HUMAN FETAL RIGHT-VENTRICULAR EJECTION FORCE UNDER ABNORMAL LOADING CONDITIONS DURING THE 2ND-HALF OF PREGNANCY

Our objective was to determine whether abnormal loading conditions can modify human fetal right ventricular ejection force during the second half of pregnancy. By Doppler echocardiography we studied 73 normal f etuses between 19 and 41 weeks of gestation, 27 fetuses with hypoelast ic left heart syndrome (chronic volume overload) between 18 and 38 wee ks of gestation, 14 fetuses with mild to moderate constriction of the ductus arteriosus (pulsatility index (PI) between 1.0 and 1.9) and sev en fetuses with severe constriction (PI < 1.0) or occlusion of the duc tus arteriosus (relatively acute pressure overload) between 28 and 34 weeks of gestation. In the normal and ductal constriction/occlusion gr oups, blood velocity waveforms were recorded at the level of the aorti c and pulmonary valves, and in the group with hypoplastic left heart s yndrome at the level of the pulmonary valve. The ventricular ejection forces were calculated. In the normal group, right (RVEF; r = 0.91, p < 0.0001) and left (LVEF; r = 0.86, p < 0.0002) ventricular ejection f orces increased and were equal during the second half of gestation. In the group with hypoplastic left heart syndrome the RVEF increased (r = 0.76, p < 0.0001) with advancing gestation. The RVEF (p < 0.0005) an d its average weekly increase (p < 0.0001) were greater in the hypoela stic left heart syndrome group than in the normal group. In the group with mild to moderate ductal constriction, both ventricular ejection f orces were similar to those of the normal group. The RVEF (p < 0.003) and its average weekly increase (p < 0.03) were lower in the group wit h severe ductal constriction or occlusion than in the normal group. Th e LVEF did not differ from that of the normal group. We conclude that chronic volume overload increases and relatively acute pressure overlo ad decreases hut;an fetal RVEF. The right ventricular performance is m odified by abnormal loading conditions.