A side-deliverable prosthetic heart valve includes an outer frame and a flow control component. The outer frame has a supra-annular region, a subannular region, and a transannular region therebetween. The flow control component is mounted to the outer frame such that at least a portion of the flow control component is disposed in the transannular region. The prosthetic valve has a delivery configuration for side-delivery via a delivery catheter and is expandable when the prosthetic valve is released from the delivery catheter. The subannular region of the outer frame is disposable in a first configuration as the prosthetic valve is seated in an annulus of a native heart valve and is transitionable to a second configuration after the prosthetic valve is seated in the annulus of the native heart valve.