Abdominal Aortic Aneurysm Screening Is Safe yet Lacks Effectiveness: Looking Beyond Size Criteria

Abstract

In this issue of Circulation, Oliver-Williams and colleagues 1 elegantly demonstrate the relatively low rate of rupture in men with abdominal aortic aneurysms (AAAs) <5.5 cm in diameter. In July 2009, the United Kingdom’s National Health Service (NHS) introduced a formal AAA screening program for all men aged >65 years.2 Since the inception of this program, the authors have compiled data on 18 652 men with AAA who were either invited for screening or self-referred. Importantly, only 31 men experienced AAA rupture during the surveillance program, which equated to an incidence of 0.06 per 100 person-years. Death ensued in almost all of these men (29 of 31), which reinforces the well-established notion that elective repair is always preferable to emergent. Maximal aortic diameter was predictive of rupture risk, because the cumulative incidence of rupture over 8 years nearly doubled when small (3–4.4 cm) and medium-sized (4.5–5.4 cm) AAAs were compared (0.35% versus 0.62%, respectively). Still, the annual rate of rupture for medium-sized AAAs was low at 0.4% per year, which suggests that the current threshold for surgical repair (>5.5 cm) is appropriate. Although AAA rupture was a relatively infrequent cause of mortality (3%) in the cohort compared with cancer (31%) or cardiovascular disease (26%), overall mortality rates were ≈60% higher in those men with AAAs who were invited to participate in the surveillance program than in ageand sex-matched control subjects. This finding likely reflects the overall poor health of those with aneurysm disease, who are often smokers with underlying cardiovascular disease. The purpose of the study by Oliver-Williams et al1 was not to justify the role of AAA screening in the NHS but rather to ensure that their efforts are in fact safe, especially in those with medium-sized aneurysms. Multiple randomized, controlled trials and meta-analyses have documented the benefit of AAA screening using a single duplex ultrasonography (DU) examination.3,4 The most notable trial, which was the basis for the NHS screening program, was the United Kingdom MASS study (Multicentre Aneurysm Screening Study).3 In this trial, >27 000 men aged 65 to 74 years were screened, and abdominal DU detected >1300 AAAs. At 13 years, the AAA-related mortality was reduced by nearly half in those men invited for screening (0.66%) compared with the control group (1.12%). This reduction equated to an incremental cost-effectiveness ratio of £7600 per life-year gained at 10 years, which compelled the NHS to initiate a formal screening program in 2009. A similar program, albeit slightly more selective, has been implemented in the United States, with AAA screening via DU offered to men aged 65 to 75 years who are active or former smokers.5 Theoretically, nearly 90% of all AAAs in this age group would be detected if only smokers were examined, hence the more selective screening criteria offered by the US Preventive Services Task Force. © 2019 American Heart Association, Inc.