Cardiac channelopathies: diagnosis and contemporary management

### Learning objectives The inherited arrhythmia (IA) syndromes are a group of disorders characterised by an increased risk of sudden cardiac death (SCD), abnormal cardiac electrical function and typically, a structurally normal heart.1 They share an underlying genetic aetiology where disease-causing genetic variants may lead to absence or dysfunction of proteins involved in generation and propagation of the cardiac action potential. They also share clinical features and management challenges. Diagnosis is largely ECG-based with significant overlap between affected individuals and the general population. Day-to-day symptoms are frequently absent such that assessment of the risk of SCD and its prevention are the primary concerns. Available tools for such risk stratification are imperfect and largely based on expert consensus without a robust evidence base. This review will focus on the diagnosis, risk stratification and treatment of the most common and well described IA syndromes, namely long QT syndrome (LQTS), Brugada syndrome (BrS) and catecholaminergic polymorphic ventricular tachycardia (CPVT). Other conditions including short QT syndrome (SQTS), early repolarisation syndrome (ERS) and idiopathic ventricular fibrillation (IVF) will also be discussed briefly. IA syndromes may present in a number of ways: following a resuscitated cardiac arrest or arrhythmic syncope, where an abnormal ECG in the absence of ischaemic and structural heart disease may heighten clinical suspicion; unexplained ECG abnormalities in an asymptomatic patient or through family screening for a specific diagnosis or following a sudden unexplained death. The 12-lead ECG, supported by extended monitoring or provocation with exercise or drugs, is the cornerstone …