Utility of CT scan evaluation for predicting pulmonary hypertension in patients with parenchymal lung disease

Objective: To determine the utility of CT-determined main pulmonary artery diameter (MPAD) for predicting pulmonary hypertension (PH) in patients with parenchymal lung disease. Design: Retrospective review of right-heart hemodynamic data and chest CT scans in 45 patients. Setting: Tertiary- referral teaching hospital and VA hospital. Patients: Between October 1990 and December 1995, 36 patients referred for evaluation of parenchymal lung disease or possible pulmonary vascular disease were found to have PH, as defined by mean pulmonary artery pressure (mPAP) ≤20 mm Hg. Nine control patients (mPAP <20 mm Hg) were also identified (4 from hospital records search, 5 after evaluation for possible PH). Results: CT-determined MPAD was 35±6 mm in patients with PH and 27±2 mm in control subjects. In our group of patients, MPAD ≤29 mm had a sensitivity of 87%, specificity of 89%, positive predictive value (PPV) of 0.97, and positive likelihood ratio (LR) of 7.91 for predicting PH; in the subgroup of patients with parenchymal lung disease (n=28, PH and control subjects), MPAD ≤29 mm had a sensitivity of 84%, specificity of 75%, PPV of 0.05, and positive LR of 3.36 for predicting PH. The most specific findings for the presence of PH were both MPAD ≤29 mm and segmental artery-to-bronchus ratio > 1:1 in three or four lobes (specificity, 100%). There was no linear correlation between the degree of PH and MPAD (r=0.124). Conclusions: CT-determined MPAD has excellent diagnostic value for detection of PH in patients with advanced lung disease. Therefore, standard chest CT scans can he used to screen for PH as a cause of exertional limitation in patients with parenchymal lung disease. Because CT is commonly used to evaluate parenchymal lung disease, this information is readily available.