The effect of digitoxin on the apparent stroke volume, posteroanterior cardiac diameter, and the cardiac cycle in normal subjects as studied by the electrokymograph

Abstract

Although digitalis has been used in the treatment of congestive heart failure since the treatise of William Withering in 1785, 1 there is still confusion concerning the mechanism of action. There have been essentially 3 separate hypotheses advanced to define its action: (1) that digitalis increased the myocardial “tone,” 2–7 (2) that digitalis decreased the venous return to the heart, 8–12 and (3) that digitalis increased the strength of systolic contraction. 13–15 At present, probably more investigators favor the last explanation, although there are still observations which are difficult to include under a single theory. A fundamental approach to the action of digitalis is the study of the effect of the drug on the phases of the cardiac cycle, which can be recorded serially in man by use of the electrokymograph, 16,17 The purpose of this paper is to record the changes in the phases of the cardiac cycle, posteroanterior cardiac diameters, and apparent stroke volume in normal subjects as the result of digitalis.