Who's at risk of sudden cardiac death?
Underlying heart disease is nearly always found in victims of sudden cardiac death. Typically in adults this takes the form of atherosclerotic heart disease. Two or more major coronary arteries are narrowed in 90 percent of cases; scarring from a prior heart attack is found in two-thirds of victims. It's not surprising, then, that predisposing factors for sudden cardiac death are similar to risk factors for atherosclerotic heart disease and include cigarette smoke and high blood pressure.
A heart that's scarred or enlarged from any cause is prone to develop life-threatening ventricular arrhythmias. The first six months after a heart attack is a particularly high-risk period for sudden cardiac death in patients who have atherosclerotic heart disease. A thickened heart muscle from any cause (typically high blood pressure or valvular heart disease) - especially when there's congestive heart failure, too - is an important predisposing factor for sudden cardiac death.
Under certain conditions, various heart medications can set the stage for arrhythmias that cause sudden cardiac death. In particular, so-called antiarrhythmic drugs, even at normally prescribed doses, sometimes may produce lethal ventricular arrhythmias (proarrhythmic effect). Regardless of whether there's organic heart disease, significant changes in blood levels of potassium and magnesium (from using diuretics, for example) also can cause life-threatening arrhythmias and cardiac arrest. When sudden cardiac death occurs in young adults, atherosclerotic heart disease usually isn't the cause. More often these young victims have a thickened heart muscle (hypertrophic cardiomyopathy) without accompanying high blood pressure.
Certain electrical abnormalities within the heart may be responsible for sudden cardiac death in the young. These include a short circuit between the upper and lower chambers (Wolff-Parkinson-White syndrome). This sometimes can allow dangerously rapid rates to develop in the lower chamber when there's a rapid rhythm disturbance in the upper chamber and a congenitally prolonged electrical recovery after each heartbeat (long-QT syndrome) that may set the stage for fatal ventricular arrhythmias.
Less often, inborn abnormalities of the blood vessels, particularly the coronary arteries and aorta, may be present in young sudden death victims. Adrenalin released during intense physical or athletic activity often acts as a trigger for sudden cardiac death when these predisposing conditions are present. In young people without organic heart disease, recreational drug abuse is an important cause of sudden cardiac death. |
