Demonstration of re-entry within the His-Purkinje system in man.

Re-entry within the His-Purkinje system (HPS) was consistently observed in 15/24 consecutive patients in whom retrograde refractory period studies were performed using His bundle electrograms and the ventricular extrastimulus method. Within a narrow range of ventricular coupling intervals (V,V2), V, retrogradely conducted to the bundle of His (H2) with significant infra-His bundle conduction delay (V2H2 interval). At critical V2H2 delays another beat of ventricular origin (V3) followed V2 and was associated with H2V3 intervals greater than the H-V intervals of sinus beat. It is postulated that V2 retrogradely blocked within the right bundle branch and activated the bundle of His via the left bundle branch after which antegrade conduction occurred along the right bundle branch producing the V3 response. In support of reentry within the HPS are the following: 1) V3 occurred in a narrow range of V,V2 intervals and critical V2H2 delays, 2) V3 did not occur when V2 retrogradely blocked below the bundle of His, 3) V3 was independent of retrograde A-V nodal delay, 4) V3 rarely occurred in patients with pre-existing complete right bundle branch block pattern. These results reasonably exclude local re-entry near the site of stimulation.