Objective: To assess the ejection characteristics of both ventricles in utero in normal and IUGR fetuses with with increasing gestations
Design & Methods: We assessed right(RV) and left ventricular(LV) ejection characteristics in 24 normal fetuses(22-38 w.g.) and 12 fetuses with intra uterine grow retardation(IUGR)28-39w.g.Aortic and pulmonary valve diameters were measured and Dopplers perfomed in ascending aorta and pulmonary artery.Ejection times(ET)and acceleration times(AT)were measured and ejection forces(EF)calculated(1.06xvalve area x peak velocity2/2)
Results: In normal fetuses ET: LV(mean)198msec RV196msec;
p-0.19.AT:LV(mean)54.3msec; RV48.4msec;p-0.002.EF:LV(mean)75.6;RV122; p-0.01.In IUGR fetuses ET:LV(mean)195.6msec;RV192.6;p-0.23.AT:LV(mean)54msec;RV45.6msec p-0.05 EF:LV(mean)71.4;RV117; p-0.16. EF of LV and RV increased in linear fashion up to 34w.g. and then tapered off. This was concurrent with an increase in both valve area and peak velocity in the distal vessel.The right ventricular EF was consistantly greater than the LV.The RV ejection times was equal to or slighlu shorter than the LVin most fetuses.The AT in the pulmonary artrey was shorter than in the aorta. We found similar patterns were noted in the fetuses with IUGR however these were less significant.The ejection forces were generally lower in the IUGR group at the same gestation.
Conclusion: The study demonstrates differences in the ejection characteristics of the ventricles in utero, with the right ejection more rapidly than the left. The lower ejection forces in the IUGR fetuses were due not only to smaller valve areas but also to lower velocites in the distal vessel. Ejection force may be a reasonable means of assessing ventricular function in "stressed" fetuses however futher studies are needed.