Relative versus absolute rises in T/QRS ratio by ST analysis of fetal electrocardiograms in labour: A case-control pilot study.

INTRODUCTION: The additional value of ST analysis during labour is uncertain. In ST analysis, a T/QRS baseline value is calculated from the fetal electrocardiogram and successive T/QRS ratios are compared to this baseline. However, variation in the orientation of the electrical heart axis between fetuses may yield different T/QRS baseline values. In case of a higher T/QRS baseline value more ST events are encountered, although not always related to perinatal outcome. We hypothesised that we can partly correct for this effect by analysing T/QRS rises as a percentage from baseline (relative ST analysis). This study aimed to explore whether relative ST analysis has better diagnostic value for cord acidaemia compared to conventional ST analysis, where predefined fixed T/QRS ratios are used. METHODS AND MATERIALS: A case-control study was performed in 20 term human fetuses during labour; 10 cases (umbilical cord artery pH <7.05 at birth, defining acidaemia) and 10 controls (pH >7.20) were included. The fetal electrocardiogram was recorded using a STAN monitor. We electronically extracted all T/QRS values, baseline and episodic ST events from the STAN monitor and calculated the relative T/QRS changes. The cut-off for relative ST events was determined in a receiver operator characteristic (ROC) curve at optimal specificity for cord acidaemia. Parameters of interest were area under the curve (AUC) of the ROC curve for relative ST events and test performance of both conventional and relative ST analysis. RESULTS: Relative ST analysis showed an AUC of 0.99. The optimal cut-off value for relative T/QRS rise was determined at 0.70. Relative vs conventional (absolute) ST analysis showed a specificity of 100% vs 40% (p = 0.031); sensitivity 90% vs 90%; positive likelihood ratio infinity vs 1.5; negative likelihood ratio 0.10 vs 0.25, respectively. CONCLUSION: Relative ST analysis seems to be a promising method to detect impending fetal acidaemia during labour. Further studies are required to determine the diagnostic accuracy.

The influence of betamethasone on fetal heart rate variability, obtained by non-invasive fetal electrocardiogram recordings.

BACKGROUND: Betamethasone is widely used to enhance fetal lung maturation in case of threatened preterm labour. Fetal heart rate variability is one of the most important parameters to assess in fetal monitoring, since it is a reliable indicator for fetal distress. AIM: To describe the effect of betamethasone on fetal heart rate variability, by applying spectral analysis on non-invasive fetal electrocardiogram recordings. STUDY DESIGN: Prospective cohort study. SUBJECTS: Patients that require betamethasone, with a gestational age from 24 weeks onwards. OUTCOME MEASURES: Fetal heart rate variability parameters on day 1, 2, and 3 after betamethasone administration are compared to a reference measurement. RESULTS: Following 68 inclusions, 12 patients remained with complete series of measurements and sufficient data quality. During day 1, an increase in absolute fetal heart rate variability values was seen. During day 2, a decrease in these values was seen. All trends indicate to return to pre-medication values on day 3. Normalised high- and low-frequency power show little changes during the study period. CONCLUSIONS: The changes in fetal heart rate variability following betamethasone administration show the same pattern when calculated by spectral analysis of the fetal electrocardiogram, as when calculated by cardiotocography. Since normalised spectral values show little changes, the influence of autonomic modulation seems minor.

The electrical heart axis and ST events in fetal monitoring: A post-hoc analysis following a multicentre randomised controlled trial.

OBJECTIVE: Reducing perinatal morbidity and mortality is one of the major challenges in modern health care. Analysing the ST segment of the fetal electrocardiogram was thought to be the breakthrough in fetal monitoring during labour. However, its implementation in clinical practice yields many false alarms and ST monitoring is highly dependent on cardiotocogram assessment, limiting its value for the prediction of fetal distress during labour. This study aims to evaluate the relation between physiological variations in the orientation of the fetal electrical heart axis and the occurrence of ST events. METHODS: A post-hoc analysis was performed following a multicentre randomised controlled trial, including 1097 patients from two participating centres. All women were monitored with ST analysis during labour. Cases of fetal metabolic acidosis, poor signal quality, missing blood gas analysis, and congenital heart disease were excluded. The orientation of the fetal electrical heart axis affects the height of the initial T/QRS baseline, and therefore the incidence of ST events. We grouped tracings with the same initial baseline T/QRS value. We depicted the number of ST events as a function of the initial baseline T/QRS value with a linear regression model. RESULTS: A significant increment of ST events was observed with increasing height of the initial T/QRS baseline, irrespective of the fetal condition; correlation coefficient 0.63, p<0.001. The most frequent T/QRS baseline is 0.12. CONCLUSION: The orientation of the fetal electrical heart axis and accordingly the height of the initial T/QRS baseline should be taken into account in fetal monitoring with ST analysis.

Effect of tocolytic drugs on fetal heart rate variability: a systematic review.

INTRODUCTION: Tocolytics may cause changes in fetal heart rate (HR) pattern, while fetal heart rate variability (HRV) is an important marker of fetal well-being. We aim to systematically review the literature on how tocolytic drugs affect fetal HRV. MATERIALS AND METHODS: We searched CENTRAL, PubMed and EMBASE up to June 2016. Studies published in English, using computerized or visual analysis to describe the effect of tocolytics on HRV in human fetuses were included. Studies describing tocolytics during labor, external cephalic version, pre-eclampsia and infection were excluded. Eventually, we included six studies, describing 169 pregnant women. RESULTS: Nifedipine, atosiban and indomethacin administration show no clinically important effect on fetal HRV. Following administration of magnesium sulfate decreased variability and cases of bradycardia are described. Fenoterol administration results in a slight increase in fetal HR with no changes in variability. After ritodrine administration increased fetal HR and decreased variability is seen. The effect of co-administration of corticosteroids should be taken into account. CONCLUSION: In order to prevent iatrogenic preterm labor, the effects of tocolytic drugs on fetal HRV should be taken into account when monitoring these fetuses.

A systematic review of prenatal screening for congenital heart disease by fetal electrocardiography.

BACKGROUND: Congenital heart disease (CHD) is the most common severe congenital anomaly worldwide. Diagnosis early in pregnancy is important, but the detection rate by two-dimensional ultrasonography is only 65%-81%. OBJECTIVES: To evaluate existing data on CHD and noninvasive abdominal fetal electrocardiography (ECG). SEARCH STRATEGY: A systematic review was performed through a search of the Cochrane Library, PubMed, and Embase for studies published up to April 2016 using the terms "congenital heart disease," "fetal electrocardiogram," and other similar keywords. SELECTION CRITERIA: Primary articles that described changes in fetal ECG among fetuses with CHD published in English were included. DATA COLLECTION AND ANALYSIS: Outcomes of interest were changes in fetal ECG parameters observed for fetuses with congenital heart disease. Findings were reported descriptively. MAIN RESULTS: Only five studies described changes observed in the fetal electrocardiogram for fetuses with CHD, including heart rate, heart rate variability, and PR, QRS, and QT intervals. Fetal ECG reflects the intimate relationship between the cardiac nerve conduction system and the structural morphology of the heart. It seems particularly helpful in detecting the electrophysiological effects of cardiac anatomic defects (e.g. hypotrophy, hypertrophy, and conduction interruption). CONCLUSIONS: Fetal ECG might be a promising clinical tool to complement ultrasonography in the screening program for CHD.

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).

Fetal heart rate variability during pregnancy, obtained from non-invasive electrocardiogram recordings.

OBJECTIVE: Non-invasive spectral analysis of fetal heart rate variability is a promising new field of fetal monitoring. To validate this method properly, we studied the relationship between gestational age and the influence of fetal rest-activity state on spectral estimates of fetal heart rate variability. DESIGN: Prospective longitudinal study. SETTING: Tertiary care teaching hospital. POPULATION: Forty healthy women with an uneventful singleton pregnancy. METHODS: Non-invasive fetal electrocardiogram measurements via the maternal abdomen were performed at regular intervals between 14 and 40 weeks of gestation and processed to detect beat-to-beat fetal heart rate. Simultaneous ultrasound recordings were performed to assess fetal rest-activity state. MAIN OUTCOME MEASURES: Absolute and normalized power of fetal heart rate variability in the low (0.04-0.15 Hz) and high (0.4-1.5 Hz) frequency band were obtained, using Fourier Transform. RESULTS: 14% of all measurements and 3% of the total amount of abdominal data (330 segments) was usable for spectral analysis. During 21-30 weeks of gestation, a significant increase in absolute low and high frequency power was observed. During the active state near term, absolute and normalized low frequency power were significantly higher and normalized high frequency power was significantly lower compared with the quiet state. CONCLUSIONS: The observed increase in absolute spectral estimates in preterm fetuses was probably due to increased sympathetic and parasympathetic modulation and might be a sign of autonomic development. Further improvements in signal processing are needed before this new method of fetal monitoring can be introduced in clinical practice.

The influence of corticosteroids on fetal heart rate variability: a systematic review of the literature.

Corticosteroids play an important role in the clinical management of threatened preterm delivery between 24 and 34 weeks of gestational age. It is known that corticosteroids have a direct, transient effect on fetal heart rate (fHR) parameters. Fetal heart rate variability is a reflection of autonomic nervous system activity and a useful marker for fetal well-being. Therefore, it is important to interpret the changes that occur in fHR parameters during corticosteroid treatment correctly, to avoid unnecessary iatrogenic preterm delivery. We performed a systematic review of the literature in CENTRAL, PubMed, and EMBASE, including 15 articles. In this review, we discuss the influence of corticosteroids on fHR parameters, in particular fHR variability, and fetal behavior. Furthermore, we explain possible mechanisms of action and confounding factors.