Objective: To conduct a multicenter two-arm open label RCT among higher-risk (CSARS score≥3) ED syncope patients discharged home for comparing the diagnostic yield (detection of serious arrhythmias that required treatment or exclusion of arrhythmia) at the end of 15-days between a 15-day event monitor (intervention) and usual care (48-hour holter with patients seeking care after 48-hours based on symptoms) at 10 Canadian EDs.