Moderate Aortic Dilation and Aortic Dissection Risk

Study Questions:

What is the risk of aortic dissection among patients with an ascending aortic diameter of 40-55 mm?

Methods:

An institutional echocardiography database was used to identify 4,654 nonsyndromic adults (excluding patients with Marfan, Loeys-Dietz, and Ehlers-Danlos syndromes; and inflammatory aortic diseases; age 68.6 ± 13.1 years, 1,003 women) with maximal echocardiographic ascending aortic diameters of 40-55 mm. Competing risk analysis was performed to determine the independent risk factors of type A aortic dissection or aortic rupture.

Results:

A total of 586 individuals (12.6%) had a bicuspid aortic valve. During follow-up (14,431.5 patient-years), aortic dissection or rupture occurred in 13 patients and 1 patient, respectively; with a linearized incidence of aortic dissection and/or rupture of 0.1% per patient-year. Elective ascending aortic repair was performed in 176 individuals. On multivariable analyses, independent predictors of aortic dissection and/or rupture were age (hazard ratio [HR], 1.06; 95% confidence interval [CI], 1.01-1.12; p = 0.024) and baseline aortic diameter (HR, 1.20; 95% CI, 1.05-1.36; p = 0.006). The presence of a bicuspid aortic valve was not a significant factor (HR, 0.94; 95% CI, 0.10-8.40; p = 0.95). Estimated risks of aortic dissection 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 aortic dissection and/or rupture were significantly correlated with the aortic diameter and age in patients with a moderately dilated ascending aorta. 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.

Perspective:

These data suggest that the risk of aortic dissection or rupture gradually increases with age and with aortic diameter. Although current guidelines use a threshold diameter of 55 mm for elective intervention among most nonsyndromic patients, these data suggest that there is a small but appreciable risk of aortic catastrophe among patients with a smaller ascending aorta, and might support elective intervention for patients with a smaller aorta (e.g., 50-55 mm) if performed by a highly experienced surgeon and with a low anticipated operative risk. Interestingly, the presence of a bicuspid aortic valve did not appear to increase the risk of aortic dissection or rupture. The impact of age as a risk factor for aortic catastrophe carries significant implications. Currently accepted nomograms for ascending aorta size (e.g., Campens L, et al., Am J Cardiol 2014;114:914-20) suggest that the normal aorta increases as a function of increasing age. However, these data suggest that the observed ‘normal’ increase in size also carries an increase in risk.


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