Sudden Cardiac Death

Sudden death is usually defined as unexpected death due to natural causes, with a collapse taking place without warning or preceded by symptoms for no longer than one hour. (The World Health Organization defines sudden death in much broader terms, accepting precollapse symptoms lasting as long as 24 hours; but most

physicians recognize the one-hour limit.) Instantaneous death without warning is very common; symptoms, if any, preceding loss of consciousness almost always involve chest pain or shortness of breath.

The principal causes of sudden cardiac death include ventricular fibrillation, ventricular standstill, acute failure of a ventricle, and catastrophic complication (e.g. cardiac rupture). Autopsy performed after a sudden cardiac death often fails to determine the cause of death, for ventricular fibrillation has no pathologically identifiable features. Only in a minority of cases is a clear-cut explanation of the event available, such as a thrombus in a proximal portion of a principal coronary artery, a large pulmonary embolus, or cardiac rupture. In most cases autopsy reveals general cardiac impairment, such as coronary-artery disease; occasionally the heart may be structurally normal. Coronary-artery disease is by far the commonest cause of sudden cardiac death. Other causes include aortic stenosis and hypertrophic cardiomyopathy.

Sudden cardiac death ranks high among pressing public-health problems. Close to half a million cardiac patients die suddenly each year in the United States. Most sudden cardiac deaths occur in patients with serious heart disease. Yet there is a significant group of patients in the early stages of coronary-artery disease in whom measures aimed at prevention of sudden cardiac death and at early recognition of and resuscitation from ventricular fibrillation can yield good results with a structurally normal heart.