CT evaluation of chronic thromboembolic pulmonary hypertension

Eight patients with chronic thromboembolic pulmonary hypertension (CTPH) that had been demonstrated by perfusion lung scan, pulmonary arteriography, and right heart catheterization had their pulmonary circulation evaluated by CT. Eight subjects without lung pathology were also studied for comparison. High resolution CT from apex to base with 1 cm thick sections after intravenous injection of contrast medium was performed in each individual. Emboli lodged in main pulmonary arteries on arteriography were regularly shown by CT, whereas those in segmental or smaller arteries were not detected. Diameters of the main pulmonary arteries measured on CT correlated with systolic pulmonary artery pressure (p < 0.001). The ratio between diameters of segmental arteries and the corresponding bronchi (A/B ratio) on CT was > 1 in 72 of 144 examined pulmonary segments (18 segments for each patient) in patients with CTPH. The ratio was > 1 in only 10 of 144 examined segments in normal control subjects. Dilatation of bronchial arteries was present in four of eight patients with CTPH. The parenchymal density in patients with CTPH was significantly higher in the axial than in the middle or peripheral lung compartments. In conclusion, CT may help with the diagnosis of CTPH by detecting thrombi of main arteries and by showing characteristic findings; moreover, it is accurate in estimating pulmonary arterial pressure secondary to thromboembolic obstruction.