Two dimensional ultrasonic Doppler echocardiography was used to observe cardiac cycle. The results of the observation about time interval of physiological(of healthy man) and pathophysiological(of patients with aortic valve prostheses) cardiac cycle showed that heart rate and systolic ratio, left ventricular systolic time and eject time are highly linearly correlated in quality and direction but different quantitatively. In the regression equation ,where ejection time is a function of the time of left venti...