Ventriculoatrial intervals during narrow complex reentrant tachycardia in children

Ventriculoatrial (VA) intervals during narrow complex tachycardia were measured in a pediatric population. The VA intervals were similar to those in adults but were slightly shorter. In the pediatric subjects values less than 60 msec excluded the participation of an accessory pathway in the tachycardia circuit. Three out of 11 patients with atrioventricular nodal reentrant tachycardia (AVNRT) had VA values greater than or equal to 70 msec, while 5 of 28 patients with orthodromic reciprocating tachycardia (ORT) had values less than or equal to 70 msec. Using a cut-off value of 70 msec as the sole criteria to distinguish between ORT and AVNRT could lead to errors in classification of the underlying mechanism of the tachycardia.