Moderate Aortic Dilation and Aortic Dissection Risk
What is the risk of aortic dissection among patients with an ascending aortic diameter of 40-55 mm?
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.
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.
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.
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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