Novel Observations on the Precursor Arrhythmias of Ventricular Fibrillation in the Ambulatory Setting

ABSTRACT Introduction Ventricular fibrillation (VF) is a lethal arrhythmia documented on outpatient telemetry monitoring. Ambulatory ECG in arrhythmic sudden death has shown VF as the terminal arrhythmia in about 80% of cases. Studies of VF in the ambulatory setting are sparse but suggest VF is commonly preceded by monomorphic ventricular tachycardia (VT). This study retrospectively analyzes precursor arrhythmias of VF in Philips Mobile Cardiac Outpatient Telemetry (MCOT®) patients. Methods A retrospective data analysis was performed to identify VF events from 2021 to 2022. Baseline rhythm and the precursor arrhythmia/ECG change (PA) that later degraded to VF was identified. PA were categorized as rate dependent (bradycardia or tachycardia); intraventricular conduction defects; re‐polarization changes (ST‐depression, ST‐elevation, or prolonged QTc); or Ectopy. Results Seventy‐one adjudicated VF events occurred with 52% men and 48% women (mean age of 71.3 and 75.8 years, respectively). Baseline rhythm was predominantly normal sinus rhythm (92%), with first‐degree AV conduction delay identified in 12% of normal sinus rhythm patients. Ectopy was identified as the most common PA noted in patients (37%), followed by repolarization changes (25%), rate‐dependent changes (24%), and intraventricular conduction delay (14%). During arrhythmia progression, VF was preceded by monomorphic VT in 38% of events. Conclusion Across 71 Philips MCOT® events, VF was most commonly preceded by Ectopy, followed by re‐polarization changes and rate dependent changes. While previous reports have suggested monomorphic VT as commonly preceding VF, monomorphic VT was only noted in 38% of patients in this cohort.