The patient was a 56-year-old female diagnosed with poor lung function who had undergone an aortic valve replacement 10 years ago, receiving an SJM 19 A prosthetic valve. She suffered from dyspnea and chest pain with postural change. Her anticoagulation level was maintained therapeutic. A cinefluoroscopy showed that one of the leaflets in the prosthetic valve was not moving. The aortic peak pressure gradient was calculated to be 68 mmHg using Doppler echocardiography. The patient's clinical condition improved after thrombolytic therapy with urokinase, but a complete normalization of her prosthetic discs was not obtained, so the patient was treated surgically. After an aortotomy, a pannus formation covering the entire SJM 19 A valve was observed. The aortic annulus was estimated to be 16 mm in diameter after the excision of the SJM 19 A valve and required before a larger prosthesis could be inserted. A SJM 19 HP valve was then anchored to the enlarged annulus. Her postoperative course was uneventful. We report a case requiring reoperation after a small aortic mechanical valve prosthesis implanted 10 years previously was damaged by thrombosis and pannus. Pannus formation on small aortic prosthesis easily caused hemodynamic obstructions and mechanical failure. Intensive evaluation with Doppler echocardiography and cinefluoroscopy is required for such patients.