The difference between the systolic time intervals of the left and right ventricles during fetal life.

In order to determine if the two ventricles of the fetal heart contract synchronously the systolic time intervals of both ventricles were compared. Eight experiments were carried out on fetal lambs. The studies demonstrated that while the ejection times of both ventricles were the same, the mean pre-ejection period of the right ventricle was significantly greater than that of the left (57 +/- 8 versus 48 +/- 8 msec, p less than 0.005). These findings were further substantiated in serial studies during a 7-day period on the same fetal lamb. If changes in the systolic time intervals are to be useful in evaluating fetal myocardial function, the values should be obtained from the same ventricle.