[Wide spectrum of arrhythmias, with inductions and terminations of atrio-ventricular replica-nodal tachycardia by automaticity during successful radiofrequency ablation of long anterogradely slow conducting atrio-fasciculo-ventricular accessory pathway].

Mahaim syndrome is still a challenge. The specific characteristics of the pathway, the fact that it seldom occurs, and ambiguities about the pathophysiology and nomenclature make it, for electrophysiologists, still difficult to ablate. We present a case of a patient with anterogradely slow conducting accessory pathway, which has been effectively ablated although M potential was not observed nor was a mechanical conducting block of the accessory pathway. The accessory pathway showed a wide spectrum of electrophysiological characteristics of the "AV node physiology" including inductions and terminations of atrio-ventricular replica-nodal tachycardia by local automaticity, not only during electrophysiological study, but during successful application. The accessory pathway presented signs of two types of pseudo Mahaim fibers: atrio-fascicular and slow conducting atrio-ventricular connection.