Spironolactone for Pulmonary Arterial Hypertension

INTRODUCTION: Pulmonary arterial hypertension (PAH) is a rare disorder associated with poor survival. Endothelial dysfunction resulting from 1) genetic susceptibility, and 2) a triggering stimulus that initiates pulmonary vascular injury, the "two-hit" hypothesis, appears to play a central role both in the pathogenesis and progression of PAH. Inflammation appears to drive this dysfunctional endothelial phenotype, propagating cycles of injury and repair in genetically susceptible patients with idiopathic PAH (IPAH) and patients with disease-associated PAH. Therapy targeting pulmonary vascular inflammation to interrupt cycles of injury and repair and thereby delay or prevent RV failure and death has not been tested. Spironolactone, a mineralocorticoid receptor (MR) and androgen receptor (AR) antagonist, has been shown to improve endothelial function and reduce inflammation. Current management of patients with severe PAH and NYHA/WHO class IV symptoms includes use of MR antagonists for their diuretic and natriuretic effects once clinical right heart failure has developed. We hypothesize that initiating therapy with spironolactone at an earlier stage of disease in subjects with PAH could provide additional benefits through anti-inflammatory effects and improvements in pulmonary artery endothelial function. OBJECTIVES: Patients with IPAH and disease-associated PAH will be recruited to the NIH and enrolled in a randomized, double blinded, placebo-controlled study of early treatment with spironolactone to investigate its effects on exercise capacity, clinical worsening, and vascular inflammation in vivo. METHODS: The total number of PAH subjects enrolled will be up to 70. Subjects will undergo 1) standard clinical examinations including 6-minute walk distance and echocardiography; 2) cardiopulmonary exercise testing; 3) plasma profiling of inflammatory and neurohormonal markers; 4) gene expression profiling of peripheral blood mononuclear cells (PBMCs); and 5) high-resolution MRI-based determination of pulmonary vascular and RV structure and function. Safety and tolerability of spironolactone in PAH will be assessed with periodic monitoring for hyperkalemia and renal insufficiency as well as the incidence of drug discontinuation for untoward effects.