Syncope as a predictor of sudden cardiac arrest: a nationwide population-based study

Background/Aims: The risk of sudden cardiac arrest (SCA) in patients with prior syncope events is not fully understood. We examined the association between syncope and the risk of future SCA.Methods: Data were obtained from the Korean National Health Insurance Service database. Of those individuals who underwent the 2012 health screening, 40% were randomly sampled. The diagnoses of syncope and SCA were based on the International Classification of Disease, 10th edition.Results: A total of 4,600,635 subjects were analyzed with a mean of 9.2 ± 1.3 years of follow-up. The incidence of SCA per 1,000 person-years were 0.96 and 0.50 in people with and without syncope, respectively, within 5 years prior to health screening (hazard ratio [HR], 1.91; p < 0.001). After adjusting for various confounders, the presence of syncope was associated with a 29% increased risk of developing SCA (HR, 1.29; p < 0.001). Syncope within 3 years and within 1 year prior to health screening was associated with a 30% and 36% increased risk of SCA, respectively. Dizziness was not associated with the risk of future SCA. Significant interactions of syncope with age/hypertension were observed in young and hypertension-free individuals, who were more vulnerable to SCA.Conclusions: Syncope may be a surrogate marker of future SCA. The association was attenuated after adjusting for various confounders. The risk increased by 91% and 29% before and after adjustment, respectively. Individuals with prior syncope, older age, male sex, and cardiometabolic disorders had a higher risk of future SCA.