The effects of asymmetric volume conductor modeling on non-invasive fetal ECG extraction

Abstract

Objective: Non-invasive fetal electrocardiography (NI-FECG) shows promise for capturing novel physiological information that may indicate signs of fetal distress. However, significant deterioration in NI-FECG signal quality occurs during the presence of a highly non-conductive layer known as vernix caseosa which forms on the fetal body surface beginning in approximately the 28 th week of gestation. This work investigates asymmetric modeling of vernix caseosa and other maternal-fetal tissues in accordance with clinical observations and assesses their impacts for NI-FECG signal processing. Methods: We develop a process for simulating dynamic maternal-fetal abdominal ECG mixtures using a synthetic cardiac source model embedded in a finite element volume conductor. Using this process, changes in NI-FECG signal morphology are assessed in an extensive set of finite element models including spatially variable distributions of vernix caseosa. Results: Our simulations show that volume conductor asymmetry can result in over 70% error in the observed T/QRS ratio and significant changes to signal morphology compared to a homogeneous volume conductor model. Conclusion: Volume conductor effects must be considered when analyzing T/QRS ratios obtained via NI-FECG and should be considered in future algorithm benchmarks using simulated data. Significance: This work shows that without knowledge of the influence of volume conductor effects, clinical evaluation of the T/QRS ratio derived via NI-FECG should be avoided.Index Terms-Finite element method, non-invasive fetal electrocardiography (NI-FECG), T/QRS ratio, vernix caseosa, volume conductor model.

Quality of fetal heart rate monitoring with transabdominal fetal ECG during maternal movement in labor: A prospective study

“…Also, the majority of the study population were multiparous, had an epidural analgesia, and had a vaginal delivery, which may not represent most laboring women in some settings. The results are also limited to term pregnancies, as it is known that a poorly conductive layer (vernix caseosa) forms on the fetal body surface between the 28th and the 34th week of gestation, affecting the quality of TAfECG signals 8,9 …”

Distribution of Vernix Caseosa and Associated Factors Among Newborns Delivered at Adama Comprehensive Specialized Hospital Medical College, Ethiopia, in 2022: Cross-Sectional Study

“…The body mapping technique ( Figure 1 ) was used to assess the specific regions of NB skin covered by vernix, which is adopted from previously done research. 17 According to the body mapping technique, the body of newborn is delineated into seven regions those are head, arm (upper limb), chest, back, inguinal, sacrum, and leg (lower limb). The distribution of VC was assessed by observing the NB skin for the presence or absence of vernix immediately after delivery.…”

A Review of Signal Processing Techniques for Non-Invasive Fetal Electrocardiography

“…For example, Keenan et al showed that volume conductor asymmetry results in significant changes in fECG waveform amplitude and morphology (over 70% errors in the observed T/QRS ratio) [64]. Therefore, this method is most effective in the later stages of pregnancy, especially during the labor [50].…”

“…Besides the benefit of a more objective evaluation, the synthetic data enable modelling of different stages of pregnancy, fetal position based on the fetal vectorcardiogram, pathologic states. Four of the artificial fECG signal generators were introduced by Sameni et al [101], Behar et al [44], [45], Martinek et al [46], and Keenan et al [64]. 2 Despite the advantages provided by synthetic data, they fail to compete with thorough performance evaluations using real data.…”