Studies on Digitalis
VI. Reduction of the Oxygen Debt after Exercise with Digoxin in Cardiac Patients without Heart Failure
Three patients with acquired valvular heart disease and cardiac enlargement who were able to perform normal everyday activity without difficulty in the absence of digitalis therapy were exercised while receiving a placebo and again while receiving digoxin. Digoxin administration did not produce a significant change in body weight or in the subjective condition of the individuals. Varying degrees of exercise were performed on a treadmill in a Metabolic Chamber and oxygen consumption was measured cotinuously before, during, and after the period of exercise, utilizing a continuous gas flow paramagnetic oxygen analyzer. The oxygen debt that developed during digoxin administration was compared to that observed during placebo administration.
In all patients the oxygen debt was smaller during the period of digoxin administration, although the external work performed was identical. In the first patient, following a 7-minute walk, the oxygen debt was 53 per cent more and following a 10-minute walk it averaged 40 per cent more while not receiving digoxin than when receiving this drug. In the second subject the oxygen debt following a 7-minute walk was 34 per cent more and following 10-minute walk it averaged 74 per cent more when he was not receiving digoxin than when receiving this drug. In the third subject the oxygen debts were 46 per cent and 41 per cent greater following 10- and 15- minute walks respectively, when she was not receiving digoxin.
The accumulation of a smaller oxygen debt following exercise while these subjects were receiving digoxin indicates that the functional status of their circulatory system was improved by the drug. It would appear that digitalis administration is beneficial to at least some patients who have cardiac disease and enlarged hearts and some decrease in cardiac reserve without signs or symptoms of heart failure.
- © 1963 American Heart Association, Inc.