ABSTRACT: Background The aim of this study was to determine the role of ascending aortic length and diameter in type A aortic dissection. Methods and Results Computed tomography scans from patients with acute type A dissections (n=51), patients with proximal thoracic aortic aneurysms (n=121), and controls with normal aortas (n=200) were analyzed from aortic annulus to the innominate artery using multiplanar reconstruction. In the control group, ascending aortic length correlated with diameter (r2=0.35, P<0.001), age (r2=0.17, P<0.001), and sex (P<0.001). As a result of immediate changes in aortic morphology at the time of acute dissection, predissection lengths and diameters were estimated based on models from published literature. Ascending aortic length was longer in patients immediately following acute dissection (median, 109.7 mm; interquartile range [IQR], 101.0-115.1 mm), patients in the estimated predissection group (median, 104.2 mm; IQR, 96.0-109.3 mm), and patients in the aneurysm group (median, 107.0 mm; IQR, 99.6-118.7 mm) in comparison to controls (median, 83.2 mm; IQR, 74.5-90.7 mm) (P<0.001 all comparisons). The diameter of the ascending aorta was largest in the aneurysm group (median, 52.0 mm; IQR, 45.9-58.0 mm), followed by the dissection group (median, 50.3 mm; IQR, 46.6-57.5 mm), and not significantly different between controls and the estimated predissection group (median, 33.4 mm [IQR, 30.7-36.7 mm] versus 35.2 mm [IQR, 32.6-40.3 mm], P=0.09). After adjustment for diameter, age, and sex, the estimated predissection aortic lengths were 16 mm longer than those in the controls and 12 mm longer than in patients with nondissected thoracic aneurysms. Conclusions The length of the ascending aorta, after adjustment for age, sex, and aortic diameter, may be useful in discriminating patients with type A dissection from normal controls and patients with nondissected thoracic aneurysms.
