What is pulmonary hypertension, and what CT and MRI findings are suggestive?
Pulmonary hypertension is comprised of a heterogeneous group of disorders that cause abnormal elevation of pressure in the pulmonary circulation, with a mean pulmonary artery pressure higher than 25 mm Hg, regardless of the underlying mechanism. There are 5 World Health Organization (WHO) classifications of pulmonary hypertension, which can be broadly categorized into precapillary (wedge pressure <15 mm Hg) and postcapillary (wedge pressure >15 mm Hg) etiologies. CT and MRI findings in pulmonary hypertension may vary depending on the underlying etiology, but typical findings may include
- • Main pulmonary artery caliber >29 mm.
- • Main pulmonary artery diameter greater than that of the ascending aorta.
- • Enlargement of segmental pulmonary arteries relative to the adjacent segmental bronchi.
- • Right ventricular hypertrophy.
- • Right ventricular and right atrial dilation.
- • Straightening or leftward bowing of the interventricular septum.
- • Delayed phase contrast enhancement with a midwall distribution at the right ventricular septal insertion that points into the interventricular septum, more prominent at the base of the heart (only on MRI).
- • Dilation of the inferior vena cava and hepatic veins.
- • Mosaic attenuation of the lungs (only on CT).
- • Centrilobular ground glass attenuation nodules (due to cholesterol granulomas or pulmonary capillary hemangiomatosis, only on CT).
