Electrophysiologic Interaction between Class I Antiarrhythmic Drugs and Volatile Anesthetics in Depressant Effects on Ventricular Activation in a Canine Myocardial Infarction Model

Previous studies showed that volatile anesthetics depressed ventricular delayed activation in a canine myocardial infarction model. It is well known that class I antiarrhythmic drugs depress the ventricular activation in the infarcted myocardium. In the present study, we examined the electrophysiologic interaction between volatile anesthetics (sevoflurane, isoflurane) and class I antiarrhythmic drugs (lidocaine, procainamide) in effects on the ventricular delayed activation in a canine myocardial infarction model. The conduction time of the premature stimulation-induced ventricular excitation was measured in both normal and infarcted zones of the ventricle. An interval from the premature stimulus artifact to the epicardial activation was measured on bipolar electrograms as an index of conduction time, i.e., activation time. In the infarcted zone, the volatile anesthetics and class I antiarrhythmic drugs prolonged the activation time in the infarcted zone, and the combination of the volatile anesthetics and the class I antiarrhythmic drugs markedly prolonged the activation time or blocked the delayed activation. In the normal zone, a similar synergistic interaction was observed, but the effect of these drugs was less compared with that in the infarcted zone. From these results, possible mechanisms to explain the synergistic interaction were discussed.