Effects of diabetes on small aortic aneurysms under surveillance according to a subgroup analysis from a randomized trial

Background: This study aims to investigate the impact of diabetes in the management of patients with small abdominal aortic aneurysms (AAA). Methods: Three-hundred sixty patients with small AAA (4.1-5.4 cm), enrolled in a randomized trial comparing early endovascular repair versus surveillance and delayed repair (after achievement of >5.5 cm or growth >1 cm/yr), were analyzed with standard survival methods to assess the relation between diabetes and risk of all-cause mortality, complications, and aneurysm growth (on computed tomography as per trial protocol) at 36 months. Baseline covariates were selected with partial likelihood stepwise method to investigate factors (demographic, morphologic, medications) associated with risk of aneurysm growth during surveillance. Results: Prevalence of diabetes was 13.6%. The hazard ratio (HR) for all-cause mortality at 36 months was higher in diabetic compared with nondiabetic patients: (HR, 7.39; 95% confidence interval [CI], 1.55-35.13; P = .012). Baseline aneurysm diameter was comparable between diabetic and nondiabetic patients enrolled in the surveillance arm and was related to subsequent aneurysm growth in covariance analyses adjusted for diabetes (49.3 mm for nondiabetic; 50.2 mm for diabetic). Cox analyses found diabetes as the strongest independent negative predictor of 63% lower probability of aneurysm growth >5 mm during surveillance (HR, 0.37; 95% CI, 0.15-0.92; P = .003). Kaplan-Meier cumulative probability of aneurysm growth >5 mm at 36 months was 40.8% in diabetics versus 85.1% in nondiabetics (HR, 0.32; 95% CI, 0.17-0.61). Conclusions: Progression of small AAA seems to be more than 60% lower in patients with diabetes. This may help to identify high-risk subgroups at higher likelihood of AAA enlargement, such as nondiabetics, for surveillance protocols in patients with small AAA. (J Vasc Surg 2012;56:1555-63.)