A prosthetic heart valve can include an outer frame coupled to an inner frame such that the outer frame can be moved between a first position and a second position in which the outer frame is inverted relative to the inner frame. The inner frame and the outer frame define between them an annular space, and a pocket closure can bound the annular space to form a pocket in which thrombus can form and be retained. The pocket closure can include a stretchable pocket covering that can move from a first position in which the pocket covering has a first length when the outer frame is in the first position relative to the inner frame and a second position in which the pocket covering has a second length greater than the first length when the outer frame is in the second position relative to the inner frame.
