The current treatment of pulmonary arterial hypertension (PAH) uses vasodilator drugs. Although they improve symptoms associated with PAH, their chronic effects on the pulmonary vasculature and the right ventricle (RV) in humans remain unknown. We report the autopsy findings from a patient with idiopathic PAH treated with epoprostenol successfully for 18 years. The patient died of colon cancer. The pulmonary vasculature surprisingly showed extensive changes of a proliferative vasculopathy. Immunohistochemical studies confirmed ongoing cellular proliferation. Studies of the RV demonstrated concentric hypertrophy with seemingly preserved contractility. The myocardium shifted to glycolytic metabolism. Although the long-term use of epoprostenol contributed to the patient's increased survival, it did not prevent progression of the underlying vascular disease. Remarkably, the RV was able to sustain a normal cardiac output in the face of advanced vascular pathology. The mechanisms by which the RV adapts to chronic PAH need further study.