Patent Application
20090287290
The present invention relates to prosthetic heart valves. More particularly, it relates to delivery systems for percutaneously implanting prosthetic heart valves comprising a stent.
Diseased or otherwise deficient heart valves can be repaired or replaced using heart valve surgery. Typical heart valve surgeries involve an open-heart surgical procedure that is conducted under general anesthesia, during which the heart is stopped while blood flow is controlled by a heart-lung bypass machine. This type of valve surgery is highly invasive and exposes the patient to a number of potentially serious risks, such as infection, stroke, renal failure, and adverse effects associated with use of the heart-lung machine, for example.
Recently, there has been increasing interest in minimally invasive and percutaneous replacement of cardiac valves. Such surgical techniques involve making a very small opening in the skin of the patient into which a valve assembly is inserted in the body and delivered to the heart via a delivery device similar to a catheter. This technique is often preferable to more invasive forms of surgery, such as the open-heart surgical procedure described above. In the context of pulmonary valve replacement, U.S. Patent Application Publication Nos. 2003/0199971 A1 and 2003/0199963 A1, both filed by Tower, et al., describe a valved segment of bovine jugular vein, mounted within an expandable stent, for use as a replacement pulmonary valve. The replacement valve is mounted on a balloon catheter and delivered percutaneously via the vascular system to the location of the failed pulmonary valve and expanded by the balloon to compress the valve leaflets against the right ventricular outflow tract, anchoring and sealing the replacement valve. As described in the articles: “Percutaneous Insertion of the Pulmonary Valve”, Bonhoeffer, et al., Journal of the American College of Cardiology 2002; 39: 1664-1669 and “Transcatheter Replacement of a Bovine Valve in Pulmonary Position”, Bonhoeffer, et al., Circulation 2000; 102: 813-816, the replacement pulmonary valve may be implanted to replace native pulmonary valves or prosthetic pulmonary valves located in valved conduits.
Various types and configurations of prosthetic heart valves are used in percutaneous valve procedures to replace diseased natural human heart valves. The actual shape and configuration of any particular prosthetic heart valve is dependent to some extent upon the valve being replaced (i.e., mitral valve, tricuspid valve, aortic valve, or pulmonary valve). In general, the prosthetic heart valve designs attempt to replicate the function of the valve being replaced and thus will include valve leaflet-like structures used with either bioprostheses or mechanical heart valve prostheses.
That is, the replacement valves may include a valved vein segment that is mounted in some manner within an expandable stent to make a stented valve. In order to prepare such a valve for percutaneous implantation, the stented valve can be initially provided in an expanded or uncrimped condition, then crimped or compressed around the balloon portion of a catheter until it is as close to the diameter of the catheter as possible.
Other percutaneously-delivered prosthetic heart valves have been suggested having a generally similar configuration, such as by Bonhoeffer, P. et al., “Transcatheter Implantation of a Bovine Valve in Pulmonary Position.” Circulation, 2002; 102:813-816, and by Cribier, A. et al. “Percutaneous Transcatheter Implantation of an Aortic Valve Prosthesis for Calcific Aortic Stenosis.” Circulation, 2002; 106:3006-3008, the disclosures of which are incorporated herein by reference. These techniques rely at least partially upon a frictional type of engagement between the expanded support structure and the native tissue to maintain a position of the delivered prosthesis, although the stents can also become at least partially embedded in the surrounding tissue in response to the radial force provided by the stent and any balloons used to expand the stent. Thus, with these transcatheter techniques, conventional sewing of the prosthetic heart valve to the patient's native tissue is not necessary. Similarly, in an article by Bonhoeffer, P. et al. titled “Percutaneous Insertion of the Pulmonary Valve.” J Am Coll Cardiol, 2002; 39:1664-1669, the disclosure of which is incorporated herein by reference, percutaneous delivery of a biological valve is described. The valve is sutured to an expandable stent within a previously implanted valved or non-valved conduit, or a previously implanted valve. Again, radial expansion of the secondary valve stent is used for placing and maintaining the replacement valve.
Although there have been advances in percutaneous valve replacement techniques and devices, there is a continued desire to provide delivery systems and corresponding valves having features that allow for valve implantation in a minimally invasive and percutaneous manner.
The delivery systems and replacement valves of the invention are configured to provide complimentary features that promote optimal placement of the replacement heart valve in a native heart valve, such as the aortic valve, mitral valve, pulmonic valve, and/or tricuspid valve. In some embodiments, the replacement heart valves of the invention are highly amenable to transvascular delivery using a transapical approach (either with or without cardiopulmonary bypass and either with or without rapid pacing). The methodology associated with the present invention can be repeated multiple times, such that several prosthetic heart valves of the present invention can be mounted on top of or within one another, if necessary or desired.
Heart valves that can be placed in a patient using delivery systems of the invention include a stent to which a valve structure is attached. The stents can include a wide variety of structures and features that can be used alone or in combination with features of other stents. In particular, these stents provide a number of different docking and/or anchoring structures that are conducive to percutaneous delivery thereof. Many of the structures are thus compressible to a relatively small diameter for percutaneous delivery to the heart of the patient, and then are expandable either via removal of external compressive forces (e.g., self-expanding stents), or through application of an outward radial force (e.g., balloon expandable stents). The devices delivered by the delivery systems described herein can be used to deliver stents, valved stents, or other interventional devices such as ASD (atrial septal defect) closure devices, VSD (ventricular septal defect) closure devices, or PFO (patent foramen ovale) occluders.
Methods for insertion of the replacement heart valves of the invention include delivery systems that can maintain the stent structures in their compressed state during their insertion and allow or cause the stent structures to expand once they are in their desired location. In addition, some delivery methods of the invention can include features that allow the stents to be retrieved for removal or relocation thereof after they have been deployed or partially deployed from the stent delivery systems. The methods may include implantation of the stent structures using either an antegrade or retrograde approach. Further, in many of the delivery approaches of the invention, the stent structure is rotatable in vivo to allow the stent structure to be positioned in a desired orientation.
The present invention will be further explained with reference to the appended Figures, wherein like structure is referred to by like numerals throughout the several views, and wherein:
As referred to herein, the prosthetic heart valves used in accordance with the various devices and methods may include a wide variety of different configurations, such as a prosthetic heart valve having tissue leaflets or a synthetic heart valve having polymeric, metallic, or tissue-engineered leaflets, and can be specifically configured for replacing any heart valve. That is, while much of the description herein refers to replacement of aortic valves, the prosthetic heart valves of the invention can also generally be used for replacement of native mitral, pulmonic, or tricuspid valves, for use as a venous valve, or to replace a failed bioprosthesis, such as in the area of an aortic valve or mitral valve, for example.
Although each of the valves used with the delivery devices and methods described herein would typically include leaflets attached within an interior area of a stent, the leaflets are not shown in many of the illustrated embodiments for clarity purposes. In general, the stents described herein include a support structure comprising a number of strut or wire portions arranged relative to each other to provide a desired compressibility and strength to the heart valve. Other details on particular configurations of the stents of the invention are also described below; however, in general terms, stents of the invention are generally tubular support structures, and leaflets will be secured to the support structure. The leaflets can be formed from a variety of materials, such as autologous tissue, xenograph material, or synthetics as are known in the art. The leaflets may be provided as a homogenous, biological valve structure, such as a porcine, bovine, or equine valve. Alternatively, the leaflets can be provided independent of one another (e.g., bovine or equine pericardial leaflets) and subsequently assembled to the support structure of the stent. In another alternative, the stent and leaflets can be fabricated at the same time, such as may be accomplished using high strength nano-manufactured NiTi films produced at Advanced Bio Prosthetic Surfaces (ABPS), for example. The support structures are generally configured to accommodate three leaflets; however, the replacement prosthetic heart valves of the invention can incorporate more or less than three leaflets.
In more general terms, the combination of a support structure with one or more leaflets can assume a variety of other configurations that differ from those shown and described, including any known prosthetic heart valve design. In certain embodiments of the invention, the support structure with leaflets can be any known expandable prosthetic heart valve configuration, whether balloon expandable, self-expanding, or unfurling (as described, for example, in U.S. Pat. Nos. 3,671,979; 4,056,854; 4,994,077; 5,332,402; 5,370,685; 5,397,351; 5,554,185; 5,855,601; and 6,168,614; U.S. Patent Application Publication No. 2004/0034411; Bonhoeffer P., et al., “Percutaneous Insertion of the Pulmonary Valve”, Pediatric Cardiology, 2002; 39:1664-1669; Anderson H R, et al., “Transluminal Implantation of Artificial Heart Valves”, EUR Heart J., 1992; 13:704-708; Anderson, J. R., et al., “Transluminal Catheter Implantation of New Expandable Artificial Cardiac Valve”, EUR Heart J., 1990, 11: (Suppl) 224a; Hilbert S. L., “Evaluation of Explanted Polyurethane Trileaflet Cardiac Valve Prosthesis”, J Thorac Cardiovascular Surgery, 1989; 94:419-29; Block P C, “Clinical and Hemodynamic Follow-Up After Percutaneous Aortic Valvuloplasty in the Elderly”, The American Journal of Cardiology, Vol. 62, Oct. 1, 1998; Boudjemline, Y., “Steps Toward Percutaneous Aortic Valve Replacement”, Circulation, 2002; 105:775-558; Bonhoeffer, P., “Transcatheter Implantation of a Bovine Valve in Pulmonary Position, a Lamb Study”, Circulation, 2000:102:813-816; Boudjemline, Y., “Percutaneous Implantation of a Valve in the Descending Aorta In Lambs”, EUR Heart J, 2002; 23:1045-1049; Kulkinski, D., “Future Horizons in Surgical Aortic Valve Replacement: Lessons Learned During the Early Stages of Developing a Transluminal Implantation Technique”, ASAIO J, 2004; 50:364-68; the teachings of which are all incorporated herein by reference).
Orientation and positioning of the stents of the invention may be accomplished either by self-orientation of the stents (such as by interference between features of the stent and a previously implanted stent or valve structure) or by manual orientation of the stent to align its features with anatomical or previous bioprosthetic features, such as can be accomplished using fluoroscopic visualization techniques, for example. For example, when aligning the stents of the invention with native anatomical structures, they should be aligned so as to not block the coronary arteries, and native mitral or tricuspid valves should be aligned relative to the anterior leaflet and/or the trigones/commissures.
Some embodiments of the support structures of the stents described herein can be a series of wires or wire segments arranged so that they are capable of transitioning from a collapsed state to an expanded state. In some embodiments, a number of individual wires comprising the support structure can be formed of a metal or other material. These wires are arranged in such a way that a support structure allows for folding or compressing to a contracted state in which its internal diameter is greatly reduced from its internal diameter in an expanded state. In its collapsed state, such a support structure with attached valves can be mounted over a delivery device, such as a balloon catheter, for example. The support structure is configured so that it can be changed to its expanded state when desired, such as by the expansion of a balloon catheter. The delivery systems used for such a stent should be provided with degrees of rotational and axial orientation capabilities in order to properly position the new stent at its desired location.
The wires of the support structure of the stents in other embodiments can alternatively be formed from a shape memory material such as a nickel titanium alloy (e.g., Nitinol). With this material, the support structure is self-expandable from a contracted state to an expanded state, such as by the application of heat, energy, and the like, or by the removal of external forces (e.g., compressive forces). This support structure can also be compressed and re-expanded multiple times without damaging the structure of the stent. In addition, the support structure of such an embodiment may be laser cut from a single piece of material or may be assembled from a number of different components. For these types of stent structures, one example of a delivery system that can be used includes a catheter with a retractable sheath that covers the stent until it is to be deployed, at which point the sheath can be retracted to allow the stent to expand. Further details of such embodiments are discussed below.
Referring now to the Figures, wherein the components are labeled with like numerals throughout the several Figures, and initially to
The proximal end of the stent 12 can be secured to the delivery system 10 in a number of different ways, such as with wires having hook tips that engage with the crowns of proximal end of the stent 12, for example. In this particular example, angled wire tips or protrusions extend at an angle relative to their respective wires, where the angle between each tip and its respective wire can be approximately 90 degrees, for example, although it can be any angle that provides for engagement between the wires and the stent crowns.
In order to keep the crowns 14 of the stent 12 engaged with the hubs 16 at the distal end of the delivery device 10 until it is desired to release the stent, the delivery system 10 is provided with a distal tip 20 that is hollow at its proximal end. In this way, the proximal end of the tip 20 can slide over the base portion 18 and its extending hubs 16 over which stent crowns 14 are positioned, thereby maintaining the system components in this arrangement. In order to release the stent 12 from the delivery system 10, the tip 20 and base portion 18 can be moved relative to each other until the tip 20 no longer covers the stent crowns 14. The crowns 14 will then be able to move outwardly from the hubs 16 to disengage the stent 12 from the hubs 16.
The view of this area of a heart in
With the delivery system 10 of the invention, it is contemplated that the user can choose in which sequence the various portions of the stent are deployed or released while other portions are being held or compressed. For example, referring now to
Another delivery system 180 is illustrated in
It is noted that in the above procedure, the stent can be retracted back into a lumen of the delivery system 10 at any point in the process until the wires are disengaged from the stent, such as for repositioning of the stent if it is determined that the stent has been improperly positioned relative to the patient's anatomy. In this case, the steps described above can be repeated until the desired positioning of the stent is achieved.
With the delivery systems described herein, full or partial blood flow through the valve can advantageously be maintained during the period when the stented valve is being deployed into the patient but is not yet released from its delivery system. This feature can help to prevent complications that may occur when blood flow is stopped or blocked during valve implantation with some other known delivery systems. In addition, it is possible for the clinician to thereby evaluate the opening and closing of leaflets, examine for any paravalvular leakage and evaluate coronary flow and proper positioning of the valve within the target anatomy before final release of the stented valve.
Stent 52 further includes a loop or eyelet 62 at the end of each wire structure 60, where each eyelet 62 is sized and shaped for engagement with an extending element 56. All of the eyelets 62 of a particular stent 60 may be the same size and shape as each other, or the eyelets 62 may be differently sized and shaped. In an alternative embodiment, the stent may include crowns at one end that are engageable with the extending elements 56, such as would be the case if the stent did not include eyelets at the end of its wire structures. Once the eyelets 62 (and/or stent crowns) are engaged with their respective elements 56 of the delivery system, a collar 64 can be slid at least partially over the eyelets 62, as is best illustrated in
Stent 82 further includes a loop or eyelet 92 at the end of each wire structure 90, where each eyelet 92 is sized and shaped for engagement with an extending element 86. All of the eyelets 92 of a particular stent 90 may be the same size and shape as each other, or the eyelets 92 may be differently sized and shaped. In an alternative embodiment, the stent may include crowns at one end that are engageable with the extending elements 86, such as would be the case if the stent did not include eyelets at the end of its wire structures. The stent delivery system 80 further includes a spring-loaded collar 96 that can be configured so that it needs to be actuated to cover the eyelets 92 and the extending elements 86 with which they are engaged, or the collar 96 can be configured so that it needs to be actuated to uncover or release the eyelets 92. In either case, once the eyelets 92 (and/or stent crowns) are all engaged with their respective elements 86 of the delivery system, the collar 96 can be slid at least partially over the eyelets 92. When it is desired to release the stent eyelets 92 from the delivery system 80, the collar 96 can be slid proximally to expose the eyelets 92 and extending elements 86.
Stent 102 further includes a loop or eyelet 112 at the end of each of its wire structures 110, where each eyelet 112 is sized and shaped for engagement with a sprocket tooth 106. All of the eyelets 112 of a particular stent may be the same size and shape as each other, or the eyelets 112 may be differently sized and shaped. In an alternative embodiment, the stent may include crowns at one end that are engageable with the teeth 106, such as would be the case if the stent did not include eyelets at the end of its wire structures.
The delivery system 100 further includes a sleeve 118 that is incorporated into the valve cover or sheath. In one exemplary embodiment, the delivery system will include a lock pin on its handle that would limit the travel of the valve cover to provide the additional control over the release of the stent, when desired.
Although the number of extending elements, teeth, and/or hubs of the delivery systems described herein can vary, one preferred embodiment includes nine of such extending elements for engagement with a stent having nine attachment points. The stent attachment points can include stent crowns, eyelets at the end of stent crowns or at the end of extending stent wires, or the like. More or less than nine attachment points and extending elements can be provided; however, the size, shape, and spacing of the elements around a base portion can be adjusted accordingly to achieve a desired configuration and size for the overall delivery system. Further, the height of the various extending elements can be relatively large or small, depending on the thickness of the stent wires that will engage with it, the stresses to which the stent will be subjected during the delivery process, and the like. Because it is often desirable to minimize the diameter of the delivery system for percutaneous delivery of stented valves, the number of stent wires and corresponding extending elements can be designed or chosen to optimize the quality of the attachment between the stent and the delivery system, while providing a stent that has certain desirable characteristics when implanted in a patient.
With the various delivery systems of the invention, once the crowns, eyelets, or other stent features are engaged with sprocket teeth or other extending members of a delivery system, the stent can then be moved relative to a sheath of the delivery system to enclose the stent within the sheath by pulling the wires toward the proximal end of the delivery system, by pushing the sheath toward the distal end of the delivery system, or by some combination of these two movements. In order to release the stent once the delivery system is positioned within the patient, moving the sheath and stent in opposite directions relative to each other will provide the stent with the freedom to move. When the stent is a self-expanding stent, it can expand to a larger diameter once the constraint of the sheath is removed. Other motions can be performed to move the stent away from the teeth or engaging members with which it is engaged, if desired. The stent is thereby released from the delivery system.
One exemplary process for apically deploying a stent to the aorta using the delivery systems of the invention is described below. This method can also be used for other delivery approaches, such as for transarterial retrograde delivery. In particular, the stent is loaded onto the delivery system and a sheath is positioned over the stent to maintain it in its compressed condition. The delivery system is then advanced to the area in which the stent will be implanted using known delivery techniques and devices. Once the delivery system has been located within the patient so that the stent and/or valve is in its desired position within the aortic valve, the sheath is pulled back toward the proximal end of the delivery system (or the delivery system is moved distally away from the sheath), which allows the stent to expand radially. Alternatively, in a transarterial retrograde delivery approach, the inflow or annular end of the stent can remain compressed while the middle of the stent, along with other features such as petals, are radially expanded. Any minor positional adjustments, if necessary, can be made at this point. However, if it is determined that the stent is not in the desired position, the sheath can be moved back toward the distal end of the delivery system until the entire stent is again enclosed within the sheath, then the delivery system can be repositioned until it is in its desired location. The delivery system may also include a stop on its handle or some other portion of its structure that requires a positive action by the user to prevent inadvertent release of the stent from the delivery system.
Delivering any balloon-expandable stents to an implantation location can be performed percutaneously using modified versions of the delivery systems of the inventions. In general terms, this includes providing a transcatheter assembly, including a delivery catheter, a balloon catheter, and a guide wire. Some delivery catheters of this type are known in the art, and define a lumen within which the balloon catheter is received. The balloon catheter, in turn, defines a lumen within which the guide wire is slideably disposed. Further, the balloon catheter includes a balloon that is fluidly connected to an inflation source. It is noted that if the stent being implanted is the self-expanding type of stent, the balloon would not be needed and a sheath or other restraining means would be used for maintaining the stent in its compressed state until deployment of the stent, as described herein. In any case, for a balloon-expandable stent, the transcatheter assembly is appropriately sized for a desired percutaneous approach to the implantation location. For example, the transcatheter assembly can be sized for delivery to the heart valve via an opening at a carotid artery, a jugular vein, a sub-clavian vein, femoral artery or vein, or the like. Essentially, any percutaneous intercostals penetration can be made to facilitate use of the transcatheter assembly.
Prior to delivery, the stent is mounted over the balloon in a contracted state to be as small as possible without causing permanent deformation of the stent structure. As compared to the expanded state, the support structure is compressed onto itself and the balloon, thus defining a decreased inner diameter as compared to an inner diameter in the expanded state. While this description is related to the delivery of a balloon-expandable stent, the same basic procedures can also be applicable to a self-expanding stent, where the delivery system would not include a balloon, but would preferably include a sheath or some other type of configuration for maintaining the stent in a compressed condition until its deployment.
With the stent mounted to the balloon, the transcatheter assembly is delivered through a percutaneous opening (not shown) in the patient via the delivery catheter. The implantation location is located by inserting the guide wire into the patient, which guide wire extends from a distal end of the delivery catheter, with the balloon catheter otherwise retracted within the delivery catheter. The balloon catheter is then advanced distally from the delivery catheter along the guide wire, with the balloon and stent positioned relative to the implantation location. In an alternative embodiment, the stent is delivered to an implantation location via a minimally invasive surgical incision (i.e., non-percutaneously). In another alternative embodiment, the stent is delivered via open heart/chest surgery. In one embodiment of the stents of the invention, the stent includes a radiopaque, echogenic, or MRI visible material to facilitate visual confirmation of proper placement of the stent. Alternatively, other known surgical visual aids can be incorporated into the stent. The techniques described relative to placement of the stent within the heart can be used both to monitor and correct the placement of the stent in a longitudinal direction relative to the length of the anatomical structure in which it is positioned.
Once the stent is properly positioned, the balloon catheter is operated to inflate the balloon, thus transitioning the stent to an expanded state. Alternatively, where the support structure is formed of a shape memory material, the stent can self-expand to its expanded state.
The present invention has now been described with reference to several embodiments thereof. The foregoing detailed description and examples have been given for clarity of understanding only. No unnecessary limitations are to be understood therefrom. It will be apparent to those skilled in the art that many changes can be made in the embodiments described without departing from the scope of the invention. Thus, the scope of the present invention should not be limited to the structures described herein.
The present application claims priority to U.S. Provisional Application No. 61/062,207, filed Jan. 24, 2008, and titled “Delivery Systems and Methods of Implantation for Prosthetic Heart Valves”, the entire contents of which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61062207 | Jan 2008 | US |
