BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a radially expandable endoprosthesis device with an at least two stage deployment capability and, more particularly, pertains to an annularly expandable heart valve prosthesis which is adapted for the long-term treatment of valvular diseases in infants, children and adolescents.

[0003] Basically, radially expandable endoprosthesis devices are employed in connection with the insertion and positioning of stents or stent-grafts into corporeal vessels, such as arteries or the like, and generally are constituted of stainless steel or nitinol (nickel-titanium alloy) or similar alloys. In the instance in which an endoprothesis employed as a stent, it is adapted to counteract acute vessel spasms which are frequently encountered in the emplacement of nitinol (nickel-titanium alloy) stents in arteries or body vessels. In coronary arteries, any secondary enlargement of the stent would be adapted to serve for offsetting contractile forces which may result from intimal hyperplasia; however, the prior art pursuant to the state of the technology, does not address itself to this aspect. When employed in connection with abdominal aortic aneurysms (AAA), current stent-graft devices merely concern themselves with anchoring devices the stent-graft in its location of emplacement.

[0004] Heretofore, in the prior art, the problems encountered the use of such endoprosthesis devices have been addressed by various methods and physical and biological means. Thus, in intimal hyperplasia of coronary arteries, additional angioplasty, or in the use of chemicals and pharmaceutical preparates, such as various drugs or radio-isotopes, these may be readily employed in order to attempt to reduce the hyperplasia. Furthermore, the emplacement of external bands around abdominal aortic aneurysms (AAA) which are treated with stent-grafts has also been employed in order to account for any aneurysmal progression which may occur at a site which has been thought to be free of disease. When employed in pediatric heart valve disease cases, secondary surgeries are frequently needed in order to replace the smaller-sized valve prosthesis as the infant or child grows, as a result of an increase in the heart valve sizes requiring larger-sized prosthesis, this being at times the cause of severe discomfort, and even morbidity and increased morbidity rates for such tender patients.

[0005] 2. Discussion of the Prior Art

[0006] As disclosed in Duerig et al. U.S. Pat. No. 6,179,878, a composite self-expanding stent device incorporates a restraining element, in which a restraint sleeve is generally formed of a shape memory alloy, such as binary nickel titanium alloy, referred to generally as nitinol, and wherein restraint can be provided in the form of either sleeve, covering a mesh or perforated sheet. In that instance, the restraining element can be formed of a polymeric material which, in any event is not considered to be possessed of a property to enable the stent device to undergo multiple dimensionally changing configurations at predetermined intervals in time so as provided a device with an at least two-stage deployment in a patient.

[0007] Lenker et al. U.S. Pat. No. 6,176,875 discloses an endoluminal prosthesis and methods in the use thereof, which provides for limited radial expansion in controlled mode. However, the stent-graft construction illustrated and described therein is primarily equipped with a belt which may frangible or expansible in order to allow for further or subsequent expansion of the implanted or emplaced stent-graft device. This device also fails to provide for a combination of super-elastic shape memory alloys such as nitinol, and bioresorbable medical materials which enable the devices to undergo at least a two-stage or multiple deplacement stages at predetermined intervals in time.

[0008] Finally, Lock et al. U.S. Pat. No. 5,383,926 discloses an expandable endoprosthesis device which is constituted of the combination of a memory alloy, possibly such as nitinol, with an expansion limiting structure which is selectively removable in order two subsequently allow for further radial expansion of the emplaced device, whereby the expansion limiting structure can be constituted of a dissolvable or severable band-like material. Although this endoprosthesis device may generally incorporate bioresorbable materials, the device described in this patent is not adapted for heart valve prostheses, particularly such as are intended for pediatric applications, which will enable the treatment of valvular diseases in children, whereby the annulus of the heart valve prosthesis can be caused over periods of time to expand as the child grows, thereby obviating the need for further surgical procedures normally required in order to substitute larger-sized heart valve prosthesis structures or devices in the growing patients.

SUMMARY OF THE INVENTION

[0009] Accordingly, in order to provide an endoprosthesis device which is adapted to essentially provide for a multi-stage deployment and which facilitates a radially and annular expansion which may be required during continual use thereof, the inventive device, such as a stent, stent-graft, or pursuant to a preferred embodiment, a heart valve prosthesis particularly for pediatric case is drawn to a novel combination of superelastic or shape memory alloys and bioresorbable materials, which enables the devices to undergo multiple or at least two-stage configurations at predetermined time intervals depending upon the type of material employed in conformance with the needs of patients in which the devices are deployed. The bioresorbable materials may also serve as reservoirs for therapeutic agents, such as antibiotics, anticoagulants, and cytostatic drugs.

[0010] In one aspect, the device may comprise a coronary stent which is capable of having at least one deployment stage, and that is constituted of a superelastic material with a bioresorbable coating or constraint structure operatively combined therewith. This type of stent may be suitable for counteracting or addressing problems relative to initmal hyperplasmia when utilized in coronary vessels, and can also be employed for the stenting of other body vessels subjected to abdominal aortic aneurysms (AAA) when there is encountered the need to maintain contact with a dynamic vessel wall of a body vessel or lumen. In those last-mentioned instances, a stent for the counteracting the effects of the aneurysms, when constituted of the combination of superelastic alloys and bioresorabable materials can offset post-deployment aneurismal dilatation.

[0011] In a particularly preferred embodiment of the invention, the endoprosthesis device, which is constituted of a combination of a superelastic alloy and bioresorabable material, is in the configuration of a heart valve prosthesis especially adapted for pediatric medical uses, and which can be made to expand in at least two-steps of its deployment as the infant or child grows, over an extended period of time. In that connection, the endoprosthesis device may be constructed so as to incorporate various types of polymer systems in order to afford multiple stage deployments, wherein particular types of polymers may degrade at time intervals of, for example, ranging from about 6 months to about 200 months after the implanting of the device in the pediatric patient. In particular, such a system is useful in long-term heart valve prostheses, whereas contrastingly another system may utilize a polymer which absorbs in 15 minutes and which is useful in implanting anastomotic devices.

[0012] Accordingly, it is a primary object of the present invention to provide an endoprosthesis device which is constituted of a combination of superelastic alloys and bioresorbable materials which facilitates the devices to undergo multistage deployments at predetermined intervals while emplaced in the body vessels or lumens of patients.

[0013] Another object of the present invention is to provide an endoprosthesis device as described herein, wherein the device may undergo at least two-stage deployment so as to assume different or expanded annular or radial dimensions at predetermined time intervals responsive to degradation of bioresorbable components of the device which have been combined with a superelastic alloy.

[0014] A more specific object of the present invention is to provide an endoprosthesis device which is constituted of a heart valve prosthesis for pediatric medical applications, wherein the annulus of the valve prosthesis can be constructed so as to expand in at least two stages of deployment over periods of time during the growth of an infant or child, and wherein the device is constituted of a novel combination of superelastic alloy-materials and bioresorbable materials preferably selected from polymer systems.