Dependency of premature ventricular contractions on heart rate and circadian rhythms during childhood

The aim of the present study was to identify and quantify the rare dependen ce of premature ventricular contractions (PVC) during childhood. A 24-hour Holter recording was performed in 16 consecutive children, aged 22 days to 11 years (mean age 5.6 years), with frequent (> 5,000/day), isolated monomo rphic PVC. Those PVC were identified and the length of the preceding sinus cycle was measured. The values were ordered into 50-ms class intervals, and the percentage of PVC for each class was calculated and then analyzed by l inear regression analysis. On the basis of the significance of the p value, and the positive or negative value of the slope, we identified a tachycard ia-enhanced, a bradycardia-enhanced, and an indifferent pattern. Chronobiol ogic analysis was made by the cosinor method. All the patients had upper an d lower limits of cycle length beyond which PVC disappeared. A tachycardia- enhanced pattern was present in 7 patients and an indifferent one in 9 pati ents. In the latter a second-degree polynomial correlation was systematical ly found. Children but not infants had a significant circadian variation in the frequency of PVC with a very variable time of highest incidence. In co nclusion, it is possible to identify a circadian rhythm of PVC and a sponta neous trend between their incidence and the length of the preceding cardiac cycle in children. Copyright (C) 2000 S. Karger AG, Basel.