To the best of our knowledge, normal limits of heart rate with respect to gender, and as established using 24-hour ambulatory Holter electrocardiography, have yet to be published for the entire age range of children and adolescents.

To establish the normal limits for heart rate in newborns, infants, children, and adolescents of both genders.

We obtained 24-hour Holter recordings from 616 healthy subjects aged from birth to 20 years with structurally normal hearts. The subjects were not receiving medication, and had not been submitted to prior cardiac intervention. Off-line analysis was performed with Mars 8000 scanners, analysing 5 consecutive RR intervals by the software available for automatic calculation of heart rate. All subjects were in sinus rhythm. Best-fit non-linear regressions were applied to correlate age and gender with minimum and mean heart rate, as well as with maximal RR-interval, and to calculate the 5th, 25th, 75th and 95th percentiles.

We observed significant gender-dependent differences in heart rate for persons aged 10 years and older, with the males exhibiting lower minimal and mean heart rates, and higher RR-intervals, than the females. Correlation of heart rate with age and gender could be established with sufficient accuracy using non-linear regression (p less than 0.0001): Minimum heart rate (male: R2=0.778, female: R2 = 0.664) and mean heart rate (male: R2 = 0.820, female: R2 = 0.736) decreased with age, while the maximal RR-interval prolonged (male: R2 = 0.562, female: R2 = 0.486). Age and gender-related graphs of centiles were constructed.

Heart rate, as documented using Holter recodings, can be correlated with age and gender, permitting establishments of normal gender-specific limits for children and adolescents.