Dysfunction of any mechanical prosthesis due to thrombus or pannus requires prompt definite diagnosis and therapy. A 55-year-old woman had received a prosthetic valve for aortic regurgitation 3 years before and was admitted for intermittent chest pain. Electrocardiography showed remarkable ST depression in broad leads during chest pain. Coronary angiography and cinefluoroscopy performed for definite diagnosis at the time of the third attack revealed no stenotic lesion in the coronary artery, but an artificial valve stuck in the completely open position. The diagnosis was acute aortic regurgitation caused by the stuck open valve. Urgent reoperation was performed. Abnormal proliferation of pannus trapping the artificial aortic valve was found at the left ventricular-side orifice of the prosthetic valve. Intermittent valvular sticking can cause acute aortic regurgitation and caused the symptomatic intermittent chest pain and ST depression in this patient.