Characteristic differences and reference ranges for mitral, tricuspid, aortic, and pulmonary Doppler velocity waveforms during fetal life

Assessment of fetal cardiac function in early fetal life: feasibility, reproducibility, and early fetal nomograms

BACKGROUND

Fetal cardiology has shown a rapid development in the past decades. Fetal echocardiography is not only used for the detection of structural anomalies but also to assess fetal cardiac function. Assessment of the fetal cardiac function is performed mostly in the second and third trimesters. The study of fetal cardiac function at the end of first trimester has not been investigated properly, and there is a lack of reference values at early gestational weeks.

OBJECTIVE

This study aimed to assess if the measurement of time-related parameters of cardiac function in the left ventricle of the fetal heart is feasible and reproducible at the end of the first trimester. If possible, we provide nomograms of these parameters from 11 to 13+6 gestational weeks.

STUDY DESIGN

We conducted a prospective observational study from March to September 2022. The study was carried out in 2 hospitals (Hospital Universitari Dexeus, Barcelona, and Hospital VITAHS 9 Octubre, Valencia, Spain). The scans were performed by 3 specialists in fetal medicine. The exclusion criteria were fetal cardiac rhythm abnormalities, abnormal nuchal translucency, abnormal ductus venosus, fetal malformations, stillbirth, estimated fetal weight <10 percentile, diabetes, and gestational hypertensive disorders. The cardiac function parameters studied in the left ventricle were isovolumetric contraction time, isovolumetric relaxation time, ejection time, filling time, cycle time, myocardial performance index, ejection time fraction, and filling time fraction. We study the feasibility and intra- and interobserver reproducibility of these parameters using the interclass correlation coefficient. Nomograms were created and the percentiles of the values of the different parameters were calculated.

RESULTS

A total of 409 cases were recruited but only 296 could be included in the statistical analysis once the exclusion criteria were applied. The intraobserver reproducibility study was excellent (interclass correlation coefficient >0.900), and the interobserver reproducibility study was good (interclass correlation coefficient >0.700). The data regression analysis showed that cycle time, filling time, isovolumetric contraction time, and filling time fraction increased with gestational age, whereas ejection time fraction decreased with gestational age and myocardial performance index (mean, 0.43±0.08), isovolumetric relaxation time (mean, 0.04±0.01), and ejection time (mean, 0.16±0.01) remained constant from 11 to 13 weeks.

CONCLUSION

The study of fetal cardiac function is feasible and reproducible at 11 to 13+6 gestational weeks. Nomograms of the studied parameters are provided.

Fetal cardiac filling and ejection time fractions by pulsed-wave Doppler: reference ranges 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 time fraction (FTF) and ejection time fraction (ETF), are promising but rarely studied. We aimed to report the feasibility and reproducibility of fetal FTF and ETF measurements using pulsed-wave Doppler, to provide reference ranges for fetal FTF and ETF, 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 singleton pregnancies and a high-risk population of fetuses with severe twin-twin transfusion syndrome (TTTS), aortic stenosis (AoS) or aortic coarctation (CoA), from 18 to 41 weeks' gestation. Left ventricular (LV) and right ventricular inflow and outflow pulsed-wave Doppler signals were analyzed, using valve clicks as landmarks. FTF was calculated as: (filling time/cycle time) × 100. ETF was calculated as: (ejection time/cycle time) × 100. Intraclass correlation coefficients (ICC) were used to evaluate the intra- and interobserver reproducibility of FTF and ETF measurements in low-risk fetuses. The relationships of FTF and ETF with HR, GA and EFW were evaluated using multivariate regression analysis. Reference ranges for FTF and ETF were then constructed using the low-risk population. Z-scores of FTF and ETF in the high-risk fetuses were calculated and analyzed.

RESULTS

In total, 602 low-risk singleton pregnancies and 54 high-risk fetuses (nine pairs of monochorionic twins with severe TTTS, 16 fetuses with AoS and 20 fetuses with CoA) were included. Adequate Doppler traces for FTF and ETF could be obtained in 95% of low-risk cases. Intraobserver reproducibility was good to excellent (ICC, 0.831-0.905) and interobserver reproducibility was good (ICC, 0.801-0.837) for measurements of all timing parameters analyzed. Multivariate analysis of FTF and ETF in relation to HR, GA and EFW in low-risk fetuses identified HR as the only variable predictive of FTF, while ETF was dependent on both HR and GA. FTF increased with decreasing HR in low-risk fetuses, while ETF showed the opposite behavior, decreasing with decreasing HR. 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 univentricular vs 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 using pulsed-wave Doppler is feasible and reproducible in the fetus. The presented reference ranges account for associations of FTF with HR and of ETF with HR and GA. These time fractions are potentially useful for clinical monitoring of cardiac function in severe TTTS, AoS and other fetal conditions overloading the heart. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Z-score reference ranges for pulsed-wave Doppler indices of the cardiac outflow tracts in normal fetuses

To determine Z-score equations and reference ranges for Doppler flow velocity indices of cardiac outflow tracts in normal fetuses. A prospective cross-sectional echocardiographic study was performed in 506 normal singleton fetuses from 18 to 40 weeks. Twelve pulsed-wave Doppler (PWD) measurements were derived from fetal echocardiography. The regression analysis of the mean and the standard deviation (SD) for each parameter were performed against estimated fetal weight (EFW) and gestational age (GA), in order to construct Z-score models. The correlation between these variables and fetal heart rate were also investigated. Strong positive correlations were found between the twelve PWD indices and the independent variables. A linear-quadratic regression model was the best description of the mean and SD of most parameters, with the exception of the velocity time interval (VTI) of ascending aorta against EFW, which was best fitted by a fractional polynomial. Z-score equations and reference values for PWD indices of fetal cardiac outflow tracts were proposed against GA and EFW, which may be useful for quantitative assessment of potential hemodynamic alternations, particularly in cases of intrauterine growth retardation and structural cardiac defects.

Time-interval changes of cardiac cycles in fetal growth restriction

OBJECTIVE

The aims of this study were to investigate the time intervals of each component of cardiac flow velocity waveforms (FVWs) in fetuses with fetal growth restriction (FGR) and to compare these with those of normal fetuses using reference ranges.

METHODS

The durations of atrioventricular (AV) valve opening (AVVO), AV valve closure (AVVC), total E- (total-E) and A- (total-A) waves, total ejection time (total-ET), acceleration time (acc-E for E-wave, acc-A for A-wave, and acc-ET for ejection time), and deceleration time (dec-E for E-wave, dec-A for A-wave, and dec-ET for ejection time) were measured in fetuses with FGR. All variables were analyzed using z-scores.

RESULTS

Measurements of 17 growth-restricted fetuses were obtained. The time intervals between the last Doppler examination and delivery ranged from 0 to 6 days, with a median of 1 day. Significant increases were observed in AVVO, total-E, dec-E, and acc-A of the left heart. acc-E, acc-ET and AVVC of the left heart were significantly decreased. In the right heart, AVVO, total-E and dec-E were significantly increased.

CONCLUSION

A prolonged time interval between early ventricular inflow and atrial contraction, as well as increased duration of AV valve opening, may reflect hemodynamic alterations in FGR fetuses.