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sources and undergo autopsy, which is required to reliably exclude non-cardiac causes of sudden death (SD). The incidence of SCD increases markedly with age. With a very low incidence during infancy and childhood (1 per 100 000 personyears),25–27 the incidence is approximately 50 per 100 000 personyears in middle-aged individuals (in the fifth to sixth decades of life).28–30 In the eighth decade of life, it reaches an annual incidence of at least 200 per 100 000 person-years.20 At any age, males have higher SCD rates compared with females, even after adjustment for risk factors of coronary artery disease (CAD).24,31–33 Ethnic background also seems to have large effects.34,35 It is estimated that 10–20% of all deaths in Europe are SCD.36,37 Approximately 300 000 people in Europe have out-of-hospital cardiac arrest (OHCA) treated by emergency medical systems every year.38,39 In the Western world, the epidemiology of SCD is closely related to CAD, which is responsible for up to 75–80% of SCD cases.40 While the prevalence of CAD has not decreased, there has been a significant decline in mortality due to CAD. Reports show that the incidence of SCD is declining,40–42 but the risk of SCD as a proportion of the overall cardiovascular deaths may have increased.43,44 Although regular physical activity benefits cardiovascular health, sport, particularly when practiced vigorously, has been shown to be associated with SCD during or shortly after exercise in selected populations.45–51 Reports have suggested that the majority of sportsrelated SCD occurs in a recreational52,53 rather than competitive setting, especially among middle-aged male participants, suggesting that CAD is the most common underlying cause.46,54,55

4.2 Causes of sudden cardiac death in

different age groups Cardiac diseases associated with SCD vary depending on the individual’s age. In the young there is a predominance of primary electric diseases and cardiomyopathies, as well as myocarditis, and coronary anomalies.25,27,56–61 However, half of SCD cases during the fourth decade are related to CAD, especially acute coronary syndrome (ACS).62,63 In older populations, chronic structural diseases predominate (CAD either through acute coronary events or chronic coronary stenoses, valvular heart diseases, and heart failure), while potentially inherited electrical diseases or structural non-ischaemic diseases may cause more than 50% of SCD in individuals under the age of 50 years.27 Age distribution at presentation with ventricular arrhythmias and sudden cardiac death, dominant arrhythmia subtypes, triggers, genetic factors, and gender associated with increased risk for ventricular arrhythmias in selected primary electrical and structural heart diseases are presented in Figure 1.

4.3 Population vs. individual risk

prediction In the general population (individuals without known heart disease), the most effective approach for preventing SCD resides in quantification of the individual risk of developing CAD based on risk score charts.64,65 Several studies have provided evidence that there is a genetic predisposition to die suddenly during acute ischaemia.66–70 The goal would be to identify the relatively small, high-risk subgroups from the general population at risk of SCD as their first cardiac event. Models for novel SCD risk stratification in the general population have recently been proposed.71–73 There are no clear data supporting the benefit of mass screening programs in the general population for preventing SCD.74–76

For decades, investigators have envisioned a broad range of ‘indicators’ for SCD, especially occurring in the setting of CAD. Several non-invasive markers of risk have been proposed (including late potentials, heart rate variability, periodic repolarization dynamics, and baroreflex sensitivity).77 Despite the promising outcomes of initial studies, however, these ‘predictors’ have not yet influenced clinical practice. Left ventricular ejection fraction (LVEF) is only used, often in combination with New York Heart Association (NYHA) class, for primary prevention indication of an ICD in the setting of chronic CAD and dilated cardiomyopathy (DCM). Risk stratification schemes and calculators have been developed for inheritable arrhythmogenic diseases, such as hypertrophic cardiomyopathy (HCM), arrhythmogenic right ventricular cardiomyopathy (ARVC), and lamin A/C (LMNA) cardiomyopathy.78–82 What is considered low, intermediate, or high risk will depend on the type of event (e.g. fatal or not) and the risk of an event in the background population. For instance, mortality depends on age, sex, and other risk factors including comorbidities. The situation is further complicated when considering a specific type of death, e.g. SCD. Then non-SCD deaths are competing events (or competing risks) to SCD in the sense that their occurrence prevents the observation of SCD, and may make interventions to prevent SCD, such as an ICD, of limited benefit.

4.4 Risk calculators for sudden cardiac

death and review of the methodology A number of risk calculators for SCD have been proposed for adult and paediatric populations.80,81,83–85 The field of prediction modelling has evolved over the past decades, establishing standards for the development, validation (internal and external), and reporting of prediction models in SCD.86,87 In addition to discrimination measures such as the c-index, measures of calibration such as the calibration slope have recently received more attention because it is not only important to distinguish patients with higher risks from those with lower risks but also to obtain a robust quantification of the risk itself from the risk calculators.88 Typical shortcomings in the development and validation of risk calculators include, but are not limited to, the use of historic samples not representative of contemporary patient cohorts, missing values, composite outcomes with composite events of different clinical importance, lack of external validation, and missing calibration. In this document different cut-off for 5 years risk of SCD/VA is used for indication of ICD. Each cut-off was chosen by the original authors and the task force group considering the competing risk, the outcome measured (SCD vs VA) and the robustness of each risk calculator.

4.5 Awareness and intervention: public

basic life support, and access to automated external defibrillators Survival rate remains strikingly low after OHCA,89–95 although major regional disparities have been described.96 Early implementation of Downloaded from academic.oup.com/eurheartj/article/43/40/3997/6675633 by guest on 07 October 2026