Cardiac electrophysiologic effects of lidocaine and bupivacaine

The cardiac electrophysiologic effects of bupivacaine (B) and lidocaine (L) were evaluated in an isolated rabbit Purkinje fiber-ventricular muscle model to determine the effects of a) progressively increasing and b) decreasing concentrations of B and L on transmembrane action potentials. Bupivacaine (3 and 5 micrograms/ml) significantly decreased diastolic resting potential, maximum rate of depolarization, and action potential amplitude. Lidocaine (10-20 micrograms/ml) also decreased maximum rate of depolarization and action potential amplitude, but the decreases were significantly different from those produced by B. High concentrations of B (30 micrograms/ml) and L (100 micrograms/ml) resulted in delayed conduction between Purkinje fibers and ventricular muscle cells and, ultimately, conduction blockade. The duration of conduction blockade was significantly longer with B than with L. The results of this study indicate that B produces electrophysiologic changes in cardiac tissue that may produce ventricular arrhythmias of a reentrant type.