Abstract

The direct effects of tetracaine, bupivacaine, etidocaine, lidocaine, mepivacaine, and prilo caine were investigated, using an isolated rabbit heart preparation. All of the agents produced a concentration-related depression of intra-atrial, A-V nodal, intraventricular conduction, and myocardial contractility. The more potent local anesthetic agents depress cardiac conduction and contractility at significantly lower concentrations than the less potent local anesthetic drugs. The A-V node appears to be more resistant to the depressant effects of the local anesthetic agents compared to atrial and ventricular conduction pathways. In general, the degree of myocardial depression produced by the various drugs is related to their relative local anesthetic potency as determined on an isolated nerve. Tetracaine is the most potent drug in terms of inhibition of nerve conduction and is also the most potent depressant of cardiac conduction and contractility.