Left Atrial Area and Right Ventricle Dimensions in Non-gated Axial Chest CT can Differentiate Pulmonary Hypertension Due to Left Heart Disease from Other Causes

• A dilated pulmonary artery (PA) on CT may be suggestive of pulmonary hypertension, however does not identify the subgroup.
• When PA is dilated, left atrial and right ventricle size on an axial CT may help to distinguish group 2 from non-group 2 PH.
• In patients with a dilated PA on an axial CT, a dilated left atrium with normal right ventricle is indicative of group 2 PH.
• An enlarged right ventricle and normal left atrial size with a dilated PA on chest CT suggests non-group 2 PH.
• These findings may be helpful in detecting the undiagnosed, unsuspected PH and distinguishing group 2 PH from others.

BackgroundIt is unknown whether axial non-gated CT can distinguish World Health Organization Group 2 pulmonary hypertension (pulmonary hypertension due to left heart disease) from non-Group 2 pulmonary hypertension.ObjectiveThe study was performed to identity imaging parameters in non-gated chest CT that differentiate Group 2 from non-Group 2 pulmonary hypertension.MethodsAmong 158 patients who underwent right heart catheterization for evaluation of pulmonary hypertension, 112 had sufficient data and chest CT for review. Invasive hemodynamic data and numerous variables obtained from axial CT images (maximum diameters of main, right, left pulmonary arteries, ascending aorta, main pulmonary artery to ascending aorta diameter ratio, right atrial diameter, left atrial area and right ventricular size) were collected. CT variables were validated against hemodynamic data to identify parameters that would allow to differentiate pulmonary hypertension due to left heart disease (Group 2) from non-Group 2 pulmonary hypertension.ResultsBased on right heart catheterization data, we identified 53 patients with Group 2 pulmonary hypertension, 50 patients with non-Group 2 pulmonary hypertension, and 9 subjects with no pulmonary hypertension. In patients with a dilated pulmonary artery (n = 84), the ROC curve for left atrial area (area under the ROC curve 0.76 ± 0.06) independently distinguished patients with Group 2 pulmonary hypertension (n = 42) from patients with non-Group 2 pulmonary hypertension (n = 42). A dilated left atrium (>20 mm2) in combination with a normal right ventriuclar size had a sensitivity of 77% and specificity of 94% for Group 2 pulmonary hypertension.ConclusionsIn patients with a dilated pulmonary artery on chest CT, left atrial area and right ventricular dimensions may aid to diagnose pulmonary hypertension and to distinguish underlying cardiac disease from other causes.