RELATION OF DIURNAL-VARIATION OF VENTRICULAR REPOLARIZATION TO VENTRICULAR ECTOPIC ACTIVITY AND MODIFICATION BY SOTALOL

The relation between disturbances of ventricular repolarization and malignant ventricular arrhythmias and sudden death has been the focus of intense interest. An example is the long QT syndrome which is characterized by life-threatening ventricular arrhythmias and a prolonged QT interval. The disorder has been ascribed to an abnormally low activity of the right stellate ganglion,1 failure of the action potential to shorten commensurately with the abbreviated RR interval,2 or an intracardiac abnormality. Another example is the sudden infant death syndrome which has been attributed to inappropriate adjustment of ventricular repolarization to heart rate changes.3 Recent investigations have demonstrated a circadian variation of cardiovascular diseases,4 including sudden cardiac death5 and ventricular arrhythmias. 6 However, only scant data exist with respect to diurnal changes of ventricular repolarization and its adjustment to fluctuations in heart rate. The present study addressed this question in patients with symptomatic complex ventricular arrhythmia. In addition, the relation of changes in QT interval and the occurrence of ventricular arrhythmias was examined before and after treatment with sotalol, a β-adrenergic blocking agent that prolongs ventricular repolarization.7,8 This compound is increasingly being recognized as an important class III antiarrhythmic agent. Finally, an attempt was made to elucidate a possible causal relation between sotalol-induced changes in ventricular repolarization and its antiarrhythmic action. © 1993.