The R-on-T phenomenon during supraventricular tachycardia in childhood.

The electrocardiographic R-on-T phenomenon was observed in the absence of Wolff-Parkinson-White syndrome during recurrent episodes of supraventricular tachycardia (SVT) with rates between 240 to 275 per minute in a 5 year old boy. The rapid ventricular response during SVT corroborates the recent finding of a short refractory period of the A-V node in children. The demonstration of the R-on-T phenomenon in this child may be important in attempting to understand the pathogenesis of sudden death in children.