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A Septal Angle Measured on Computed Tomographic Pulmonary Angiography Can Noninvasively Estimate Pulmonary Vascular Resistance in Patients With Chronic Thromboembolic Pulmonary Hypertension

Liu, Min MD*; Ma, Zhan Hong MD*; Guo, Xiao Juan MD*; Wang, Shuan Kun MD*; Chen, Xiang Yun MD, PhD; Yang, Yuan Hua MD; Wang, Chen MD

doi: 10.1097/RTI.0b013e3182541142
Original Articles

Purpose: To explore the correlation between a septal angle measured on computed tomographic pulmonary angiography (CTPA) and pulmonary vascular resistance (PVR) determined by right heart catheterization in patients with chronic thromboembolic pulmonary hypertension (CTEPH).

Materials and Methods: Eighty-six patients with CTEPH (54 men, mean age: 53.08±12.43 y) were retrospectively reviewed, and 86 sex-matched and age-matched individuals without pulmonary artery hypertension and pulmonary embolism were used as the control group. All patients with CTEPH underwent CTPA before right heart catheterization. Septal angle was measured on transverse CTPA images as the angle between the interventricular septum and the line joining the midpoint of the sternum to the thoracic vertebral spinous process. Hemodynamic PVR was calculated on the basis of the data from right heart catheterization.

Results: Septal angle was 65.27±12.24 degrees and 39.43±9.79 degrees in the CTEPH group and control group, respectively, which was statistically significant (t=18.139, P=0.000). The septal angle correlated positively with PVR (r=0.629, P=0.000). By stepwise linear regression analysis, the septal angle was shown to be the only variable (r=0.578) that was independently associated with PVR levels, leading to the following equation: PVR=21.591×septal angle−374.641. By receiver operating characteristic analysis, septal angle ≥67.55 degrees had a sensitivity of 71.6% and a specificity of 73.4% for predicting PVR≥1000 dyne s/cm5 with an area under the curve of 0.739±0.055, which was higher than the area under the curve of right ventricular area/left ventricular area (0.627±0.061) and that of transverse diameter of right ventricle/transverse diameter of left ventricle (0.612±0.060).

Conclusion: The septal angle is a useful tool for estimating PVR in patients with CTEPH.

*Department of Radiology, Beijing Chao Yang Hospital of Capital Medical University

Department of Radiology, Respiratory Diseases Researching Institution, Beijing Chao Yang Hospital of Capital Medical University, Beijing, China

Supported by the Chinese National 11th Five-Year Researching Foundation (No. 2006BAI01A06) and the Youth Researching Foundation of Chao Yang Hospital (No. 2009-22).

The authors declare no conflicts of interest.

Reprints: Chen Wang, MD, Gong Ti Nan Road No. 8, Chao Yang District, Beijing 100020, China (e-mail:

© 2012 Lippincott Williams & Wilkins, Inc.