Atrioventricular nodal reentrant tachycardia with 2:1 block in pediatric patients

A pattern of 2:1 block occurs in 17% of pediatric patients with AVNRT undergoing ablation. Although this incidence is higher than in older patients, the mechanism appears identical. These data provide further evidence that functional block within or below the His bundle is the mechanism of 2:1 AVNRT, regardless of the presence of a His potential. Oscillations in atrial cycle length are common during 2:1 AVNRT in children and may contribute to the block pattern, but are not a requisite.