Model based estimation of QT intervals in non-invasive fetal ECG signals

Abstract

The end timing of T waves in fetal electrocardiogram (fECG) is important for the evaluation of ST and QT intervals which are vital markers to assess cardiac repolarization patterns. Monitoring malignant fetal arrhythmias in utero is fundamental to care in congenital heart anomalies preventing perinatal death. Currently, reliable detection of end of T waves is possible only by using fetal scalp ECG (fsECG) and fetal magnetocardiography (fMCG). fMCG is expensive and less accessible and fsECG is an invasive technique available only during intrapartum period. Another safer and affordable alternative is the non-invasive fECG (nfECG) which can provide similar assessment provided by fsECG and fMECG but with less accuracy (not beat by beat). Detection of T waves using nfECG is challenging because of their low amplitudes and high noise. In this study, a novel model-based method that estimates the end of T waves in nfECG signals is proposed. The repolarization phase has been modeled as the discharging phase of a capacitor. To test the model, fECG signals were collected from 58 pregnant women (age: (34 ± 6) years old) bearing normal and abnormal fetuses with gestational age (GA) 20-41 weeks. QT and QTc intervals have been calculated to test the level of agreement between the model-based and reference values (fsECG and Doppler Ultrasound (DUS) signals) in normal subjects. The results of the test showed high agreement between modelbased and reference values (difference < 5%), which implies that the proposed model could be an alternative method to detect the end of T waves in nfECG signals.

Non-Invasive Fetal Electrocardiogram Extraction Based on Novel Hybrid Method for Intrapartum ST Segment Analysis

“…Finally, we compared the results obtained with the results of a very few studies that have dealt with the morphological analysis of the fECG signal (these are summarized in Table 8). Objective comparison of results is very difficult since the authors use different databases for testing (the Non-Invasive Fetal ECG Arrhythmia Database [46], the Fetal ECG Synthetic Generator [38], use their own synthetically generated signals [1] or used their own real signals [20]. It is clear that most authors use synthetic data for experiments, on which they achieve very accurate results.…”

“…No statistical evaluation was presented in the study, but according to the authors the method was efficient especially for partly noisy signals, but good results were also achieved for very noisy data. • The model-based estimation was used in [20], where the authors primarily dealt with the analysis of the length of the QT interval. The authors used their own real records recorded on 58 women (gestational age: 20-41 weeks) for testing.…”

“…The fHR estimation and ST segment analysis were performed based on real recordings. • In [20] the authors performed QT interval analysis on real recordings using model-based estimation method. First, R peaks were detected based on threshold value and RR intervals were determined.…”

A novel algorithm based on ensemble empirical mode decomposition for non-invasive fetal ECG extraction

“…In addition to fHR, which is the main parameter assessing the fetal well-being, new techniques focusing on the changes of the fECG waveform (P-R interval, QT interval, T/QRS ratio and ST segment) caused by the hypoxic states have been developed and presented in the literature [41,[48][49][50][51][52][53][54][55]. However, the STAN 1 Method (Neoventa Medical, Sweden) is the only analysis tool that is available in the clinical practice.…”

Model-based estimation of QT intervals of mouse fetal electrocardiogram

“…In this study, a mathematical model for the estimation of end of T waves of fECG collected from normal fetal mice is proposed. The model discussed in this study was developed from our earlier mathematical model that addressed fECG of humans [ 7 ]. The model was developed based on the similarity between the human’s repolarization phase of an AP and the discharging phase of capacitors in resistor–capacitor (RC) circuits.…”