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 1 V 2 ), V 2 retrogradely conducted to the bundle of His (H 2 ) with significant infra-His bundle conduction delay (V 2 H 2 interval). At critical V 2 H 2 delays another beat of ventricular origin (V 3 ) followed V 2 and was associated with H 2 V 3 intervals greater than the H-V intervals of sinus beat. It is postulated that V 2 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 V 3 response. In support of re-entry within the HPS are the following: 1) V 3 occurred in a narrow range of V 1 V 2 intervals and critical V 2 H 2 delays, 2) V 3 did not occur when V 2 retrogradely blocked below the bundle of His, 3) V 3 was independent of retrograde A-V nodal delay, 4) V 3 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.