The futility of surveillance for old and small aneurysms

Abstract

ObjectiveWe investigated the yield of ultrasound surveillance for small abdominal aortic aneurysms (AAAs) in patients older than 80 years compared with a younger population for detecting AAA growth reaching the threshold size for repair. Secondary objectives included analysis of the incidence of AAA repair and the cost-benefit of surveillance. MethodsA retrospective cohort study was performed of all patients undergoing AAA surveillance in Ottawa between 2007 and 2015. Patients were dichotomized by enrollment age (<80 years vs ≥80 years) and stratified by enrollment AAA size. Cohorts were cross-referenced with the Ottawa surgical database, leveraging the common health region to ensure complete data capture. The threshold size for repair was sex specific (female, 5.0 cm; male, 5.5 cm). Factors influencing AAA growth rate were assessed with a general linear multiple mixed model. Analyses with Cox proportional hazards models with competing risk for mortality assessed aorta-related events, and cost-benefit was analyzed by referencing Ontario billing codes. ResultsA total of 1231 patients underwent serial ultrasound surveillance, of whom 500 were older than 80 years at some point during the study period. The mean AAA growth rate was 1.63 mm/y (95% confidence interval [CI], 1.54-1.71). Old age and small enrollment aneurysm size were significantly protective against AAA growth. Overall, 357 (29%) patients reached the AAA size threshold for repair, and 272 (22%) underwent AAA repair. Patients older than 80 years were less likely to reach the AAA threshold size for repair compared with their younger counterparts (adjusted hazard ratio, 0.77; 95% CI, 0.61-0.97). Of the 357 patients whose AAA reached the threshold size for repair, octogenarians were substantially less likely to undergo elective AAA repair (adjusted hazard ratio, 0.34; 95% CI, 0.24-0.47). Repair of ruptured AAA was rare (0.8%), and age differences were insignificant. For every octogenarian with an enrollment AAA size between 3.0 and 3.9 cm who ultimately received elective AAA repair, 51 patients were enrolled in surveillance without elective repair. This corresponded to an estimated $33,139 in ultrasound fees. ConclusionsSurveillance of most patients with small AAA is appropriate. However, patients older than 80 years were significantly less likely than their younger counterparts to experience aortic growth reaching the threshold size for repair. Furthermore, in the unlikely event of AAA growth, patients older than 80 years were substantially less likely to undergo repair. These results suggest that in the context of patient-specific health and wishes, surveillance of AAAs <4 cm in octogenarians is costly and unlikely to be beneficial.