Recurrent sustained ventricular tachycardia: report of a case with His-bundle branches reentry as the mechanism.

A 57-yr-old man with coronary artery disease presented with recurrent sustained ventricular tachycardia. During electrophysiologic study, the following observations suggested His-bundle branches (His-BB) reentry as the underlying mechanism of ventricular tachycardia: (1) the initiation of ventricular tachycardia by a premature ventricular beat was related to the presence of retrograde His--Purkinje conduction (V2H2) delay; (2) the QRS configuration of tachycardia complexes was similar to that of V1 and V2; (3) each QRS complex of tachycardia was consistently preceded by a His bundle deflection with an H-V interval which was equal to or longer than that of sinus beats; (4) atrioventricular dissociation was present during tachycardia; and (5) after procainamide a greater V2H2 delay was required to initiate the tachycardia. The therapeutic implications of identifying and differentiating the His-BB (macro) reentry from micro reentry are discussed.