Cardiac systolic time intervals in fetal monkeys: ventricular ejection time.

The VET of the fetal cardiac cycle, measured as the interval between the semilunar valve opening and closing signals of the ultrasound Doppler cardiogram, was studied in chronically catheterized fetal rhesus monkeys. VET varied inversely with FHR between approximately 150 and 250 bpm. Below 150 bpm, however, there was no further prolongation of VET. VET was not related to gestational age. VET, corrected for heart rate, was shortened in the presence of combined hypoxemia and acidosis, but not when either hypoxemia or acidemia was present alone. Corrected VET was shortened by epinephrine, but was not consistently altered by atropine. VET was not affected by changes in the concentration of glucose in fetal blood.