Repetitive ventricular responses to ventricular extrastimulation studies in children and adolescents.

The effect of single premature ventricular extrastimuli during ventricular pacing was evaluated in 22 children with a mean age of 8.8+/-5.8 years. A repetitive ventricular response (V(3)) was observed at a critical coupling interval of prematurity in 10 of 22 children (45%). This response was similar in morphology and axis orientation to the premature and paced beats and was preceded by a His bundle depolarization. The V(3) response occurred nearly as frequently in patients without ventricular dysrhythmias as in those with ventricular dysrhythmias. The V(3) response is a normal phenomenon during ventricular stimulation.