Evaluation of conventional Doppler fetal cardiac function parameters: E/A ratios, outflow tracts, and myocardial performance index

The (Pulsed-Wave) Doppler Fetal Myocardial Performance Index: Technical Challenges, Clinical Applications and Future Research

Functional cardiovascular assessment is becoming an increasingly important tool in the study of fetal pathology. The myocardial performance index (MPI) is a parameter measuring global myocardial function. Since its introduction, several studies have proposed methods to improve its reproducibility and have constructed normative reference ranges. Fetal heart evaluation using the MPI is technically challenging, requiring specific training and expertise, and a consensus has yet to be reached on the method of delineating the time periods used to calculate the index. Despite these limitations, it has been shown to be a useful and highly sensitive parameter of dysfunction in a number of fetal pathologies. Further research is warranted into the effect of pathology on MPI, parameters of unilateral cardiac strain that utilise MPI, and automation of the MPI to encourage incorporation of the MPI as a useful tool in clinical practice.

Further insights into diastolic dysfunction in first-trimester trisomy-21 fetuses

OBJECTIVE

To assess fetal cardiac function in first-trimester trisomy-21 fetuses as compared with fetuses with other aneuploidies, euploid fetuses with cardiac defects or isolated increased nuchal translucency (NT) and controls.

METHODS

During a 2.5-year period, NT, ductus venosus (DV) blood flow, diastolic filling time, early filling time, tricuspid flow, tricuspid and mitral valve E/A velocity ratios, left ventricle shortening fraction, left myocardial performance index and fetal heart rate were assessed in fetuses with a crown-rump length between 45 and 84 mm undergoing chorionic villus sampling at our center. Cardiac parameters among study groups were compared with the use of 95% CIs.

RESULTS

The study population comprised 28 fetuses with trisomy 21, 25 with other aneuploidies, 94 euploid fetuses with abnormal findings (27 with cardiac defects, 31 with other structural anomalies and 36 with isolated increased NT) and 271 controls. Trisomy-21 fetuses showed signs of diastolic dysfunction such as increased DV pulsatility index and E/A ratios together with a higher prevalence of tricuspid regurgitation. However, no differences were found in euploid fetuses with cardiac defects or isolated increased NT.

CONCLUSIONS

No signs of cardiac dysfunction were observed in euploid fetuses with increased NT or cardiac defects, while in trisomy-21 fetuses signs of diastolic dysfunction could be potentially attributed to volume overload.

The effect of pregestational diabetes on fetal heart function

Pregestational diabetes affects nearly 2% of all pregnancies. Moreover, Type 2 diabetes in child-bearing women is on the rise because of the childhood obesity epidemic. Pregestational diabetes can affect the fetal heart in several ways. First, the risk of fetal congenital heart disease is markedly increased; second, fetal hypertrophic cardiomyopathy may occur even with good glycemic control; third, studies have shown impaired function of the hearts of some infants and fetuses of diabetic pregnancies, which can occur with and without septal hypertrophy. Small-for-gestational-age infants of diabetic mothers may have diminished cardiovascular health in the long term. This review mainly discusses methods to detect fetal diabetic cardiomyopathy prenatally. The focus is on the noninvasive diagnostic markers that can serve as an outcome measure for future therapeutic trials, which are still lacking. There is some experimental research on treatment strategies to prevent fetal heart disease in diabetic pregnancies but little clinical data.

Foetal cardiac function: assessing new technologies

Assessment of foetal cardiac function is more challenging than in the adult, in whom emerging technologies are tested. The postnatal cardio-respiratory interaction is replaced by the cardio-placental circulation and impedance of the brain, and distal vascular beds play an important role in modulating flow to enable its redistribution in the foetal body. Prenatal specialists, comprising obstetricians and cardiologists, have tested a variety of traditional methodologies, as well as non-Doppler offline ultrasound methods in the foetus. This article reviews the development of techniques, outlines their use, and draws attention to pitfalls in adapting technologies validated in the adult heart to the small, fast beating, remote, and largely ungated foetal heart.

A fetal cardiovascular score to predict infant hypertension and arterial remodeling in intrauterine growth restriction

OBJECTIVE

Intrauterine growth restricted (IUGR) fetuses experience cardiovascular remodeling that persists into infancy and has been related to cardiovascular outcomes in adulthood. Hypertension in infancy has been demonstrated to be a strong risk factor for later cardiovascular disease. Close monitoring together with dietary interventions have shown to improve cardiovascular health in hypertensive children; however, not all IUGR infants show increased blood pressure. We evaluated the potential of fetal echocardiography for predicting hypertension and arterial remodeling in 6-month-old IUGR infants.

STUDY DESIGN

One hundred consecutive IUGR and 100 control fetuses were observed into infancy. Fetal assessment included perinatal Doppler imaging, cardiac morphometry, ejection fraction, cardiac output, isovolumic relaxation time (IVRT), tricuspid annular-plane systolic excursion (TAPSE), and tissue Doppler imaging. Infant hypertension and arterial remodeling were defined as mean blood pressure of >95th percentile together with aortic intima-media thickness of >75th percentile at 6 months of age. Odds ratio were obtained for fetal parameters that were associated with infant outcomes.

RESULTS

Fetal TAPSE, right sphericity index, IVRT, and cerebroplacental ratio were the strongest predictors for postnatal vascular remodeling. A cardiovascular risk score that was based on fetal TAPSE, cerebroplacental ratio, right sphericity index, and IVRT was highly predictive of infant hypertension and arterial remodeling (area under the curve, 0.87; 95% confidence interval, 0.79-0.93; P < .001).

CONCLUSION

Fetal echocardiographic parameters identify a high-risk group within the IUGR fetuses who could be targeted for early screening of blood pressure and other cardiovascular risk factors and for promoting healthy diet and physical exercise.

Ultrasound assessment of fetal cardiac function

Introduction: Fetal heart evaluation with US is feasible and reproducible, although challenging due to the smallness of the heart, the high heart rate and limited access to the fetus. However, some cardiac parameters have already shown a strong correlation with outcomes and may soon be incorporated into clinical practice. Materials and Methods: Cardiac function assessment has proven utility in the differential diagnosis of cardiomyopathies or prediction of perinatal mortality in congenital heart disease. In addition, some cardiac parameters with high sensitivity such as MPI or annular peak velocities have shown promising results in monitoring and predicting outcome in intrauterine growth restriction or congenital diaphragmatic hernia. Conclusion: Cardiac function can be adequately evaluated in most fetuses when appropriate expertise, equipment and time are available. Fetal cardiac function assessment is a promising tool that may soon be incorporated into clinical practice to diagnose, monitor or predict outcome in some fetal conditions. Thus, more research is warranted to further define specific protocols for each fetal condition that may affect cardiac function.

Reference values for fetal tissue velocity imaging and a new approach to evaluate fetal myocardial function

OBJECTIVES

Myocardial function can be evaluated using color-coded tissue velocity imaging (TVI) to analyze the longitudinal myocardial velocity profile, and by expressing the motion of the atrioventricular plane during a cardiac cycle as coordinated events in the cardiac state diagram (CSD). The objective of this study was to establish gestational age specific reference values for fetal TVI measurements and to introduce the CSD as a potential aid in fetal myocardial evaluation.

METHODS

TVI recordings from 125 healthy fetuses, at 18 to 42 weeks of gestation, were performed with the transducer perpendicular to the apex to provide a four-chamber view. The myocardial velocity data was extracted from the basal segment of septum as well as the left and right ventricular free wall for subsequent offline analysis.

RESULTS

During a cardiac cycle the longitudinal peak velocities of septum increased with gestational age, as did the peak velocities of the left and right ventricular free wall, except for the peak velocity of post ejection. The duration of rapid filling and atrial contraction increased during pregnancy while the duration of post ejection decreased. The duration of pre ejection and ventricular ejection did not change significantly with gestational age.

CONCLUSION

Evaluating fetal systolic and diastolic performance using TVI together with CSD could contribute to increase the knowledge and understanding of fetal myocardial function and dysfunction. The pre and post ejection phases are the variables most likely to indicate fetuses with abnormal myocardial function.