A high risk syncope is characterized by at least one high-risk characteristic (based on 2015 "Syncope clinical management in the emergency department consensus"): syncope during exertion, in supine position, with new onset of chest discomfort, palpitations before the loss of consciousness, family history of sudden death, congestive heart failure, aortic stenosis, left ventricular outflow tract disease, dilated cardiomyopathy, hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy, left ventricular ejection fraction <35%, previously documented ventricular arrhythmia, coronary artery disease, congenital heart disease, previous myocardial infarction, pulmonary hypertension, previous ICD implantation, anemia (i.e. Hb <9 g/dl), lowest systolic blood pressure in the ED <90 mmHg, sinus bradycardia (<40 bpm), new (or previously unknown) left bundle branch block, bifascicular block plus a first degree AV block, Brugada ECG pattern, ECG changes consistent with acute ischemia, a new non-sinus rhythm, bifascicular block, and a prolonged QTc (>450 ms).