Object: The object of this study was to examine the relationship between hospital volume and long-term mortality after treatment of intracranial aneurysms.
Methods: The authors identified patients treated for intracranial aneurysms between 2002 and 2010 from patient registries of Denmark, Norway, and Sweden, and linked to data on 1-year mortality from the population registry of each country. Cox regression models were used to relate hospital volume to the risk of death and adjusted for potential confounders (age, sex, year of treatment, Charlson comorbidity index, country, and surgical treatment).
Results: The authors identified 5773 patients with ruptured and 1756 patients with unruptured intracranial aneurysms, treated at 15 hospitals. One-year mortality rates were 15.6% for patients with ruptured aneurysms and 2.7% for patients with unruptured aneurysms. No consistent relationship was found between hospital volume and 1-year mortality for ruptured aneurysms in the unadjusted analyses, but higher hospital volume was associated with increased mortality in the analyses adjusted for potential confounders (hazard ratio [HR] per 10-patient increase 1.04, 95% CI 1.00-1.07). There was a trend toward a lower mortality rate in higher-volume hospitals after treatment for unruptured intracranial aneurysms, but this was not statistically significant after adjustment for potential confounders (HR per 10-patient increase 0.69, 95% CI 0.42-1.10). There were large variations in mortality after treatment for both ruptured and unruptured intracranial aneurysms across hospitals and between the Scandinavian countries (p < 0.01).
Conclusions: The findings in this study did not confirm a relationship between higher hospital volume and reduced long-term mortality after treatment of ruptured intracranial aneurysms. Prospective registries for evaluating outcomes after aneurysm treatment are highly warranted.
Keywords: CCI = Charlson Comorbidity Index; CI = confidence interval; HR = hazard ratio; ICD-10 = International Classification of Diseases, 10th revision; NCSP = NOMESCO Classification of Surgical Procedures; SAH = subarachnoid hemorrhage; Scandinavia; endovascular treatment; hospital volume; intracranial aneurysm; rupture; surgery; vascular disorders.