Objective: To estimate the proportion of patients with aneurysmal subarachnoid hemorrhage (SAH) who die before receiving medical attention.
Methods: We performed a systematic literature review.
Results: Eighteen population-based studies between 1965 and 2001 described the incidence of death from SAH before the patients received medical attention. The combined overall risk of sudden death was 12.4% (95% confidence interval, 11-14%). Patient level analysis was possible for two studies. No significant association between age and sudden death was identified. Aneurysms in the posterior circulation had an estimated probability of sudden death of 44.7% (95% confidence interval, 7.4-86%). Statistical sensitivity analysis was performed to examine some possible causes for the heterogeneity between the studies. Study factors statistically associated with a higher rate of sudden death include origin in England, computed tomographic scans not available for diagnosis, inclusion of patients with SAH from arteriovenous malformations, lower or not stated rate of autopsy for deaths in the community, and a higher rate of patients with confirmed aneurysms.
Conclusion: The combined overall estimated risk of sudden death was 12.4% for aneurysmal SAH and 44.7% for posterior circulation aneurysms. However, there are several sources of heterogeneity or possible bias in the reported studies. Further information on patient and aneurysm characteristics is required.