaced toward one another. Likewise, the fingers  106 ,  110  are retracted radially inwardly by opposite movement of the drivers  130 ,  132 . 
     A sequence of steps in the delivery and deployment of a heart valve utilizing the deployment mechanism  102  of  FIG. 4  is seen in  FIGS. 7A-7F .  FIG. 7A  shows the deployment mechanism and heart valve in their radially contracted configurations such that the entire assembly resembles an elongated bullet for easy passage through the vasculature of the patient, which is indicated by a generic vessel  190 . After reaching the site of implantation, the valve  112  is permitted to self expanded under control of the deployment fingers. Namely, the proximal and distal drivers move axially toward one another permitting the fingers to pivot open which in turn allows the spirally wound expandable heart valve to unwind. The heart valve unwinds at a controlled rate into its initial expanded configuration in contact with the surrounding tissue, as explained above. 
     Now with reference to  FIG. 7C , the distal and proximal collets are axially displaced away from one another so that the claws at the end of the fingers release from the ends of the heart valve. Subsequently, as seen in  FIG. 7D , movement of the proximal and distal drivers away from one another and with respect to the associated collets retracts the fingers inward a slight amount.  FIG. 7E  shows the deployment mechanism after the collets have been axially advanced toward one another such that the claws at the end of the fingers are disposed within the heart valve. In a final deployment step, as seen in  FIG. 7F , the proximal and distal drivers are again advanced toward one another and with respect to the stationary collets so that the fingers pivot outward into contact with the interior of the valve. The fingers force the valve outward against the surrounding vessel and into its locked position. The deployment mechanism is then removed from the body by retracting the deployment fingers and pulling the catheter along the guide wire. 
       FIGS. 8-10A  illustrates a second alternative heart valve delivery and deployment system  200  of the present invention that operates in much the same manner as the first two embodiments described above, although without pivoting deployment members.  FIG. 8  illustrates the distal end of the system  200  with an expandable heart valve  202  held therewithin in its initial expanded configuration.  FIG. 9  illustrates the distal end of the system  200  in the same configuration but without the heart valve. The system  200  includes a valve deployment mechanism  204  having a plurality of distal deployment pads  206  and a plurality of proximal deployment pads  208  that engage the valve  202 . The pads  206 ,  208  are shown in  FIG. 8  on the exterior of the valve that enables the aforementioned control of the valve self-expansion. The pads  206 ,  208  are desirably relatively rigid and have rounded edges and/or are otherwise coated with a material that prevents damage to the valve  202 . 
     With specific reference to  FIG. 9 , each of the distal pads  206  (preferably three) couples to a distal end cap  210  via a tension spring  212 . Likewise, each of the proximal pads  208  (preferably three) couples to a proximal end cap  214  via a tension spring  216 . The springs  212 ,  216  exert radially inward forces on each of the pads  206 ,  208 . The end caps  210 ,  214  are mounted on separately movable shafts such that their axial spacing may be varied. 
       FIG. 10  illustrates the deployment mechanism  204  in a deployment stage that converts the heart valve from its initial expanded configuration to its final, locked out configuration.  FIG. 10A  is a longitudinal sectional view taken along line  10 A- 10 A of  FIG. 10  and shows in detail the various components of the distal end of the deployment mechanism  204 . The distal end cap  210  is shown having a recess in its distal end that houses a plurality of shafts  220  about which coils each tension spring  212 . The radial position of each pad  206  is controlled by use of a distal wire tong  222  that is highly flexible but possesses column strength. Various nickel-titanium alloys are well-suited for use as the wire tongs  222 . Each tong  222  attaches to an inner side of a distal pad  206  and extends radially inward through a 90 degree channel formed in the distal end cap  210  into fixed engagement with a tong driver  224 . The tong driver  224  attaches to a tong driver shaft  226  and is adapted for axial movement within the mechanism  204 . The tong driver shaft  226  fits closely and is linearly slidable over a distal end cap shaft  228  fixed to a bore in the end cap  210 . The distal end cap shaft  228  includes a lumen that closely receives a guidewire (not shown) used in positioning the heart valve at the site of implantation. 
     For the purpose of describing radial movement of the distal pads  206  with reference to  FIG. 10A , the reader will ignore the interposition of a plurality of expansion bars  230  and brace links  232 . Initially, the tong driver  224  is positioned to the right of where it is located in  FIG. 10A  and toward a distal slide collar  234 . As such, the majority of the distal wire tong  222  is pulled through the distal end cap  210  such that its radial length is minimized, in contrast to the illustration. Therefore, the distal pads  206  are pulled radially inward and constrain the heart valve in its spirally wound configuration. During regulating self-expansion of the valve, the tong driver shaft  226  is advanced in the distal direction with respect to the end cap shaft  228  such that the tong driver  224  moves to the left, pushing the distal wire tongs  222  radially outward. Because of the column strength of the wire tongs  222 , this operation forces the distal pads  206  radially outward against the inward forces of the tension springs  212 , and permits the spirally wound valve to unwind. 
     The final outward position of the distal and proximal pads  206 ,  208  is seen in  FIG. 9 .  FIG. 9  also illustrates the distal tong shaft  226  and the distal end cap shaft  228 , along with a proximal tong shaft  236  and a proximal end cap shaft  238 . Again, regulated self-expansion of the heart valve is accomplished by holding the end cap shafts  228 ,  238  stationery, while displacing the tong shaft  226 ,  236  away from one another. Because the pads  206 ,  208  displace directly radially outward, there is no need for any accommodating axial movement as with the earlier pivoting finger embodiments. 
     After permitting the heart valve  202  to self-expand to its initial expanded configuration as seen in  FIG. 8 , the pads  206 ,  208  are repositioned inside the valve and displaced outward to force the valve further outward into its final, expanded configuration. The position of the deployment mechanism  204  in this phase of the deployment operation is seen in  FIGS. 10 and 10A . It will be noted that various components of the distal end of the deployment mechanism  204  will be numbered the same on the proximal end. 
     As seen in  FIG. 10A , each of the expansion bars  230  pivots at one end about a point  239  on the respective slide collar  234 . The opposite end of each expansion bar  230  is free to pivot radially outward into contact with the inner side of one of the pads  206 ,  208 . Each brace link  232  pivots at one end about a point  240  at the midpoint of an expansion bar  230 , and at the other and about a pivot point  242  fixed with respect to one of the end caps  210 . Axial movement of the end caps  210  toward one another causes the expansion bars  230  to pivot outward by virtue of their connection to the end caps through the brace links  232 . This umbrella-like expansion structure provides substantial strength in forcing the heart valve  202  into its locked out position. 
       FIGS. 11A-11F  illustrate several stages in the use of the second alternative deployment mechanism  204  to deliver and deploy the heart valve  202 .  FIG. 11A  shows the assembly in its radially contracted configuration for delivery through the patient&#39;s vasculature.  FIG. 11B  illustrates release of the wire tongs to push the pads radially outward which permits controlled self-expansion of a heart valve to its initial expanded configuration. In  FIG. 11C , the end caps are axially displaced away from one another so that the pads disengage from the heart valve. In this regard, the tension provided by springs  212 ,  216  on the pads  206 ,  208  provides an axial force that helps disengage the pads from between the valve and the surrounding tissue. At this stage, the wire tongs remain pushed radially outward.  FIG. 11D  shows the end caps in the same axial position but after the wire tongs have been retracted such that the tension springs pull the pads inward. In  FIG. 11E , the end caps are displaced axially toward one another which causes the expansion bars to pivot outward, and in addition, the pads moved inside the valve. Finally,  FIG. 11F  shows further end cap movement toward each other such that the expansion bars push the pads radially outward in conjunction with movement of the wire tongs so as to further expand the valve into its locked out configuration. 
       FIGS. 12-13  illustrate the distal end of a further alternative heart valve delivery and deployment system  300  that utilizes a gearing mechanism to expand a heart valve  302  into its initial and final expanded configurations. The system includes a deployment mechanism  304  at the distal end of a shaft  306  having a distal end keeper  308  and retaining bar  310  and a proximal end keeper  312  and retaining bar  314 . The axial spacing between the distal and proximal end keepers  308 ,  312  may be varied by movement of a connecting rod  316  ( FIG. 12A ) about which a gear shaft  318  rotates. The heart valve  302  includes a sheet-like stent body bordered by a distal end  320 , a proximal end  322 , an outer side edge  324 , and an inner side edge (not shown). The stent body further includes a distal gear track  326  extending circumferentially adjacent the distal end  320  and a proximal gear track  328  extending circumferentially adjacent the proximal end  322 . The assembly rides over a guide wire  330  as mentioned previously. 
     With reference to  FIGS. 12A and 13 , details of the distal end keeper  308  and retaining bar  310  will be described. The retaining bar  310  extends axially in a proximal direction from the end keeper  308  includes an inwardly formed tab  340  that engages a retaining slot  342  in an outer valve body winding  344  adjacent to the outer side edge  324 .  FIG. 12A  illustrates in cross-section an inner winding  346  spaced from the outer winding  344  by a distance A. Of course, there may be more than two windings of the valve body in the contracted configuration thereof, as previously illustrated, for example, in  FIG. 3A . Therefore, the distance A varies as the valve unwinds. 
     The gear shaft  318  includes gear teeth  350  positioned to engage the distal gear track  324 . In a similar manner, a second set of gear teeth (not shown) is provided on the proximal end of the gear shaft  318  to engage the proximal gear track  326 . As mentioned, the gear shaft  318  rotates about the connecting rod  316 , which is held by a shaft retainer  352  in a winding variance slot  354  in the distal end keeper  308 . The end of the connecting rod  316  includes a flat or other such feature that registers with a cooperating feature in the winding variance slot  354  to prevent rotation of the rod, and provide a counter-torque to rotation of the gear shaft  318 . The slot  354  is elongated in the radial direction to permit radial movement of the connecting rod  316  and accompanying gear shaft  318 . Provision of a pusher  356  spring loaded against the connecting rod  316  by a spring  358  and set screw  360  maintains the gear teeth  350  in engagement with the gear track  324 . 
     With reference to  FIG. 12 , it can be seen that the deployment mechanism  304  remains circumferentially fixed with respect to the outer side edge  324  by virtue of the engagement between the retaining bar tabs  340  and retaining slots  342 . The gear shaft  318 , on the other hand, circumferentially displaces the inner winding  346  in a direction that unwinds the valve from its contracted configuration to its expanded configuration. During the unwinding process, the distance A between the outer winding  34  and the inner winding  346  is regulated by the spring loaded pusher  356 . The valve  302  may be converted to its initial expanded configuration, and then further balloon expanded to a final lockout position, or the deployment mechanism  304  can fully expand the valve into its lockout position. When the deployment mechanism  304  is no longer needed, the end keepers  308 ,  312  are displaced axially apart such that the retaining bars  310 ,  314  disengage from their respective retaining slots  342 . The deployment mechanism  304  can then be pulled over the guide wire  330  from within the deploying valve. 
     One advantage of such a deployment system  300  that utilizes a gearing mechanism is that both unwinding and winding of the valve  302  may be easily controlled. Therefore, the surgeon may initially expand the valve  302  but then contract it somewhat to modify its position prior to locking it into its final expanded shape. In the worst case, the valve  302  may be completely contracted into its thin profile and removed from the patient if desired, such as if the sizing is not optimal or from other complications. 
       FIG. 14  illustrates in plan view an exemplary aortic valve body  400  for use with a deployment mechanism similar to that shown in  FIG. 12 . The valve body  400  includes a distal end  402 , a proximal end  404 , an inner side edge  406 , and an outer side edge  408 . A distal gear track  410  is shown adjacent the distal end  402 , while a proximal gear track  412  extends along an outflow band  414 . A plurality of leaflet openings  416  is provided between the distal end  402  in the outflow band  414 . A flared mesh  418  separates the outflow band  414  from the proximal end  404 . A supplemental gear track  420  is provided adjacent the proximal end  404 . The distal, proximal, and supplemental retaining slots  422 ,  424 ,  426  are located adjacent the outer side edge  408  and receive respective retaining tabs from the retaining bars of the deployment mechanism. Finally, lockout tabs  430  are provided to engage lockout channels  432  and maintain the valve in its expanded configuration. 
     In contrast to the valve  302  shown  FIG. 12 , the flared mesh  418  extends in the outflow direction and may be used to engage the ascending aorta. To facilitate flaring of the mesh  418  during deployment of the valve, the supplemental gear track  420  has a smaller number of openings per length than the distal or proximal gear tracks  410 ,  412 . Likewise, the gear shaft utilized in deploying the valve body  400  has three sets of gear teeth, one of which has fewer teeth per rotation so as to mate with the supplemental gear track  420 . In this manner, the proximal end  404  is expanded at a faster rate then either the distal end  402  or outflow band  414  such that it flares outward with respect thereto. 
     While the foregoing describes the preferred embodiments of the invention, various alternatives, modifications, and equivalents may be used. Moreover, it will be obvious that certain other modifications may be practiced within the scope of the appended claims.