Cardiac filling and ejection time fractions by pulsed Doppler: fetal nomograms and potential clinical application.

OBJECTIVES Fetal cardiac function can be evaluated using a variety of parameters. Among these, cardiac cycle time-related parameters such as filling (FTF) and ejection time fractions (ETF) are promising but scarcely studied. We aimed to report the feasibility and reproducibility of FTF and ETF measurements by spectral Doppler, to provide reference ranges in fetal life, after evaluating their relationship with heart rate (HR), gestational age (GA) and estimated fetal weight (EFW) and to evaluate their potential clinical utility in selected fetal conditions. METHODS This study included a low-risk prospective cohort of 602 singleton pregnancies and a high-risk population of 54 fetuses (9 pairs of monochorionic twins with severe twin-twin transfusion syndrome (TTTS), 16 aortic stenosis (AoS) and 20 aortic coarctation (CoA)) from 18-41 weeks. Left (LV) and right ventricular (RV) inflow and outflow spectral Doppler signals were analysed. Valve clicks were used as landmarks. FTF was calculated as: (Filling time/Cycle time)*100 and ETF as (Ejection time/Cycle time)*100. Interclass correlation coefficient (ICC) was used to evaluate intra and inter-observer reproducibility. The relations between FTF, ETF, HR, GA and EFW were evaluated using multivariate regression analysis. Nomograms for these parameters were then constructed using the low risk population. Z-scores of FTF and ETF of the high-risk fetuses were calculated and analysed. RESULTS Adequate Doppler traces for FTF and ETF could be obtained in 95% of cases. Intra-observer reproducibility was excellent (ICC>0.900) and inter-observer reproducibility was good (ICC>0.800) for all timing parameters analysed. Multivariate analysis of FTF and ETF in relation to HR, GA and EFW identified HR as the only variable predicting FTF. In contrast, ETF was dependent on both HR and GA. While FTF increased with HR reduction, ETF showed the opposite behaviour, decreasing with HR (more markedly at lower GA) in low-risk fetuses. Most recipient twins with severe TTTS showed reduced FTF and preserved ETF. AoS was associated with decreased FTF and increased ETF in the LV with seemingly different patterns associated with a univentricular versus biventricular postnatal outcome. The majority of fetuses with CoA had FTF and ETF within the normal range in both ventricles. CONCLUSIONS Measurement of FTF and ETF are feasible and reproducible in the fetus. Nomograms account for associations of FTF with HR and ETF with HR and GA. These time fractions are potentially useful for clinical monitoring of cardiac function in TTTS, aortic stenosis and other fetal conditions overloading the heart. This article is protected by copyright. All rights reserved.