To find out whether an enhanced cardiopulmonary fitness (exercise capacity and RV function) improves the quality of life, Spironolactone in combination with an endothelin receptor type A blocker will be administered to PAH patients with a LV ejection fraction > 50% in a prospective, double blind, placebo-controlled phase 4 study (ClinicalTrials.gov identifier: NCT02253394). This evidence concerns the gene EDNRA and pulmonary arterial hypertension.