LONG-TERM ARRHYTHMIC OUTCOMES AMONG CARDIAC ARREST SURVIVORS WITH PRESERVED EJECTION FRACTION REGISTRY (CASPER)

BACKGROUND Following an unexplained cardiac arrest, patients and family members typically undergo a comprehensive series of investigations to identify the underlying cause of arrest, with a diagnosis identified in more than half of cardiac arrest survivors. However, the long-term arrhythmic outcomes among cardiac arrest survivors remains unclear. METHODS AND RESULTS The Cardiac Arrest Survivors with Preserved Ejection Fraction Registry (CASPER) prospectively enrolls cardiac arrest survivors and their first-degree relatives (FDR) across 16 Canadian centers. Patient demographics, cardiac investigations, working diagnoses, and follow-up events are recorded. Those with a history of significant coronary artery disease or manifest cause of cardiac arrest are excluded. Arrhythmic events, including implantable cardioverter-defibrillator (ICD) shock or anti-tachycardia pacing (ATP) are recorded. Patients with at least one follow-up visit were included. Hazard ratios for arrhythmic events were calculated using Cox proportional hazards models. 741 patients were enrolled, with a median age of 42 years (interquartile range [IQR] 29-53), 56% being male, and mostly Caucasian (82%). Patients included cardiac arrest suvivors/probands (n=480, 66%) and first-degree relatives (n=243, 34%). In addition to baseline investigations, patients undertook signal-averaged ECG (56%), exercise testing (70%), extended monitoring (50%), cardiac MRI (62%), and provocative testing with procainamide (39%), adrenaline (31%) or an electrophysiologic study (14%). After excluding 18 patients with ongoing diagnosis adjudication, the working diagnoses of probands and FDRs are reported in the Table. Working diagnoses among probands were divided into three categories, including unexplained/idiopathic (after comprehensive investigations, n=351), structural/cardiomyopathy (including arrhythmogenic right ventricular cardiomyopathy and others, n=64), and electrical/channelopathy (including Long QT Syndrome, Brugada Syndrome, and others, n=65). During a median follow-up of 3.3 years (IQR 1.7-5.9), 69 patients (9%) suffered an ICD shock or ATP with a median time-to-event of 1.0 years (IQR 0.5-2.8). Probands had a significantly higher rate of events (hazard ratio [HR] 16.9, 95% confidence interval [CI] 4.1-69.0, p CONCLUSION In a cohort of unexplained cardiac arrest survivors and first-degree relatives, probands had a significant rate of recurrent events. Probands with structural/cardiomyopathy diagnoses had twice the risk of arrhythmia recurrence. Patients with structural diagnoses may be more likely to have arrhythmic events in follow-up, potentially due to a progressive disease process compared to other diagnoses.