Ventilation-perfusion lung scanning in the evaluation of pulmonary hypertension

The objective of this study was to define the sensitivity, specificity and accuracy of ventilation-perfusion (V/Q) lung scanning in distinguishing chronic thromboembolic pulmonary hypertension (PHT) from other nonembolic causes of PHT.

The V/Q lung scans from 75 patients in whom a confirmed cause of PHT was established were retrospectively reviewed. Twenty-five patients (33%) had chronic thromboembolic PHT, whereas 35 patients (47%) and 15 patients (20%) suffered from primary PHT and secondary nonthromboembolic PHT, respectively.

A high-probability V/Q scan interpretation had a sensitivity of 96% and a specificity of 94% for detecting patients with thromboembolic PHT. The combination of high- and intermediate-probability V/Q scan interpretations had a sensitivity of 100% for detecting patients with thromboembolic PH; however, the specificity decreased to 86%. Of the 35 patients with primary PHT, all but one patient had low-probability V/Q scan interpretations.

In this series, a low-probability V/Q scan interpretation effectively excluded the diagnosis of chronic thromboembolic PHT. In patients with an intermediate- or high-probability V/Q scan interpretation, pulmonary angiography was required to confirm the diagnosis of chronic thromboembolic PHT and determine whether surgical intervention was indicated. The V/Q lung scan appears to be a highly sensitive test for chronic thromboembolism in the diagnostic evaluation of patients with PHT. However, its role needs to be defined further by application to a prospectively recruited cohort of patients with PHT.