Sudden cardiac death

Sudden cardiac death (SCD) is defined as unexpected death due to a cardiac disease, in a patient with or without known cardiac disease and which occurs within 1 hour from the appearance of the first clinical symptoms. The sudden cessation of cardiac activity leads to haemodynamic collapse, typically due to sustained ventricular tachyarrhythmias. The event is described as an aborted SCD (or sudden cardiac arrest) when an intervention (e.g. defibrillation) or spontaneous reversion restores circulation. The lack of uniformity with this definition complicates SCD statistics. By convention, the use of SCD to describe both fatal and non-fatal cardiac arrests persists. SCD continues to be a leading cause of death in Western countries, and accounts for 15%–20% of all natural deaths in adults in the US and Western Europe, and up to 50% of all cardiovascular deaths. In the US, estimates of SCDs from retrospective death certificate analyses range from 300 000 to 350 000 annually, giving an incidence of 0.1%–0.2% per year amongst the population above the age of 35 years. Event rates are said to be similar in Europe, although worldwide incidence is difficult to estimate and varies in accordance to the prevalence of CHD. The incidence of SCD increases with age and underlying cardiac disease. There is also a male preponderance, with men 2–3 times more likely to experience SCD than women, and this reflects the higher incidence of CHD in men.