Infra-Hisian block as cause of Wenckebach's phenomenon in an asymptomatic middle-aged man.

We report the case of a 60-year-old man with asymptomatic sinus bradycardia and Holter recording showing episodes of Wenckebach block alternating with episodes of 2:1 block. Electrophysiological testing revealed Infra-Hisian block with progressive prolongation of the H-V interval resulting in block after H potential. This produced typical Wenckebach-type block on surface electrocardiogram resembling the clinical one.