title: Prolongation of refractoriness and activation time in normal canine ventricular myocardium following bolus administration of lidocaine.
abstract: This study examines the electrophysiologic effects of an intravenous bolus of lidocaine in the normal canine ventricle. In 14 open-chest dogs, left ventricular effective refractory period, ventricular repolarization time, and activation time were measured continuously during ventricular pacing (150/min) before, during, and after intravenous lidocaine given over 4 minutes. Lidocaine doses of 1.25, 2.5, and 5.0 mg/kg transiently prolonged the ventricular effective refractory period from 177 +/- 4 (X +/- standard error of the mean) to 185 +/- 5 msec (p less than 0.05), 176 +/- 3 to 188 +/- 6 msec (p less than 0.05), and 176 +/- 5 to 197 +/- 5 msec, (p less than 0.05), respectively, at 6 +/- 1.5 minutes from the onset of the bolus. Serum lidocaine levels obtained at the peak of the effective refractory period prolongation averaged 4.3 +/- 1.0, 9.0 +/- 3.0, and 22.3 +/- 4.7 micrograms/ml, respectively. Ventricular repolarization time was not prolonged. Activation time also transiently increased from 43 to 45 msec (p less than 0.05) and from 47 to 52 msec with the 2.5 mg/kg and 5.0 mg/kg doses, respectively. Cardiac denervation and administration of propranolol, 1 mg/kg intravenously, did not influence these responses to lidocaine. We conclude that a bolus of lidocaine transiently prolongs the effective refractory period and activation time in the normal canine ventricle because of its direct membrane rather than autonomic effects.
mesh_terms: D000758:Anesthesia; D000818:Animals; D001341:Autonomic Nervous System / Q000187:drug effects; D002304:Cardiac Pacing, Artificial; D004285:Dogs; D004562:Electrocardiography; D004594:Electrophysiology; D006329:Heart Conduction System / Q000187:drug effects*; D006352:Heart Ventricles / Q000187:drug effects; D007263:Infusions, Parenteral; D008012:Lidocaine / Q000008:administration & dosage / Q000494:pharmacology*; D013997:Time Factors; D016276:Ventricular Function
chemical_list: D008012:Lidocaine