Transmembrane fluxes in ventricular fibrillation

¹ Department of Pharmacology, University of Mississippi Medical Center, Jackson, Mississippi

Transmembrane fluxes of K and the rate of net entry of Na were determined in isolated perfused rabbit hearts before and during ventricular fibrillation. These results were compared to previous flux measurements in atrial fibrillation. Control ventricles in low (K)₀ media lost K at a rate of 8 pmoles cm^–2sec^–1. This was 2 1/2 times greater than the rate of K loss in control atria. The initiation of both atrial and ventricular fibrillation was associated with an increased K efflux, decreased K influx and marked increase of Na influx. The data were interpreted to suggest that both atrial and ventricular fibrillation are initiated by the same basic mechanism; that is an increase in Na entry above a critical value (K leaving the tissue in exchange). This critical value can be easily attained in perfused ventricles by lowering the (K)₀.