The Effect of Adrenaline on the Contraction of the Human Heart under Normal Circulatory Conditions

Summary. The effect of the infusion of small doses of adrenaline in man with intact circulation has been studied. The analyses have been made with electrokymography, phonocardiography and electrocardiography. It has been found that adrenaline (1) shortens the isometric contraction phase, (2) accelerates the speed of contraction, (3) increases the systolic emptying of the left ventricle, (4) increases the amplitude of the first and second heart sounds, (5) lowers the diastolic pressure, (6) increases the amplitude of the pulse pressure and (7) usually increases the heart rate. In addition, adrenaline causes an alteration of the T wave of the E.C.G. with a division into two components. One of these components corresponds to the T wave at rest, when correlated to mechanical systole; the other appears to be a positive after‐potential. The effect on the contraction of the left ventricle was produced with the same concentrations in the blood as those that cause a decrease in the resistance in the systemic circulation and affect the metabolism of glucose. With larger doses, causing a more marked elevation in blood pressure, toxic symptoms, such as extrasystoles and auricular fibrillation, were noted. In addition to glycogenolysis and the formation of lactic acid the physiological effects of adrenaline thus appear to consist mainly of adaptation to an increased circulatory response. The increase in the stroke volume of the left ventricle is not associated with any increase in the volume of the heart during diastole. This implies a more complete emptying of the ventricle, i. e. a decrease in its residual blood volume. The results are discussed with reference to the significance of the distribution of the blood when the effects of adrenaline or other factors acting on the circulation are examined.