Supra-his alternate-beat Wenckebach dysrhythmia.

Abstract

Alternate-beat Wenckebach, an uncommon dysrhythmia, usually is attributed to block within the His bundle or bundle branches (or in both). A patient with features of the "sick sinus" syndrome demonstrated A-V nodal (supra-His) alternate-beat Wenckebach during atrial pacing and His bundle electrocardiography. Electrophysiologic mechanisms are proposed.