 Follow-up: Patients will be followed based on severity of presentation previous cardiac arrest or arrhythmic syncope, or family cascade screening. Vital statuscadiac events will be determined in person or by telephone annually in all patients enrolled. As per standard care, participants with previous cardiac arrest or arrhythmic syncope on beta-blockers will be followed in person every 12 months Group 1, and asymptomatic patients, those free of syncope on beta blocker, or gene negative unaffected family members Group 2 every 2 years or at the discretion of the site investigator. An annual resting ECG is possible for all participants, and exercise testing will be repeated every 2 years in Group 1, and every 3-4 years in Group 2 based on the clinical practice of the enrolling centre. 