A novel technique for fetal heart rate estimation from Doppler ultrasound signal

<p>Abstract</p> <p>Background</p> <p>The currently used fetal monitoring instrumentation that is based on Doppler ultrasound technique provides the fetal heart rate (FHR) signal with limited accuracy. It is particularly noticeable as significant decrease of clinically important feature - the variability of FHR signal. The aim of our work was to develop a novel efficient technique for processing of the ultrasound signal, which could estimate the cardiac cycle duration with accuracy comparable to a direct electrocardiography.</p> <p>Methods</p> <p>We have proposed a new technique which provides the true beat-to-beat values of the FHR signal through multiple measurement of a given cardiac cycle in the ultrasound signal. The method consists in three steps: the dynamic adjustment of autocorrelation window, the adaptive autocorrelation peak detection and determination of beat-to-beat intervals. The estimated fetal heart rate values and calculated indices describing variability of FHR, were compared to the reference data obtained from the direct fetal electrocardiogram, as well as to another method for FHR estimation.</p> <p>Results</p> <p>The results revealed that our method increases the accuracy in comparison to currently used fetal monitoring instrumentation, and thus enables to calculate reliable parameters describing the variability of FHR. Relating these results to the other method for FHR estimation we showed that in our approach a much lower number of measured cardiac cycles was rejected as being invalid.</p> <p>Conclusions</p> <p>The proposed method for fetal heart rate determination on a beat-to-beat basis offers a high accuracy of the heart interval measurement enabling reliable quantitative assessment of the FHR variability, at the same time reducing the number of invalid cardiac cycle measurements.</p

Detection of atrial fibrillation episodes in long-term heart rhythm signals using a support vector machine

Atrial fibrillation (AF) is a serious heart arrhythmia leading to a significant increase of the risk for occurrence of ischemic stroke. Clinically, the AF episode is recognized in an electrocardiogram. However, detection of asymptomatic AF, which requires a long-term monitoring, is more efficient when based on irregularity of beat-to-beat intervals estimated by the heart rate (HR) features. Automated classification of heartbeats into AF and non-AF by means of the Lagrangian Support Vector Machine has been proposed. The classifier input vector consisted of sixteen features, including four coefficients very sensitive to beat-to-beat heart changes, taken from the fetal heart rate analysis in perinatal medicine. Effectiveness of the proposed classifier has been verified on the MIT-BIH Atrial Fibrillation Database. Designing of the LSVM classifier using very large number of feature vectors requires extreme computational efforts. Therefore, an original approach has been proposed to determine a training set of the smallest possible size that still would guarantee a high quality of AF detection. It enables to obtain satisfactory results using only 1.39% of all heartbeats as the training data. Post-processing stage based on aggregation of classified heartbeats into AF episodes has been applied to provide more reliable information on patient risk. Results obtained during the testing phase showed the sensitivity of 98.94%, positive predictive value of 98.39%, and classification accuracy of 98.86%.Web of Science203art. no. 76

Fetal electrocardiograms, direct and abdominal with reference heartbeat annotations

Monitoring fetal heart rate (FHR) variability plays a fundamental role in fetal state assessment. Reliable FHR signal can be obtained from an invasive direct fetal electrocardiogram (FECG), but this is limited to labour. Alternative abdominal (indirect) FECG signals can be recorded during pregnancy and labour. Quality, however, is much lower and the maternal heart and uterine contractions provide sources of interference. Here, we present ten twenty-minute pregnancy signals and 12 five-minute labour signals. Abdominal FECG and reference direct FECG were recorded simultaneously during labour. Reference pregnancy signal data came from an automated detector and were corrected by clinical experts. The resulting dataset exhibits a large variety of interferences and clinically significant FHR patterns. We thus provide the scientific community with access to bioelectrical fetal heart activity signals that may enable the development of new methods for FECG signals analysis, and may ultimately advance the use and accuracy of abdominal electrocardiography methods.Web of Science71art. no. 20

Wartość wybranych parametrów mechanicznej i bioelektrycznej aktywności mięśnia macicy w przewidywaniu zagrożenia porodem przedwczesnym

Abstract Objectives: To record and analyse bioelectrical activity of the uterine muscle in the course of physiological pregnancy, labour and threatening premature labour; to define which parameters from the analysis of both electrohysterogram and mechanical activity signal allow us to predict threatening premature labour. Material and methods: Material comprised 62 pregnant women: Group I -– 27 patients in their first physiological pregnancy, Group II -– 21 patients in their first pregnancy with symptoms of threatening premature labour, and Group III -– 14 patients in the first labour period. The on-line analysis of the mechanical (TOCO) and electrical (EHG) contraction activity relied on determination of quantitative parameters of detected uterine contractions. Results: The obtained statistical results demonstrated a possibility to differentiate between Group I and II through the amplitude and contraction area for EHG signal, and only the contraction amplitude for TOCO signal. Additionally, significant differentiating parameters for electrohysterogram are: contraction power and its median frequency. Analyzing Group I and III, significant differences were noted for contraction amplitude and area obtained both from EHG and TOCO signals. Similarly, the contraction power (from EHG) enables us to assign the contractions either to records from Group I or to labour type. There was no significant difference noted between Group II and III. Conclusions: Identification of pregnant women at risk of premature labour should lead to their inclusion in rigorous perinatal surveillance. This requires novel, more sensitive methods that are able to detect early symptoms of the uterine contraction activity increase. Electrohysterography provides complete information on principles of bioelectrical uterine activity. Quantitative parameters of EHG analysis enable the detection of records (contractions) with the symptoms of premature uterine contraction activity.Streszczenie Cel pracy: Rejestracja i analiza bioelektrycznej aktywności mięśnia macicy w przebiegu ciąży fizjologicznej, w czasie porodu i w przypadkach zagrożenia porodem przedwczesnym oraz określenie, które z parametrów analizy zarówno elektrohisterogramu jak i sygnału czynności mechanicznej umożliwia przewidywanie zagrożenia porodem przedwczesnym. Materiał i metoda: Badaniem objęto 62 kobiety ciężarne: Grupa I – 27 pierwiastek w ciąży niepowikłanej, Grupa II – 21 pierwiastek w ciąży powikłanej objawami zagrażającego porodu przedwczesnego, oraz Grupa III – 14 w pierwszym okresie porodu ciąży donoszonej. W sygnałach mechanicznej (TOCO) i elektrycznej (EHG) aktywności mięśnia macicy po wykryciu skurczy, wyznaczono podstawowe parametry ich opisu ilościowego. Wyniki: W oparciu o otrzymane zależności statystyczne, wykazano możliwość różnicowania grupy I i II. W przypadku sygnału EHG są to: amplituda i powierzchnia, zaś dla sygnału TOCO tylko amplituda skurczu. Dodatkowe istotne parametry różnicujące dla EHG to: moc i częstotliwość medianowa skurczu. Analizując grupę I i III istotne różnice dotyczyły amplitudy i powierzchni skurczu zarówno w odniesieniu do sygnału EHG jak i TOCO. Podobnie moc skurczu (dla EHG) pozwala stwierdzić czy skurcze pochodzą z zapisów z Grupy I, czy raczej są to skurcze o charakterze porodowym. Pomiędzy Grupa II i III nie wykazano żadnych różnic istotnych statystycznie. Wnioski: Identyfikacja ciężarnych zagrożonych porodem przedwczesnym umożliwia natychmiastowe objęcie ich ścisłym nadzorem położniczym. W tym celu niezbędne są nowe, bardziej czułe metody zdolne wykryć wczesne objawy nasilenia aktywności skurczowej macicy. Elektrohisterografia dostarcza pełnej informacji o funkcjonowaniu mechanizmów bioelektrycznej aktywności mięśnia macicy. Ilościowe parametry analizy EHG pozwalają na wykrywanie zapisów (skurczy) świadczących o przedwczesnej czynności skurczowej mięśnia macicy

Aktywność mechaniczna i elektryczna macicy. Część I. Monitorowanie skurczów

Summary Correct uterine contraction activity during labour determines physiological fetal delivery and ensures its satisfactory outcome. Contraction activity monitoring may be accomplished by either recording of the mechanical properties of the uterine muscle and/or by measurement of the action potentials produced by the uterus during contraction. In the following paper, the current state of knowledge concerning the methods for assessment and monitoring of the uterine contraction activity was evaluated. The electrophysiological properties of the uterus were given. The mechanical methods of uterine activity monitoring: internal and external tocography were described. The development of the electrohysterography as the method providing the signal comprising complete information on bioelectrical properties of the uterine muscle was presented. The conclusion was that the analysis of the electrohysterogram enables a description of the source of the uterine contraction activity, whereas currently applied mechanical methods merely record the results of this activity.Streszczenie Prawidłowa czynność skurczowa w terminie porodu determinuje fizjologiczny poród płodu i pozwala na urodzenie zdrowego noworodka. Monitorowanie czynności skurczowej macicy może być prowadzone albo poprzez rejestrację zmian parametrów mechanicznych mięśnia macicy albo w oparciu o pomiar potencjałów czynnościowych generowanych przez kurczący się miesień. W pierwszym przypadku jako podstawowe techniki stosowane są tokografia wewnętrzna (pomiar ciśnienia wewnątrzmacicznego) oraz tokografia zewnętrzna (pomiar siły nacisku macicy na powłoki brzuszne) z kolei pomiar potencjałów czynnościowych jest podstawą dla elektrohisterografii. W pracy przedstawiono dotychczasowy stan wiedzy na temat tych dwóch podejść do oceny i monitorowania czynności skurczowej macicy. Omówiono podstawy elektrofizjologii mięśnia macicy oraz prześledzono historię powstania i współczesne badania nad elektrohisterografią, jako metodą pozwalającą na rejestrację sygnału, który zawiera pełniejszą informację o bioelektrycznych właściwościach mięśnia macicy. Stwierdzono, iż analiza elektrohisterogramu prowadzi do opisu źródła czynności skurczowej macicy, podczas gdy stosowane do tej pory mechaniczne metody rejestrują jedynie skutki tej czynności

ТЕЛЕСНЫЕ НАКАЗАНИЯ

Great expectations are connected with application of indirect fetal electrocardiography (FECG), especially for home telemonitoring of pregnancy. Evaluation of fetal heart rate (FHR) variability, when determined from FECG, uses the same criteria as for FHR signal acquired classically—through ultrasound Doppler method (US). Therefore, the equivalence of those two methods has to be confirmed, both in terms of recognizing classical FHR patterns: baseline, accelerations/decelerations (A/D), long-term variability (LTV), as well as evaluating the FHR variability with beat-to-beat accuracy—short-term variability (STV). The research material consisted of recordings collected from 60 patients in physiological and complicated pregnancy. The FHR signals of at least 30 min duration were acquired dually, using two systems for fetal and maternal monitoring, based on US and FECG methods. Recordings were retrospectively divided into normal (41) and abnormal (19) fetal outcome. The complex process of data synchronization and validation was performed. Obtained low level of the signal loss (4.5% for US and 1.8% for FECG method) enabled to perform both direct comparison of FHR signals, as well as indirect one—by using clinically relevant parameters. Direct comparison showed that there is no measurement bias between the acquisition methods, whereas the mean absolute difference, important for both visual and computer-aided signal analysis, was equal to 1.2 bpm. Such low differences do not affect the visual assessment of the FHR signal. However, in the indirect comparison the inconsistencies of several percent were noted. This mainly affects the acceleration (7.8%) and particularly deceleration (54%) patterns. In the signals acquired using the electrocardiography the obtained STV and LTV indices have shown significant overestimation by 10 and 50% respectively. It also turned out, that ability of clinical parameters to distinguish between normal and abnormal groups do not depend on the acquisition method. The obtained results prove that the abdominal FECG, considered as an alternative to the ultrasound approach, does not change the interpretation of the FHR signal, which was confirmed during both visual assessment and automated analysis

Aktywność mechaniczna i elektryczna macicy. Część II. Parametry skurczów

Abstract Frequency and strength of the uterine contractions monitoring enables to control the labour progress and also, although in a restricted way, to determine the beginning of labour, as long as it is not preterm. Mechanical approach provides only the low frequency signal, which describes the contractions more or less accurately , depending on whether an intrauterine pressure measurement is used in the former case or whether an external stress measurement is applied in the latter case. This signal does not comprise information on contractions characteristics and enables only to estimate their basic timing parameters. Description of the electrophysiological properties may be obtained only by means of the uterine electrical signals measurement. In the following paper, the classical interpretation of the uterine contraction activity which relies upon its mechanical and electrical activity was presented. Additionally, the frequency parameters provided exclusively by the electrical signal were proposed. The possibility of the electrohysterogram analysis may provide more complete information on uterine muscle functioning. Results of the research studies show that further development of electrohysterography will enable its wider application in pregnancy and labour diagnostics.Streszczenie Rejestracja częstości i siły skurczów umożliwia kontrolę poprawności przebiegu porodu oraz w ograniczonym stopniu pozwala określić początek porodu, o ile nie jest to poród przedwczesny. Pomiar mechaniczny dostarcza jedynie składową wolnozmienna, która bardziej (pomiar ciśnienia) lub mniej (pomiar naprężenia) dokładnie obrazuje skurcze, ale jest pozbawiona informacji o charakterze samych skurczów. W oparciu o ten sygnał wyznaczane są podstawowe – amplitudowe i czasowe parametry skurczu. Uzyskuje się wyłącznie informację o mechanicznej aktywności mięśnia macicy. Charakterystykę właściwości elektrofizjologicznych można otrzymać jedynie na drodze pomiaru sygnałów elektrycznych macicy. W pracy przedstawiono klasyczna interpretację aktywności skurczowej w oparciu o mechaniczną i elektryczną aktywność macicy oraz omówiono częstotliwościowe parametry skurczów charakterystyczne wyłącznie dla sygnału elektrycznego. Możliwość analizy elektrohisterogramu zarówno klasycznej tj. w dziedzinie czasu jak i w dziedzinie częstotliwości może dostarczyć pełniejszej informacji o funkcjonowaniu mięśnia macicy. Wyniki wstępnych badań pozwalają sądzić, że elektrohisterografia zostanie doprowadzona do poziomu, który umożliwiłby jej powszechne zastosowanie w diagnostyce ciąży i porodu

Non-invasive fetal electrocardiogram extraction based on novel hybrid method for intrapartum ST segment analysis

This study focuses on non-invasive fetal electrocardiogram extraction based on a novel hybrid method, which combines the advantages of non-adaptive and adaptive approaches for non-invasive fetal electrocardiogram morphological analysis. Besides estimating fetal heart rate, which is the main parameter used in the clinical practice, this study provides non-invasive ST segment analysis on data from Abdominal and Direct Fetal Electrocardiogram Database consisting of simultaneous traditional - gold standard invasive fetal scalp electrode and non-invasive fetal electrocardiogram recorded during delivery. This innovative approach utilizing the combination of independent component analysis and recursive least squares algorithms has the potential to extract valuable information from non-invasive fetal electrocardiogram in order to identify eventual sign of fetal distress. This was a prospective observational study of non-invasive fetal electrocardiogram, using 4 abdominally sited electrodes, against the traditional fetal scalp electrode on 8 patients. In terms of fetal heart rate estimation, the accuracy was high for all 8 tested patients with average value equaled 0.20 beats per minute and average value of 1.96 standard deviation equaled 5.80 beats per minute. In 7 patients, it was possible to perform the ST segment analysis with high accuracy in determining T/QRS in comparison with the reference fetal scalp electrode signal with average values and 1.96 standard deviation equaled 0.008 and 0.031 respectively. This study thus demonstrates that ST segment analysis is feasible using non-invasive fECG using the proposed hybrid method.Web of Science9286312860

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

Non-invasive fetal electrocardiography appears to be one of the most promising fetal monitoring techniques during pregnancy and delivery nowadays. This method is based on recording electrical potentials produced by the fetal heart from the surface of the maternal abdomen. Unfortunately, in addition to the useful fetal electrocardiographic signal, there are other interference signals in the abdominal recording that need to be filtered. The biggest challenge in designing filtration methods is the suppression of the maternal electrocardiographic signal. This study focuses on the extraction of fetal electrocardiographic signal from abdominal recordings using a combination of independent component analysis, recursive least squares, and ensemble empirical mode decomposition. The method was tested on two databases, the Fetal Electrocardiograms, Direct and Abdominal with Reference Heartbeats Annotations and the PhysioNet Challenge 2013 database. The evaluation was performed by the assessment of the accuracy of fetal QRS complexes detection and the quality of fetal heart rate determination. The effectiveness of the method was measured by means of the statistical parameters as accuracy, sensitivity, positive predictive value, and F1-score. Using the proposed method, when testing on the Fetal Electrocardiograms, Direct and Abdominal with Reference Heartbeats Annotations database, accuracy higher than 80% was achieved for 11 out of 12 recordings with an average value of accuracy 92.75% [95% confidence interval: 91.19-93.88%], sensitivity 95.09% [95% confidence interval: 93.68-96.03%], positive predictive value 96.36% [95% confidence interval: 95.05-97.17%] and F1-score 95.69% [95% confidence interval: 94.83-96.35%]. When testing on the Physionet Challenge 2013 database, accuracy higher than 80% was achieved for 17 out of 25 recordings with an average value of accuracy 78.24% [95% confidence interval: 73.44-81.85%], sensitivity 81.79% [95% confidence interval: 76.59-85.43%], positive predictive value 87.16% [95% confidence interval: 81.95-90.35%] and F1-score 84.08% [95% confidence interval: 80.75-86.64%]. Moreover, the non-invasive ST segment analysis was carried out on the records from the Fetal Electrocardiograms, Direct and Abdominal with Reference Heartbeats Annotations database and achieved high accuracy in 7 from in total of 12 records (mean values mu < 0.1 and values of +/- 1.96 sigma < 0.1).Web of Science168art. no. e025615