STUDIES ON THE EFFECT OF THE ACTION OF DIGITALIS ON THE OUTPUT OF BLOOD FROM THE HEART

Abstract

Recent research on the peripheral action of digitalis, more particularly upon the hepatic veins, has been taken as proof that this action is responsible for decrease of volume output attending administration of the drug to normal dogs. Anatomical evidence makes this mechanism seem unlikely to be responsible for the decrease observed in normal human beings. Data are presented obtained from experiments involving the use of the heart-lung preparation (dog) in which a constant peripheral circulation is provided and in which, therefore, change in condition of the heart muscle can be considered responsible for changes in state of the circulation. Under these conditions when the heart fails, i.e., output of the heart decreases, the right auricular pressure rises and the heart enlarges, the exhibition of digitalis reverses these phenomena. The output increases, the right auricular pressure falls, and the heart becomes smaller. In some experiments a considerable and identical impediment to inflow, and hence to outflow, in the form of constriction of the passage-way from the peripheral circulation to the right auricle was applied before and after administration of digitalis. The volume output for a given degree of constriction was, however, greater after than before the drug was administered. These facts indicate that the action of digitalis on the hepatic veins is of little consequence in diminishing the volume output from a failing heart. The point is emphasized that the most important effect is to decrease the size of the heart.