The electrophysiologic effects of lidocaine in patients with intraventricular conduction defects.

A 6 mg/kg lidocaine infusion was administered (over 22 min) to 10 patients with the electrocardiographic findings of bundle branch block. His bundle electrograms, heart rate, blood pressure, and plasma lidocaine levels were obtained before, every 5 min during, and for 20 min after the infusion was terminated. Control atrioventricular nodal conduction time (AH) was prolonged in two patients (130-175 msec) and infranodal conduction time was abnormally prolonged in four (60-100 msec). Therapeutic lidocaine levels were achieved in all patients and peak levels ranged from 3.3-11.0 ,ug/ml. No significant changes in mean heart rate, blood pressure, AH, His-Purkinje conduction time, or QRS duration were noted between control values and during or after the lidocaine infusion. Toxic central nervous system side effects including somnolence, dysarthria, and euphoria were noted in five subjects. Therapeutic levels of lidocaine were effective in the eradication of premature ventricular beats and safe in the sense that no higher degrees of atrioventricular or intraventricular conduction block were found; however, mild symptoms of central nervous svstem toxicity were commonly observed.