Modulation of procainamide's effect on cardiac conduction in dogs by extracellular potassium concentration. A quantitative analysis.

Antiarrhythmic drugs are known to have state-dependent interactions with cardiac sodium channels, and these have potentially important implications for drug effects on cardiac conduction, particularly in situations of changed resting potential and heart rate. Recent advances in theoretical approaches permit beat-to-beat changes in sodium channel block to be inferred from conduction changes in vivo and allow for an analysis of state-dependent drug action from conduction changes occurring on the onset of pacing at different rates. The purpose of the present study was to use this method to analyze the interaction between hyperkalemia and procainamide's sodium channel-blocking action in terms of resulting changes in left ventricular conduction.