Treatment of Exercise-Induced Pulmonary Vascular Dysfunction After Pulmonary Thromboendarterectomy or Balloon Pulmonary Angioplasty

After obtaining baseline data, patients will be placed on oral riociguat at a dose of 0.5 mg TID which will be up titrated over two months to a maximum dose of 2.5 mg TID or maximum tolerated dose. After 3 months from onset of riociguat initiation, the University of California San Diego (UCSD) shortness of breath score, 6 Minute Walk Test (6MWD), and resting/exercise Right Heart Catheterization (RHC) will be repeated.