OBJECTIVES:The purpose of this study was to assess the prevalence of an HAV pattern (i.e. the atrial electrogram following the His bundle -HB- electrogram and preceding the ventricular one) in the HB channel in pediatric patients with atrioventricular node reentry (AVNRT).MATHERIAL AND METHODS:The pediatric eplectrophysiology databases of two separate institutions were analysed, and 33 pediatric patients with a diagnosis of AVNRT were identified. Demographic and clinical data were assessed, as well as the electrophysiology study (EPS) information, including induction manouvers, tachycardia cycle length and the presence of an HAV pattern in the HB channel. RESULTS: Of the 33 patients, 11 were male. Thirty of them were caucasian and 4 were hyspanic The average age at the time of the EPS was 12,11 ± 3,77years. Induction was achieved with atrial pacing in 16 patients, with one atrial extrastimulus in 8 and with 2 atrial extrastimuli in 5. Isoproterenol was necessary to induce tachycardia in 17 patients. During the EPS tachycardia cycle length 328 ± 50 ms. An HAV pattern was present in 35 (80%) of the patients. All the pts. under 10 years of age had an HAV pattern. CONCLUSIONS: An HAV pattern in the His bundle channel is a common finding in pediatric patients with AVNRT. It’s presence in patients under 10 years of age is pathognomonic of this tachyarrhythmia.