Sudden cardiac death--an approach to management of the patient at risk.

Sudden cardiac death due to ventricular fibrillation is the most common cause of death in industrialized countries. Patients with an increased risk of sudden cardiac death may be found to have, in addition to high-grade ventricular arrhythmias, impaired left ventricular function. Mechanisms responsible for precipitation of ventricular fibrillation include risk factors such as increased sympathetic nervous system activity, electrolyte disturbances, coronary artery spasm and transient, thrombotic coronary artery occlusion. For detection of high-grade arrhythmias as well as for assessment of treatment, continuous 24-hour EKG monitoring and exercise EKG should be employed. The indication for antiarrhythmic therapy should be regarded as established in patients successfully resuscitated after unexpected ventricular fibrillation as well as in patients status-post myocardial infarction, with angina pectoris, cardiomyopathies, QT-prolongation, mitral valve prolapse, congenital or other markedly symptomatic heart disease and high-grade ventricular arrhythmias. The treatment initiated, after discontinuation of all antiarrhythmic drugs for at least four half lives and ambulatory EKG monitoring for 48 hours as well as maximal symptom-limited exercise testing, should be evaluated after acute drug administration and after 72 hours of maintained therapy with the aid of continuous EKG monitoring and exercise EKG. In patients with a history of malignant arrhythmias in whom no evidence of high-grade ventricular arrhythmias can be found in either the continuous EKG recording or in the exercise EKG, initiation of drug treatment should be based on the results of programmed electrical stimulation. Effective treatment can be assumed on documentation of complete suppression of arrhythmias grade IVb and V or prevention of precipitation of ventricular tachycardias, respectively, as well as 90% reduction of grade IVa and 50% reduction of premature ventricular beats. During acute testing, aggravation of arrhythmias after administration of antiarrhythmic drugs was seen in 11.1%. While the yearly mortality of successfully controlled patients ranged between 2.3 and 2.8%, the yearly mortality rate in those in whom the arrhythmias were inadequately controlled ranged from 43.6 to 56%.