Abstract
A two-dimensional echocardiography and a two-dimensionally directed M-mode echocardiography were performed on 168 normal human fetuses ranging from 20 to 39 weeks of gestation to assess the growth pattern, relative left ventricular (LV) and right ventricular (RV) sizes, function and volumes. These findings were compared with those in postmortem hearts of normal human fetuses ranging from 18 to 36 weeks of gestation. LV amd RV diameters, wall thicknesses, mitral and tricuspid valve diamiters, and the aortic diameter all increased linearly with gestational age, biparietal diameter and estimated body weight. However, the ratios of LV and, RV diameters, mitral and tricuspid valve diameters and LV, RV and septal wall thicknesses were constant and approximated at 1.0 throughout the period studied in the echocardiograms and postmortem hearts. Moreover, the ratio of LV and RV volumes in postmortem hearts were constant (1.02±.17). The percent changes in ventricular diameters and wall thicknesses as indexes of systolic function did not change significantly throughout and were similar between LV and RV. LV volume in the postmortem hearts was best approximated by an ellipsoid model (r=.95). The estimated LV volumes from echocardiograms by this model increased linearly with gestational age (r=.85), but LV ejection fraction and output per estimated body weight remained constant throughout the period studied. These findings indicate. that fetal hearts show a linear growth pattern and that LV and RV are similar insize, and systolic function remains constant, throughout the second half of gestation. LV volume of the fetal heart may, be estimated by an ellipsoid model.
