The Futility of Surveillance for Old and Small Aneurysms

Abstract

Inspired by the Canadian Choosing Wisely campaign, we investigated the yield and cost of ultrasound surveillance for small abdominal aortic aneurysms (AAAs) in octogenarians, compared with a younger population, for detecting AAA growth that reaches a sex-specific threshold size for repair. A retrospective cohort review was performed of all patients undergoing AAA surveillance in Ottawa between 2007 and 2017. Patients were dichotomized by enrollment age (<80 years vs ≥80 years) with crossover to prevent lead time bias and stratified by enrollment AAA size. These cohorts were cross-referenced with the Ottawa AAA repair database, leveraging the common Local Health Integration Network to ensure data capture. Survival analysis with Cox proportional hazards models adjusted for significant covariates, and cost-effectiveness analysis was performed referencing Ontario Health Insurance Plan codes. A total of 1378 patients underwent serial ultrasound surveillance. In 355 (25.8%), the AAA size threshold for repair was reached, and 313 (22.1%) underwent AAA repair. Octogenarians were half as likely as their younger counterparts to experience significant AAA growth (hazard ratio, 0.51; 95% confidence interval [CI], 0.37-0.83; Fig 1, A). Similarly, octogenarians were half as likely to experience an aortic event, a composite outcome including threshold-sized AAA, elective aortic repair, or aortic rupture (hazard ratio, 0.54; 95% CI, 0.43-0.68; Fig 1, B). When a threshold-sized AAA was identified, octogenarians were half as likely to undergo elective AAA repair (relative risk, 0.52; 95% CI, 0.45-0.59; Fig 2, A). Both ruptured AAA repair (0.94%) and procedure-related 30-day mortality (0.58%) were rare, and age differences were insignificant (Fig 2, B). AAA surveillance for octogenarians was substantially less cost-effective, incurring $12,080 in surveillance fees to identify one octogenarian with an AAA size of 3 to 3.9 cm who later underwent elective AAA repair (Fig 2, C and D). Octogenarians with small aneurysms are half as likely to experience significant aortic growth. Furthermore, in the unlikely event of AAA growth, octogenarians are half as likely to undergo repair, without a significantly increased risk of requiring repair for AAA rupture. The differences in natural history between the young and elderly patients suggest a difference in aneurysm pathophysiology. In the context of patient-specific factors, surveillance of AAAs <4 cm in octogenarians is costly and unlikely to be beneficial.Fig 2Incidence of abdominal aortic aneurysm (AAA) repair and resulting cost-effectiveness analysis. Groups are stratified by enrollment age and size of AAA at time of enrollment. A, When a threshold-sized AAA was reached, octogenarians were less likely to undergo elective AAA repair than their younger counterparts (overall relative risk, 0.52; 95% confidence interval, 0.45-0.59). B, Repair of ruptured AAA for patients in the surveillance program was rare, and differences were not statistically significant. C, Cost-effectiveness analysis incorporates a base cost of $89.20 for each surveillance ultrasound (Ontario Health Insurance Plan: code H 2, $57.00 technical cost; code P J202, $32.20 professional cost). D, Whereas the cost of surveillance to identify threshold-sized AAA was comparable between age cohorts, there was substantially more discrepancy in the cost of surveillance to prompt elective AAA repair.View Large Image Figure ViewerDownload Hi-res image Download (PPT)