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3 Definitions

3.1 Ventricular arrhythmia subtypes

Premature ventricular complex (PVC): Premature occurrence of an abnormal QRS complex (duration typically ≥120 ms, corresponding T-wave typically broad and in the opposite direction of the major QRS deflection, no preceding P-wave). Unifocal or monomorphic PVCs: PVCs with a single QRS morphology. Multifocal, multiform, or polymorphic PVCs: PVCs with different QRS morphologies. Short-coupled PVC: A PVC that interrupts the T-wave of the preceding conducted beat. Ventricular tachycardia (VT): ≥3 consecutive beats with a rate .100 b.p.m. originating from the ventricles, independent from atrial and atrioventricular (AV) nodal conduction. Non-sustained ventricular tachycardia (NSVT): Run of consecutive ventricular beats persisting for 3 beats to 30 s. Monomorphic ventricular tachycardia (MVT): Same QRS morphology from beat to beat. Polymorphic ventricular tachycardia (PVT): Continually changing QRS morphology. Sustained monomorphic/polymorphic ventricular tachycardia (SMVT/ SPVT): Continuous VT for at least 30 s, or which requires an intervention for termination. Bidirectional ventricular tachycardia: Beat to beat alternation of the frontal QRS axis (e.g. in catecholaminergic polymorphic ventricular tachycardia [CPVT], Andersen–Tawil, digoxin toxicity, acute myocarditis). Torsades de pointes ventricular tachycardia (TdP): Subtype of a polymorphic VT in the context of QT prolongation with continually changing QRS complexes that appear to spiral around the baseline of the electrocardiogram (ECG) lead in a sinusoidal pattern. Ventricular fibrillation (VF): A chaotic rhythm with undulations that are irregular in timing and morphology, without discrete QRS complexes on the surface ECG. Electrical storm: VA that occurs 3 or more times within 24 h (separated by at least 5 min), each requiring termination by an intervention. Incessant VT: Continuous sustained VT that recurs promptly despite repeated intervention for termination over several hours.

3.2 Sudden cardiac death

Sudden cardiac arrest (SCA): Sudden cessation of normal cardiac activity with haemodynamic collapse. Sudden cardiac death (SCD): Sudden natural death presumed to be of cardiac cause that occurs within 1 h of onset of symptoms in witnessed cases, and within 24 h of last being seen alive when it is unwitnessed. SCD in autopsied cases is defined as the natural unexpected death of unknown or cardiac cause. Sudden unexplained death: Unexplained sudden death occurring in an individual older than 1 year. Sudden infant death syndrome (SIDS): Unexplained sudden death occurring in an individual younger than 1 year with negative pathological and toxicological assessment and negative forensic examination of the circumstances of death. Sudden arrhythmic death syndrome (SADS): Unexplained sudden death occurring in an individual older than 1 year with negative pathological and toxicological assessment. Note: Synonymous with ‘autopsy-negative sudden unexplained death’.

3.3 Syncope

Unexplained syncope: Transient loss of consciousness due to cerebral hypoperfusion, characterized by a rapid onset, short duration, and spontaneous complete recovery, but unexplained after conventional workup. Work-up and differential diagnosis are provided in the 2018 ESC Guidelines for the diagnosis and management of syncope.1 Arrhythmic syncope: as above, but highly suspicious for intermittent bradycardia, rapid supraventricular tachycardia (SVT), or VA.

3.4 Specialized centres

Multidisciplinary teams: A multidisciplinary team across specialties is characterized by open communication, positive management and leadership, appropriate resources, and a mix of skills. Decision-making should be shared in the team. Specialized centre for catheter ablation of VA: Patient and procedural complexity vary widely. Some patients require a more experienced operator and a centre with more capabilities, which is more likely in patients with a non-ischaemic aetiology. A specialized centre has at least one operator with appropriate experience in interventions that may be required for a successful procedure (e.g. percutaneous epicardial access). The centre performs catheter ablation of VT in structural heart disease (SHD) on a regular basis. In addition, the centre has the required resources to manage medical conditions, comorbidities, and potential complications in patients undergoing complex VA ablation; this includes interventional cardiology expertise, acute placement of mechanical circulatory assist devices, and cardiothoracic surgical back-up. Considering the variable availability across European countries, it is preferable to treat complex patients in the most experienced centre within reasonable distance.

3.5 Genetics

Pathogenic variant and likely pathogenic variant: The American College of Medical Genetics has provided a framework for the interpretation of disease causation by genetic variants standardized into classes. The genetic variants most likely to cause an associated disease are termed V, ‘pathogenic’, and IV, ‘likely pathogenic’. Mutation: This term is used in this document to mean a Class IV or V variant. Variant of uncertain significance: A change in a gene’s deoxyribonucleic acid (DNA) sequence that has an unknown effect on a person’s health.

4 Epidemiology of sudden cardiac

death, public awareness, and risk stratification

4.1 Incidence of sudden cardiac death

SCD accounts for approximately 50% of all cardiovascular deaths, with up to 50% being the first manifestation of cardiac disease.19–24 Ideally, cases suspicious of SCD should be identified from multiple Downloaded from academic.oup.com/eurheartj/article/43/40/3997/6675633 by guest on 07 October 2026