Abstract 13050: Antegrade Late Diastolic Arterial Flow in the Fetus: Insight Into Early Fetal Hemodynamics
Antegrade late diastolic pulmonary arterial flow is a hallmark of restrictive right ventricular physiology after birth. We recently discovered that antegrade late diastolic arterial flow (ALDAF) occurs in the early fetus (Figure). We hypothesized that ALDAF in the fetus represents flow during atrial systole and that it potentially contributes to fetal cardiac output.
Methods: Three hundred and five normal fetal echocardiograms performed on 113 patients between 6–30 weeks of gestation were evaluated for ALDAF. The velocity time integral (VTI) of the ALDAF and ventricular systolic Doppler signal (V) were measured and the relative contribution of the ALDAF VTI to the total forward VTI, as a measure of ventricular output, was expressed as a percentage. Timing of onset of ALDAF to the ventricular systolic Doppler onset was measured and compared to the atrio-ventricular (A-V) interval measured from a simultaneous ventricular inflow-outflow Doppler recording. Statistical analysis was performed using one-way ANOVA.
Results: ALDAF was present in one or both ventricular outflows in 242 of 305 fetal studies, including all studies prior to 12 weeks gestation, and declining in frequency with increasing gestational age. At <10 weeks gestation, median ALDAF contribution to total forward arterial VTI was 21% (range 8–47%) with a progressive decrease with age (p=0.02). Time between onset of ALDAF and systolic flow did not differ significantly from the measured A-V interval.
Conclusions: ALDAF in the early fetus suggests that in late diastole the pressure in atrial systole exceeds the systemic pressure and that the early fetal myocardium must be sufficiently restrictive to allow antegrade flow through the semilunar valve during this time. With maturation, improved myocardial diastolic function results in less ALDAF. The relative proportion of ALDAF to total forward VTI in the great arteries suggests atrial systole may contribute importantly to early fetal cardiac output.
- © 2010 by American Heart Association, Inc.