Role of antiarrhythmic therapy in patients at risk for sudden cardiac death: An evidence-based review

Sudden cardiac death (SCD) accounts for more than half of all cardiac death s occurring, each year in the United States. Although it has several causes , patients at greatest risk are those with coronary artery disease and impa ired left ventricular function, heart failure secondary to ischemia or idio pathic Hated cardiomyopathy hypertrophic cardiomyopathy, documented sustain ed ventricular tachycardia or ventricular fibrillation, and survivors of ca rdiac arrest. The presence of asymptomatic ventricular arrhythmias, positiv e signal-averaged electrocardiogram (ECG), low heart rate variability index , or inducible ventricular tachycardia or ventricular fibrillation increase s the risk. In primary prevention trials in patients with ischemic heart di sease, beta -blockers reduced both total mortality and SCD, whereas class I antiarrhythmic drugs, especially class IC, increased mortality. Among clas s III agents, d,l-sotalol and dofetilide have a neutral effect on mortality , whereas d-sotalol increases mortality. Amiodarone has a neutral effect on total and cardiac mortality but does reduce the risk of arrhythmic death a nd cardiac arrest. Three primary prevention trials in patients with ischemi c heart disease were conducted with implantable cardioverter-defibrillators (ICDs). Patients with low ejection fractions (EFs), asymptomatic ventricul ar arrhythmias, and inducible ventricular tachycardia. or ventricular fibri llation had significant reductions in total, cardiac, and arrhythmic death with ICDs compared with either no drug therapy or conventional antiarrhythm ic agents. The ICDs did not reduce mortality in patients with low EFs and a positive signal-averaged ECG undergoing coronary bypass graft. in those wi th heart failure, beta -blockers reduced total and SCD mortality but dofeti lide and amiodarone had a neutral effect on mortality. In the secondary pre vention of SCD, antiarrhythmic drugs alone generally are not thought to imp rove survival. In three trials in patients with documented sustained ventri cular tachycardia or ventricular fibrillation, or survivors of SCD, ICDs re duced cardiac and arrhythmic mortality. Total mortality, however, was signi ficantly reduced in only one of these trials. The role of antiarrhythmic dr ugs in secondary prevention of SCD is limited to patients in whom ICD is in appropriate or in combination with ICD. Antiarrhythmics can be given select ively with ICDs to decrease episodes of ventricular tachycardia or fibrilla tion to reduce ICD discharges, to suppress episodes of nonsustained ventric ular tachycardia that trigger ICD discharges, to slow the rate of ventricul ar tachycardia to increase hemodynamic stability,, to allow effective antit achycardia pacing, or to suppress supraventricular arrhythmias.