Indications for antiarrhythmic suppression of ventricular arrhythmias: a definition of life-threatening ventricular arrhythmias.

A surprising finding of the Cardiac Arrhythmia Suppression Trial (CAST), reported in 1989, is that well-tolerated and effective antiarrhythmic drugs may also be associated with an increase in mortality due to arrhythmia. Consequently, attention has been focused on the importance of the benefit-versus-risk assessment of such therapy. The benefits of antiarrhythmic therapy are reduction or elimination of arrhythmia-caused symptoms (both hemodynamic and nonhemodynamic) and of the associated risk of death. The risks of such treatment include not only noncardiac adverse effects and organ toxicity, but also early cardiac effects (proarrhythmia, heart failure, and conduction defects), as well as the newly recognized potential for late proarrhythmia or late arrhythmic death. Unfortunately, as the potential benefits of antiarrhythmic therapy increase in patients with poorer left ventricular function (owing to their being at greater risk for sudden death), the effectiveness of suppression decreases and the incidence of life-threatening complications increases. The impact of this benefit-risk profile is that the indication for most currently approved antiarrhythmic drugs needs to be limited to those patients with definite life-threatening ventricular arrhythmias that take the form of sustained ventricular tachyarrhythmias with associated hemodynamic symptoms. Broadening this indication to include patients with probable life-threatening or even possible life-threatening arrhythmias must await the availability of drugs with better benefit-risk profiles.