Relationship between annual hospital volume and outcome following carotid endarterectomy for symptomatic carotid stenosis in Sweden

OBJECTIVES: In several European countries, declining volumes of surgery for symptomatic carotid stenosis have been reported, likely as a consequence of reduced smoking rates and improved medical therapy. In Sweden, 21 centers are performing carotid endarterectomy (CEA), 5 of them performing nearly 50% of the total volume. The aim of the present study was to compare outcome after CEA in high volume and low volume centers and to see whether there is an optimal volume threshold. METHODS: Registry based study on all patients treated with CEA (n=12169) for symptomatic carotid stenosis during the period July 2008 - December 31 2023. All centres were analysed separately, and also dichotomised if performing more than 50 CEAs annually (high volume centers) or less than 50 procedures (low volume centres). Multivariable logistic regression models were used to assess independent predictors of ipsilateral and contralateral stroke, while Cox proportional hazards models were employed for death and stroke-or-death outcomes, accounting for patient-level covariates and centre effects. Sensitivity analyses: exclusion of smallest centers, alternative thresholds and stratification for early and late study periods where performed. RESULTS: In the crude analysis, stroke or death was more frequent in the low volume group, occurring in 4.48% of cases (95% CI 3.98-5.03) compared to 3.62% (95% CI 3.17-4.13) in the high-volume group (p = 0.018) After adjusting for differences in comorbidities and demographic data, low volume centres demonstrated significantly higher odds of stroke or death within 30 days after CEA with a hazard ratio of 1.23 (95% CI: 1.03-1.47, p = 0.023) CONCLUSIONS: There is an inverse relationship between hospital volume and the rate of stroke or death following carotid endarterectomy in Sweden. Reorganisation of carotid surgery services should be considered.