SOME FURTHER FACTORS INFLUENCING THE NORMAL ISOMETRIC PERIOD OF THE HUMAN HEART

Abstract

By means of simultaneous optical records of heart sounds and aortic pulse tracings, the length of the isometric contraction periods of 59 men and 65 women in standing, sitting, and recumbent postures has been determined. The average length of the period is 0.0417 sec. The duration is modified little by age, sex, or blood-pressure, but is altered by heart rate, particularly in the standing position, because its length is determined largely by the length of the preceding diastole. This influence is due to the amount of blood and therefore the pressure in the ventricle at the close of diastole.