The Effect of Lidocaine

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 (S,S,) coupling intervals. RE-HPS was characterized by a spontaneous beat (V9) inducible by critically timed premature stimuli (S) during constant ventricular drive (SS), and was dependent upon critical retrograde conduction delay within the HPS (S^H2 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 S,S2 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 SIS2 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.