Spironolactone Therapy in Chronic Stable Right HF Trial

Inclusion Criteria: * Provide a personally signed and dated inform consent form. * Male or female ≥ 18 years. * Able to comply with all study procedures. * History of right heart failure (RHF) secondary to either: i) WHO, group 1 pulmonary arterial hypertension PAH OR ii) WHO group II PH with normal LV systolic function OR iii) WHO group III or IV PH OR iv) primary RV cardiomyopathy. * Current NYHA II-IV * RV dysfunction as measured by 2D echocardiogram: i)defined as a tricuspid annular plane systolic excursion (TAPSE) \<16 mm ii) and /or a two dimensional fractional area change \<35% on screening echo plus * NT-proBNP\>400 pg/ml * Chronic use of diuretics * Clinical stability: defined as no need for increased diuretics, hospitalization or emergency room visit 3 months prior to enrollment Exclusion Criteria: * Patients on chronic MRA therapy or other potassium sparing diuretics. * Baseline serum potassium\>5 ummol/l. * Estimated glomerular filtration rate \<30 ml/min. * LV ejection fraction \<45%, * Moderate or severe LV diastolic function, * Moderate or severe aortic or valvular disease. * Patients requiring augmentation of diuretics or otherwise not meeting definition for clinical stability. * Severe Liver Failure (Child-Pugh Class C) * Claustrophobia or inability lie still in a supine position * Patients with contraindications to either PET or CMR imaging * Pregnancy or lactation. * Unable to provide consent and comply with follow up visits.