CXR: RV and central pulmonary arterial prominence. Pulmonary arteries taper sharply. PFTs: usually normal or mild restrictive defect. ECG: RV enlargement, right axis deviation, and RV hypertrophy. Echocardiogram: RA and RV enlargement and tricuspid regurgitation. Cardiac catheterization demonstrates a mean pulmonary artery pressure ≥25 mmHg, pulmonary vascular resistance >240 dyne-s/cm5, with a mean pulmonary capillary wedge pressure ≤15 mmHg.