Inclusion Criteria:

• 1. Age ≥ 18 years' old
• 2. Be on the lung transplant waiting list at Duke University Medical Center.
• 3. PH as defined by RHC - mPAP \> 20 mmHg, PVR \> 3 WU, PCWP \< 15 mmHg
• 4. Groups defined as:
• PAH: Clinical diagnosis of PAH (Group 1 PH) in the absence of severe chronic lung disease, left heart disease, chronic thromboembolism, sarcoidosis, sickle cell disease, or other causes of non-Group 1 PH.
• COPD-noPH: Clinical diagnosis of COPD in the absence of precapillary PH.
• COPD-PH: Clinical diagnosis of COPD with precapillary PH.
• IPF-noPH: Clinical diagnosis of IPF in the absence of precapillary PH.
• IPF-PH: Clinical diagnosis of IPF with precapillary PH.
• 5. 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:

• 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 and pregnant women will not be approached for the study.
• 7. Inability to obtain consent.
• 8. Conditions that will prohibit MRI scanning (metal in eye, claustrophobia, inability to lie supine).
• 9. 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