Objectives: The objective is to compare the diagnostic yield (detection of serious arrhythmias that required treatment or caused death, or exclusion of arrhythmia by symptom-rhythm correlation) at the end of 15-days between a 15-day external cardiac event monitor (intervention) and usual care (48-hour holter monitor with patients seeking medical care after 48-hours based on symptoms) among high-risk ED syncope patients discharged home.