Abstract
The relationship between the initial heart rate and the cardiotoxic dose of ouabain was investigated in the dog heart-lung preparation. It was observed that with a relatively slower heart rate, the dose of ouabain necessary to produce ventricular tachycardia as well as ventricular fibrillation or cardiac arrest was increased significantly (p<0.05). When the heart was paced at either 150 or 180 beats/min, the dose of ouabain needed to produce ventricular tachycardia was significantly greater than that in the control group (heart rate 128±4 beats/min). However, in these groups, there was no difference in the dose of ouabain necessary to produce lethal effects. Thus to some extent, an inverse relationship between the heart rate and the cardiotoxic dose of ouabain was observed. The significance of these findings is discussed.
