Incessant atrial tachycardia in childhood: association with rate-dependent conduction in an accessory atrioventricular pathway.

A detailed electrophysiologic study in a 7 year old boy with incessant atrial tachycardia revealed the presence of an atrioventricular pathway conducting only in the ventriculoatrial direction. The results indicate a reentrant mechanism with the retrograde limb of the circuit entering the atrium in the region of the proximal to mid coronary sinus. The accessory pathway exhibited relatively long conduction times and conduction properties suggesting decremental conduction. Thus, an electrophysiologically atypical anomalous conduction pathway may be responsible for the occurrence of incessant atrial tachycardial in some children.