Effect of Sildenafil for Sustained PAH After MV Surgery (SUPERIOR Trial)

Inclusion Criteria: * New York Heart Association Functional class (NYHA Fc) ≥ 2 dyspnea which was sustained till one year after the previous mitral valve surgery (repair or replacement) * TR Vmax ≥ 3.5m/s by echocardiography * Normal left ventricle ejection fraction (EF ≥ 50%) * Pulmonary vascular resistance ≥ 3 Wood Unit or diastolic pressure gradient ≥ 7mmHg by cardiac catheterization Exclusion Criteria: * Other valve disease more than moderate degree (ex. aortic stenosis, aortic regurgitation) * Liver cirrhosis * Chronic renal failure with serum creatinine ≥ 1.7mg/dL * Lung disease (ex. chronic obstructive pulmonary disease, Asthma) * Thyroid dysfunction * Other causes which can lead to pulmonary hypertension