Research Assistant Hearts in Rhythm Organization (HiRO) Surrey, British Columbia, Canada
Background: Early repolarization syndrome (ERS) is diagnosed in patients who survive an unexplained cardiac arrest (UCA) and show a distinct pattern on the electrocardiogram (ECG) called early repolarization (ER), defined as contiguous J-point elevation ≥ 0.1 mV in the inferolateral ECG leads. This study aimed to clarify the long-term outcomes of patients with ERS and identify markers associated with arrhythmia recurrence.
METHODS AND RESULTS: This retrospective cohort analyzed 530 patients from the Canadian CASPER registry (Cardiac Arrest Survivors with Preserved Ejection Fraction), all of whom survived a UCA and had structurally normal hearts. Patients were categorized into three patient groups: UCA with ER pattern and a primary diagnosis (Dx + ER), UCA with ER pattern but without another diagnosis (i.e. ER Syndrome - ERS), and UCA without ER or a primary diagnosis, called idiopathic ventricular fibrillation (IVF). Among 530 patients, 12 were classified as Dx + ER (2.3%), 48 as ERS (9.1%), and 470 (88.7%) as IVF. QTc intervals were significantly shorter in ERS than in IVF (412±25 ms vs. 432±42 ms; p< 0.01). Among the 60 ER-positive patients, notching was a more common morphology than slurring (33% vs. 25%, p=0.588), and a horizontal or descending ST-segment slope was more common than an ascending slope (62 vs. 38%, p=0.07). Intermittent ER was observed in 38% of ERS patients. ICD interventions occurred in 15% of the total cohort, with higher rates in ERS (23%) than IVF (13%) (p=0.104), and highest in Dx + ER (42%, p=0.006). Time to first ICD intervention was shorter in ERS than IVF (mean 4.13±6.57 vs. 5.65±5.59 years, p=0.482). After adjusting for age, sex and ethnicity, presence of the ER pattern was an independent predictor of arrhythmia recurrence (OR: 2.56, 95% CI: 1.32-4.79; p = 0.004). Kaplan-Meier analysis also demonstrated significantly lower survival free from ICD therapy in ERS vs. IVF (log-rank p=0.035).
Conclusion: ERS represents a distinct phenotype among UCA patients, characterized by specific ER patterns and shorter QTc intervals. ER pattern may be a compounding risk in patients with UCA and alternate diagnoses, who have elevated risk of recurrent syncope and cardiac arrest. These findings provide critical insights into ER that appears responsible for 10% of unexplained cardiac arrests, and may be a risk factor in other latent causes.
