1
|
Wray S, Taggart MJ. An update on pacemaking in the myometrium. J Physiol 2024. [PMID: 39073139 DOI: 10.1113/jp284753] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Accepted: 04/24/2024] [Indexed: 07/30/2024] Open
Abstract
Timely and efficient contractions of the smooth muscle of the uterus - the myometrium - are crucial to a successful pregnancy outcome. These episodic contractions are regulated by spontaneous action potentials changing cell and tissue electrical excitability. In this short review we will document and discuss current knowledge of these processes. Those seeking a conclusive account of myometrial pacemaking mechanisms, or indeed a definitive description of the anatomical site of uterine pacemaking, may be disappointed. Rather, after almost a century of investigation, and in spite of promising studies in the last decade or so, there remain many gaps in our knowledge. We review the progress that has been made using recent technologies including in vivo and ex vivo imaging and electrophysiology and computational modelling, taking evidence from studies of animal and human myometrium, with particular emphasis on what may occur in the latter. We have prioritized physiological studies that bring us closer to understanding function. From our analyses we suggest that in human myometrium there is no fixed pacemaking site, but rather mobile, initiation sites produce the connectivity for synchronizing electrical and contractile activity. We call for more studies and funding, as physiological understanding of pacemaking gives hope to being better able to treat clinical conditions such as preterm and dysfunctional labours.
Collapse
Affiliation(s)
- Susan Wray
- Women's & Children's Health, Faculty of Health & Life Sciences, University of Liverpool, Liverpool, Merseyside, UK
| | - Michael J Taggart
- Biosciences Institute, International Centre for Life, Newcastle University, Newcastle, UK
| |
Collapse
|
2
|
Shen J, Liu Y, Zhang M, Pumir A, Mu L, Li B, Xu J. Multi-channel electrohysterography enabled uterine contraction characterization and its effect in delivery assessment. Comput Biol Med 2023; 167:107697. [PMID: 37976821 DOI: 10.1016/j.compbiomed.2023.107697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Revised: 11/03/2023] [Accepted: 11/07/2023] [Indexed: 11/19/2023]
Abstract
Uterine contractions are routinely monitored by tocodynamometer (TOCO) at late stage of pregnancy to predict the onset of labor. However, TOCO reveals no information on the synchrony and coherence of contractions, which are important contributors to a successful delivery. The electrohysterography (EHG) is a recording of the electrical activities that trigger the local muscles to contract. The spatial-temporal information embedded in multiple channel EHG signals make them ideal for characterizing the synchrony and coherence of uterine contraction. To proceed, contractile time-windows are identified from TOCO signals and are then used to segment out the simultaneously recorded EHG signals of different channels. We construct sample entropy SamEn and Concordance Correlation based feature ψ from these EHG segments to quantify the synchrony and coherence of contraction. To test the effectiveness of the proposed method, 122 EHG recordings in the Icelandic EHG database were divided into two groups according to the time difference between the gestational ages at recording and at delivery (TTD). Both SamEn and ψ show clear difference in the two groups (p<10-5) even when measurements were made 120 h before delivery. Receiver operating characteristic curve analysis of these two features gave AUC values of 0.834 and 0.726 for discriminating imminent labor defined with TTD ≤ 24 h. The SamEn was significantly smaller in women (0.1433) of imminent labor group than in women (0.3774) of the pregnancy group. Using an optimal cutoff value of SamEn to identify imminent labor gives sensitivity, specificity, and accuracy as high as 0.909, 0.712 and 0.743, respectively. These results demonstrate superiority in comparing to the existing SOTA methods. This study is the first research work focusing on characterizing the synchrony property of contractions from the electrohysterography signals. Despite the very limited dataset used in the validation process, the promising results open a new direction to the use of electrohysterography in obstetrics.
Collapse
Affiliation(s)
- Junhua Shen
- Women's Hospital, School of Medicine, Zhejiang University, Hangzhou, China; Zhejiang Provincial Clinical Research Center for Obstetrics and Gynecology, Hangzhou, China
| | - Yan Liu
- College of Computer Science, Zhejiang University of Technology, Hangzhou, China
| | - Meiyu Zhang
- College of Computer Science, Zhejiang University of Technology, Hangzhou, China
| | - Alain Pumir
- Laboratoire de Physique, Ecole Normal Superieure de Lyon, Lyon, France
| | - Liangshan Mu
- Women's Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Baohua Li
- Women's Hospital, School of Medicine, Zhejiang University, Hangzhou, China.
| | - Jinshan Xu
- College of Computer Science, Zhejiang University of Technology, Hangzhou, China.
| |
Collapse
|
3
|
Garrett AS, Means SA, Roesler MW, Miller KJW, Cheng LK, Clark AR. Modeling and experimental approaches for elucidating multi-scale uterine smooth muscle electro- and mechano-physiology: A review. Front Physiol 2022; 13:1017649. [PMID: 36277190 PMCID: PMC9585314 DOI: 10.3389/fphys.2022.1017649] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Accepted: 09/21/2022] [Indexed: 11/13/2022] Open
Abstract
The uterus provides protection and nourishment (via its blood supply) to a developing fetus, and contracts to deliver the baby at an appropriate time, thereby having a critical contribution to the life of every human. However, despite this vital role, it is an under-investigated organ, and gaps remain in our understanding of how contractions are initiated or coordinated. The uterus is a smooth muscle organ that undergoes variations in its contractile function in response to hormonal fluctuations, the extreme instance of this being during pregnancy and labor. Researchers typically use various approaches to studying this organ, such as experiments on uterine muscle cells, tissue samples, or the intact organ, or the employment of mathematical models to simulate the electrical, mechanical and ionic activity. The complexity exhibited in the coordinated contractions of the uterus remains a challenge to understand, requiring coordinated solutions from different research fields. This review investigates differences in the underlying physiology between human and common animal models utilized in experiments, and the experimental interventions and computational models used to assess uterine function. We look to a future of hybrid experimental interventions and modeling techniques that could be employed to improve the understanding of the mechanisms enabling the healthy function of the uterus.
Collapse
Affiliation(s)
| | | | | | | | | | - Alys R. Clark
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| |
Collapse
|
4
|
Garrett AS, Roesler MW, Athavale ON, Du P, Clark AR, Cheng LK. In vivo multi-channel measurement of electrical activity of the non-pregnant rat uterus. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2022; 2022:3682-3685. [PMID: 36085904 DOI: 10.1109/embc48229.2022.9871943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
In the uterus, the characteristics of smooth muscle contraction and the electrical activity that drives this contraction depends on hormonal cycles, and pregnancy status. Smooth muscle contraction is initiated by a change in membrane electrical potential, due to the flux of ions in and out of the intracellular space. Chains of action potentials throughout a section of muscle can result in coordinated contraction events. In this study, flexible printed circuit electrode arrays were applied to measure the bioelectric signals on the surface of a rat uterus in vivo. Variations in the electrical activity were quantified, including intermittent periods of activity and inactivity, which contain both slow-wave type activity (0.039 Hz ±0.017 Hz) and faster, spike-like activity (3.26 Hz ±0.27 Hz). The spike activity initiated at the ovarian end of the uterine horn, spreading towards the cervical end with a propagation velocity of 5.34 ± 2.32 mm [Formula: see text]. In conclusion, this pilot study outlines a new method of in vivo measurement of uterine electrical activity in rats. Clinical Relevance- Measurement of bioelectrical data using in vivo techniques provides insight into the electromechanical function of uterine smooth muscle, which could provide insights into what drives coordinated contraction in the uterus.
Collapse
|
5
|
Zhang Y, Hao D, Yang L, Zhou X, Ye-Lin Y, Yang Y. Assessment of Features between Multichannel Electrohysterogram for Differentiation of Labors. SENSORS (BASEL, SWITZERLAND) 2022; 22:3352. [PMID: 35591042 PMCID: PMC9104769 DOI: 10.3390/s22093352] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2022] [Revised: 04/12/2022] [Accepted: 04/22/2022] [Indexed: 06/15/2023]
Abstract
Electrohysterogram (EHG) is a promising method for noninvasive monitoring of uterine electrical activity. The main purpose of this study was to characterize the multichannel EHG signals to distinguish between term delivery and preterm birth, as well as deliveries within and beyond 24 h. A total of 219 pregnant women were grouped in two ways: (1) term delivery (TD), threatened preterm labor (TPL) with the outcome of preterm birth (TPL_PB), and TPL with the outcome of term delivery (TPL_TD); (2) EHG recording time to delivery (TTD) ≤ 24 h and TTD > 24 h. Three bipolar EHG signals were analyzed for the 30 min recording. Six EHG features between multiple channels, including multivariate sample entropy, mutual information, correlation coefficient, coherence, direct partial Granger causality, and direct transfer entropy, were extracted to characterize the coupling and information flow between channels. Significant differences were found for these six features between TPL and TD, and between TTD ≤ 24 h and TTD > 24 h. No significant difference was found between TPL_PB and TPL_TD. The results indicated that EHG signals of TD were more regular and synchronized than TPL, and stronger coupling between multichannel EHG signals was exhibited as delivery approaches. In addition, EHG signals propagate downward for the majority of pregnant women regardless of different labors. In conclusion, the coupling and propagation features extracted from multichannel EHG signals could be used to differentiate term delivery and preterm birth and may predict delivery within and beyond 24 h.
Collapse
Affiliation(s)
- Yajun Zhang
- Faculty of Environment and Life, Beijing University of Technology, Beijing International Science and Technology Cooperation Base for Intelligent Physiological Measurement and Clinical Transformation, Beijing 100124, China; (Y.Z.); (L.Y.); (Y.Y.)
| | - Dongmei Hao
- Faculty of Environment and Life, Beijing University of Technology, Beijing International Science and Technology Cooperation Base for Intelligent Physiological Measurement and Clinical Transformation, Beijing 100124, China; (Y.Z.); (L.Y.); (Y.Y.)
| | - Lin Yang
- Faculty of Environment and Life, Beijing University of Technology, Beijing International Science and Technology Cooperation Base for Intelligent Physiological Measurement and Clinical Transformation, Beijing 100124, China; (Y.Z.); (L.Y.); (Y.Y.)
| | - Xiya Zhou
- Department of Obstetrics, Peking Union Medical College Hospital, Beijing 100730, China;
| | - Yiyao Ye-Lin
- Centro de Investigación e Innovación en Bioingeniería, Universitat Politècnica de València, 46022 Valencia, Spain;
| | - Yimin Yang
- Faculty of Environment and Life, Beijing University of Technology, Beijing International Science and Technology Cooperation Base for Intelligent Physiological Measurement and Clinical Transformation, Beijing 100124, China; (Y.Z.); (L.Y.); (Y.Y.)
| |
Collapse
|
6
|
Xu J, Wang M, Zhang J, Chen Z, Huang W, Shen G, Zhang M. Network theory based EHG signal analysis and its application in preterm prediction. IEEE J Biomed Health Inform 2022; 26:2876-2887. [PMID: 34986107 DOI: 10.1109/jbhi.2022.3140427] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
OBJECTIVE Preterm birth is the leading cause of neonatal morbidity and mortality. Early identification of high-risk patients followed by medical interventions is essential to the prevention of preterm birth. Based on the relationship between uterine contraction and the fundamental electrical activities of muscles, we extracted effective features from EHG signals recorded from pregnant women, and use them to train classifiers with the purpose of providing high precision in classifying term and preterm pregnancies. METHODS To characterize changes from irregularity to coherence of the uterine activity during the whole pregnancy, network representations of the original electrohysterogram (EHG) signals are established by applying the Horizontal Visibility Graph (HVG) algorithm, from which we extract network degree density and distribution, clustering coefficient and assortativity coefficient. Concerns on the interferences of different noise sources embedded in the EHG signal, we apply Short-Time Fourier Transform (STFT) to expand the original signal in the time-frequency domain. This allows a network representation and the extraction of related features on each frequency component. Feature selection algorithms are then used to filter out unrelated frequency components. We further apply the proposed feature extraction method to EHG signals available in the Term-Preterm EHG database (TPEHG), and use them to train classifiers. We adopt the Partition-Synthesis scheme which splits the original imbalanced dataset into two sets and synthesizes artificial samples separately within each subset to solve the problem of dataset imbalance. RESULTS The optimally selected network-based features, not only contribute to the identification of the essential frequency components of uterine activities related to preterm birth, but also to improved performance in classifying term/preterm pregnancies, i.e., the SVM (Support Vector Machine) classifier trained with the available samples in the TPEHG gives sensitivity, specificity, overall accuracy, and auc values as high as 0.89, 0.93, 0.91, and 0.97, respectively.
Collapse
|
7
|
Xu J, Chen Z, Zhang J, Lu Y, Yang X, Pumir A. Realistic preterm prediction based on optimized synthetic sampling of EHG signal. Comput Biol Med 2021; 136:104644. [PMID: 34271407 DOI: 10.1016/j.compbiomed.2021.104644] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2021] [Revised: 07/07/2021] [Accepted: 07/07/2021] [Indexed: 01/28/2023]
Abstract
Preterm labor is the leading cause of neonatal morbidity and mortality in newborns and has attracted significant research attention from many scientific areas. The relationship between uterine contraction and the underlying electrical activities makes uterine electrohysterogram (EHG) a promising direction for detecting and predicting preterm births. However, due to the scarcity of EHG signals, especially those leading to preterm births, synthetic algorithms have been used to generate artificial samples of preterm birth type in order to eliminate bias in the prediction towards normal delivery, at the expense of reducing the feature effectiveness in automatic preterm detection based on machine learning. To address this problem, we quantify the effect of synthetic samples (balance coefficient) on the effectiveness of features and form a general performance metric by using several feature scores with relevant weights that describe their contributions to class segregation. In combination with the activation/inactivation functions that characterize the effect of the abundance of training samples on the accuracy of the prediction of preterm and normal birth delivery, we obtained an optimal sample balance coefficient that compromises the effect of synthetic samples in removing bias toward the majority group (i.e., normal delivery and the side effect of reducing the importance of features). A more realistic predictive accuracy was achieved through a series of numerical tests on the publicly available TPEHG database, therefore demonstrating the effectiveness of the proposed method.
Collapse
Affiliation(s)
- Jinshan Xu
- College of Computer Science, Zhejiang University of Technology, Hangzhou, 310023, China; Research Center for AI Social Experiment, Zhejiang Lab, Hangzhou, 311321, China
| | - Zhenqin Chen
- College of Computer Science, Zhejiang University of Technology, Hangzhou, 310023, China
| | - Jinpeng Zhang
- College of Computer Science, Zhejiang University of Technology, Hangzhou, 310023, China
| | - Yanpei Lu
- College of Computer Science, Zhejiang University of Technology, Hangzhou, 310023, China
| | - Xi Yang
- College of Computer Science, Zhejiang University of Technology, Hangzhou, 310023, China.
| | - Alain Pumir
- Laboratoire de Physique, ENS-Lyon, Lyon, 69007, France
| |
Collapse
|
8
|
Malik M, Roh M, England SK. Uterine contractions in rodent models and humans. Acta Physiol (Oxf) 2021; 231:e13607. [PMID: 33337577 PMCID: PMC8047897 DOI: 10.1111/apha.13607] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 12/07/2020] [Accepted: 12/11/2020] [Indexed: 12/18/2022]
Abstract
Aberrant uterine contractions can lead to preterm birth and other labour complications and are a significant cause of maternal morbidity and mortality. To investigate the mechanisms underlying dysfunctional uterine contractions, researchers have used experimentally tractable small animal models. However, biological differences between humans and rodents change how researchers select their animal model and interpret their results. Here, we provide a general review of studies of uterine excitation and contractions in mice, rats, guinea pigs, and humans, in an effort to introduce new researchers to the field and help in the design and interpretation of experiments in rodent models.
Collapse
Affiliation(s)
- Manasi Malik
- Center for Reproductive Health SciencesDepartment of Obstetrics and GynecologyWashington University School of MedicineSt. LouisMOUSA
| | - Michelle Roh
- Center for Reproductive Health SciencesDepartment of Obstetrics and GynecologyWashington University School of MedicineSt. LouisMOUSA
| | - Sarah K. England
- Center for Reproductive Health SciencesDepartment of Obstetrics and GynecologyWashington University School of MedicineSt. LouisMOUSA
| |
Collapse
|
9
|
Wu W, Wang H, Zhao P, Talcott M, Lai S, McKinstry RC, Woodard PK, Macones GA, Schwartz AL, Cahill AG, Cuculich PS, Wang Y. Noninvasive high-resolution electromyometrial imaging of uterine contractions in a translational sheep model. Sci Transl Med 2020; 11:11/483/eaau1428. [PMID: 30867320 DOI: 10.1126/scitranslmed.aau1428] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 10/09/2018] [Accepted: 02/20/2019] [Indexed: 12/20/2022]
Abstract
In current clinical practice, uterine contractions are monitored via a tocodynamometer or an intrauterine pressure catheter, both of which provide crude information about contractions. Although electrohysterography/electromyography can measure uterine electrical activity, this method lacks spatial specificity and thus cannot accurately measure the exact location of electrical initiation and location-specific propagation patterns of uterine contractions. To comprehensively evaluate three-dimensional uterine electrical activation patterns, we describe here the development of electromyometrial imaging (EMMI) to display the three-dimensional uterine contractions at high spatial and temporal resolution. EMMI combines detailed body surface electrical recording with body-uterus geometry derived from magnetic resonance images. We used a sheep model to show that EMMI can reconstruct uterine electrical activation patterns from electrodes placed on the abdomen. These patterns closely match those measured with electrodes placed directly on the uterine surface. In addition, modeling experiments showed that EMMI reconstructions are minimally affected by noise and geometrical deformation. Last, we show that EMMI can be used to noninvasively measure uterine contractions in sheep in the same setup as would be used in humans. Our results indicate that EMMI can noninvasively, safely, accurately, robustly, and feasibly image three-dimensional uterine electrical activation during contractions in sheep and suggest that similar results might be obtained in clinical setting.
Collapse
Affiliation(s)
- Wenjie Wu
- Center for Reproductive Health Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA.,Department of Biomedical Engineering, Washington University, St. Louis, MO 63110, USA.,Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Hui Wang
- Center for Reproductive Health Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA.,Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, MO 63110, USA.,Department of Physics, Washington University, St. Louis, MO 63110, USA
| | - Peinan Zhao
- Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Michael Talcott
- Division of Comparative Medicine, Washington University, St. Louis, MO 63110, USA
| | - Shengsheng Lai
- Department of Medical Devices, Guangdong Food and Drug Vocational College, Guangzhou, Guangdong Province, P.R. China
| | - Robert C McKinstry
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Pamela K Woodard
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - George A Macones
- Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Alan L Schwartz
- Department of Pediatrics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Alison G Cahill
- Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Phillip S Cuculich
- Department of Cardiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
| | - Yong Wang
- Center for Reproductive Health Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA. .,Department of Biomedical Engineering, Washington University, St. Louis, MO 63110, USA.,Department of Obstetrics and Gynecology, Washington University School of Medicine, St. Louis, MO 63110, USA.,Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| |
Collapse
|
10
|
|
11
|
Hulls CM, Lentle RG, Chua WH, Suisted P, King QM, Chagas JAB, Chambers JP, Stewart L. Spatiotemporal Mapping of the Contracting Gravid Uterus of the Rabbit Shows Contrary Changes With Increasing Gestation and Dosage With Oxytocin. Front Endocrinol (Lausanne) 2019; 10:802. [PMID: 31824420 PMCID: PMC6882407 DOI: 10.3389/fendo.2019.00802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 11/04/2019] [Indexed: 12/11/2022] Open
Abstract
Spontaneous and oxytocin induced contractile activity was quantified in the bicornuate uteri of pregnant rabbits maintained in situ, using data from two- and uni- dimensional video spatiotemporal maps (VSTM) of linear and area strain rate and compared statistically. Spontaneous contractions occurred over a range of frequencies between 0.1 and 10 cpm, in gravid animals at 18-21 and at 28 days of gestation, and propagated both radially and longitudinally over the uterine wall overlying each fetus. Patches of contractions were randomly distributed over the entire surface of the cornua and were pleomorphic in shape. No spatial coordination was evident between longitudinal and circular muscle layers nor temporal coordination that could indicate the activity of a localized pacemaker. The density and duration of contractions decreased, and their frequency increased with the length of gestation in the non-laboring uterus. Increasing intravenous doses of oxytocin had no effect on the mean frequencies, or the mean durations of contractions in rabbits of 18-21 days gestation, but caused frequencies to decrease and durations to increase in rabbits of 28 days gestation, from greater spatial and temporal clustering of individual contractions. This was accompanied by an increase in the distance of propagation, the mean size of the patches of contraction, the area of the largest patch of contraction and the overall density of patches. Together these results suggest that progressive smooth muscle hypertrophy and displacement with increasing gestation is accompanied by a decrease in smooth muscle connectivity causing an increase in wall compliance and that oxytocin restores connectivity and decreases compliance, promoting volumetric expulsion rather than direct propulsion of the fetus by peristalsis. The latter effects were reversed by the β2 adrenergic receptor agonist salbutamol thus reducing area of contraction, and the duration and distance of propagation.
Collapse
Affiliation(s)
- Corrin M. Hulls
- Medical Physiology Research Unit, School of Health Sciences, College of Health, Massey University, Palmerston North, New Zealand
| | - Roger G. Lentle
- Medical Physiology Research Unit, School of Health Sciences, College of Health, Massey University, Palmerston North, New Zealand
| | - Wei-Hang Chua
- Medical Physiology Research Unit, School of Health Sciences, College of Health, Massey University, Palmerston North, New Zealand
| | - Philip Suisted
- Division of Obstetrics and Gynaecology, Palmerston North Hospital, Palmerston North, New Zealand
| | - Quinten M. King
- Division of Urology, Palmerston North Hospital, Palmerston North, New Zealand
| | - Joana A. B. Chagas
- School of Veterinary Science, Massey University, Palmerston North, New Zealand
| | - John P. Chambers
- School of Veterinary Science, Massey University, Palmerston North, New Zealand
| | - Lauren Stewart
- School of Veterinary Science, Massey University, Palmerston North, New Zealand
| |
Collapse
|
12
|
Tocolytic activity of the Lippia alba essential oil and its major constituents, citral and limonene, on the isolated uterus of rats. Chem Biol Interact 2019; 297:155-159. [DOI: 10.1016/j.cbi.2018.11.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2018] [Revised: 10/30/2018] [Accepted: 11/13/2018] [Indexed: 12/11/2022]
|
13
|
Performance of source imaging techniques of spatially extended generators of uterine activity. INFORMATICS IN MEDICINE UNLOCKED 2019. [DOI: 10.1016/j.imu.2019.100167] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
|
14
|
Zhang M, La Rosa PS, Eswaran H, Nehorai A. Estimating uterine source current during contractions using magnetomyography measurements. PLoS One 2018; 13:e0202184. [PMID: 30138376 PMCID: PMC6121809 DOI: 10.1371/journal.pone.0202184] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2017] [Accepted: 05/29/2018] [Indexed: 11/28/2022] Open
Abstract
Understanding the uterine source of the electrophysiological activity of
contractions during pregnancy is of scientific interest and potential clinical
applications. In this work, we propose a method to estimate uterine source
currents from magnetomyography (MMG) temporal course measurements on the
abdominal surface. In particular, we develop a linear forward model, based on
the quasistatic Maxwell’s equations and a realistic four-compartment volume
conductor, relating the magnetic fields to the source currents on the uterine
surface through a lead-field matrix. To compute the lead-field matrix, we use a
finite element method that considers the anisotropic property of the myometrium.
We estimate the source currents by minimizing a constrained least-squares
problem to solve the non-uniqueness issue of the inverse problem. Because we
lack the ground truth of the source current, we propose to predict the
intrauterine pressure from our estimated source currents by using an
absolute-value-based method and compare the result with real abdominal
deflection recorded during contractile activity. We test the feasibility of the
lead-field matrix by displaying the lead fields that are generated by putative
source currents at different locations in the myometrium: cervix and fundus,
left and right, front and back. We then illustrate our method by using three
synthetic MMG data sets, which are generated using our previously developed
multiscale model of uterine contractions, and three real MMG data sets, one of
which has simultaneous real abdominal deflection measurements. The numerical
results demonstrate the ability of our method to capture the local contractile
activity of human uterus during pregnancy. Moreover, the predicted intrauterine
pressure is in fair agreement with the real abdominal deflection with respect to
the timing of uterine contractions.
Collapse
Affiliation(s)
- Mengxue Zhang
- Preston M. Green Department of Electrical and Systems Engineering,
Washington University in Saint Louis, Saint Louis, Missouri, United States of
America
| | - Patricio S. La Rosa
- Geospatial Analytics, Global IT Analytics, Monsanto Company, Saint Louis,
Missouri, United States of America
| | - Hari Eswaran
- Department of Obstetrics and Gynecology, University of Arkansas for
Medical Sciences, Little Rock, Arkansas, United States of America
| | - Arye Nehorai
- Preston M. Green Department of Electrical and Systems Engineering,
Washington University in Saint Louis, Saint Louis, Missouri, United States of
America
- * E-mail:
| |
Collapse
|
15
|
Young RC. The uterine pacemaker of labor. Best Pract Res Clin Obstet Gynaecol 2018; 52:68-87. [PMID: 29866432 DOI: 10.1016/j.bpobgyn.2018.04.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Accepted: 04/10/2018] [Indexed: 10/17/2022]
Abstract
The laboring uterus is generally thought to initiate contractions much similar to the heart, with a single, dedicated pacemaker. Research on human and animal models over decades has failed to identify such pacemaker. On the contrary, data indicate that instead of being fixed at a site similar to the sinoatrial node of the heart, the initiation site for each uterine contraction changes during time, often with each contraction. The enigmatic uterine "pacemaker" does not seem to fit the standard definition of what a pacemaker should be. The uterine pacemaker must also mesh with the primary physiological function of the uterus - to generate intrauterine pressure. This requires that most areas of the uterine wall contract in a coordinated, or synchronized, manner for each contraction of labor. It is not clear whether the primary mechanism of the uterine pacemaker is a slow-wave generator or an impulse generator. Slow waves in the gut initiate localized smooth muscle contractions. Because the uterus and the gut have somewhat similar cellular and tissue structure, it is reasonable to consider if uterine contractions are paced by a similar mechanism. Unfortunately, there is no convincing experimental verification of uterine slow waves. Similarly, there is no convincing evidence of a cellular mechanism for impulse generation. The uterus appears to have multiple widely dispersed mechanically sensitive functional pacemakers. It is possible that the coordination of organ-level function occurs through intrauterine pressure, thus creating wall stress followed by activation of many mechanosensitive electrogenic pacemakers.
Collapse
|
16
|
Mischi M, Chen C, Ignatenko T, de Lau H, Ding B, Oei SGG, Rabotti C. Dedicated Entropy Measures for Early Assessment of Pregnancy Progression From Single-Channel Electrohysterography. IEEE Trans Biomed Eng 2017; 65:875-884. [PMID: 28692959 DOI: 10.1109/tbme.2017.2723933] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE Preterm birth is a large-scale clinical problem involving over 10% of infants. Diagnostic means for timely risk assessment are lacking and the underlying physiological mechanisms unclear. To improve the evaluation of pregnancy before term, we introduce dedicated entropy measures derived from a single-channel electrohysterogram (EHG). METHODS The estimation of approximate entropy (ApEn) and sample entropy (SampEn) is adjusted to monitor variations in the regularity of single-channel EHG recordings, reflecting myoelectrical changes due to pregnancy progression. In particular, modifications in the tolerance metrics are introduced for improving robustness to EHG amplitude fluctuations. An extensive database of 58 EHG recordings with 4 monopolar channels in women presenting with preterm contractions was manually annotated and used for validation. The methods were tested for their ability to recognize the onset of labor and the risk of preterm birth. Comparison with the best single-channel methods according to the literature was performed. RESULTS The reference methods were outperformed. SampEn and ApEn produced the best prediction of delivery, although only one channel showed a significant difference () between labor and nonlabor. The modified ApEn produced the best prediction of preterm delivery, showing statistical significance () in three channels. These results were also confirmed by the area under the receiver operating characteristic curve and fivefold cross validation. CONCLUSION The use of dedicated entropy estimators improves the diagnostic value of EHG analysis earlier in pregnancy. SIGNIFICANCE Our results suggest that changes in the EHG might manifest early in pregnancy, providing relevant prognostic opportunities for pregnancy monitoring by a practical single-channel solution.
Collapse
|
17
|
Domino M, Pawlinski B, Gajewski Z. Biomathematical pattern of EMG signal propagation in smooth muscle of the non-pregnant porcine uterus. PLoS One 2017; 12:e0173452. [PMID: 28282410 PMCID: PMC5345803 DOI: 10.1371/journal.pone.0173452] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Accepted: 02/22/2017] [Indexed: 01/20/2023] Open
Abstract
Uterine contractions are generated by myometrial smooth muscle cells (SMCs) that comprise most of the myometrial layer of the uterine wall. Aberrant uterine motility (i.e., hypo- or hyper-contractility or asynchronous contractions) has been implicated in the pathogenesis of infertility due to the failure of implantation, endometriosis and abnormal estrous cycles. The mechanism whereby the non-pregnant uterus initiates spontaneous contractions remains poorly understood. The aim of the present study was to employ linear synchronization measures for analyzing the pattern of EMG signal propagation (direction and speed) in smooth muscles of the non-pregnant porcine uterus in vivo using telemetry recording system. It has been revealed that the EMG signal conduction in the uterine wall of the non-pregnant sow does not occur at random but it rather exhibits specific directions and speed. All detectable EMG signals moved along the uterine horn in both cervico-tubal and tubo-cervical directions. The signal migration speed could be divided into the three main types or categories: i. slow basic migration rhythm (SBMR); ii. rapid basic migration rhythm (RBMR); and iii. rapid accessory migration rhythm (RAMR). In conclusion, the EMG signal propagation in smooth muscles of the porcine uterus in vivo can be assessed using a linear synchronization model. Physiological pattern of the uterine contractile activity determined in this study provides a basis for future investigations of normal and pathologicall myogenic function of the uterus.
Collapse
Affiliation(s)
- Malgorzata Domino
- Department of Large Animal Diseases with Clinic, Veterinary Research Centre and Center for Biomedical Research, Faculty of Veterinary Medicine, Warsaw University of Life Sciences (WULS – SGGW), Warsaw, Poland
| | - Bartosz Pawlinski
- Department of Large Animal Diseases with Clinic, Veterinary Research Centre and Center for Biomedical Research, Faculty of Veterinary Medicine, Warsaw University of Life Sciences (WULS – SGGW), Warsaw, Poland
| | - Zdzislaw Gajewski
- Department of Large Animal Diseases with Clinic, Veterinary Research Centre and Center for Biomedical Research, Faculty of Veterinary Medicine, Warsaw University of Life Sciences (WULS – SGGW), Warsaw, Poland
| |
Collapse
|
18
|
Young RC. Mechanotransduction mechanisms for coordinating uterine contractions in human labor. Reproduction 2016; 152:R51-61. [PMID: 27165050 DOI: 10.1530/rep-16-0156] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 05/09/2016] [Indexed: 11/08/2022]
Abstract
This review presents evolving concepts of how the human uterus contracts in pregnancy, with emphasis on the mechanisms of long-distance signaling. Action potential propagation has historically been assumed to be the sole mechanism for signaling and tissue recruitment over both short and long distances. However, data in animals and humans indicate that a single action potential does not travel distances greater than a few centimeters. To address this enigma, a long-distance signaling mechanism based on hydraulic signaling and mechanotransduction is developed. By combining this mechanism for long-distance signaling with the action potential propagation mechanism for signaling over short distances, a comprehensive dual mechanism model (or 'dual model') of uterine function is formulated. Mechanotransduction is an accepted phenomenon of myometrium, but the dual model identifies mechanotransduction as relevant to normal labor. For hydraulic signaling, a local contraction slightly increases intrauterine pressure, which globally increases wall tension. Increased wall tension then mechanically induces additional local contractions that further raise pressure. This leads to robust, positive feedback recruitment that explains the emergence of consistently strong contractions of human labor. Three key components of the dual model - rapid long-distance signaling, mechanical triggering, and electrical activity - converge with the concept of mechanically sensitive electrogenic pacemakers distributed throughout the wall. The dual model retains excitation-contraction coupling and action potential propagation for signaling over short distances (<10cm) and hence is an extension of the action potential model rather than a replacement.
Collapse
Affiliation(s)
- Roger C Young
- PreTel, Inc.Memphis, TN, USA University of NewcastleNewcastle, Australia Imperial College of LondonChelsea and Westminster Hospital, London, UK
| |
Collapse
|
19
|
de Lau H, Yang KT, Rabotti C, Vlemminx M, Bajlekov G, Mischi M, Oei SG. Toward a new modality for detecting a uterine rupture: electrohysterogram propagation analysis during trial of labor after cesarean. J Matern Fetal Neonatal Med 2016; 30:574-579. [PMID: 27160153 DOI: 10.1080/14767058.2016.1178227] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
OBJECTIVE Observational cohort study which aimed to explore the potential of electrohysterogram (EHG) analysis for detecting a uterine rupture during trial of labor after cesarean. The EHG propagation characteristics surrounding the uterine scar of six patients with a previous cesarean section were compared to a control group of five patients without a scarred uterus. METHODS The EHG was recorded during the first stage of labor using a high-resolution 64-channel electrode grid positioned on the maternal abdomen across the cesarean scar. Based on simulations, the inter-channel correlation and propagation direction were adopted as EHG parameters for evaluating possible disruption of electrical propagation by the uterine scar. RESULTS No significant differences in inter-channel correlation or propagation direction were observed between the group of patients with an intact uterine scar and the control group. A strong predominance of vertical propagation was observed in one case, in which scar rupture occurred. CONCLUSIONS The results support unaffected propagation of electrical activity through the intact uterine scar tissue suggesting that changes in the EHG might only occur in case of rupture.
Collapse
Affiliation(s)
- Hinke de Lau
- a Department of Obstetrics and Gynecology , Máxima Medical Center , Veldhoven , the Netherlands and
| | - Kai Tao Yang
- b Department of Electrical Engineering , University of Technology Eindhoven , Eindhoven , the Netherlands
| | - Chiara Rabotti
- b Department of Electrical Engineering , University of Technology Eindhoven , Eindhoven , the Netherlands
| | - Marion Vlemminx
- a Department of Obstetrics and Gynecology , Máxima Medical Center , Veldhoven , the Netherlands and
| | - Galin Bajlekov
- b Department of Electrical Engineering , University of Technology Eindhoven , Eindhoven , the Netherlands
| | - Massimo Mischi
- b Department of Electrical Engineering , University of Technology Eindhoven , Eindhoven , the Netherlands
| | - Swan Gie Oei
- a Department of Obstetrics and Gynecology , Máxima Medical Center , Veldhoven , the Netherlands and
| |
Collapse
|
20
|
Zhang M, Tidwell V, La Rosa PS, Wilson JD, Eswaran H, Nehorai A. Modeling Magnetomyograms of Uterine Contractions during Pregnancy Using a Multiscale Forward Electromagnetic Approach. PLoS One 2016; 11:e0152421. [PMID: 27019202 PMCID: PMC4809542 DOI: 10.1371/journal.pone.0152421] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 03/14/2016] [Indexed: 01/22/2023] Open
Abstract
Understanding the mechanisms of uterine contractions during pregnancy is especially important in predicting the onset of labor and thus in forecasting preterm deliveries. Preterm birth can cause serious health problems in newborns, as well as large financial burdens to society. Various techniques such as electromyography (EMG) and magnetomyography (MMG) have been developed to quantify uterine contractions. However, no widely accepted method to predict labor based on electromagnetic measurement is available. Therefore, developing a biophysical model of EMG and MMG could help better understand uterine contractions, interpret real measurements, and detect labor. In this work, we propose a multiscale realistic model of uterine contractions during pregnancy. At the cellular level, building on bifurcation theory, we apply generalized FitzHugh-Nagumo (FHN) equations that produces both plateau-type and bursting-type action potentials. At the tissue level, we introduce a random fiber orientation model applicable to an arbitrary uterine shape. We also develop an analytical expression for the propagation speed of transmembrane potential. At the organ level, a realistic volume conductor geometry model is provided based on magnetic resonance images of a pregnant woman. To simulate the measurements from the SQUID Array for Reproductive Assessment (SARA) device, we propose a sensor array model. Our model is able to reproduce the characteristics of action potentials. Additionally, we investigate the sensitivity of MMG to model configuration aspects such as volume geometry, fiber orientation, and pacemaker location. Our numerical results show that fiber orientation and pacemaker location are the key aspects that greatly affect the MMG as measured by the SARA device. We conclude that sphere is appropriate as an approximation of the volume geometry. The initial step towards validating the model against real MMG measurement is also presented. Our results show that the model is flexible to mimic the limited-propagation magnetic signature during the emergence and decay of a uterine contraction.
Collapse
Affiliation(s)
- Mengxue Zhang
- Department of Electrical and Systems Engineering, Washington University in Saint Louis, Saint Louis, Missouri, United States of America
| | - Vanessa Tidwell
- Department of Electrical and Systems Engineering, Washington University in Saint Louis, Saint Louis, Missouri, United States of America
| | - Patricio S. La Rosa
- Research & Development/Technology Pipeline Solutions, Monsanto Company, Saint Louis, Missouri, United States of America
- Joint Undergraduate Engineering Program - University of Missouri and Washington University in Saint Louis, Saint Louis, Missouri, United States of America
| | - James D. Wilson
- Graduate Institute of Technology, University of Arkansas at Little Rock, Little Rock, Arkansas, United States of America
| | - Hari Eswaran
- Department of Obstetrics and Gynecology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States of America
| | - Arye Nehorai
- Department of Electrical and Systems Engineering, Washington University in Saint Louis, Saint Louis, Missouri, United States of America
- * E-mail:
| |
Collapse
|
21
|
Smith R, Imtiaz M, Banney D, Paul JW, Young RC. Reply. Am J Obstet Gynecol 2016; 214:300-301. [PMID: 26454125 DOI: 10.1016/j.ajog.2015.09.104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Accepted: 09/30/2015] [Indexed: 12/01/2022]
|
22
|
Characterizing the Propagation of Uterine Electrophysiological Signals Recorded with a Multi-Sensor Abdominal Array in Term Pregnancies. PLoS One 2015; 10:e0140894. [PMID: 26505624 PMCID: PMC4624716 DOI: 10.1371/journal.pone.0140894] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 10/01/2015] [Indexed: 11/19/2022] Open
Abstract
The objective of this study was to quantify the number of segments that have contractile activity and determine the propagation speed from uterine electrophysiological signals recorded over the abdomen. The uterine magnetomyographic (MMG) signals were recorded with a 151 channel SARA (SQUID Array for Reproductive Assessment) system from 36 pregnant women between 37 and 40 weeks of gestational age. The MMG signals were scored and segments were classified based on presence of uterine contractile burst activity. The sensor space was then split into four quadrants and in each quadrant signal strength at each sample was calculated using center-of-gravity (COG). To this end, the cross-correlation analysis of the COG was performed to calculate the delay between pairwise combinations of quadrants. The relationship in propagation across the quadrants was quantified and propagation speeds were calculated from the delays. MMG recordings were successfully processed from 25 subjects and the average values of propagation speeds ranged from 1.3-9.5 cm/s, which was within the physiological range. The propagation was observed between both vertical and horizontal quadrants confirming multidirectional propagation. After the multiple pairwise test (99% CI), significant differences in speeds can be observed between certain vertical or horizontal combinations and the crossed pair combinations. The number of segments containing contractile activity in any given quadrant pair with a detectable delay was significantly higher in the lower abdominal pairwise combination as compared to all others. The quadrant-based approach using MMG signals provided us with high spatial-temporal information of the uterine contractile activity and will help us in the future to optimize abdominal electromyographic (EMG) recordings that are practical in a clinical setting.
Collapse
|
23
|
Lammers WJEP, Stephen B, Al-Sultan MA, Subramanya SB, Blanks AM. The location of pacemakers in the uteri of pregnant guinea pigs and rats. Am J Physiol Regul Integr Comp Physiol 2015; 309:R1439-46. [PMID: 26377559 DOI: 10.1152/ajpregu.00187.2015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Accepted: 09/01/2015] [Indexed: 01/31/2023]
Abstract
The pregnant uterus is a smooth muscle organ whose pattern of contraction is dictated by the propagation of electrical impulses. Such electrical activity may originate from one or more pacemakers, but the location of these sites has not yet been determined. To detect the location of the pacemaker in the gravid uterus, two approaches were used: 1) determine the site from where the contraction started using isolated uteri from the pregnant guinea pig, and videotape their contractions; and 2) record, in isolated uteri from pregnant term rats, with 240 extracellular electrodes simultaneously, and determine where the electrical bursts started. In both the contractile and electrophysiological experiments, there was not a single, specific pacemaker area. However, most contractions (guinea pig 87%) and bursts (rat 76%) started close to the mesometrial border (mean 2.7 ± 4.0 mm SD in guinea pigs and 1.3 ± 1.4 mm in rats). In addition, in the rat, most sites of initiations were located closer to the ovarial end of the horn (mean distance from the ovarial end 6.0 ± 6.2 mm SD), whereas such an orientation was not seen in the guinea pig. In both guinea pig and rat uteri at term, there is not one specific pacemaker area. Rather, contractile and electrical activity may arise from any site, with the majority starting close to the mesometrial border. Furthermore, in the rat, most activities started at the ovarial end of the horn. This may suggest a slightly different pattern of contraction in both species.
Collapse
Affiliation(s)
- Wim J E P Lammers
- Department of Physiology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates; and
| | - Betty Stephen
- Department of Physiology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates; and
| | - Mahmood Ahmed Al-Sultan
- Department of Physiology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates; and
| | - Sandeep B Subramanya
- Department of Physiology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates; and
| | - Andrew M Blanks
- Division of Translational and Systems Medicine, Warwick Medical School, Clinical Sciences Research Laboratory, Coventry, United Kingdom
| |
Collapse
|
24
|
The role of cellular coupling in the spontaneous generation of electrical activity in uterine tissue. PLoS One 2015; 10:e0118443. [PMID: 25793276 PMCID: PMC4368634 DOI: 10.1371/journal.pone.0118443] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 01/16/2015] [Indexed: 11/19/2022] Open
Abstract
The spontaneous emergence of contraction-inducing electrical activity in the uterus at the beginning of labor remains poorly understood, partly due to the seemingly contradictory observation that isolated uterine cells are not spontaneously active. It is known, however, that the expression of gap junctions increases dramatically in the approach to parturition, by more than one order of magnitude, which results in a significant increase in inter-cellular electrical coupling. In this paper, we build upon previous studies of the activity of electrically excitable smooth muscle cells (myocytes) and investigate the mechanism through which the coupling of these cells to electrically passive cells results in the generation of spontaneous activity in the uterus. Using a recently developed, realistic model of uterine muscle cell dynamics, we investigate a system consisting of a myocyte coupled to passive cells. We then extend our analysis to a simple two-dimensional lattice model of the tissue, with each myocyte being coupled to its neighbors, as well as to a random number of passive cells. We observe that different dynamical regimes can be observed over a range of gap junction conductances: at low coupling strength, corresponding to values measured long before delivery, the activity is confined to cell clusters, while the activity for high coupling, compatible with values measured shortly before delivery, may spread across the entire tissue. Additionally, we find that the system supports the spontaneous generation of spiral wave activity. Our results are both qualitatively and quantitatively consistent with observations from in vitro experiments. In particular, we demonstrate that the increase in inter-cellular electrical coupling observed experimentally strongly facilitates the appearance of spontaneous action potentials that may eventually lead to parturition.
Collapse
|
25
|
Rabotti C, Mischi M. Propagation of electrical activity in uterine muscle during pregnancy: a review. Acta Physiol (Oxf) 2015; 213:406-16. [PMID: 25393600 DOI: 10.1111/apha.12424] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Revised: 08/13/2014] [Accepted: 11/07/2014] [Indexed: 11/29/2022]
Abstract
The uterine muscle (the myometrium) plays its most evident role during pregnancy, when quiescence is required for adequate nourishment and development of the foetus, and during labour, when forceful contractions are needed to expel the foetus and the other products of conception. The myometrium is composed of smooth muscle cells. Contraction is initiated by the spontaneous generation of electrical activity at the cell level in the form of action potentials. The mechanisms underlying uterine quiescence during pregnancy and electrical activation during labour remain largely unknown; as a consequence, the clinical management of preterm contractions during pregnancy and inefficient uterine contractility during labour remains suboptimal. In an effort to improve clinical management of uterine contractions, research has focused on understanding the propagation properties of the electrical activity of the uterus. Different perspectives have been undertaken, from animal and in vitro experiments up to clinical studies and dedicated methods for non-invasive parameter estimation. A comparison of the results is not straightforward due to the wide range of different approaches reported in the literature. However, previous studies unanimously reveal a unique complexity as compared to other organs in the pattern of uterine electrical activity propagation, which necessarily needs to be taken into consideration for future studies to be conclusive. The aim of this review is to structure current variegated knowledge on the properties of the uterus in terms of pacemaker position, pattern, direction and speed of the electrical activity during pregnancy and labour.
Collapse
Affiliation(s)
- C. Rabotti
- Electrical Engineering Department; Eindhoven University of Technology; Eindhoven the Netherlands
| | - M. Mischi
- Electrical Engineering Department; Eindhoven University of Technology; Eindhoven the Netherlands
| |
Collapse
|
26
|
Wray S, Burdyga T, Noble D, Noble K, Borysova L, Arrowsmith S. Progress in understanding electro-mechanical signalling in the myometrium. Acta Physiol (Oxf) 2015; 213:417-31. [PMID: 25439280 DOI: 10.1111/apha.12431] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Revised: 11/11/2014] [Accepted: 11/17/2014] [Indexed: 11/30/2022]
Abstract
In this review, we give a state-of-the-art account of uterine contractility, focussing on excitation-contraction (electro-mechanical) coupling (ECC). This will show how electrophysiological data and intracellular calcium measurements can be related to more modern techniques such as confocal microscopy and molecular biology, to advance our understanding of mechanical output and its modulation in the smooth muscle of the uterus, the myometrium. This new knowledge and understanding, for example concerning the role of the sarcoplasmic reticulum (SR), or stretch-activated K channels, when linked to biochemical and molecular pathways, provides a clearer and better informed basis for the development of new drugs and targets. These are urgently needed to combat dysfunctions in excitation-contraction coupling that are clinically challenging, such as preterm labour, slow to progress labours and post-partum haemorrhage. It remains the case that scientific progress still needs to be made in areas such as pacemaking and understanding interactions between the uterine environment and ion channel activity.
Collapse
Affiliation(s)
- S. Wray
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| | - T. Burdyga
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| | - D. Noble
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| | - K. Noble
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| | - L. Borysova
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| | - S. Arrowsmith
- Department of Cellular and Molecular Physiology; Institute of Translational Medicine; University of Liverpool; Liverpool Women's Hospital; Liverpool UK
| |
Collapse
|
27
|
Young RC, Barendse P. Linking myometrial physiology to intrauterine pressure; how tissue-level contractions create uterine contractions of labor. PLoS Comput Biol 2014; 10:e1003850. [PMID: 25330227 PMCID: PMC4199482 DOI: 10.1371/journal.pcbi.1003850] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 08/09/2014] [Indexed: 11/18/2022] Open
Abstract
The mechanisms used to coordinate uterine contractions are not known. We develop a new model based on the proposal that there is a maximum distance to which action potentials can propagate in the uterine wall. This establishes "regions", where one action potential burst can rapidly recruit all the tissue. Regions are recruited into an organ-level contraction via a stretch-initiated contraction mechanism (myometrial myogenic response). Each uterine contraction begins with a regional contraction, which slightly increases intrauterine pressure. Higher pressure raises tension throughout the uterine wall, which initiates contractions of more regions and further increases pressure. The positive feedback synchronizes regional contractions into an organ-level contraction. Cellular automaton (CA) simulations are performed with Mathematica. Each "cell" is a region that is assigned an action potential threshold. An anatomy sensitivity factor converts intrauterine pressure to regional tension through the Law of Laplace. A regional contraction occurs when regional tension exceeds regional threshold. Other input variables are: starting and minimum pressure, burst and refractory period durations, enhanced contractile activity during an electrical burst, and reduced activity during the refractory period. Complex patterns of pressure development are seen that mimic the contraction patterns observed in laboring women. Emergent behavior is observed, including global synchronization, multiple pace making regions, and system memory of prior conditions. The complex effects of nifedipine and oxytocin exposure are simulated. The force produced can vary as a nonlinear function of the number of regions. The simulation directly links tissue-level physiology to human labor. The concept of a uterine pacemaker is re-evaluated because pace making activity may occur well before expression of a contraction. We propose a new classification system for biological CAs that parallels the 4-class system of Wolfram. However, instead of classifying the rules, biological CAs should classify the set of input values for the rules that describe the relevant biology.
Collapse
Affiliation(s)
- Roger C. Young
- Department of Obstetrics and Gynecology, University of Tennessee Health Science Center, Memphis, Tennessee, United States of America
- * E-mail: .
| | - Peter Barendse
- Wolfram Research, Somerville, Massachusetts, United States of America
| |
Collapse
|
28
|
Store-operated Ca²⁺ entry and depolarization explain the anomalous behaviour of myometrial SR: effects of SERCA inhibition on electrical activity, Ca²⁺ and force. Cell Calcium 2014; 56:188-94. [PMID: 25084623 PMCID: PMC4169181 DOI: 10.1016/j.ceca.2014.07.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Revised: 07/03/2014] [Accepted: 07/09/2014] [Indexed: 11/23/2022]
Abstract
SERCA pump inhibition by CPA caused membrane depolarization, activation of action potentials, Ca2+ spikes and force. Depletion of Ca2+ store by agonists leads to membrane depolarization and activation of electrical and mechanical activity. Ca2+ release/Ca2+ entry coupling is playing a key role in control of spontaneous electrical and mechanical activity in rat pregnant myometrium.
In the myometrium SR Ca2+ depletion promotes an increase in force but unlike several other smooth muscles, there is no Ca2+ sparks-STOCs coupling mechanism to explain this. Given the importance of the control of contractility for successful parturition, we have examined, in pregnant rat myometrium, the effects of SR Ca2+-ATPase (SERCA) inhibition on the temporal relationship between action potentials, Ca2+ transients and force. Simultaneous recording of electrical activity, calcium and force showed that SERCA inhibition, by cyclopiazonic acid (CPA 20 μM), caused time-dependent changes in excitability, most noticeably depolarization and elevations of baseline [Ca2+]i and force. At the onset of these changes there was a prolongation of the bursts of action potentials and a corresponding series of Ca2+ spikes, which increased the amplitude and duration of contractions. As the rise of baseline Ca2+ and depolarization continued a point was reached when electrical and Ca2+ spikes and phasic contractions ceased, and a maintained, tonic force and Ca2+ was produced. Lanthanum, a non-selective blocker of store-operated Ca2+ entry, but not the L-type Ca2+ channel blocker nifedipine (1–10 μM), could abolish the maintained force and calcium. Application of the agonist, carbachol, produced similar effects to CPA, i.e. depolarization, elevation of force and calcium. A brief, high concentration of carbachol, to cause SR Ca2+ depletion without eliciting receptor-operated channel opening, also produced these results. The data obtained suggest that in pregnant rats SR Ca2+ release is coupled to marked Ca2+ entry, via store operated Ca2+ channels, leading to depolarization and enhanced electrical and mechanical activity.
Collapse
|
29
|
de Lau H, Rabotti C, Oosterbaan HP, Mischi M, Oei GS. Study protocol: PoPE-Prediction of Preterm delivery by Electrohysterography. BMC Pregnancy Childbirth 2014; 14:192. [PMID: 24898548 PMCID: PMC4057931 DOI: 10.1186/1471-2393-14-192] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2013] [Accepted: 05/28/2014] [Indexed: 11/10/2022] Open
Abstract
Background Traditional methods used for prediction of preterm delivery are subjective and inaccurate. The Electrohysterogram (EHG) and in particular the estimation of the EHG conduction velocity, is a relatively new promising method for detecting imminent preterm delivery. To date the analysis of the conduction velocity has relied on visual inspection of the signals. As a next step towards the introduction of EHG analysis as a clinical tool, we propose an automated method for EHG conduction velocity estimation for both the speed and direction of single spike propagation. Methods/Design The study design will be an observational cohort study. 100 pregnant women, gestational age between 23 + 5 and 34 weeks, admitted for threatening preterm labor or preterm prelabor rupture of membranes, will be included. The length of the cervical canal will be measured by transvaginal ultrasound. The EHG will be recorded using 4 electrodes in a fixed configuration. Contractions will be detected by analysis of the EHG and using an estimation of the intra uterine pressure. In the selected contractions, the delays between channels will be estimated by cross-correlation, and subsequently, the average EHG conduction velocity will be derived. Patients will be classified as labor group and non-labor group based on the time between measurement and delivery. The average conduction velocity and cervical length will be compared between the groups. The main study endpoints will be sensitivity, specificity, and area under the ROC curve for delivery within 1,2,4,7, and 14 days from the measurement. Discussion In this study, the diagnostic accuracy of EHG conduction velocity analysis will be evaluated for detecting preterm labor. Visual and automatic detection of contractions will be compared. Planar wave propagation will be assumed for the calculation of the CV vector. Trial registration Current Controlled Trials ISRCTN07603227.
Collapse
Affiliation(s)
- Hinke de Lau
- Department of Electrical Engineering, University of Technology Eindhoven, Den Dolech 2, 5612 AZ Eindhoven, the Netherlands.
| | | | | | | | | |
Collapse
|
30
|
Hammad FT, Stephen B, Lubbad L, Morrison JFB, Lammers WJ. Macroscopic electrical propagation in the guinea pig urinary bladder. Am J Physiol Renal Physiol 2014; 307:F172-82. [PMID: 24899061 DOI: 10.1152/ajprenal.00215.2014] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
There is little knowledge about macroscopic electrical propagation in the wall of the urinary bladder. Recording simultaneously from a large number of extracellular electrodes is one technology that could be used to study the patterns of macroscopic electrical propagations. The urinary bladders from 14 guinea pigs were isolated and placed in an organ bath. A 16 × 4-electrode array was positioned at various sites on the serosal bladder surface, and recordings were performed at different intravesical volumes. In four experiments, carbachol (CCH; 10(-6) M), nifedipine (10 mM), or tetrodotoxin (TTX; 10(-6) M) was added to the superfusing fluid. After the experiments, the extracellular signals were analyzed and propagation maps were constructed. Electrical waves were detected at all sites on the bladder surface and propagated for a limited distance before terminating spontaneously. The majority of waves (>90%) propagated in the axial direction (i.e., from dome to base or vice versa). An increase in vesicle volume significantly decreased the conduction velocity (from 4.9 ± 1.5 to 2.7 ± 0.7 cm/s; P < 0.05). CCH increased, nifedipine decreased, while TTX had little effect on electrical activities. In addition, a new electrical phenomenon, termed a "patch," was discovered whereby a simultaneous electrical deflection was detected across an area of the bladder surface. Two types of electrical activities were detected on the bladder surface: 1) electrical waves propagating preferentially in the axial direction and 2) electrical patches. The propagating electrical waves could form the basis for local spontaneous contractions in the bladder during the filling phase.
Collapse
Affiliation(s)
- F T Hammad
- Department of Surgery, United Arab Emirates University, Al Ain, United Arab Emirates; and
| | - B Stephen
- Department of Physiology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - L Lubbad
- Department of Surgery, United Arab Emirates University, Al Ain, United Arab Emirates; and
| | - J F B Morrison
- Department of Physiology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - W J Lammers
- Department of Physiology, College of Medicine and Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| |
Collapse
|
31
|
Lange L, Vaeggemose A, Kidmose P, Mikkelsen E, Uldbjerg N, Johansen P. Velocity and directionality of the electrohysterographic signal propagation. PLoS One 2014; 9:e86775. [PMID: 24466235 PMCID: PMC3897754 DOI: 10.1371/journal.pone.0086775] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Accepted: 12/15/2013] [Indexed: 11/19/2022] Open
Abstract
OBJECTIVE The initiation of treatment for women with threatening preterm labor requires effective distinction between true and false labor. The electrohysterogram (EHG) has shown great promise in estimating and classifying uterine activity. However, key issues remain unresolved and no clinically usable method has yet been presented using EHG. Recent studies have focused on the propagation velocity of the EHG signals as a potential discriminator between true and false labor. These studies have estimated the propagation velocity of individual spikes of the EHG signals. We therefore focus on estimating the propagation velocity of the entire EHG burst recorded during a contraction in two dimensions. STUDY DESIGN EHG measurements were performed on six women in active labor at term, and a total of 35 contractions were used for the estimation of propagation velocity. The measurements were performed using a 16-channel two-dimensional electrode grid. The estimates were calculated with a maximum-likelihood approach. RESULTS The estimated average propagation velocity was 2.18 (±0.68) cm/s. No single preferred direction of propagation was found. CONCLUSION The propagation velocities estimated in this study are similar to those reported in other studies but with a smaller intra- and inter-patient variation. Thus a potential tool has been established for further studies on true and false labor contractions.
Collapse
Affiliation(s)
- Lasse Lange
- Department of Engineering, Faculty of Science and Technology, Aarhus University, Aarhus, Denmark
| | - Anders Vaeggemose
- Department of Engineering, Faculty of Science and Technology, Aarhus University, Aarhus, Denmark
| | - Preben Kidmose
- Department of Engineering, Faculty of Science and Technology, Aarhus University, Aarhus, Denmark
| | - Eva Mikkelsen
- Department of Obstetrics and Gynecology, Aarhus University Hospital, Aarhus, Denmark
| | - Niels Uldbjerg
- Department of Obstetrics and Gynecology, Aarhus University Hospital, Aarhus, Denmark
| | - Peter Johansen
- Department of Engineering, Faculty of Science and Technology, Aarhus University, Aarhus, Denmark
| |
Collapse
|
32
|
Automated conduction velocity analysis in the electrohysterogram for prediction of imminent delivery: a preliminary study. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2013; 2013:627976. [PMID: 24489602 PMCID: PMC3891613 DOI: 10.1155/2013/627976] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/29/2013] [Accepted: 10/01/2013] [Indexed: 11/17/2022]
Abstract
Background. Analysis of the electrohysterogram (EHG) is a promising diagnostic tool for preterm delivery. For the introduction in the clinical practice, analysis of the EHG should be reliable and automated to guarantee reproducibility. Study Goal. Investigating the feasibility of automated analysis of the EHG conduction velocity (CV) for detecting imminent delivery. Materials and Methods. Twenty-two patients presenting with uterine contractions (7 preterm) were included. An EHG was obtained noninvasively using a 64-channel high-density electrode grid. Contractions were selected based on the estimated intrauterine pressure derived from the EHG, the tocodynamometer, and maternal perception. Within the selected contractions, the CV vector was identified in two dimensions. Results. Nine patients delivered within 24 hours and were classified as a labor group. 64 contractions were analyzed; the average amplitude of the CV vector was significantly higher for the labor group, 8.65 cm/s ± 1.90, compared to the nonlabor group, 5.30 cm/s ± 1.47 (P < 0.01). Conclusion. The amplitude of the CV is a promising parameter for predicting imminent (preterm) delivery. Automated estimation of this parameter from the EHG signal is feasible and should be regarded as an important prerequisite for future clinical studies and applications.
Collapse
|
33
|
Effect of an oxytocin receptor antagonist (atosiban) on uterine electrical activity. Am J Obstet Gynecol 2013; 209:384.e1-7. [PMID: 23727522 DOI: 10.1016/j.ajog.2013.05.053] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2013] [Revised: 05/22/2013] [Accepted: 05/29/2013] [Indexed: 11/21/2022]
Abstract
OBJECTIVE The purpose of this study was to investigate the effect of atosiban (Tractocile; Ferring, Limhamn, Sweden), an oxytocin receptor antagonist, on uterine electrical activity in women with preterm labor and to determine whether this information can assist in the prediction of preterm delivery. STUDY DESIGN Uterine electrical activity was recorded prospectively in 21 women with preterm labor before and during treatment with Tractocile and, for purpose of comparison, in 4 pregnant women without uterine contractions to set the baseline of uterine electrical activity in a quiescent uterus. Uterine activity was recorded with a noninvasive, 9-channel recorder with an electromyography amplifier and a 3-dimensional position sensor with an automatic data analyzer. Uterine electrical activity was quantified by an electrical uterine monitor (EUM) and measured in microwatts per second (μW/s). RESULTS The overall pre-Tractocile EUM index was 3.43 ± 0.58 μW/s, which was significantly higher than baseline uterine activity in women without preterm contractions (2.3 ± 0.11 μW/s; P = .001). During the administration of Tractocile, the EUM index gradually decreased in a relatively constant rate from 3.43 ± 0.58 μW/s to 2.56 ± 0.88 μW/s after 330 minutes of continuous therapy (P < .001). The peak effect of Tractocile was observed 4 hours after the initiation of treatment and was followed by a relative plateau. Women with a latency of <7 days from treatment to delivery were characterized by a distinct EUM-pattern in response to Tractocile, compared with women with a latency of ≥7 days (P < .001). A similar EUM-pattern after the administration of Tractocile was also observed for women who delivered at <37 weeks of gestation compared with the women who delivered at term. CONCLUSION Tractocile reduces uterine electrical activity in women with preterm labor. This information can provide more insight into the effects of tocolytic agents and to aid in the risk stratification of preterm delivery in women with preterm contractions.
Collapse
|
34
|
|
35
|
Abstract
In contrast to the current state of knowledge of cardiac and of gastrointestinal electrophysiology, our current knowledge of the physiology of the uterus during pregnancy is still very rudimentary. Despite seminal work performed in the past decades, there are still significant areas that we know little about. In this review, some of these areas are explored. For example, although many studies have tried to find the site of the uterus pacemaker, such a site has not yet been found and its mechanism and location remain, to date, a mystery. Similarly, there is much confusion as to the mechanism of propagation of the electrical impulse. Although the existence of gap junctions, connecting neighboring myometrial cells to each other, have been known since 1977, alternative or additional mechanisms are being suggested such as the potential existence of a network of interstitial cells, similar to the one that is functioning in the gut, or the involvement of stretch receptors to synchronize activity and contraction. In recent years, high-resolution studies have been introduced enabling detailed analysis of the location and spatial patterns of propagation. This work is being developed at the in-vitro level in isolated tissues, in the whole organ and in several animal species. Most recently, a surge in new technology enabling high fidelity and high resolution recording from the human uterus through the abdominal wall are being explored which could ultimately lead to new diagnostic tools and a clearer understanding of the physiology of pregnancies and (premature) labor.
Collapse
Affiliation(s)
- Wim J E P Lammers
- Department of Physiology, Faculty of Medicine and Health Sciences, UAE University, Al Ain, United Arab Emirates.
| |
Collapse
|
36
|
Singh R, Xu J, Garnier NG, Pumir A, Sinha S. Self-organized transition to coherent activity in disordered media. PHYSICAL REVIEW LETTERS 2012; 108:068102. [PMID: 22401124 DOI: 10.1103/physrevlett.108.068102] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Revised: 12/02/2011] [Indexed: 05/31/2023]
Abstract
Synchronized oscillations are of critical functional importance in many biological systems. We show that such oscillations can arise without centralized coordination in a disordered system of electrically coupled excitable and passive cells. Increasing the coupling strength results in waves that lead to coherent periodic activity, exhibiting cluster, local and global synchronization under different conditions. Our results may explain the self-organized transition in a pregnant uterus from transient, localized activity initially to system-wide coherent excitations just before delivery.
Collapse
Affiliation(s)
- Rajeev Singh
- The Institute of Mathematical Sciences, CIT Campus, Taramani, Chennai, India
| | | | | | | | | |
Collapse
|
37
|
Rabotti C, Bijloo R, Oei G, Mischi M. Vectorial analysis of the electrohysterogram for prediction of preterm delivery: a preliminary study. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2012; 2011:3880-3. [PMID: 22255187 DOI: 10.1109/iembs.2011.6090964] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Electrophysiological measurement of uterine contractions, referred to as electrohysterogram (EHG), is potentially more informative than methods currently used during pregnancy for timely recognition of complications such as preterm labor. Unfortunately, EHG measurement and interpretation remain challenging. Recently, some attention has been dedicated to the analysis of the EHG propagation, which is hypothetically predictive of the delivery time. This hypothesis, though physiologically reasonable, has not been investigated yet. A dedicated maximum likelihood (ML) method has been proposed and validated for identifying the conduction velocity vector of single EHG spikes. This validated ML method is here employed for comparing the conduction velocity vector in two groups of pregnant women with uterine contractions that were prospectively classified as productive or unproductive contractions. The estimated conduction velocity vector showed significant differences in the two groups. The spikes extracted from those contractions eventually classified as unproductive showed a significantly lower conduction velocity amplitude (CV = 4.89 ± 1.19 cm.s(-1) vs CV = 8.63 ± 2.92 cm.s(-1)) and a higher occurrence of upward propagation relative to productive contractions. These results suggest that productive and unproductive uterine contractions are associated to significantly different properties of the conduction velocity vector, which is likely to be proven fundamental in predicting preterm delivery.
Collapse
Affiliation(s)
- Chiara Rabotti
- Department of Electrical Engineering, Eindhoven University of Technology, Eindhoven, the
| | | | | | | |
Collapse
|
38
|
Buchner T, Pietkun J, Kuklik P. Complex activity patterns in arterial wall: results from a model of calcium dynamics. Comput Biol Med 2011; 42:267-75. [PMID: 22204868 DOI: 10.1016/j.compbiomed.2011.12.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Revised: 11/24/2011] [Accepted: 12/01/2011] [Indexed: 11/17/2022]
Abstract
Using a dynamical model of smooth muscle cells in an arterial wall, defined as a system of coupled five-dimensional nonlinear oscillators, on a grid with cylindrical symmetry, we compare the admissible activity patterns with those known from the heart tissue. We postulate on numerical basis the possibility to induce a stable spiral wave in the arterial wall. Such a spiral wave can inhibit the propagation of the axial calcium wave and effectively stop the vasomotion. We also discuss the dynamics of the circumferential calcium wave in comparison to rotors in venous ostia that are a common source of supraventricular ectopy. We show that the velocity and in consequence the frequency range of the circumferential calcium wave is by orders of magnitude too small compared to that of the rotors. The mechanism of the rotor is not likely to involve the calcium-related dynamics of the smooth muscle cells. The calcium-related dynamics which is voltage-independent and hard to be reset seems to actually protect the blood vessels against the electric activity of the atria. We also discuss the microreentry phenomenon, which was found in numerical experiments in the studied model.
Collapse
Affiliation(s)
- Teodor Buchner
- Physics of Complex Systems Division, Faculty of Physics, Warsaw University of Technology, ul Koszykowa 75, 00-662 Warsaw, Poland.
| | | | | |
Collapse
|
39
|
Rabotti C, Oei SG, van 't Hooft J, Mischi M. Electrohysterographic propagation velocity for preterm delivery prediction. Am J Obstet Gynecol 2011; 205:e9-10; author reply e10. [PMID: 21880294 DOI: 10.1016/j.ajog.2011.06.071] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Accepted: 06/21/2011] [Indexed: 10/18/2022]
|
40
|
Aslanidi O, Atia J, Benson A, van den Berg H, Blanks A, Choi C, Gilbert S, Goryanin I, Hayes-Gill B, Holden A, Li P, Norman J, Shmygol A, Simpson N, Taggart M, Tong W, Zhang H. Towards a computational reconstruction of the electrodynamics of premature and full term human labour. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2011; 107:183-92. [DOI: 10.1016/j.pbiomolbio.2011.07.004] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Accepted: 07/05/2011] [Indexed: 01/02/2023]
|
41
|
Tong WC, Choi CY, Karche S, Holden AV, Zhang H, Taggart MJ. A computational model of the ionic currents, Ca2+ dynamics and action potentials underlying contraction of isolated uterine smooth muscle. PLoS One 2011; 6:e18685. [PMID: 21559514 PMCID: PMC3084699 DOI: 10.1371/journal.pone.0018685] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Accepted: 03/15/2011] [Indexed: 11/18/2022] Open
Abstract
Uterine contractions during labor are discretely regulated by rhythmic action potentials (AP) of varying duration and form that serve to determine calcium-dependent force production. We have employed a computational biology approach to develop a fuller understanding of the complexity of excitation-contraction (E-C) coupling of uterine smooth muscle cells (USMC). Our overall aim is to establish a mathematical platform of sufficient biophysical detail to quantitatively describe known uterine E-C coupling parameters and thereby inform future empirical investigations of physiological and pathophysiological mechanisms governing normal and dysfunctional labors. From published and unpublished data we construct mathematical models for fourteen ionic currents of USMCs: currents (L- and T-type), current, an hyperpolarization-activated current, three voltage-gated currents, two -activated current, -activated current, non-specific cation current, - exchanger, - pump and background current. The magnitudes and kinetics of each current system in a spindle shaped single cell with a specified surface area∶volume ratio is described by differential equations, in terms of maximal conductances, electrochemical gradient, voltage-dependent activation/inactivation gating variables and temporal changes in intracellular computed from known fluxes. These quantifications are validated by the reconstruction of the individual experimental ionic currents obtained under voltage-clamp. Phasic contraction is modeled in relation to the time constant of changing . This integrated model is validated by its reconstruction of the different USMC AP configurations (spikes, plateau and bursts of spikes), the change from bursting to plateau type AP produced by estradiol and of simultaneous experimental recordings of spontaneous AP, and phasic force. In summary, our advanced mathematical model provides a powerful tool to investigate the physiological ionic mechanisms underlying the genesis of uterine electrical E-C coupling of labor and parturition. This will furnish the evolution of descriptive and predictive quantitative models of myometrial electrogenesis at the whole cell and tissue levels.
Collapse
Affiliation(s)
- Wing-Chiu Tong
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
- Maternal and Fetal Health Research Centre, St. Mary's Hospital, University of Manchester, Manchester, United Kingdom
| | - Cecilia Y. Choi
- School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom
| | - Sanjay Karche
- School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom
| | - Arun V. Holden
- Institute of Membrane and System Biology, University of Leeds, Leeds, United Kingdom
| | - Henggui Zhang
- School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom
- * E-mail: (HZ); (MT)
| | - Michael J. Taggart
- Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne, United Kingdom
- Maternal and Fetal Health Research Centre, St. Mary's Hospital, University of Manchester, Manchester, United Kingdom
- * E-mail: (HZ); (MT)
| |
Collapse
|
42
|
Rabotti C, Mischi M. Two-dimensional estimation of the electrohysterographic conduction velocity. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2011; 2010:4262-5. [PMID: 21096643 DOI: 10.1109/iembs.2010.5627172] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Propagation of action potentials (APs) through an adequate number of uterine muscle cells induces contraction of the uterus. Monitoring uterine contractions, as the first sign of labor, can provide important information on the course of pregnancy and delivery. Unfortunately, current monitoring methods are affected by serious limitations. The electrohysterogram (EHG), which is the noninvasive recording of the APs propagating through the uterine smooth muscle cells, is here analyzed as a potential alternative to current methods. We focus on estimating the conduction velocity (CV) of surface APs extracted from an EHG recorded in a multielectrode configuration. In this work, a two-dimensional, 64-channel, high density electrode grid is used. Maximum likelihood methods are employed for analyzing the EHG AP propagation in two dimensions. The use of different weighting strategies of the derived cost function is introduced to deal with poor interchannel signal similarity. The presented methods were evaluated by specific simulations proving the best weighting strategy to lead to an accuracy improvement of 58%. EHG measurements on women with uterine contractions confirmed the feasibility of the method by leading to values of conduction velocity within the expected physiological range.
Collapse
Affiliation(s)
- Chiara Rabotti
- Department of Electrical Engineering, Eindhoven University of technology, the Netherlands.
| | | |
Collapse
|
43
|
Barclay M, Andersen H, Simon C. Emergent behaviors in a deterministic model of the human uterus. Reprod Sci 2010; 17:948-54. [PMID: 20713971 DOI: 10.1177/1933719110376544] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The human birth process is powered by uterine contractions that have observable patterns that depend on the physiology of muscular activity. We explored a previously designed model(1) simulating the uterus to assess global contractile patterns. The model is a cellular automaton that simulates the complexities of uterine activity from a few simple rules of cellular interaction and uterine geometry. Multiple experiments using the cellular automaton involved different uterine shapes, cell numbers, and initial distributions of active and resting cells. Results demonstrate complex contraction patterns similar to those observed in human labor. At least 2 modes of behavior appear in the simulations, one consistent with effective labor and one not. Experiments with cellular automata provide insights into stereotypic and disordered labor patterns that produce patient discomfort without progress in labor. We hypothesize that complex uterine contraction patterns may have other roles in the preparation for labor and birth.
Collapse
Affiliation(s)
- Mel Barclay
- University of Michigan, Obstetrics and Gynecology, Ann Arbor, MI, USA
| | | | | |
Collapse
|
44
|
Nifedipine-induced changes in the electrohysterogram of preterm contractions: feasibility in clinical practice. Obstet Gynecol Int 2010; 2010:325635. [PMID: 20613994 PMCID: PMC2896617 DOI: 10.1155/2010/325635] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2009] [Accepted: 04/16/2010] [Indexed: 11/17/2022] Open
Abstract
Objective. Evaluating changes in the power spectral density (PSD) peak frequency of the electrohysterogram (EHG) caused by nifedipine in women with preterm contractions. Methods. Calculation of the PSD peak frequency in EHG contraction bursts at different times of nifedipine treatment in women in gestational age 24 to 32 weeks with contractions. Results. A significant (P < .05) decrease of PSD peak frequency between EHG signals measured before and 15 minutes after administration of nifedipine. A significant (P < .05) decrease in PSD peak frequency comparing signals recorded within 24 hours after administration of nifedipine to signals 1 day after tocolytic treatment. A higher average PSD peak frequency for patients delivering within 1 week than that for patients delivering after 1 week from nifedipine treatment (P > .05). Conclusions. EHG signal analysis has great potential for quantitative monitoring of uterine contractions. Treatment with nifedipine leads to a shift to lower PSD peak frequency in the EHG signal.
Collapse
|
45
|
Rabotti C, Mischi M, Oei SG, Bergmans JWM. Noninvasive estimation of the electrohysterographic action-potential conduction velocity. IEEE Trans Biomed Eng 2010; 57:2178-87. [PMID: 20460202 DOI: 10.1109/tbme.2010.2049111] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Electrophysiological monitoring of the fetal-heart and the uterine-muscle activity, referred to as an electrohysterogram, is essential to permit timely treatment during pregnancy. While remarkable progress is reported for fetal-cardiac-activity monitoring, the electrohysterographic (EHG) measurement and interpretation remain challenging. In particular, little attention has been paid to the analysis of the EHG propagation, whose characteristics might be predictive of the preterm delivery. Therefore, this paper focuses, for the first time, on the noninvasive estimation of the conduction velocity of the EHG-action potentials. To this end, multichannel EHG recording and surface high-density electrodes are used. A maximum-likelihood method is employed for analyzing the EHG-action-potential propagation in two dimensions. The use of different weighting strategies of the derived cost function is introduced to deal with the poor signal similarity between different channels. The presented methods were evaluated by specific simulations proving the best weighting strategy to lead to an accuracy improvement of 56.7%. EHG measurements on ten women with uterine contractions confirmed the feasibility of the method by leading to conduction velocity values within the expected physiological range.
Collapse
Affiliation(s)
- Chiara Rabotti
- Department of Electrical Engineering, Eindhoven University of Technology, Eindhoven 5600MB, The Netherlands.
| | | | | | | |
Collapse
|
46
|
Rabotti C, Mischi M, Beulen L, Oei G, Bergmans JWM. Modeling and identification of the electrohysterographic volume conductor by high-density electrodes. IEEE Trans Biomed Eng 2009; 57:519-27. [PMID: 19884073 DOI: 10.1109/tbme.2009.2035440] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The surface electrohysterographic (EHG) signal represents the bioelectrical activity that triggers the mechanical contraction of the uterine muscle. Previous work demonstrated the relevance of the EHG signal analysis for fetal and maternal monitoring as well as for prognosis of preterm labor. However, for the introduction in the clinical practice of diagnostic and prognostic EHG techniques, further insights are needed on the properties of the uterine electrical activation and its propagation through biological tissues. An important contribution for studying these phenomena in humans can be provided by mathematical modeling. A five-parameter analytical model of the EHG volume conductor and the cellular action potential (AP) is proposed here and tested on EHG signals recorded by a grid of 64 high-density electrodes. The model parameters are identified by a least-squares optimization method that uses a subset of electrodes. The parameters representing fat and abdominal muscle thickness are also measured by echography. The mean correlation coefficient and standard deviation of the difference between the echographic and EHG estimates were 0.94 and 1.9 mm, respectively. No bias was present. These results suggest that the model provides an accurate description of the EHG AP and the volume conductor, with promising perspectives for future applications.
Collapse
Affiliation(s)
- Chiara Rabotti
- Department of Electrical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.
| | | | | | | | | |
Collapse
|
47
|
Mitchell BF, Taggart MJ. Are animal models relevant to key aspects of human parturition? Am J Physiol Regul Integr Comp Physiol 2009; 297:R525-45. [PMID: 19515978 DOI: 10.1152/ajpregu.00153.2009] [Citation(s) in RCA: 191] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Preterm birth remains the most serious complication of pregnancy and is associated with increased rates of infant death or permanent neurodevelopmental disability. Our understanding of the regulation of parturition remains inadequate. The scientific literature, largely derived from rodent animal models, suggests two major mechanisms regulating the timing of parturition: the withdrawal of the steroid hormone progesterone and a proinflammatory response by the immune system. However, available evidence strongly suggests that parturition in the human has significantly different regulators and mediators from those in most of the animal models. Our objectives are to critically review the data and concepts that have arisen from use of animal models for parturition and to rationalize the use of a new model. Many animal models have contributed to advances in our understanding of the regulation of parturition. However, we suggest that those animals dependent on progesterone withdrawal to initiate parturition clearly have a limitation to their translation to the human. In such models, a linear sequence of events (e.g., luteolysis, progesterone withdrawal, uterine activation, parturition) gives rise to the concept of a "trigger" mechanism. Conversely, we propose that human parturition may arise from the concomitant maturation of several systems in parallel. We have termed this novel concept "modular accumulation of physiological systems" (MAPS). We also emphasize the urgency to determine the precise role of the immune system in the process of parturition in situations other than intrauterine infection. Finally, we accentuate the need to develop a nonprimate animal model whose physiology is more relevant to human parturition. We suggest that the guinea pig displays several key physiological characteristics of gestation that more closely resemble human pregnancy than do currently favored animal models. We conclude that the application of novel concepts and new models are required to advance translational research in parturition.
Collapse
Affiliation(s)
- Bryan F Mitchell
- Department of Obstetrics & Gynecology, Heritage Medical Research Centre, University of Alberta, Edmonton, Alberta, Canada.
| | | |
Collapse
|
48
|
Burdyga T, Borisova L, Burdyga AT, Wray S. Temporal and spatial variations in spontaneous Ca events and mechanical activity in pregnant rat myometrium. Eur J Obstet Gynecol Reprod Biol 2009; 144 Suppl 1:S25-32. [PMID: 19282086 DOI: 10.1016/j.ejogrb.2009.02.017] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
OBJECTIVES The aim of this study was to investigate the temporal and spatial characteristics of spontaneous Ca signals in pregnant rat myometrium. STUDY DESIGN Confocal imaging of longitudinal strips of 21-day pregnant rats loaded with the Ca sensitive indicator Fluo-4, was combined with measurements of mechanical activity in uterine smooth muscle cells, in situ and freshly isolated. RESULTS Our results show that the Ca transients in pregnant uterine tissue are composed of Ca spikes, which are associated with the spike-like action potentials. There is large variation in the pattern of spontaneous activity in myometrium, ranging from non-propagating Ca spikes confined to individual smooth muscle cells, through to regional and global propagating Ca spikes. Irrespective of the pattern of activity displayed, the Ca signals were always in the form of Ca spikes, singularly or in bursts. These Ca spikes did not show fixed initiations sites, propagated in longitudinal and transverse directions from the initiation regions, and had a variable pattern of propagation in preparations which were not synchronously active. In preparations which showed synchronous activity, Ca spikes singularly or bursts propagated mainly in the transverse direction from the initiation regions. The amplitude of force generated by single spikes was dependent on the number of bundles recruited by the propagating Ca spike within the strip, and was about 30-40% of the maximal force produced by carbachol or high-K stimulation. If Ca spikes appeared in the form of bursts they generated longer lasting fused contractions, the amplitudes of which were dependent on the number and the frequency of Ca spikes in the burst. CONCLUSIONS Longitudinal myometrium from pregnant rats generates spontaneous Ca spikes which vary in their initiation sites, spatial spread and frequency and are associated with the spike-like action potentials. They are sensitive to the L-type Ca channel blocker, nifedipine. Contractile activity was dependent on the spatial spread of individual Ca spikes and when fully synchronized, produced single submaximal phasic contraction. The number and frequency of bursts of Ca spikes controlled the amplitude and duration of contraction.
Collapse
Affiliation(s)
- Theodor Burdyga
- Department of Physiology, School of Biomedical Sciences, University of Liverpool, Crown Street, Liverpool L693BX, UK.
| | | | | | | |
Collapse
|
49
|
Most O, Langer O, Kerner R, David GB, Calderon I. Can myometrial electrical activity identify patients in preterm labor? Am J Obstet Gynecol 2008; 199:378.e1-6. [PMID: 18928979 DOI: 10.1016/j.ajog.2008.08.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2008] [Revised: 07/10/2008] [Accepted: 08/01/2008] [Indexed: 11/29/2022]
Abstract
OBJECTIVE The objective of the study was to determine whether myometrial electrical activity can differentiate false from true preterm labor. STUDY DESIGN Electrical uterine myography (EUM) was measured prospectively on 87 women, gestational age less than 35 weeks. The period between contractions, power of contraction peaks and movement of center of electrical activity (RMS), was used to develop an index score (1-5) for prediction of preterm delivery (PTD) within 14 days of the test. The score was compared with fetal fibronectin (fFN) and cervical length (CL). RESULTS Patients delivering within 14 days from testing showed a higher index and mean RMS (P = .000). No patients with EUM index scores of 1-2 delivered in this time frame. Combining EUM with CL or fFN increased predictability. Logistic regression revealed that history of PTD and EUM index had 4- to 5-fold increased risk for PTD. Gestational age at testing, body mass index, fFN, and CL were nonsignificant contributors to PTD risk. CONCLUSION Measuring myometrial electrical activity may enhance identification of patients in true premature labor.
Collapse
Affiliation(s)
- Orli Most
- Department of Obstetrics and Gynecology, New York University Medical Center, New York, NY, USA
| | | | | | | | | |
Collapse
|
50
|
Garfield RE. Is knowledge of the pattern of electrical activity in the pregnant uterus helpful to our understanding of uterine function? Focus on “Patterns of electrical propagation in the intact pregnant guinea pig uterus” by Lammers et al. Am J Physiol Regul Integr Comp Physiol 2008; 294:R917-8. [DOI: 10.1152/ajpregu.00857.2007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|