Abstract

A recently developed technique for the perfusion of isolated preparations of canine cardiac Purkinje fibers (PF) with arterial blood from a donor dog was used to observe drug-induced changes in the PF transmembrane potential and in the donor electrocardiogram (ECG). Standard microelectrode techniques were used to study the electrophysiologic properties of the PF, and the donor arterial pressure and ECG were recorded. In five control experiments the donor ECG and arterial pressure and the PF transmembrane potentials were stable for 6 hours of blood perfusion. In other experiments ouabain (O) and tritated ouabain (O-³H) were given intravenously to the donor. Occurrence of O-induced electrocardiographic arrhythmias was seen simultaneously with decreases in action potential amplitude, resting membrane potential, maximal slope of phase zero depolarization and shorteiming of action potential duration. O-³H uptake by isolated PF and uptake by PF excised from the donor heart after an equal period of O-³H exposure were similar if corrected for differences between heart and stimulus rates. Similarly, when PF bundles were removed from the donor heart at varying times after an O injection, their action potential characteristics were nearly identical with those of the isolated PF exposed to the same intravenous dose of O for the same time. This method for blood perfusion provides a reliable means for evaluating the effects of known drug concentrations on the electrical activity of isolated PF and for correlation with changes in the donor ECG.