SLEEP SUPPRESSION OF VENTRICULAR ARRHYTHMIAS - A PREDICTOR OF BETA-BLOCKER EFFICACY

It has been reported that the frequency of premature ventricular contr actions in some patients tend to decrease during the hours of sleep wh en modifications in autonomic tone and bradycardia occur. The aim of t his study was to evaluate whether the phenomenon of sleep suppression may be a sensitive and specific parameter for predicting the antiarrhy thmic effect of beta-blockers on premature ventricular contractions. T he presence of sleep suppression was evaluated in 45 patients (mean ag e 50 +/- 17 years) with frequent premature ventricular contractions at two baseline Holler recordings. Sleep suppression was defined as > 50 % reduction in the number of nighttime as opposed to daytime premature ventricular contractions. Three groups of patients were identified: t hose with sleep suppression at both Holter recordings (group 1); those with sleep suppression at only one Holter recording (group 2); and th ose without sleep suppression at either Holter recording (group 3). A third Holter was performed 5 days after nadolol administration. In gro up 1, nadolol led to a mean reduction in the number of premature ventr icular contractions of 90% ( > 70% in 21/23 patients). In group 2, the mean reduction was 76% ( > 70% in three out of six patients). In grou p 3, there was a mean increase in the number of premature ventricular contractions of 33%. The positive predictive accuracy of sleep suppres sion in relation to the antiarrhythmic efficacy of nadolol is very hig h (88%) when sleep suppression is present during two baseline Holler r ecordings. Sleep suppression is a sensitive parameter for identifying the premature ventricular contractions likely to benefit from beta-blo cker administration.