Predicting aortic complications after endovascular aneurysm repair

Background: Lifelong surveillance is standard after endovascular repair of abdominal aortic aneurysm (EVAR), but remains costly, heterogeneous and poorly calibrated. This study aimed to develop and validate a scoring system for aortic complications after EVAR, informing rationalized surveillance. Methods: Patients undergoing EVAR at two centres were studied from 2004 to 2010. Preoperative morphology was quantified using three-dimensional computed tomography according to a validated protocol, by investigators blinded to outcomes. Proportional hazards modelling was used to identify factors predicting aortic complications at the first centre, and thereby derive a risk score. Sidak tests between risk quartiles dichotomized patients to low-or high-risk groups. Aortic complications were reported by Kaplan-Meier analysis and risk groups were compared by log rank test. External validation was by comparison of aortic complications between risk groups at the second centre. Results: Some 761 patients, with a median age of 75 (interquartile range 70-80) years, underwent EVAR. Median follow-up was 36 (range 11-94) months. Physiological variables were not associated with aortic complications. A morphological risk score incorporating maximum aneurysm diameter (P < 0.001) and largest common iliac diameter (measured 10mm from the internal iliac origin; P = 0.004) allocated 75 per cent of patients to a low-risk group, with excellent discrimination between 5-year rates of aortic complication in low-and high-risk groups at both centres (centre 1:12 versus 31 per cent, P < 0.001; centre 2: 12 versus 45 per cent, P = 0.002). Conclusion: The risk score uses commonly available morphological data to stratify the rate of complications after EVAR. The proposals for rationalized surveillance could provide clinical and economic benefits.