Contribution of Doppler atrioventricular flow waves to ventricular fillingin the human fetus

The normal fetal flow velocity profile across the atrioventricular valves i s characterized by an early peak (E), which is related to preload and to ac tive ventricular muscle relaxation, and a higher late peak (A), which is ca used by the atrial contraction and also influenced by ventricular complianc e. The purpose of this study was to determine how these two elements of ven tricular filling change during gestation in both ventricles. A total of 485 normal fetuses from 17 weeks to term were examined by Doppler echocardiogr aphy. We measured E and A peak velocities and E/A ratio for both mitral and tricuspid valves. Simple regression analysis was applied to assess possibl e correlation between Doppler variables and gestational age. Moreover, E an d A peak velocities were compared using paired Student's t-test. With the a dvance of gestation a significant linear increase in the E wave and E/A rat io was found for both mitral and tricuspid valves. The A wave shows little change throughout pregnancy. We found significantly higher Doppler velociti es for the tricuspid valve than for the mitral valve. The relationship betw een the E/A ratios for the two valves and gestational age diverge slightly, with higher values for the mitral E/A ratio. This study shows that the A w ave velocity remains constant throughout gestation, suggesting little or no change in ventricular compliance. The E wave is mainly responsible for the change in E/A ratio for both atrioventricular valves during gestation. The se findings suggest progressive enhancement of relaxation and elastic recoi l, an increase in preload, or both, throughout gestation, rather than a cha nge in myocardial compliance as an explanation for the observed increase in the E/A ratio.