Evaluation of patients with complex ventricular arrhythmias: current noninvasive and invasive methods

Ventricular tachycardia (VT) or ventricular fibrillation is the most frequently documented mechanism of sudden cardiac death (SCD) in patients with coronary heart disease. There is no definitive proof that the abolition of complex ventricular ectopy, accomplished conventionally by pharmacologic therapy, results in the prevention of SCD; in the recent Cardiac Arrhythmia Suppression Trial (CAST), patients treated with encainide or flecainide demonstrated a greater incidence of cardiac death and arrhythmic death than a placebo group. Traditionally, the role of invasive electrophysiologic testing has been reserved for the evaluation of patients with complex ventricular ectopy associated with unexplained syncope, presyncope, or SCD, and for those patients who have sustained VT or ventricular fibrillation. Management of patients with complex ventricular arrhythmias by noninvasive methods (such as the 24-hour ambulatory ECG and exercise testing) has been the approach implemented for most patients thought to be at risk of SCD who have not experienced syncope, presyncope, or sustained VT. The CAST results, coupled with the fact that ambulatory ECG may lack sensitivity and overpredict successful therapy, warrant a discussion of noninvasive and invasive methods currently available for the evaluation and management of patients with complex ventricular arrhythmias. Among some of the relatively new techniques are programmed electrical stimulation and signal-averaged electrocardiography, both of which have been shown to be valuable in delineating high- and low-risk SCD groups.