Association of Annual Caseload and Short Term Outcomes after Elective Open Abdominal Aortic Aneurysm Repair in Germany.

Abstract

The aim of this study was to determine the association between annual open surgical case volume and short term outcomes after open abdominal aortic aneurysm (AAA) repair, with explicit adjustment for differential patient selection in the contemporary era of low open caseload. This was a retrospective multilevel observational study of prospectively collected multicentre registry data from the German Institute for Vascular Research quality registry (2018 - 2025) and external mandatory quality reports (2018 - 2024). All patients undergoing elective open repair of intact AAA at participating centres were included. The primary exposure was mean annual open surgical volume per centre, assessed continuously (per standard deviation increase), and dichotomised at ≥ ten and ≥ 15 mean annual open cases and ≥ 15 mean annual open and ≥ 15 mean annual endovascular cases. Outcomes included in hospital death, major complications, failure to rescue, and the composite of in hospital death or major complication. Selection bias arising from differential case mix was addressed by including individual level propensity scores alongside covariate adjustment in mixed effects generalised additive models with facility level random effects. Of 28 730 patients with AAA repair, 5 716 (19.9%) underwent open AAA repair across 146 centres. Higher annual caseload was independently associated with lower odds of in hospital death (odds ratio [OR] 0.72, 95% confidence interval [CI] 0.62 - 0.84), major complication (OR 0.84, 95% CI 0.78 - 0.90), the composite of in hospital death or major complication (OR 0.83, 95% CI 0.78 - 0.89), and failure to rescue (OR 0.80, 95% CI 0.67 - 0.96) per standard deviation increase. Centres performing ≥ 15 open repairs annually showed more pronounced risk reductions with additional reductions in centres also performing ≥ 15 endovascular repairs. Volume effects were consistent across alternative exposure definitions and different subgroups. Higher annual open AAA case volume is associated with better short term outcomes, confirming contemporary recommendations on thresholds for open AAA repair.