 The U.S. CTEPH Registry is a multicenter, observational, U.S.-based study of the clinical course and treatment of patients diagnosed with chronic thromboembolic pulmonary hypertension CTEPH, WHO Group IV Classification for Pulmonary Hypertension. The mission of the Registry will be to promote a greater understanding of the prevalence, pathophysiology, evaluation, and treatment of patients with CTEPH through shared information, education, and collaborative investigation among pulmonary hypertension PH centers of excellence throughout the U.S. 