Risk of Aortic Dissection in the Moderately Dilated Ascending Aorta

Recent studies have demonstrated that many patients with acute type A aortic dissection (AD) have aortic diameters of <55 mm at presentation, prompting discussion of lowering the prophylactic surgical guidelines. However, risk of dissection at these smaller diameters is poorly defined.

The purpose of this study is to understand the risk of AD in moderately dilated ascending aortas using a large echocardiographic data set.

Using an institutional echocardiography database, we identified 4,654 nonsyndromic adults (age: 68.6 ± 13.1 years; 1,003 women) with maximal ascending aortic diameters of 40 to 55 mm. We performed competing risk analysis to determine the independent risk factors of AD or aortic rupture.

Five hundred eighty-six individuals (12.6%) had bicuspid aortic valves (BAVs). During follow-up (14,431.5 patient-years), AD and rupture occurred in 13 and 1 patients, respectively, which demonstrated a linearized incidence of AD and/or rupture of 0.1% per patient-year. Elective ascending aortic repair was performed in 176 individuals. On multivariable analyses, independent predictors of AD and/or rupture were age (hazard ratio [HR]: 1.06; 95% confidence interval [CI]: 1.01 to 1.12; p= 0.024) and baseline aortic diameters (HR: 1.20; 95% CI: 1.05 to 1.36; p = 0.006). The presence of a BAV was not a significant factor (HR: 0.94; 95% CI: 0.10 to 8.40; p = 0.95). Estimated risks of AD and/or rupture within 5 years were 0.4%, 1.1%, and 2.9% at baseline aortic diameters of 45, 50, and 55 mm, respectively.

Risks of AD and/or rupture were significantly correlated with the aortic diameter and age in patients with moderately dilated ascending aortas. However, the risks were low for diameters <5.0 cm when timely elective aortic repair was performed, regardless of the morphology of the aortic valve.