| Abstract: | For many years there has been a debate about the definition and nature of ‘sudden death’ or out-of-hospital cardiac arrest.1-8 Issues pertaining to this debate have been the temporal definition of ‘sudden’, whether death was unexpected, whether death was witnessed, and the aetiology of the event. The time frame used to describe the duration of the terminal event initially was 24 hours. The current definition of sudden cardiac death (SCD) describes death within one hour of the onset of symptoms,2 since this period seems to describe most accurately patients with arrhythmic sudden cardiac death.9A very difficult issue is the classification of unwitnessed deaths. Most authors have erred in favour of classifying such events as SCDs, even though it is often impossible to determine when the patient was last seen alive or the duration of symptoms prior to death. Hence, SCD can be defined as follows: ‘Natural death due to cardiac causes, heralded by abrupt loss of consciousness within one hour of the onset of acute symptoms’. Pre-existing heart disease may have been known to be present, but the time and mode of death are unexpected.1The incidence of SCD occurring out of hospital varies with age, gender and presence or absence of cardiovascular disease. Incidence rates of SCD between 0.36 and 1.28 per 1 000 inhabitants per year have been reported in Europe and the United states.10-13 In these studies, only witnessed victims seen or resuscitated by the emergency medical services are included; these data therefore underestimate the incidence of SCD in the general population. Sudden cardiac death is responsible for about 300 000 to 400 000 deaths per year in Europe and the United States, respectively.14Several diseases linked with sudden cardiac arrest (SCA) have been reported.15,16 Autopsy studies in unselected subjects suggest that about two-thirds of such deaths are cardiac in origin, with coronary artery disease and its complications accounting for the overwhelming majority of deaths in the industrialised world.17,18 Indeed, coronary artery disease (CAD) is the leading cause of sudden death worldwide.3In Europe, cardiovascular diseases (CVD) account for around 40% of all deaths under the age of 75 years. SCA is responsible for more than 60% of adult deaths from ischaemic heart disease (IHD).2 Conversely, in young populations under 40 years, inherited ‘arrhythmogenic’ cardiac disorders are the main cause.8 The initial recorded rhythm in patients presenting with a sudden cardiovascular collapse is ventricular fibrillation (VF) in 75 to 80%, whereas bradyarrhythmias and asystole are thought to contribute to a minority of SCDs.4,16 |
