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To study the possible role of autonomic influences on the occurrence of frequent premature ventricular beats (VPBs) in subjects without structural heart disease.24-hour Holter ECG recordings (≥1500 VPBs/d, sinus rhythm) of 20 symptomatic patients (9 women, 11 men, mean age 58.9 years) without structural heart disease were used for the study. The circadian distribution pattern of VPBs was studied (paired t test) by dividing the day into 3 periods (16:00–22:00–06:00–16:00), and correlations were analyzed between the absolute (ln transformed) and relative (% of total beats) average hourly numbers of VPBs and the hourly mean values of global and vagal time domain parameters of heart rate variability (Pearson correlation).No significant (P > .3 for every comparison) tendency for circadian distribution of VPBs was found. However, VPBs showed a significant correlation with rMSSD (r = 0.51 and P = .02 for the relative number), which became even stronger if VPBs were > 8000/d (r = 0.65 and P = .04 for both numbers).The significant correlation between the number of VPBs and a vagally mediated parameter underlines the triggering/permitting effect of parasympathetic tone on ventricular ectopy. This fact suggests that initiation of beta-blocker therapy could not be recommended routinely in these patients.