Editor's Choice – Systematic Review and Meta-Analysis of Contemporary Abdominal Aortic Aneurysm Growth Rates

Objective: To evaluate the contemporary growth rate of small abdominal aortic aneurysms (AAAs) in view of recent epidemiological changes, such as decreasing smoking rates and establishment of population screening programmes. Data sources: MEDLINE, CENTRAL, PsycINFO, Web of Science Core Collection, and OpenGrey databases. Review methods: Systematic review following the PRISMA guidelines. In October 2021, databases were queried for studies reporting on AAA growth rates published from 2015 onwards. The primary outcome was contemporary AAA growth rates in mm/year. Data were pooled in a random effects model meta-analysis, and heterogeneity was assessed through the I2 statistic. GRADE assessment of the findings was performed. The protocol was published in PROSPERO (CRD42022297404). Results: Of 8 717 titles identified, 43 studies and 28 277 patients were included: 1 241 patients from randomised controlled trials (RCTs), 23 941 from clinical observational studies, and 3 095 from radiological or translational research studies. The mean AAA growth rate was 2.38 mm/year (95% CI 2.16 – 2.60 mm/year; GRADE = low), with meta-regression analysis adjusted for baseline diameter showing an increase of 0.08 mm/year (95% CI 0.024 – 0.137 mm/year; p = .005) for each millimetre of increased baseline diameter. When analysed by study type, the growth rate estimated from RCTs was 1.88 mm/year (95% CI 1.69 – 2.06 mm/year; GRADE = high), while it was 2.31 mm/year (95% CI 1.95 – 2.67 mm/year; GRADE = moderate) from clinical observational studies, and 2.85 mm/year (95% CI 2.44 – 3.26 mm/year; GRADE = low) from translational and radiology based studies (p < .001). Heterogeneity was high, and small study publication bias was present (p = .003), with 27 studies presenting a moderate to high risk of bias. The estimated growth rate from low risk studies was 2.09 mm/year (95% CI 1.87 – 2.32; GRADE = high). Conclusion: This study estimated a contemporaneous AAA growth rate of 2.38 mm/year, being unable to demonstrate any clinically meaningful AAA growth rate reduction concomitant with changed AAA epidemiology. This suggests that the RESCAN recommendations on small AAA surveillance are still valid. However, sub-analysis results from RCTs and high quality study data indicate potential lower AAA growth rates of 1.88 – 2.09 mm/year, findings that should be validated in a high quality prospective registry.