CROSS REFERENCES TO RELATED APPLICATIONS
This application is a divisional of U.S. Ser. No. 11/364,724, filed Feb. 27, 2006, which is fully incorporated by reference herein.
FIELD OF THE INVENTION
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The present invention relates generally to medical devices and methods. More particularly, the present invention relates to methods and devices for delivering and deploying prosthetic heart valves and similar structures using minimally invasive surgical methods.
BACKGROUND OF THE INVENTION
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Diseases and other disorders of the heart valve affect the proper flow of blood from the heart. Two categories of heart valve disease are stenosis and incompetence. Stenosis refers to a failure of the valve to open fully, due to stiffened valve tissue. Incompetence refers to valves that cause inefficient blood circulation by permitting backflow of blood in the heart.
Medication may be used to treat some heart valve disorders, but many cases require replacement of the native valve with a prosthetic heart valve. Prosthetic heart valves can be used to replace any of the native heart valves (aortic, mitral, tricuspid or pulmonary), although repair or replacement of the aortic or mitral valves is most common because they reside in the left side of the heart where pressures are the greatest. Two primary types of prosthetic heart valves are commonly used, mechanical heart valves and prosthetic tissue heart valves.
The caged ball design is one of the early mechanical heart valves. The caged ball design uses a small ball that is held in place by a welded metal cage. In the mid-1960s, another prosthetic valve was designed that used a tilting disc to better mimic the natural patterns of blood flow. The tilting-disc valves had a polymer disc held in place by two welded struts. The bileaflet valve was introduced in the late 1970s. It included two semicircular leaflets that pivot on hinges. The leaflets swing open completely, parallel to the direction of the blood flow. They do not close completely, which allows some backflow.
The main advantages of mechanical valves are their high durability. Mechanical heart valves are placed in young patients because they typically last for the lifetime of the patient. The main problem with all mechanical valves is the increased risk of blood clotting.
Prosthetic tissue valves include human tissue valves and animal tissue valves. Both types are often referred to as bioprosthetic valves. The design of bioprosthetic valves are closer to the design of the natural valve. Bioprosthetic valves do not require long-term anticoagulants, have better hemodynamics, do not cause damage to blood cells, and do not suffer from many of the structural problems experienced by the mechanical heart valves.
Human tissue valves include homografts, which are valves that are transplanted from another human being, and autografts, which are valves that are transplanted from one position to another within the same person.
Animal tissue valves are most often heart tissues recovered from animals. The recovered tissues are typically stiffened by a tanning solution, most often glutaraldehyde. The most commonly used animal tissues are porcine, bovine, and equine pericardial tissue.
The animal tissue valves are typically stented valves. Stentless valves are made by removing the entire aortic root and adjacent aorta as a block, usually from a pig. The coronary arteries are tied off, and the entire section is trimmed and then implanted into the patient.
A conventional heart valve replacement surgery involves accessing the heart in the patent'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.
A less invasive approach to valve replacement is desired. The percutaneous implantation of a prosthetic valve is a preferred procedure because the operation is performed under local anesthesia, does not require cardiopulmonary bypass, and is less traumatic. Current attempts to provide such a device generally involve stent-like structures, which are very similar to those used in vascular stent procedures with the exception of being larger diameter as required for the aortic anatomy, as well as having leaflets attached to provide one way blood flow. These stent structures are radially contracted for delivery to the intended site, and then expanded/deployed to achieve a tubular structure in the annulus. The stent structure needs to provide two primary functions. First, the structure needs to provide adequate radial stiffness when in the expanded state. Radial stiffness is required to maintain the cylindrical shape of the structure, which assures the leaflets coapt properly. Proper leaflet coaption assures the edges of the leaflets mate properly, which is necessary for proper sealing without leaks. Radial stiffness also assures that there will be no paravalvular leakage, which is leaking between the valve and aorta interface, rather than through the leaflets. An additional need for radial stiffness is to provide sufficient interaction between the valve and native aortic wall that there will be no valve migration as the valve closes and holds full body blood pressure. This is a requirement that other vascular devices are not subjected to. The second primary function of the stent structure is the ability to be crimped to a reduced size for implantation.
Prior devices have utilized traditional stenting designs which are produced from tubing or wire wound structures. Although this type of design can provide for crimpability, it provides little radial stiffness. These devices are subject to “radial recoil” in that when the device is deployed, typically with balloon expansion, the final deployed diameter is smaller than the diameter the balloon and stent structure were expanded to. The recoil is due in part because of the stiffness mismatches between the device and the anatomical environment in which it is placed. These devices also commonly cause crushing, tearing, or other deformation to the valve leaflets during the contraction and expansion procedures. Other stenting designs have included spirally wound metallic sheets. This type of design provides high radial stiffness, yet crimping results in large material strains that can cause stress fractures and extremely large amounts of stored energy in the constrained state. Replacement heart valves are expected to survive for many years when implanted. A heart valve sees approximately 500,000,000 cycles over the course of 15 years. High stress states during crimping can reduce the fatigue life of the device. Still other devices have included tubing, wire wound structures, or spirally wound sheets formed of nitinol or other superelastic or shape memory material. These devices suffer from some of the same deficiencies as those described above.
A number of improved prosthetic heart valves and scaffolding structures are described in co-pending U.S. patent application Ser. No. 11/066,126, entitled “Prosthetic Heart Valves, Scaffolding Structures, and Methods for Implantation of Same,” filed Feb. 25, 2005, (“the '126 application”) which application is hereby incorporated by reference in its entirety. Several of the prosthetic heart valves described in the '126 application include a support member having a valvular body attached, the support member preferably comprising a structure having three panels separated by three foldable junctions. The '126 application also describes several delivery mechanisms adapted to deliver the described prosthetic heart valve. Although the prosthetic heart valves and delivery systems described in the '126 application represent a substantial advance in the art, additional delivery systems and methods are desired, particularly such systems and methods that are adapted to deliver and deploy the prosthetic heart valves described therein.
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OF THE INVENTION
The present invention provides methods and devices for deploying prosthetic heart valves and other prosthetic devices in body lumens. The methods and devices are particularly adapted for use in percutaneous aortic valve replacement. The methods and devices may also find use in the peripheral vasculature, the abdominal vasculature, and in other ducts such as the biliary duct, the fallopian tubes, and similar lumen structures within the body of a patient. Although particularly adapted for use in lumens found in the human body, the apparatus and methods may also find application in the treatment of animals.
Without intending to limit the scope of the methods and devices described herein, the deployment devices and methods are particularly adapted for delivery of prosthetic heart valves and scaffolding structures identical or similar to those described in the '126 application described above. A particularly preferred prosthetic heart valve includes a generally cylindrical support structure formed of three segments, such as panels, interconnected by three foldable junctions, such as hinges, a representative embodiment of which is illustrated in FIG. 1A of the '126 application, which is reproduced herein as FIG. 1A. The exemplary prosthetic valve 30 includes a generally cylindrical support member 32 made up of three generally identical curved panels 36 and a valvular body 34 attached to the internal surface of the support member. Each panel includes an aperture 40 through which extends a plurality of interconnecting braces 42 that define a number of sub-apertures 44, 46, 48, 50. A hinge 52 is formed at the junction formed between each pair of adjacent panels. The hinge may be a membrane hinge comprising a thin sheet of elastomeric material 54 attached to the external edge 56 of each of a pair of adjacent panels 36.
Turning to FIG. 1B-C, a method for transforming a prosthetic valve from its expanded state to its contracted state is illustrated. These Figures show a three-panel support member without a valvular body attached. The method for contracting a full prosthetic valve, including the attached valvular body, is similar to that described herein in relation to the support member alone. As shown in FIG. 1B, each of the panels 36 is first inverted, by which is meant that a longitudinal centerline 80 of each of the panels 36 is forced radially inward toward the central longitudinal axis 82 of the support member. This action is facilitated by having panels formed of a thin, resilient sheet of material having generally elastic properties, and by the presence of the hinges 52 located at the junction between each pair of adjacent panels 36. During the inversion step, the edges 56 of each of the adjacent pairs of panels fold upon one another at the hinge 52. The resulting structure, shown in FIG. 1B, is a three-vertex 58 star shaped structure, referred to herein as a “tri-star” shape. Those skilled in the art will recognize that a similar procedure may be used to invert a four (or more) panel support member, in which case the resulting structure would be a four- (or more) vertex star shaped structure.
The prosthetic valve 30 may be further contracted by curling each of the vertices 58 of the star shaped structure to form a multi-lobe structure, as shown in FIG. 1C. As shown in that Figure, each of the three vertices 58 is rotated toward the center longitudinal axis 82 of the device, causing each of the three folded-upon edges of the adjacent pairs of panels to curl into a lobe 84. The resulting structure, illustrated in FIG. 1C, is a “tri-lobe” structure that represents the fully contracted state of the prosthetic valve. Those skilled in the art will recognize that a similar procedure may be used to fully contract a four (or more) panel support member, in which case the resulting structure would be a four- (or more) lobed structure.
The foregoing processes are performed in reverse to transform the prosthetic valve from its contracted state to its expanded state. For example, beginning with the prosthetic valve in its “tri-lobe” position shown in FIG. 1C, the three vertices 58 may be extended radially to achieve the “tri-star” shape shown in FIG. 1B. The “tri-star” shape shown in FIG. 1B is typically not stable, as the panels 36 tend to spontaneously expand from the inverted shape to the fully expanded shape shown in FIG. 1A unless the panels are otherwise constrained. Alternatively, if the panels do not spontaneously transition to the expanded state, it will typically only require a slight amount of force over a relatively short amount of distance in order to cause the panels to fully expand. For example, because of the geometry of the three panel structure, a structure having an expanded diameter of about 21 mm would be fully expanded by insertion of an expanding member having a diameter of only 16 mm into the interior of the structure. In such a circumstance, the 16 mm diameter member would contact the centerline of each panel and provide sufficient force to cause each panel to transform from the inverted shape shown in FIG. 1B to the fully expanded shape shown in FIG. 1A. This is in contrast to a typical “stent”-like support structure, which requires an expanding member to expand the stent to its full radial distance.
Additional details of this and other embodiments of the prosthetic heart valve and scaffolding structures are provided in the '126 application, to which the present description refers. It is to be understood that those prosthetic heart valves and scaffolding structures are only examples of such valves and prosthetic devices that are suitable for use with the devices and methods described herein. For example, the present devices and methods are suitable for delivering valves and prosthetic devices having any cross-sectional or longitudinal profile, and is not limited to those valves and devices described in the '126 application or elsewhere.
Turning to the deployment devices and methods, in one aspect of the present invention, a delivery catheter for prosthetic heart valves and other devices is provided. The delivery catheter is preferably adapted for use with a conventional guidewire, having an internal longitudinal lumen for passage of the guidewire. The delivery catheter includes a handle portion located at a proximal end of the catheter, a deployment mechanism located at the distal end of the catheter, and a catheter shaft interposed between and operatively interconnecting the handle portion and the deployment mechanism. The deployment mechanism includes several components that provide the delivery catheter with the ability to receive and retain a prosthetic valve or other device in a contracted, delivery state, to convert the prosthetic device to a partially expanded state, and then to release the prosthetic valve completely from the delivery device. In several preferred embodiments, the deployment mechanism includes an outer slotted tube, a plurality of wrapping pins attached to a hub and located on the interior of the slotted tube, and a plurality of restraining members that extend through the wrapping pins to the distal end of the catheter. Each of the deployment mechanism components is individually controlled by a corresponding mechanism carried on the handle portion of the catheter. The deployment mechanism preferably also includes a nosecone having an atraumatic distal end.
In several particularly preferred embodiments, the restraining members comprise tethers in the form of a wire, a cable, or other long, thin member made up of one or more of a metal such as stainless steel, metallic alloys, polymeric materials, or other suitable materials. A particularly preferred form of the tethers is suture material. In several embodiments, the tethers are adapted to engage the guidewire that extends distally past the distal end of the delivery catheter. The tethers preferably engage the guidewire by having a loop, an eyelet, or other similar construction at the distal end of the tether. Optionally, the tether is simply looped around the guidewire and doubles back to the catheter handle. Thus, the tethers are released when the guidewire is retracted proximally into the delivery catheter. In still other embodiments, the tethers may be released from the guidewire by actuation of a member carried on the handle mechanism at the proximal end of the catheter. In still other embodiments, a post or tab is provided on the guidewire, and the tether engages the post or tab but is able to bend or break free from the post or tab when a proximally-oriented force is applied to the tethers.
In a second aspect of the present invention, several optional active deployment mechanisms are described. The active deployment mechanisms are intended to convert a prosthetic valve, scaffolding structure, or similar device from an undeployed, partially deployed, or not-fully deployed state to its fully expanded state. Several of the active deployment mechanisms take advantage of the fact that the preferred prosthetic valves and scaffolding structures require only a small amount of force applied any any of a large number of points or locations on the valve or structure in order to cause the valve to fully expand. Exemplary embodiments of the active deployment mechanisms include embodiments utilizing expandable members that are placed into the interior of the prosthetic valve and then expanded; embodiments that operate by causing the hinges of the undeployed prosthetic valve to open, thereby transitioning to the fully expanded state; embodiments that include implements that engage one or more of the panels to cause the panel to expand to its deployed state; and other embodiments described herein.
Other aspects, features, and functions of the inventions described herein will become apparent by reference to the drawings and the detailed description of the preferred embodiments set forth below.
DESCRIPTION OF THE DRAWINGS
FIG. 1A is a perspective view of a prosthetic valve suitable for use by the delivery catheter of the present invention.
FIG. 1B is a top view of a partially contracted support member illustrating inverted panels to form a “tri-star” shape.
FIG. 1C is a top view of a fully contracted support member illustrating inverted and curled panels to form a “tri-lobe” shape.
FIG. 2 is a perspective view of a delivery catheter in accordance with the present invention.
FIG. 3 is a perspective view of a deployment mechanism of the delivery catheter of FIG. 2.
FIG. 3A is a cross-sectional view of the deployment mechanism shown in FIG. 3.
FIG. 3B is a perspective view of several of the internal components included in the deployment mechanism shown in FIG. 3.
FIG. 3C is a perspective view of a wrapping pin stabilizer.
FIGS. 3D-F are cross-sectional views of wrapping pins and their associated tethers.
FIG. 3G is another perspective view of a wrapping pin stabilizer.
FIG. 4 is a perspective view of a handle mechanism of the delivery catheter shown in FIG. 2.
FIG. 5 is a cross-sectional view of the handle mechanism shown in FIG. 4.
FIG. 6 is a side view of the handle mechanism of the delivery catheter shown in FIG. 2, illustrating several positions corresponding with steps performed during use of the delivery catheter to deliver a prosthetic device.
FIG. 7 is a perspective view of the deployment mechanism, shown with a prosthetic valve in a star shape and with the slotted tube fully advanced.
FIG. 8 is a perspective view of the deployment mechanism, shown with a prosthetic valve in a star shape with the wrapping pins fully advanced and with the slotted tube retracted.
FIG. 9 is a perspective view of the deployment mechanism, shown with a prosthetic valve in a star shape with the wrapping pins and the slotted tube retracted.
FIG. 9A is a closeup view of the nosecone and guidewire shown in FIG. 9, showing detail of the manner in which a tether is looped over the guidewire.
FIG. 10 is a perspective view of the deployment mechanism, shown with a prosthetic valve in expanded shape with tethers retaining the valve in place.
FIG. 11 is a perspective view of the deployment mechanism, shown with a prosthetic valve in expanded shape, and showing the guidewire and tethers withdrawn to release the valve.
FIGS. 12A-B are side cross-sectional and end views, respectively, of a portion of the distal end of a delivery catheter, illustrating an eyelet formed on the ends of each tether.
FIGS. 12C-D are side cross-sectional views of a first wrapping pin having no recess, and a second wrapping pin having an eyelet recess formed therein.
FIG. 12E is an end cross-sectional view of a prosthetic valve partially restrained by three dual tethers.
FIGS. 12F-G are illustrations of two methods for selectively attaching dual tethers to a guidewire.
FIG. 13 is a side view of a portion of a delivery catheter illustrating a valve stop formed on each tether.
FIGS. 14A-B are side partial cross-sectional views of a portion of a delivery catheter illustrating tethers including linkage members. FIG. 14A shows a valve in its expanded state, and FIG. 14B shows the valve in its “tri-star” state.
FIG. 15 is a side view in partial cross-section of a delivery catheter illustrating tethers having loops that are routed through throughholes in the nosecone.
FIGS. 16A-B are a side view in partial cross-section and an end view showing a slotted nosecone.
FIG. 17 is a side view in partial cross-section of a delivery catheter illustrating tethers having primary and secondary sections.
FIGS. 18A-B are side views of a portion of a prosthetic valve having loops for engaging a tether to prevent migration.
FIGS. 19A-D are side views of several embodiments of wrapping pins.
FIGS. 20A-B are side views in partial cross-section showing a pair (out of three) of articulating wrapping pins, forming a gripper mechanism.
FIGS. 21A-B are an end perspective view in partial cross-section and a top view in partial cross-section of a slotted tube.
FIG. 21C is a side cross-sectional view of a slotted tube having runners and a valve panel in its contracted state.
FIGS. 22A-B are a perspective view and an end view, respectively, of an alternative deployment mechanism for a delivery catheter.
FIG. 23A is an illustration of a shape set nosecone shaft.
FIG. 23B is a cross-sectional end view of the shape set nosecone shaft of FIG. 23A.
FIG. 23C is a side view of the shape set nosecone shaft of FIG. 23A showing the tensioning member in tension.
FIGS. 24A-C illustrate a side view in partial cross-section and two end views, respectively, of an active deployment mechanism for deploying a valve, in accordance with the present invention.
FIGS. 25A-C illustrate side views in partial cross-section of another active deployment mechanism for deploying a valve, in accordance with the present invention.
FIGS. 26A-E illustrate several embodiments of active deployment mechanism employing inflatable members, such as balloons.
FIGS. 27A-B illustrates another embodiment of an active deployment mechanism employing inflatable members, such as balloons.
FIG. 28 illustrates an active deployment mechanism utilizing a roller and pincher.
FIGS. 29A-B illustrate an active deployment mechanism utilizing a wedge.
FIG. 30 illustrates an active deployment mechanism utilizing a torsion spring.
FIGS. 31A-B illustrate an active deployment mechanism utilizing a membrane balloon mounted on a slotted tube.
FIG. 32 illustrates an active deployment mechanism utilizing a plurality of linkages able to be expanded by an inflatable member.
FIGS. 33A-B illustrate an active deployment mechanism utilizing an expansion balloon mounted within the nosecone of a delivery catheter.
FIGS. 34A-C illustrate an active deployment mechanism utilizing a yoke and linkage system adapted to extend radially outward upon actuation.
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OF THE PREFERRED EMBODIMENTS
Before the present invention is described, it is to be understood that this invention is not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which these inventions belong. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention, the preferred methods and materials are now described. All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited.
It must be noted that as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise.
The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed.
As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present inventions.
This application relates to U.S. Ser. No. 11/066,126, filed Feb. 25, 2005, which is fully incorporated by reference herein. The \'126 application claims the benefit of U.S. Provisional Ser. No. 60/548,731, filed Feb. 27, 2004, and U.S. Provisional Ser. No. 60/559,199, filed Apr. 1, 2004, both of which are fully incorporated by reference herein.
A. Delivery Devices and Methods of Use
Devices for delivering prosthetic valves and other devices to a treatment location in a body lumen are described below, as are methods for their use. The delivery devices are particularly adapted for use in minimally invasive interventional procedures, such as percutaneous aortic valve replacements. FIG. 2 illustrates a preferred embodiment of the device, in the form of a delivery catheter. The delivery catheter 100 includes a handle mechanism 102 located at the proximal end of the catheter, a deployment mechanism 104 located at the distal end of the device, and a shaft 106 extending between and interconnecting the handle mechanism 102 and the deployment mechanism 104. The catheter 100 is preferably provided with a guidewire lumen extending through the entire length of the catheter, such that a guidewire 108 is able to extend through the delivery catheter in an “over-the-wire” construction. In an optional embodiment (not shown in the drawings), the catheter 100 is provided with a “rapid-exchange” construction whereby the guidewire exits the catheter shaft through an exit port located near the distal end of the catheter. The cross-sectional profile of the deployment mechanism 104 and the shaft 106 are of a sufficiently small size that they are able to be advanced within the vasculature of a patient to a target location, such as the valve root of one or more of the valves of the heart. A preferred route of entry is through the femoral artery in a manner known to those skilled in the art. Thus, the deployment mechanism 104 has a preferred maximum diameter of approximately 24 Fr. It is understood, however, that the maximum and minimum transverse dimensions of the deployment mechanism 104 may be varied in order to obtain necessary or desired results.
The deployment mechanism 104 is provided with components, structures, and/or features that provide the delivery catheter with the ability to retain a prosthetic valve (or other prosthetic device) in a contracted state, to deliver the valve to a treatment location, to convert the prosthetic valve to its deployed state (or to allow the valve to convert to its deployed state on its own), to retain control over the valve to make any necessary final position adjustments, and to convert the prosthetic valve to its contracted state and withdraw the valve (if needed). These components, structures, and/or features of the preferred deployment mechanism are described below.
Turning to FIGS. 3 and 3A, the deployment mechanism 104 is shown in its fully contracted state for use when the mechanism 104 has not yet reached the target site within the body of a patient, such as prior to use and during the delivery process. The deployment mechanism 104 includes a slotted tube 110 that is connected to an outer sheath 112 of the catheter shaft 106, such as by way of the attachment collar 111 (shown in FIG. 3A). Thus, longitudinal movement or rotation of the outer sheath 112 causes longitudinal movement or rotation of the slotted tube 110. The slotted tube 110 is a generally cylindrical body that includes a plurality of longitudinal slots 114 that extend from the distal end of the slotted tube 110 to near its proximal end. In the preferred delivery catheter, the slotted tube 110 includes three slots 114 spaced equidistantly about the circumference of the slotted tube 110. The slots 114 have a length and width that are sufficient to accommodate the extension of portions of the prosthetic valve 30 therethrough, as described more fully below in reference to FIG. 7, described elsewhere herein. The slotted tube 110 is preferably formed of stainless steel or other generally rigid material suitable for use in medical devices or similar applications.
The deployment mechanism 104 may also include a retainer ring 116 and a nosecone 118. Although the retainer ring 116 and nosecone 118 are not necessary parts of the delivery catheter, each of these components may provide additional features and functionality when present. The nosecone 118 is located at the distal end of the delivery catheter and is preferably provided with a generally blunt, atraumatic tip 120 to facilitate passage of the catheter through the patient\'s vasculature while minimizing damage to the vessel walls. The nosecone 118 is preferably formed of any suitable biocompatible material. In several preferred embodiments, the nosecone is formed of a relatively soft elastomeric material, such as a polyurethane, a polyester, or other polymeric or silicone-based material. In other embodiments, the nosecone is formed of a more rigid material, such as a plastic, a metal, or a metal alloy material. The nosecone may be coated with a coating material or coating layer to provide advantageous properties, such as reduced friction or increased protection against damage. It is also advantageous to provide the nosecone with an atraumatic shape, at least at its distal end, or to form the nosecone 118 of materials that will provide the atraumatic properties while still providing structural integrity to the distal end of the device. The nosecone 118 preferably includes a plurality of throughholes 122 that extend through the length of the nosecone to allow passage of a plurality of tethers 124, which are described more fully below. A pair of slots 119 are formed on the exterior of the nosecone 118. The slots 119 provide a pair of surfaces for a wrench or other tool to grasp the nosecone 118 to enable manual manipulation of the nosecone 118, for purposes to be described below.
The retainer ring 116 is a generally cylindrically shaped ring that is located generally between the slotted tube 110 and the nosecone 118. More precisely, when the deployment mechanism 104 is in the fully contracted state shown in FIGS. 3 and 3A, the retainer ring 116 preferably overlaps a ledge 126 formed on the distal end of the slotted tube 110. Alternatively, the inner diameter of the retainer ring 116 may be formed slightly larger than the outer diameter of the slotted tube 110, thereby allowing the distal ends of the slotted tube 110 to slide within the retainer ring 116 without the need for a ledge 126. In this way, the retainer ring 116 prevents the distal ends of the slotted tube 110 from bowing outward due to pressure caused by the prosthetic valve being stored within the deployment mechanism 104.