4. Suspected chronic thromboembolic pulmonary hypertension (CTEPH) including RV hypertrophy (RV free wall >5 mm on echocardiography), severe pulmonary hypertension (systolic pulmonary artery pressure > 80 mmHg on echocardiography), or CT findings suggestive of CTEPH including intraluminal webs, bands, strictures, or eccentric filling defects adjacent to the wall of the pulmonary arteries