Effects of Combination Medical Therapy Followed by BPA on Right Ventricular-PA Coupling and Hemodynamics in CTEPH

Inclusion Criteria: Subjects must meet all of the following inclusion criteria to be eligible for enrollment into the trial: 1. Age ≥ 18 years' old 2. Diagnosis of CTEPH 3. Not a candidate for PTE 4. Candidate for BPA based on suitable anatomy and disease burden 5. Treatment-naïve (no CTEPH or pulmonary arterial hypertension (PAH)-specific medical therapies) with plans for initiation of CTEPH/PAH-specific medical therapy and treatment with BPA. 6. Willing and able to give informed consent and adhere to visit/protocol schedules (Consent must be given before any study procedures are performed). Exclusion Criteria: * Subjects presenting with any of the following will not be included in the trials: 1. Moderate to severe heart disease (LVEF \< 45% or severe LV Hypertrophy) 2. Sarcoidosis 3. Active cancer 4. Sickle cell anemia 5. Liver disease (Childs-Pugh class C) 6. Prisoners 7. Pregnant, planning pregnancy or lactating 8. Conditions that will prohibit MRI scanning (metal in eye, claustrophobia, inability to lie supine) 9. Contraindication to riociguat or macitentan 10. Medical or psychological conditions which, in the opinion of the investigator, might create undue risk to the subject or interfere with the subject's ability to comply with the protocol requirements