A temporary subvalvular check valve has a collar and an expandable seal structure connected by pivotable struts that together support flexible leaflets. The check valve can be introduced along a tool shaft and positioned in a chamber or vasculature by expanding the seal structure against an adjacent wall. Cardiac function is augmented during valve procedures, such as valve excision, valve implantation, or valve leaflet replacement, by placing the temporary check valve just upstream of the valve being treated. The temporary check valve is collapsible so that it can be inserted through a small incision or port in the apex of the heart or through the aorta, into the ventricular cavity. Such a system thus does not require arrest or pacing of the heart and will allow such valve repair or replacement procedures to be done without concern for time or compromise to the patients physiology.
