A collapsible and expandable prosthetic heart valve stent is provided and comprising an outer section, a valve support defining a flow channel therethrough, a transition section configured to smoothly transition the outer section to the valve support. The valve support is disposed within an interior defined by the outer section, with the inflow end of the valve support disposed inside the outer section’s interior. In some cases, the outflow end of the valve support is at least partially defined by the transition section. The prosthetic leaflets are disposed on the inner surface of the valve support’s flow channel and are located at or above the annulus of the heart chamber. A paravalvular leakage mitigation system is attached to the stent to mitigate retrograde blood flow and/or regurgitation.本發明提供一種可收縮及可擴張人造心臟瓣膜支架，其包括：一外區段；一瓣膜支撐件，其界定穿過其之一流動通道；一過渡區段，其經構形以使該外區段順利過渡至該瓣膜支撐件。該瓣膜支撐件安置於由該外區段界定之一內部內，且該瓣膜支撐件之流入端安置於該外區段之內部內。在一些情況中，該瓣膜支撐件之流出端至少部分由該過渡區段界定。人造小葉安置於該瓣膜支撐件之流動通道之內表面上且位於心室之瓣環處或心室之瓣環上方。一瓣膜周圍滲漏減緩系統附接至該支架以減緩逆行血液流動及/或反流。
