Effects of ouabain and hypoxia on the cardiac stimulation threshold in the dog (with special reference to changes in extra- and intracellular potassium concentrations).

The influence on the cardiac stimulation threshold of changes in the myocardial intra/extracellular potassium ratio induced with ouabain and hypoxia was investigated in 9 dogs with total atrioventricular block. In spite of significant elevations of extracellular potassium and reductions of intracellular potassium significant changes in stimulation threshold were not seen. It is suggested that different experimental conditions are responsible for the great variations in the results of previous studies of this subject.