Sudden cardiac death (SCD).

The sudden, abrupt loss of heart function (i.e., cardiac arrest) in a person who may or may not have diagnosed heart disease, but in whom the time and mode of death occur unexpectedly, accounts for half of all fatalities from heart disease. Approximately 250,000 sudden cardiac deaths occur each year among U.S. adults.

The shock of sudden cardiac death (SCD) lies in its unexpectedness. Although the direct medical costs are much less than for lingering illnesses, its economic and social impacts are huge. Sudden cardiac death occurs at an average age of about 60 years, claims many people during their most productive years, and devastates unprepared families.

Most cardiac arrests are due to rapid and/ or chaotic activity of the heart (ventricular tachycardia or fibrillation); some are due to extreme slowing of the heart. These events are called life-threatening arrhythmias and are responsible for sudden death.

Underlying heart disease nearly always is found in victims of sudden cardiac death. Typically in adults, this takes the form of atheroclerotric heart disease. Two or more major coronary arteries are narrowed in 90% of cases, and scarring from a prior heart attack is found in two-thirds of victims. Predisposing factors for SCD are similar to risk factors for atherosclerotic heart disease and include tobacco smoke and high blood pressure.

A heart that is scarred or enlarged from any cause...