Surgical heart valves adapted for post implant expansion
A prosthetic heart valve configured to replace a native heart valve and having a support frame configured to be reshaped into an expanded form in order to receive and/or support an expandable prosthetic heart valve therein is disclosed, together with methods of using same. The prosthetic heart valve may be configured to have a generally rigid and/or expansion-resistant configuration when initially implanted to replace a native valve (or other prosthetic heart valve), but to assume a generally expanded form when subjected to an outward force such as that provided by a dilation balloon or other mechanical expander.
1. A surgical prosthetic heart valve adapted for post-implant expansion and having an inflow end and an outflow end, comprising:
a continuous circular structural support stent surrounding a flow axis and having three upstanding commissure posts cantilevered toward the outflow end of the heart valve and three shorter cusp regions in between the commissure posts, wherein the support stent defines an implant circumference that is substantially non-compressible from a first diameter prior to implant and in normal physiological use and three biodegradable segments each located in a cusp region configured to provide resistance to prevent expansion of the support stent after implantation which resistance lessens over time as the biodegradable segments degrade in the body so as to permit expansion of the support stent at the cusp regions from the first diameter to a second diameter larger than the first diameter upon application of an outward dilatory force from within the support stent applied by a dilatation balloon, wherein the biodegradable segments comprise smile-shaped chordal segments that have a maximum axial dimension at mid-points of the cusp regions such that when they degrade they leave small cross-section cusp bridges connecting the commissures of the support stent which are susceptible to rupture or stretching upon application of an outward dilatory force from within the support stent; and
a plurality of flexible leaflets supported by the support stent and configured to close toward the flow axis and ensure one-way blood flow through the heart valve.
2. The prosthetic heart valve of claim 1 , the biodegradable segments are located in the centers of the three cusp regions.
3. The prosthetic heart valve of claim 1 , wherein the support stent further includes at least one reinforcing filament embedded therein and extending around the implant circumference, the reinforcing filament provide resistance to prevent expansion of the support stent until application of a predetermined outward dilatory force from within the support stent.
4. The prosthetic heart valve of claim 3 , wherein the prosthetic heart valve further includes a radially-expandable skirt stent secured to and projecting in an inflow direction from an inflow end of the support stent, wherein the radially-expandable skirt stent has a strength requiring a predetermined expansion force to convert to an expanded state, and wherein the reinforcing filament is configured to provide resistance to prevent expansion of the support stent when the predetermined expansion force is applied to the radially-expandable skirt stent.
5. The prosthetic heart valve of claim 1 , wherein the support stent is a single of polymer material band.
6. The prosthetic heart valve of claim 1 , the prosthetic heart valve is a two-part valve with the plurality of flexible leaflets being mounted on a detachable frame that couples to the support stent at the commissure posts thereof.
7. The prosthetic heart valve of claim 1 , further including a radiopaque marker on the support stent visible from outside the body after implant that identifies the support stent as being expandable.