The purpose of this study is to characterize the clinical and hemodynamic response of Pulmonary Arterial Hypertension (PAH) therapy in patients with atypical PAH and risk factors for left heart disease.

This is an observational prospective study to better understand the clinical impact of Pulmonary Arterial Hypertension (PAH) specific therapy in patients with atypical PAH among those with risk factors for left heart disease

The study involves detailed baseline clinical evaluation prior to initiation of PAH therapy, followed by repeat clinical assessment after 6 months of medical therapy

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

Eligible patients will be identified from screening of the pulmonary hypertension clinic who are then planned for outpatient catheterization for diagnosis and management of their atypical PAH.