The role of the angle of the ascending aortic curvature on the development of type A aortic dissection: ascending aortic angulation and dissection

OBJECTIVES: Type A aortic dissection (TAD), which consists of an intimal tear in the aorta, necessitates emergency surgery. Various risk factors related to aortic dissection have been defined in the literature. According to our hypothesis, a narrower angle of ascending aortic curvature (AAAC) may be an additional risk factor in relation to aortic dissection due to the increased force applied to the aortic wall. METHODS: Patients undergoing ascending aortic surgery due to an ascending aortic aneurysm (AsAA) (n = 105) and patients undergoing such surgery because of the occurrence of TAD (n = 101) were enrolled in this study. The AAAC was measured using Cobb's method; the measurements were made on all patients by just 1 cardiovascular radiologist using 3-dimensional computerized tomographic imaging. This measurement was made indirectly by using the aortic valve and brachiocephalic artery to avoid obtaining misleading data as a result of distortions due to dissection. A statistical comparison was also performed relating the traditional risk factors for TAD to other clinical and echocardiographic parameters: the diameter of the ascending aorta and the AAAC. RESULTS: The AAAC was found to be narrower statistically in the TAD group (α = 76.2° ± 17.5°) than it was in the AsAA group (α = 92.9° ± 13°) (P < 0.001). Furthermore, mean ascending aortic diameter (P = 0.019), the presence of a bicuspid aorta (P = 0.007) and aortic valve stenosis (P = 0.005) were higher in the AsAA group. According to multivariable analyses, a narrower AAAC is a significant predictor for the development of TAD (odds ratio 0.93, 95% confidence interval 0.91-0.95; P < 0.001). Overall hospital mortality from various causes including stroke, myocardial infarction, bleeding or renal failure was 13% in the TAD group and 7% in the AsAA group. CONCLUSIONS: According to this study, the AAAC was significantly smaller in aortic dissection patients than in aortic aneurysm patients. This may be related to higher shear stress and elevated pressure on the ascending aorta in patients with a narrower AAAC. Thus, a narrower AAAC may be an additional risk factor in the development of TAD. Therefore, we may need to be more careful in terms of looking for the development of aortic dissection in patients with narrower AAAC.