In possibly eligible patients a screening echocardiography is performed during hospitalization at the coronary care unit 2144 or 3141 HS Rigshospitalet, Denmark. If eligible and consent is obtained during hospitalisation an ambulatory exercise Doppler echocardiography with simultaneous invasive recording of pulmonary wedge pressure, pulmonary artery pressure and cardiac index and a 6 min walk test and maximal exercise test is performed 1 week after revascularization. Patients are then randomized in a 1 to 1 fashion to placebo or sildenafil 20 mg three times daily. If tolerated dosage is titrated every 2'nd week in the outpatient clinic to a target dose of 40 mg three times daily. After 9 weeks of treatment exercise echocardiography and 6 min walk test are repeated, in addition conventional maximal ergometer testing is performed.