Effects of Pulmonary Hypertension Therapy in Atypical Pulmonary Arterial Hypertension

Inclusion Criteria: * Age ≥ 18 years * Pulmonary hypertension with mean PA pressure \>20 mmHg and a planned initiation of pulmonary arterial hypertension therapy * No active treatment for precapillary pulmonary hypertension * Ambulatory (not wheelchair/scooter dependent) * Presence of any risk factor for left heart disease will qualify for inclusion (either atrial fibrillation, body mass index\>30 kg/m2, arterial hypertension, diabetes, coronary artery disease or age\>60 years) Exclusion Criteria: * Significant chronic obstructive pulmonary disease that is a primary contributor to symptoms in the opinion of the investigator * Ischemia thought to contribute to dyspnea in the opinion of the investigator * Obstructive hypertrophic cardiomyopathy * Known infiltrative cardiomyopathy (amyloid) * Constrictive pericarditis or tamponade * Active myocarditis * Complex congenital heart disease * More than mild aortic or mitral stenosis * Intrinsic (prolapse, rheumatic) valve disease with more than moderate mitral, tricuspid or aortic regurgitation * Acute or chronic severe liver disease as evidenced by any of the following: encephalopathy, variceal bleeding, INR \> 1.7 in the absence of anticoagulation treatment * Terminal illness (other than HF) with expected survival of less than 1 year * Enrollment or planned enrollment in another therapeutic clinical trial in next 3 months. * Inability to comply with planned study procedures * Pregnancy or breastfeeding mothers