Tsyvian PB, Malkin KV, Wladimiroff JW.Biophysical Laboratory, Mother and Child Care Institute, Yekaterinburg, Russian Federation. Early Hum Dev 1995 Jan 30;40(2):109-14. M-mode echo recordings of the left ventricle (LV) and inflow LV Doppler velocimetry were performed in nine normal fetuses at a gestational age of 36-39 weeks. In each fetus approximately 80 consecutive cardiac cycles were digitized. The duration of each cardiac cycle (T) and the corresponding end-diastolic (EDD), end-systolic (ESD) dimensions of LV or the peak velocity of early (E) and late atrial (A) mitral flow parameters was calculated. The role of sonographic parameters on current (Tn) and preceding (Tn-1) cardiac cycles was assessed using linear regression. Significant dependency of ventricular EDD and transmitral A peak velocity upon Tn was demonstrated. We speculate that atrial systole has an important role to play in the beat-to-beat regulation of fetal stroke volume.