Time Dependent Correlation Between Sac Behaviour and Re-intervention after Endovascular Aneurysm Repair

Abstract

This study aimed to investigate the correlation between aneurysm sac behaviour and time to re-intervention after endovascular aneurysm repair (EVAR). A retrospective observational cohort study of patients who underwent EVAR at a single centre between January 2008 and November 2011 and who were followed up for a mean of 6.6 ± 2.9 years was conducted. Based on sac appearances on pre-operative imaging and imaging at the end of follow up, patients were stratified into two groups: (1) sac regression; and (2) no sac regression. The no sac regression group was further subdivided into stable sac group and sac expansion group. Sac regression and expansion throughout follow up were defined as a decrease or increase in the abdominal aortic aneurysm sac diameter of ≥ 5 mm compared with the pre-operative size. A Cox proportional hazards model using multiple failure per subject data was used to identify sac behaviour as a predictor of re-intervention free time. Patients with sac regression had a higher probability of freedom from re-intervention compared with those with a stable or expanding aneurysm sac (94%, 57%, and 16% at 12 years, respectively; log rank, p<.001). Mean time to re-intervention was 11.3 years for the sac regression group, 8.8 years for the stable sac group, and 5.0 years for the sac expansion group (p < .001). In the stable sac group, the risk of re-intervention increased sharply six years after EVAR, whereas in the sac expansion group a sharp rise in re-intervention was noted 3.5 years after EVAR, reaching a plateau after year 6. A time dependent correlation between aneurysm sac behaviour and re-intervention was found. Such findings have implications for surveillance strategies.