Abstract 16736: Etiology of Sudden Cardiac Arrest in Young Primary and Referral Populations: The Mayo Clinic Experience

Introduction: The incidence and etiologies underlying sudden cardiac arrest (SCA) in the young are derived from population- and referral-based cohorts of young SCA survivors. The extent to which the use of these cohorts contributes to discrepancies in our understanding of SCA in the young is unknown. As such, we sought to determine and compare the spectrum of SCA etiologies observed in young SCA survivors evaluated at a single tertiary center on both a primary and referral basis. Methods: Retrospective review of 940 young SCA survivors evaluated between 1990 and 2017 was used to identify all individuals ≤ 50 years of age that experienced a SCA. SCA root cause was determined by review of the medical records and diagnoses classified as ischemic, primary electrical, structural, or unexplained. SCA survivors that initially presented to our institution were classified as primary, while those who presented for secondary evaluation received a referral classification. Results: Overall, 566 SCA survivors were identified (age at event 33 ± 14 years; 39% females). In comparison to primary SCA survivors, referral SCA survivors were younger at the time of SCA (39 ± 12 vs. 30 ± 14 years; p<0.0001) and less likely to experience pre-SCA symptoms (45% vs. 27%; p<0.0001). Among all SCA survivors, the most common etiologies were idiopathic ventricular fibrillation (27%), acute coronary syndrome (21%), long QT syndrome (10%), and hypertrophic (7%) and dilated (6%) cardiomyopathies. Ischemic etiologies were less common (45% vs. 25%; p<0.0001) and primary electrical disorders more common (6% vs. 23%; p<0.0001) in referral SCA survivors. Conversely, genetic heart diseases (hypertrophic cardiomyopathy, long QT syndrome, etc.) were over-represented in referral cases (8% vs. 29%; p<0.0001), whereas no difference was observed in the number of primary and referral SCAs that remained unexplained. Conclusion: This study demonstrates, for the first time, that differences in SCA root cause exist between young SCA survivors evaluated at the same tertiary medical center on a primary vs. referral basis. Ongoing comparison of SCA etiologies between primary and referral SCA survivors may help resolve discrepancies regarding the contribution of specific disorders to SCA in the young.