THE EFFECT OF TACHYCARDIA ON THE BLOOD FLOW IN DOGS

Abstract

The frequent.occurrence of tachycardia, both regular and irregular, in patients makes it desirable to have exact information as to the effect of these rhythms on the circulation. Up to the present few studies have been directed toward this end either in patients or in experimental aninals, because of the difficulty in the first place of obtaining samples of mixed venous blood and in the second place of inducing these rhythms under conditions which were not too far removed from normal conditions. Stewart (1) in a study of the oxygen saturation of the arterial and of the venous arm blood in patients during auricular fibrillation and after the return to the normal rhythm under quinidine sulphate, found that during the period of fibrillation the arterial oxygen saturation was practically unchanged, while that of the venous blood was decreased. It appeared therefore that the blood flow was slower during auricular fibrillation than during the normalrhythm. Goldschmidt and Light (2) have shown that the oxygen saturation of the venous arm blood varies with temperature and to some extent with position, but the consistency in the changes which Stewart observed when these factors were taken into account make it seem unlikely that these two factors were responsible for them. Meakins (3) found that neither regular nor irregular tachycardia affected the oxygen saturation of the arterial blood in dogs. There is a difficulty however in the interpretation of Meakins' experiments, for the dogs were under paraldehyde anesthesia, the chests were open and the dogs were kept alive by means of artificial respiration. In cases 435