A Study to Evaluate Whether Macitentan is an Effective and Safe Treatment for Patients With Heart Failure With Preserved Ejection Fraction and Pulmonary Vascular Disease

Inclusion Criteria: * Signs or symptoms of Heart Failure (HF) (NYHA FC I I and II I ) requiring treatment with at least one oral diuretic (any type) * Left ventricular ejection fraction (LVEF) ≥ 40% (by echocardiography at Screening) * Structural heart disease consistent with heart failure with preserved ejection fraction (HFpEF) established by echocardiography at Screening * Elevated NT-proBNP * Pulmonary vascular disease or right ventricular dysfunction Exclusion Criteria: * Any prior valid measurement of LVEF \< 40%. An echocardiogram is considered valid if its quality is sufficient to allow accurate assessment of LVEF and if it is reflective of the true status of the subject * Cardiovascular co-morbidities (e.g., significant unrepaired structural valvular heart disease; acute coronary syndrome, coronary artery bypass graft (CABG) or percutaneous coronary intervention (PCI) within 3 months of Screening; uncontrolled heart rate from atrial fibrillation or atrial flutter, history of serious life-threatening or hemodynamically significant arrhythmia; history of or anticipated heart transplant or ventricular assist device implantation, etc) * Systolic blood pressure (SBP) ≥ 180 mmHg, or diastolic blood pressure (DBP) ≥ 110 mmHg during Screening * Hemoglobin \< 100g/L (\< 10 g/dl) at Screening * Significant parenchymal lung disease (e.g., severe COPD, moderate or severe restrictive lung disease, diffuse interstitial fibrosis or alveolitis, pulmonary thromboembolism) * Severe renal dysfunction with an estimated Glomerular Filtration Rate (eGFR) \< 30 mL/min per 1.73 m2 * Severe hepatic impairment, e.g., Child Pugh Class C Other protocol-defined inclusion/exclusion criteria may apply