Effect of Giving Digitalis on the Volume Output of the Heart and its Size in Normal Individuals

Abstract

It was first shown by Harrison and Leonard 1 that digitalis decreased the cardiac output in normal dogs. In repeating these experiments, Cohn and Stewart 2 were able to confirm the observation that digitalis decreased the volume output of blood from the heart in normal dogs, but that at the same time it decreased the size of the heart although it increased the extent of ventricular contraction. Results similar to these were obtained when the drug was given to dogs in which the hearts had become pathologically enlarged, but in which there were no signs of heart failure. 3 In a parallel study, Burwell, Neighbors and Regen 4 by an unsatisfactory method published data which suggested that taking digitalis decreased the cardiac output of normal men. Since the publication of their paper, Grollmann 5 , 6 has introduced a more accurate method of measuring the cardiac output than that formerly used. In the study here reported, this method has been used, which so far as can now be judged gives accurate and reliable results. The nature of the changes which Burwell, Neighbors and Regen found resemble those described in this report.

There are observations on 4 subjects. Digitan (Merck) 0.8 to 1.0 gm. was given in a single dose. Observations were made immediately before the drug was given and at frequent intervals afterward. All observations were made with subjects in a basal metabolic state. In addition to measurements of cardiac output, the size of the heart was measured in x-ray photographs taken at a distance of 2 meters. Electrocardiograms were made; the heart rate was counted; the blood pressure was estimated.