The Incidence of Retrograde Conduction in Children

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Abstract
With the increasing use of "physiological" pacemakers in the pediatric age group, retrograde conduction in children has become of clinical importance. Pacemakers which sense atrial depolarization may sense "retrograde" P waves. The pacemaker may then act as the antegrade limb of a reciprocating tachycardia circuit, while the patient's own conduction system acts as the retrograde limb. We reviewed the data of 127 patients who underwent antegrade and retrograde electrophysiologic study at Texas Children's Hospital, with regard to retrograde conduction. Sixty percent of the patients had ventriculo-atrial conduction through the A-V node; the incidence of retrograde conduction in patients after surgical correction of a tetralogy of Fallot was significantly lower (33%). None of the patients with third-degree A-V block had retrograde conduction. The mean retrograde conduction time was 162 ms (range 70-335 ms) at the slowest pacing rate and 257 ms (range 80-475 ms) at the fastest pacing rate. This high incidence of retrograde conduction and the variability of conduction times must be taken into account when "physiological" pacemakers are to be implanted.