Risk of Aortic Dissection in the Moderately Dilated Ascending Aorta

Abstract

Background: 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.

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

Methods: 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.

Results: 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.

Conclusions: 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.

Keywords: aneurysm; aorta; aortic dissection; prognosis; risk factors.