Abstract 15687: Early Repolarization and Implantable Cardioverter Defibrillator Events in Cardiac Arrest Survivors With Preserved Ejection Fraction Registry (CASPER)

Abstract

Introduction: Early repolarization (ER) has been implicated as a rare primary arrhythmic disorder, and a more common cofactor is arrhythmia risk. Our objective was to determine if ER is associated with increased implantable cardioverter defibrillator (ICD) events in patients with unexplained cardiac arrest and their first degree relatives (FDR). Methods: The cardiac arrest survivors with preserved ejection fraction registry (CASPER) is a national registry that systematically examines unexplained cardiac arrest probands and their FDR. The presence of ER was identified in serial ECGs. ER was defined as J-point elevation ≥ 0.1 mV above the isoelectric line in ≥ 2 contiguous inferior (II, III, avF) or lateral leads (I, avL, V4-V6), excluding V1-V3. ICD event rates, including appropriate ICD shocks and anti-tachycardia pacing (ATP) and mortality were assessed. Results: One hundred and seventy-nine subjects from 13 Canadian sites were studied (age 46±17 years, 89 males). Overall, 99/104 (95%) probands and 6/75 (8%) FDR received an ICD. Eighty-eight probands and 3 FDR had at least one follow-up visit. After 4 ± 2 years of follow-up, 15 probands had appropriate ICD shock (17%), 13 had ATP (15%) and 22 had either (25%). A total of 566 ECGs were analyzed for ER (3 ± 2 ECGs/subject). Twenty-nine of the 88 probands had ER (33%), and 6 had appropriate ICD shock (21%), 5 had ATP (17%) and 9 had either (31%). For those who had ER, Cox regression demonstrated trends towards a higher risk of first ICD shock or ATP (HR=1.9, 95% CI 0.76-4.73, p=0.17), first ICD shock (HR =2.1, 95% CI 0.81-5.17, p=0.13) and first ATP (HR=1.6, 95% CI 0.49-5.32, p=0.42). ATP was seen in 1 FDR and none had ICD shock. For those who had an ICD event and ER, a diagnosis was obtained in 5/9 patients: ER syndrome in 1, long QT syndrome in 3 and mitral annular ventricular tachycardia in 1. The remaining 4 had idiopathic ventricular fibrillation. One proband died after 3.2 years of follow-up with a confirmed diagnosis of sarcoidosis without ER. Conclusion: ER may be associated with a higher risk of recurrent ICD events in apparently unexplained cardiac arrest patients, especially if the underlying etiology is presumed electrical rather than structural.