Advances in Fetal Echocardiography: Early Imaging, Three/Four Dimensional Imaging, and Role of Fetal Echocardiography in Guiding Early Postnatal Management of Congenital Heart Disease

Influence of maternal aerobic exercise during pregnancy on fetal cardiac function and outflow

BACKGROUND

Risk factors for cardiovascular disease, the leading cause of death, have been documented in children as young as 3 years of age. Maternal environment (eg, exercise) influences fetal development and long-term health. Thus, the development of the fetal cardiovascular system during pregnancy is likely a preliminary indicator of cardiac health at birth and a proxy for the future risk of cardiovascular disease throughout life.

OBJECTIVE

The purpose of this study was to assess the effects of supervised prenatal aerobic exercise at recommended levels on fetal cardiac function and outflow in the third trimester of pregnancy. We hypothesized that fetuses of aerobically trained women compared with fetuses of nonexercising women would exhibit increased cardiac function and greater cardiac output.

STUDY DESIGN

Secondary data analyses of a 20-week, randomized controlled exercise intervention trial in pregnant women between 2015 and 2018 in Eastern North Carolina were performed. Eligibility criteria included pregnant women <16 weeks gestation, singleton pregnancy, aged 18-40 years, body mass index of 18.5-34.99 kg/m², physician clearance letter for exercise participation, reliable transportation, and method of communication. Exclusion criteria included the presence of chronic conditions (eg, type 1 or 2 diabetes mellitus), current medications known to adversely affect fetal growth (eg, antidepressants), alcohol, smoking, or illicit drug use. The patient cohort consisted of 133 eligible pregnant women who were assigned randomly to either an aerobic exercise (n=66) group that participated in 150 minutes of supervised, moderate-intensity (40-59% VO_2peak; 12-14 on Borg Rating of Perceived Exertion) aerobic exercise per week or a nonexercising group (n=61) that consisted of 150 minutes per week of light (<40% VO_2peak) stretching and relaxation breathing techniques. Between 34 and 36 weeks gestation, a fetal echocardiogram was performed to assess fetal cardiac function, which included fetal heart rate, right- and left-ventricular stroke volume, stroke volume index, cardiac output, cardiac output index, and cardiac outflow that included pulmonary and aortic valve diameters, peak flow velocity, and peak flow velocity-time integral. Fetal activity state (quiet vs active) during the echocardiogram and maternal aerobic capacity served as covariates. Intention-to-treat and per-protocol (participants who attended ≥80% of exercise sessions) analysis of covariance regression models were performed.

RESULTS

Of the 127 randomly assigned participants, 66 and 50 participants were included in the intention-to-treat and per-protocol analyses, respectively. Prenatal aerobic exercise significantly increased fetal right-ventricular cardiac measures of right ventricular stroke volume (P=.001) and stroke index via velocity-time integral (P=.003), right ventricular cardiac output (P=.002), cardiac index via velocity-time integral (P=.006), pulmonary artery diameter (P=.02), and pulmonary valve velocity-time integral (P=.03). Only in the intention-to-treat analysis was a significant difference in fetal left ventricular cardiac outflow observed; there was a greater aortic valve peak velocity (P=.04) found among fetuses of aerobically trained pregnant women. No other statistically significant between-group differences were found.

CONCLUSION

The findings of this study demonstrate that participation in prenatal aerobic exercise at recommended levels may improve fetal cardiac function and outflow parameters. Follow-up cardiovascular measures in the postnatal period are needed to determine potential long-term effects on the offspring's cardiac function and outflow.

Four-Dimensional Ultrasound for Evaluating Newborn Cardiac Output: A Pilot Study of Healthy Infants

BACKGROUND

There is currently no reliable non-invasive method of measuring cardiac output in neonatal intensive care. Spatiotemporal image correlation (STIC) is a novel four-dimensional (4D) ultrasound technique that was developed to assess the foetal heart, and it may be a useful way to assess neonatal haemodynamics.

OBJECTIVE

This study aimed to evaluate the feasibility and reproducibility of determining neonatal cardiac output using STIC ultrasound in newborn infants.

DESIGN

Infants were recruited opportunistically from a neonatal intensive care unit and then examined by 2 independent observers. STIC was used to obtain images of the heart. End-diastolic and end-systolic ventricular volumes were measured using virtual organ computer-aided analysis (VOCAL) and used to calculate cardiac output. Reproducibility was assessed with intraclass correlation coefficients (ICC) and agreement with Bland-Altman analysis.

RESULTS

Twenty-four clinically stable infants of 34-43 weeks corrected gestational age were assessed. Both observers successfully acquired 4D STIC volumes in all infants. Left ventricular output showed good reproducibility, with an intra-observer ICC of 0.86 (0.69-0.94) and inter-observer ICC of 0.87 (0.70-0.95). Right ventricular output also showed good reproducibility, with an intra-observer ICC of 0.88 (0.70-95) and inter-observer ICC of 0.84 (0.63-0.93).

CONCLUSIONS

Determining cardiac output using 4D STIC ultrasound is feasible and reproducible in well newborn infants. With further evaluation, this technique may provide valuable information about haemodynamic status in newborn infants requiring intensive care.

Introduction: From fetal echocardiography to fetal cardiology: A journey of over half a century

In this Special Issue of the Journal, 8 review articles that represent the new developments and applications of fetal echocardiography and fetal cardiology for diagnosis, prognosis, and treatment of fetal cardiovascular disease are included. The goal was to provide an updated review of the evidence for the current and emerging use of fetal echocardiography and cardiac magnetic resonance, improved diagnosis of challenging congenital heart disease, new tools for evaluation of fetal systolic and diastolic function, better prognosis and risk stratification of newborns with congenital heart diseases, and new and promising therapies for fetuses with cardiovascular disease.

A Combined Independent Source Separation and Quality Index Optimization Method for Fetal ECG Extraction from Abdominal Maternal Leads

The non-invasive fetal electrocardiogram (fECG) technique has recently received considerable interest in monitoring fetal health. The aim of our paper is to propose a novel fECG algorithm based on the combination of the criteria of independent source separation and of a quality index optimization (ICAQIO-based). The algorithm was compared with two methods applying the two different criteria independently—the ICA-based and the QIO-based methods—which were previously developed by our group. All three methods were tested on the recently implemented Fetal ECG Synthetic Database (FECGSYNDB). Moreover, the performance of the algorithm was tested on real data from the PhysioNet fetal ECG Challenge 2013 Database. The proposed combined method outperformed the other two algorithms on the FECGSYNDB (ICAQIO-based: 98.78%, QIO-based: 97.77%, ICA-based: 97.61%). Significant differences were obtained in particular in the conditions when uterine contractions and maternal and fetal ectopic beats occurred. On the real data, all three methods obtained very high performances, with the QIO-based method proving slightly better than the other two (ICAQIO-based: 99.38%, QIO-based: 99.76%, ICA-based: 99.37%). The findings from this study suggest that the proposed method could potentially be applied as a novel algorithm for accurate extraction of fECG, especially in critical recording conditions.

Normal ranges for fetal electrocardiogram values for the healthy fetus of 18-24 weeks of gestation: a prospective cohort study

Background

The fetal anomaly ultrasound only detects 65 to 81 % of the patients with congenital heart disease, making it the most common structural fetal anomaly of which a significant part is missed during prenatal life. Therefore, we need a reliable non-invasive diagnostic method which improves the predictive value for congenital heart diseases early in pregnancy. Fetal electrocardiography could be this desired diagnostic method. There are multiple technical challenges to overcome in the conduction of the fetal electrocardiogram. In addition, interpretation is difficult due to the organisation of the fetal circulation in utero. We want to establish the normal ranges and values of the fetal electrocardiogram parameters in healthy fetuses of 18 to 24 weeks of gestation.

Methods/Design

Women with an uneventful singleton pregnancy between 18 and 24 weeks of gestation are asked to participate in this prospective cohort study. A certified and experienced sonographist performs the fetal anomaly scan. Subsequently, a fetal electrocardiogram recording is performed using dedicated signal processing methods. Measurements are performed at two institutes. We will include 300 participants to determine the normal values and 95 % confidence intervals of the fetal electrocardiogram parameters in a healthy fetus. We will evaluate the fetal heart rate, segment intervals, normalised amplitude and the fetal heart axis. Three months postpartum, we will evaluate if a newborn is healthy through a questionnaire.

Discussion

Fetal electrocardiography could be a promising tool in the screening program for congenital heart diseases. The electrocardiogram is a depiction of the intimate relationship between the cardiac nerve conduction pathways and the structural morphology of the fetal heart, and therefore particularly suitable for the detection of secondary effects due to a congenital heart disease (hypotrophy, hypertrophy and conduction interruption).

The Ultrasonic Microsurgical Anatomical Comparative Study of the CHD Fetuses and Their Clinical Significance

The aim of our study was to increase the detection rate of fetal cardiac malformations for congenital heart disease (CHD). The ultrasonic and microanatomical methods were combined to study the CHD cases firstly, which could provide the microsurgical anatomical basis to the prenatal ultrasonic diagnosis which was used in suspected CHD and help the sonographer to improve the quality of fetal cardiac diagnosis. We established the ultrasonic standard section of the 175 complex CHD cases and collected the fetal echocardiography image files. The induced/aborted fetuses were fixed by 4% paraformaldehyde and dissected by the ultrasonic microsurgical anatomy. This research could obtain the fetal cardiac anatomic cross-sectional images which was consistent with the ultrasonic standard section and could clearly show the internal structure of the vascular malformation that optimized the ultrasound examination individually. This method could directly display the variation of the CHD fetal heart clearly and comprehensively help us to understand the complex fetal cardiac malformation from the internal structure of the vascular malformation which was consolidated by the anatomical basis of the fetal heart. This study could improve the integrity and accuracy of the prenatal cardiac ultrasound examination tremendously.

Utility of a High-Resolution 3D MRI Sequence (3D-SPACE) for Evaluation of Congenital Heart Disease

The purpose of this study was to evaluate the role of a high-resolution 3D dark-blood turbo spin echo sequence with variable flip angles (3D-SPACE) in evaluation of congenital heart disease. SPACE sequence was performed in 20 patients (mean age, 17.6 ± 12.6 years, range 9 months-57 years, M: 13) with either unrepaired (N = 3) or post-repair (n = 17) congenital heart disease. All scans were performed on 1.5 T Aera scanners (Siemens). Two separate observers with expertise in cardiovascular imaging scored the quality of the images for blood suppression and definition of key anatomical structures in a blinded fashion using a 5 grade scoring system. Mean of average overall quality scores for two observers was 4 ± 0.62. All overall quality scores were greater than 3. None of the studies were deemed nondiagnostic. Mean length of the SPACE acquisition time was 12.7 min (4-21 min). There was no significant correlation between image quality and duration of scans. Lack of blood suppression was the limiting factor in image quality with the most common place being ascending aorta in nine patients. However, overall blood suppression score was very good with score of 3.9 ± 0.43. There was very good overall agreement between observers in rating the image quality (85.6 % agreement, kappa 0.5, standard error 0.04, p < 0.0001). The 3D-SPACE dark-blood sequence with near-isotropic spatial resolution coupled with respiratory and cardiac gating can be feasibly performed in all age groups with diagnostic image quality in all cases in this study.

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.

Assessment of flow distribution in the mouse fetal circulation at late gestation by high-frequency Doppler ultrasound

This study used high-frequency ultrasound to evaluate the flow distribution in the mouse fetal circulation at late gestation. We studied 12 fetuses (embryonic day 17.5) from 12 pregnant CD1 mice with 40 MHz ultrasound to assess the flow in 11 vessels based on Doppler measurements of blood velocity and M-mode measurements of diameter. Specifically, the intrahepatic umbilical vein (UVIH), ductus venosus (DV), foramen ovale (FO), ascending aorta (AA), main pulmonary artery (MPA), ductus arteriosus (DA), descending thoracic aorta (DTA), common carotid artery (CCA), inferior vena cava (IVC), and right and left superior vena cavae (RSVC, LSVC) were examined, and anatomically confirmed by micro-CT. The mouse fetal circulatory system was found to be similar to that of the humans in terms of the major circuit and three shunts, but characterized by bilateral superior vena cavae and a single umbilical artery. The combined cardiac output (CCO) was 1.22 ± 0.05 ml/min, with the left ventricle (flow in AA) contributing 47.8 ± 2.3% and the right ventricle (flow in MPA) 52.2 ± 2.3%. Relative to the CCO, the flow percentages were 13.6 ± 1.0% for the UVIH, 10.4 ± 1.1% for the DV, 35.6 ± 2.4% for the DA, 41.9 ± 2.6% for the DTA, 3.8 ± 0.3% for the CCA, 29.5 ± 2.2% for the IVC, 12.7 ± 1.0% for the RSVC, and 9.9 ± 0.9% for the LSVC. The calculated flow percentage was 16.6 ± 3.4% for the pulmonary circulation and 31.2 ± 5.3% for the FO. In conclusion, the flow in mouse fetal circulation can be comprehensively evaluated with ultrasound. The baseline data of the flow distribution in normal mouse fetus serve as the reference range for future studies.

Pediatric echocardiography: new developments and applications

In this Special Issue of the Journal, 6 review articles that represent the new developments and applications of echocardiography for diagnosis and assessment of congenital heart disease from fetus to adult are included. The goal is to provide an updated review of the evidence for the current and potential use of some of the new methodologies, i.e. fetal echocardiography, tissue Doppler imaging, strain imaging by speckle tracking imaging, ventricular synchrony, quantification using real time three-dimensional (3D) echocardiography, and 3D echocardiography for adults with congenital heart disease. We hope this effort will provide an impetus for more investigation and ultimately clinical application of these new methodologies to improve the care of those with congenital and acquired heart diseases in the pediatric population and beyond.