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
- Top of Page
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.
- Top of Page
OF THE INVENTION
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.
- Top of Page
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.