Heart rate, pr, and qt intervals in normal children: A 24‐hour holter monitoring study

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Abstract
A dynamic electrocardiographic Holter monitoring study was performed in 32 healthy children (20 males and 12 females, age range 6–11 years old), without heart disease, according to clinical and noninvasive instrumental examination. We evaluated atrioventricular conduction time (PR), heart rate (HR), and QT interval patterns defining the range of normality of these electrocardiographic parameters. The PR interval ranged from 154± 10 ms (mean±SD) for HR≤60 to 102±12 ms for HR ≥ 120 (range 85–180). The absolute mean HR was 87 ± 10 beats/min (range 72–104), the minimum observed HR being 61 ± 10 (range 51–79), the maximum 160±20 beats/min (range 129–186). Daytime mean HR gave a mean value of 93 ± 10 (range 71–148), while during night hours it was 74 ± 11 (range 54–98). The minimum QT interval averaged 261 ± 10 ms for HR> 120 and the maximum 389 ± 9 ms for HR ≤ 60; the corresponding mean value of QTc (i.e., QT corrected for HR) ranged from 388 ±8 for HR≤60 beats/min to 403 ±14 ms for HR> 120 beats/min. The results of the present study provide data of normal children which can be readily compared against those of subjects in whom cardiac abnormalities are suspect or patent. Some of the data reported here differ from those currently available, as for PR and HR, obtained from standard resting electrocardiogram, and cast doubt on the usefulness of correcting for HR in the QT interval in these subjects.