Patients who have had an acute myocardial infarction (MI) are at increased risk for sudden cardiac death (SCD), most commonly due to ventricular arrhythmias. Ventricular tachycardia (VT) and ventricular fibrillation (VF) are most common in the first hours after an MI, and the incidence then declines in phases during the days, weeks, and months after the event. However, the arrhythmic risk remains elevated for years after an MI [1-4]. This temporal pattern reflects the electrophysiologic manifestations of the evolving interactions between ischemia, infarction, reperfusion, and scar formation.
Although all patients with a prior MI have an elevated risk of malignant arrhythmias, the magnitude of risk varies from patient to patient. Findings such as reduced left ventricular ejection fraction (LVEF), reduced heart rate variability, abnormalities in the signal averaged ECG, and T wave alternans all predict a higher likelihood of SCD. On the other hand, the risk appears to be equivalent in patients with ST elevation and non-ST elevation infarctions .
Due to the heightened risk of malignant arrhythmias after an acute MI, antiarrhythmic drugs for the purpose of preventing SCD have been studied in two major settings: in patients with ventricular arrhythmias, and as prophylaxis.
The role of antiarrhythmic drugs for the treatment of ventricular arrhythmias after an acute MI will be reviewed here. The pathogenesis, clinical features, and general therapy of ventricular arrhythmias after MI and of risk stratification for SCD are presented separately. (See "Pathogenesis of ventricular tachycardia and ventricular fibrillation during acute myocardial infarction" and "Clinical features and treatment of ventricular arrhythmias during acute myocardial infarction" and "Incidence of and risk stratification for sudden cardiac death after acute myocardial infarction".)
Patients with ventricular arrhythmias — Ventricular arrhythmias that occur more than 48 to 72 hours after an MI usually reflect permanent substrate for malignant arrhythmias and are associated with an increased long-term risk of SCD. The prognostic significance of arrhythmias that occur within the first 48 hours is less clear. A detailed discussion of the implications of the temporal relationship of arrhythmias to MI is presented separately. (See "Clinical features and treatment of ventricular arrhythmias during acute myocardial infarction".)