The effect of lidocaine on reentry within the His-Purkinje system in man.

The effects of intravenous lidocaine were assessed in 11 patients with normal intraventricular conduction in whom reentry within the His-Purkinje system (RE-HPS) occurred consistently over a narrow range of ventricular (S1S2) coupling intervals. RE-HPS was characterized by a spontaneous beat (V3) inducible by critically timed premature stimuli (S2) during constant ventricular drive (S1S1), and was dependent upon critical retrograde conduction delay within the HPS (S2H2 interval). Lidocaine abolished RE-HPS in six of 11 patients (group 1) and shortened the zone of RE-HPS in five of 11 patients (group 2). In group 1 after lidocaine, critical S2H2 intervals for RE-HPS were not attained at any S1S2 in four patients and critical S2H2 intervals were equaled but not exceeded in two patients without resulting in RE-HPS. In group 2 after lidocaine. RE-HPS was present in all patients at S2H2 intervals comparable to control values; however, significantly closer S1S2 intervals were necessary to achieve these requisite S2H2 delays (p < 0.005). The longest S2H2 intervals at comparable S1S2 intervals were significantly shortened by lidocaine in 11 of 11 patients (p < 0.001). Thus, lidocaine causes a significant decrease in retrograde refractoriness within the HPS in patients with normal intraventricular conduction.