Sinus node function in children. Factors influencing its evaluation.

Overdrive atrial stimulation was performed in 20 electrophysiologically normal children at the time of routine diagnostic cardiac catheterization, for the determination of the sinus node recovery time (SNRT). Measurements were made at pacing rates of 120, 150, 180, and 200 beats/min. The absolute recovery times demonstrated wide range of values (420-1280 msec). Expressed as a percent of the resting P-P interval, values at pacing rates of 120 and 150 beats/min were 109-166%, with significantly less overdrive suppression (P less than 0.001) occurring at the two faster pacing rates. Atropine diminished the maximum SNRT in all patients tested. This study reports normal values for the SNRT in children. Factors which influence the SNRT are the resting heart rate, the rate of overdrive, and the autonomic tone. In children, the sinus node recovery time should be expressed in terms of the resting sinus interval.