The invention provides an apparatus (10) for endovascularly replacing a patient's heart valve. The apparatus comprises an expandable anchor (30) supporting a replacement valve (20) and a delivery catheter adapted to deliver the anchor and replacement valve to a vicinity of the heart. The anchor and replacement valve are adapted for percutaneous delivery and deployment to replace the patient's heart valve and are further adapted to permit blood flow through the replacement valve and to prevent blood backflow through the replacement valve after the replacement valve exits the catheter and before final deployment of the anchor. The apparatus further comprises a seal (380) adapted to prevent blood flow around the replacement valve when the anchor and replacement valve are fully deployed.
