Management of arrhythmias in ischemic heart disease. The role of beta blockers.

Ventricular arrhythmias can lead to sudden cardiac death (SCD), and they can be classified according to the risk they present. Lethal ventricular arrhythmias, the least common, present the highest risk for SCD and usually manifest as paroxysmal sustained ventricular tachycardia. Most of the patients have serious left ventricular dysfunction and important hemodynamic symptoms, which must be treated immediately. Potentially lethal arrhythmias are much more common, accounting for most SCD cases. The patients generally have coronary artery disease, and the ventricular arrhythmias usually do not cause hemodynamic symptoms. Premature ventricular complexes (PVCs) and nonsustained ventricular tachycardia are the usual forms. PVCs are classified as benign in the absence of coronary artery disease, structural heart disorders, and hemodynamic symptoms, and in these cases the risk for SCD is low. Beta blockers have been shown to reduce the SCD rate, and although the precise mechanism is unknown, the effect may be in part on an antiarrhythmic basis. Like the class IA and IB antiarrhythmic agents (the Vaughan Williams classification), beta blockers are effective in about 50% of patients with either potentially lethal or benign ventricular arrhythmias. However, compared with such agents, beta blockers have a more favorable side effects profile.