Decreased Pulmonary Artery Bifurcation Angle: A Novel Imaging Criterion for the Diagnosis of Chronic Pulmonary Thromboembolism

Background: Chronic pulmonary thromboembolism (CTEPH) is an unusual complication of acute pulmonary embolism (PE), which is now considered to be treatable. In modern multi-detector scanners, a detailed evaluation of pulmonary artery geometry is currently possible. This study aimed to evaluate the changes in pulmonary artery bifurcation angle (PABA) in the follow-up computed tomography angiography (CTA) of patients with acute PE.

Methods: In this cross-sectional study, the records of two tertiary-level academic hospitals were gathered from 2012 to 2019. Pulmonary artery (PA) bifurcation angle and diameter were measured. Chi square test, independent samples test, Mann-Whitney, and Pearson's tests were employed to compare data. To evaluate the cut-off point, we utilized receiver operating characteristic (ROC) curve analysis. The accuracy, sensitivity, and specificity of pulmonary artery bifurcation angle changes were calculated. A P value <0.05 was considered to be significant.

Results: Forty-six patients were included in the study. No significant differences were found between patients with and without CTEPH, and PABA in the dimeters of PA trunk, right PA, and left PA in the first CTA images (P values of 0.151, 0.142, 0.891, and 0.483, respectively), while in the secondary CTA, the mean PABA was significantly smaller in patients with CTEPH (P=0.011). In the receiver operating characteristic (ROC) analysis, delta angle revealed an area under the curve of 0.745 and an optimal cutoff of 0, leading to a sensitivity of 64%, specificity of 87%, and accuracy of 76% for diagnosing CTEPH.

Conclusion: We showed a significant decrease in PABA in patients developing CTEPH. This parameter can be easily measured in lung CTA.