Syncope recurrence and mortality: a systematic review

Aims: Data on adverse events and death rates following syncope are heterogeneous among studies, and knowledge of syncope prognosis could help to better define the correct management of patients.

Methods and results: We performed a systematic review of literature by searching for prospective observational studies enrolling consecutive patients presenting to the Emergency Department because of syncope. The outcomes considered were syncope recurrence and short- and long-term mortality. Morbidity and a composite of morbidity and mortality were also assessed. Pooled event rates and 95% confidence intervals (CI) were calculated for each outcome using the random effects model. Twenty-five studies (11 158 patients) were included. The incidence of syncope relapse linearly increased from 0.3% at 30 days to 22% at 2 years follow-up. One-year mortality rate varied between 5.7 and 15.5%; the pooled estimate was 8.4% (95% CI: 6.7-10.2%). The incidence of adverse events (morbidity) varied between 6.1 and 25.2% at 10 days and 2 years, respectively. The short-term (10 days) pooled incidence of the composite of morbidity and mortality was 9.1% (95% CI: 6.6-12.5%). We found a high statistical heterogeneity between studies.

Conclusion: This meta-analysis of prospective observational studies shows that the chance of being asymptomatic linearly progressively decreased over time after the first syncope. Short-term (10-30 days) mortality after syncope was <2% and that the overall 10-day rate of the composite endpoint of death and major events was ∼9%. The knowledge of syncope prognosis could help clinicians to understand syncope patients' prognosis and researchers to design future studies.