Peter Van Leeuwen

Universität Witten/Herdecke

It has been shown that short-term direct interaction between maternal and fetal heart rates may take place and that this interaction is affected by the rate of maternal respiration. The aim of this study was to determine the effect of maternal aerobic exercise during pregnancy on the occurrence of fetal-maternal heart rate synchronization. Methods...

Magnetocardiography (MCG) has been investigated as a tool for noninvasive detection of coronary artery disease (CAD). In this study, the area ratio of positive and negative magnetic induction extracted from an extrema circle in the magnetocardiogram was analyzed at specific time points in the cardiac cycle: P maximum, R peak, J point, T onset, T pe...

This study examines signal availability in fetal electrocardiogram (FECG) beat-to-beat acquisition and the accuracy of fetal heart rate variability (HRV) analysis in the clinical setting using a commercially available FECG monitor. Signal availability was examined in 130 FECG recordings of 0.3–17.5 h duration collected in 63 fetuses (25th–42nd week...

The analysis of symbolic dynamics applied to physiological time series is able to retrieve information about dynamical properties of the underlying system that cannot be gained with standard methods like e.g. spectral analysis. Different approaches for the transformation of the original time series to the symbolic time series have been proposed. Ye...

The change in fetal heart rate and its variability (HRV) during the course of gestation has been documented by numerous studies. The overall drop in heart rate and increase in fetal HRV is associated with fetal growth in general and with the increase in neural integration in particular. The increased complexity of the demands on the cardiovascular...

The current source reconstruction and magnetic imaging is a new technique to non-invasively obtain spatial information regarding cardiac electrical activity using magnetocardiogram (MCG) signals measured by the superconducting quantum interference device (SQUID) on the human thorax surface. Using MCG signals to reconstruct distributed current sourc...

Objective: In fetal diagnosis the myriad and diversity of heart rate variability (HRV) indices prevents a comparable routine evaluation of disturbances in fetal development and well-being. The work aims at the extraction of a small set of HRV key indices that could help to establish a universal, overarching tool to screen for any disturbance. App...

Objective: In fetal diagnosis the myriad and diversity of heart rate variability (HRV) indices prevents a comparable routine evaluation of disturbances in fetal development and well-being. The work aims at the extraction of a small set of HRV key indices that could help to establish a universal, overarching tool to screen for any disturbance. A...

We present a new approach of integrated maximum current density (IMCD) for the noninvasive detection of myocardial infarction (MI) using magnetocardiography (MCG) data acquired from a superconducting quantum interference device (SQUID) system. In this study, we investigated the relationship of the maximum current density (MCD) in the current densit...

Introduction: Fetal heart rate and its variability during the course of gestation have been extensively researched. The overall reduction in heart rate and increase in fetal HRV is associated with fetal growth and the increase in neural integration. The increased complexity of the demands on the cardiovascular system leads to more variation in the...

Basierend auf universellen Reifungsprinzipien stellten wir den Reifungsscore fABAS vor, der Parameter der Schlag-zu-Schlag-Herzfrequenzvariabilitat (fHRV) in der 30-minutigen fetalen Magnetokardiografie (fMKG) integriert und das Reifealter (MA) der autonomen Funktion reprasentiert (Hoyer, PlosOne, 2013). Hier soll nun gepruft werden, inwieweit der...

With the objective of evaluating the functional maturation age and developmental disturbances we have previously introduced the fetal autonomic brain age score (fABAS) using 30 min fetal magnetocardiographic recordings (fMCG, Jena). The score is based on heart rate pattern indices that are related to universal principles of developmental biology. T...

A fast greedy sparse (FGS) method of cardiac equivalent current sources reconstruction is developed for non-invasive detection and quantitative analysis of individual left ventricular torsion. The cardiac magnetic field inverse problem is solved based on a distributed source model. The analysis of real 61-channel magnetocardiogram (MCG) data demons...

We present a multiple time windows beamformer (MTWB) method of solving the inverse problem of magnetic field and non-invasively imaging the cardiac electrical excitation conduction using the magnetocardiac signals acquired by a 61-channel superconducting quantum interference device (SQUID). The MTWB constructs spatial filters for each location in s...

Cardiac current source reconstruction is investigated by a fast greedy sparse (FGS) method applied to simulated and real magnetocardiography (MCG) data measured using 61-channel superconducting quantum interference device. The approach reduces the size of the lead field matrix based on a priori knowledge of dipolar magnetic field map. Consequently,...

Traditional measures of heart rate variability (HRV) in the time or frequency domain (e.g. standard deviation of normal-to-normal intervals, SDNN, or the high frequency component of spectral analysis, HF) may be used to track vagal and sympathetic modulation directed to the sinus node. In this study, we assess the ability of symbolic analysis to mo...

Two diverse complexity metrics quantifying time irreversibility and local prediction, in connection with a surrogate data approach, were utilized to detect nonlinear dynamics in short heart period (HP) variability series recorded in fetuses, as a function of the gestational period, and in healthy humans, as a function of the magnitude of the orthos...

The analysis of symbolic dynamics applied to physiological time series retrieves dynamical properties of the underlying regulation which are robust against the symbolic transformation. In this study, three different transformations to produce a symbolic series were applied to fetal RR interval series to test whether they reflect individual changes...

In 51 healthy fetuses at term, we calculated fetal heart rate variability (HRV) obtained using a fetal ECG monitor which automatically determined RR interval durations. We compared the values of various HRV measures from different domains to those obtained from high quality fetal magnetocardiographic acquisitions in a similar subject group. The com...

The analysis of symbolic dynamics applied to the RR interval series is able to retrieve information about dynamical properties. Three different strategies of symbolic transformations were investigated: (1) symbolization based on the deviation from the average, (2) symbolization based on equidistant levels between the minimum and maximum, (3) binary...

Fetal heart rate and its variability (HRV) changes with gestational age reflecting fetal growth and the increase of neural integration. The individual gestational development is consistently reflected by the amount of irregularity of fetal HRV. We investigated binary symbolic dynamics of fetal heart rate with respect to individual changes during ge...

On large time scales the heart rate dynamics of healthy subjects is more complex than in patients with congestive heart failure (CHF). On a beat-to-beat basis reflecting acceleration and deceleration of heart rate the healthy heart rate dynamics can also be regular whereas CHF patients show less regularity. In this study, we investigated the impact...

The analysis of symbolic dynamics applied to physiological time series is able to retrieve information about dynamical properties of the underlying system that cannot be gained with standard methods like e.g. spectral analysis. Different approaches for the transformation of the original time series to the symbolic time series have been proposed. Ye...

Symbolic dynamics derived from heart rate variability (HRV) is able to reflect changes of cardiac autonomic modulations in healthy subjects. It has been shown that linear measures of HRV in children and adolescents monotonically increase or decrease (depending on the measure) with age whereas non-linear measures show a local extreme value at the ag...

It has been shown in a number of studies that the orientation of cardiac magnetic field maps (MFM) is affected by pathological changes resulting from coronary artery disease (CAD). Aim of this work was to examine whether specific biometric or cardiovascular parameters confound MFM orientation. We studied 102 patients who had suffered acute ST eleva...

At the end of pregnancy, fetal behavioral states can be determined by examining the fetal heart rate patterns alone. However, drawing conclusions on fetal heart rate variability (HRV) in different states which have themselves been determined on the basis of heart rate patterns may be self-predictive. In order to better understand the relationship b...

Pathological changes in cardiac electrophysiology have been investigated in coronary artery disease using magnetocardiography. Aim of this work was to examine the structure of cardiac magnetic field maps (MFM) during ventricular depolarization and repolarization in patients with acute ST elevation myocardial infarction (STEMI). Magnetocardiograms w...

The multiscale analysis of physiologic time series such as the RR interval time series has revealed that the entropy differs according to the scale. Furthermore, healthy subjects show different characteristics on the different time scales compared to patients. Instead of calculating entropies of the time series, the sequence of acceleration and dec...

Fetal breathing movements are associated with respiratory sinus arrhythmia (RSA). We present an algorithm which processes RR interval time series in the time and frequency domain, identifying spectral peaks with characteristics consistent with fetal RSA. Tested on 50 data sets from the second and third trimester, the algorithm had a sensitivity of...

The fluctuations of the cardiac interbeat series contain rich information because they reflect variations of other functions on different time scales (e.g., respiration or blood pressure control). Nonlinear measures such as complexity and fractal scaling properties derived from 24 h heart rate dynamics of healthy subjects vary from childhood to old...

Symbolic dynamics derived from heart rate variability (HRV) is able to reflect changes of cardiac autonomic modulations on short time scales in spite of the considerable reduction of information involved. However, the link between the appearance of specific symbolic patterns and the activity of the autonomic nervous system has not yet been elucidat...

The Myocardial Infarction Network Essen was initiated in order to establish a standardized procedure with immediate reopening of the infarcted vessel for patients with ST-elevation myocardial infarction (STEMI) in the city of Essen, Germany. The present study aims to evaluate gender-related differences in presentation of disease and clinical outcom...

The neurochemical environment of nontumorous white matter tissue was investigated in 135 single voxel spectra of "healthy" white matter regions of 43 tumor patients and 129 spectra of 52 healthy subjects. Spectra were acquired with short TE and TR values. With the data of tumor patients, it was examined whether differences were caused by the tumor...

Magnetic field map (MFM) orientation has been successfully applied in a number of studies investigating patients with coronary artery disease. In these patients, the degree of deviation of MFM orientation from normal values is dependent of the severity of the disease. In this work we examine MFM orientation in a large sample of patients who had jus...

Fetal development is associated with the emergence of fetal movements (FM). Gross FM involve the limbs and/or the trunk and are accompanied by changes in heart rate and heart rate variability (HRV). To detect such FM, we developed a semi-automatic technique which analyzes changes in signal morphology of multichannel fetal magnetocardiogram (FMCG) s...

Electrophysiological changes occurring in the context of coronary artery disease (CAD) have been investigated using magnetocardiography. Various approaches have been developed and studied which quantify different aspects of the magnetic signals and reconstructed magnetic field maps (MFM). In this work, we compare the coherence of MFM by determining...

Fetal development is associated with the emergence of fetal movements (FM). Gross FM involve the limbs and/or the trunk and are accompanied by changes in heart rate and heart rate variability (HRV). To detect such FM, we developed a semi-automatic technique which analyzes changes in signal morphology of multichannel fetal magnetocardiogram (FMCG) s...

Electrophysiological changes occurring in the context of coronary artery disease (CAD) have been investigated using magnetocardiography. Various approaches have been developed and studied which quantify different aspects of the magnetic signals and reconstructed magnetic field maps (MFM). In this work, we compare the coherence of MFM by determining...

Fetal heart rate and its variability (HRV) reflect not only fetal development and behavioral state but may also be indicative of fetal stress. Particularly toward the end of pregnancy, contractions of the uterus can influence fetal heart rate and HRV. Conventionally, fetal heart rate and uterine contractions are measured and observed using cardioto...

Magnetocardiography has been applied to investigate pathological electrophysiological changes in the context of coronary artery disease (CAD). Various approaches have been developed and studied which quantify different aspects of the magnetic signals and reconstructed magnetic field maps (MFM). In this work, we compare the coherence of MFM in vario...

There is evidence that, during pregnancy, fetal and maternal cardiac activity may coordinate over short periods of time. Aim of this work was to investigate whether controlled paced maternal respiration has an effect on the occurrence of fetal-maternal heart rate synchronization. In 6 healthy pregnant women (34th - 40th week of gestation) we obtain...

The influence of maternal respiration on the occurrence of short-term fetal-maternal heart-rate coordination was examined using a model, which considers both heart-rate characteristics and effects of maternal respiratory sinus arrhythmia. Epochs of fetal-maternal heart-rate coordination were identified in model data produced at varying respiratory...

Pregnant mothers often report a special awareness of and bonding with their unborn child. Little is known about this relationship although it may offer potential for the assessment of the fetal condition. Recently we found evidence of short epochs of fetal-maternal heart rate synchronization under uncontrolled conditions with spontaneous maternal b...

The investigation of foetal reaction to internal and external conditions and stimuli is an important tool in the characterization of the developing neural integration of the foetus. An interesting example of this is the study of the interrelationship between the foetal and the maternal heart rate. Recent studies have shown a certain likelihood of o...

Fetal magnetocardiography (fMCG) has been shown to augment fetal ultrasound evaluation for high-risk conditions, but the clinical utility of fMCG depends on the reliability of the cardiac traces reconstructed. We performed a methodological study to examine the influence of gestational age on the properties of the fetal magnetocardiograms extracted...

The initiation of fetal breathing movements in the second trimester of pregnancy is a sign of maturation and development. Fetal magnetocardiography permits the deter-mination of high resolution fetal heart period time series. We have developed a procedure which exploits the effect of respi-ratory sinus arrhythmia (RSA) on such time series and permi...

Recently, we developed a method for the automatic detection of gross fetal movements using multichannel fetal magnetocardiogram (FMCG) signals. This approach exploits the changes in fetal QRS morphology in specific channels when the fetal heart changes its position relative to those channels. Aim of this work was to assess this approach in a group...

Magnetocardiography and M-mode fetal echocardiography are non-invasive techniques capable of identifying fetal arrhythmias. The STAN-fetal scalp electrode system can record the fetal echocardiogram in labor. A patient was admitted to hospital with preterm contractions and cervical insufficiency at 28 weeks of gestation. After treatment with a beta-...

We present a case of supraventricular tachycardia affecting one fetus in a twin pregnancy. Before and after treatment with flecainide and cardioversion, we examined conduction times and heart rate variability (HRV) in both twins on the basis of magnetocardiography. Cardiac conduction times increased in both fetuses but HRV showed opposing effects w...

Fetal behavioural states have been defined on the basis of eye movements, body movements and heart rate patterns as presented by cardiotocography (CTG). The aim of this work was to determine whether behavioural states can be distinguished on the basis of heart rate features alone using high resolution beat-to-beat fetal magnetocardiography. Five mi...

We exploit time reversibility analysis, checking the invariance of statistical features of a series after time reversal, to detect temporal asymmetries of short-term heart period variability series. Reversibility indexes were extracted from 22 healthy fetuses between 16th to 40th wk of gestation and from 17 healthy humans (aged 21 to 54, median=28)...

We compared the stability and discriminatory power of different methods of determining cardiac magnetic field map (MFM) orientation within the context of coronary artery disease (CAD). In 27 healthy subjects and 24 CAD patients, multichannel magnetocardiograms were registered at rest. MFM orientation was determined during QT interval using: (a) loc...

Object To determine the safety and efficacy of computed tomography (CT)/fluoroscopy-guided percutaneous vertebroplasty (PVP) for the treatment of painful severe osteoporotic compression fractures. Materials and methods In 26 patients with osteoporotic severe and non-severe compression fractures experiencing pain, 55 PVP were performed. Pain relief...

First-order planar SQUID gradiometers were used to construct the fetal magnetocardiography (fMCG) system. Planar SQUID gradiometers were fabricated on the basis of the Nb/Al-O/Nb technology developed at IPHT Jena. Two gradiometer pickup loops with dimensions of 2 cm x 2 cm and a baseline of 4 cm were integrated on chip. The intrinsic noise correspo...

Multichannel biomagnetometers allow the acquisition of signals from various sources of physiological electric activity. In this work, we examined magnetic signals simultaneously registered in a pregnant woman originating from the maternal abdomen (magnetomyography MMG) as well as from the fetal heart (fetal magnetocardiography FMCG). Using a 61 cha...

Heart rate variability (HRV) is becoming increasingly important in the analysis of prepartal cardiotocography (CTG). Dawes and Redmann have developed a computer algorithm which can calculate short-term variability on the basis of CTG data. In dealing with artefacts, CTG monitors average heart rate values over several beats which makes the use of st...

Hintergrund: Die Herzfrequenzvariation gewinnt eine zunehmende Bedeutung in der Analyse antepartualer Kardiotokografien (CTG). Dawes und Redman haben einen Computeralgorithmus entwickelt, der eine Kurzzeitvariabilität aus den vom CTG-Gerät aufgezeichneten Daten errechnet. Die CTG-Geräte mitteln die Herzfrequenzwerte über mehrere Herzschläge, um die...

Aim of this work was to compare the efficacy of correlation-based template matching and independent component analysis (ICA) in the separation and identification of the cardiac signals of a mother with her triplet fetuses, recorded simultaneously in magnetocardiographic acquisitions. In 61-channel recordings obtained between the 20 th and 32 nd wee...

Automated techniques were developed for the measurement of cardiac repolarisation using magnetocardiography. This was achieved by collaboration with the Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany and the Grönemeyer Institute of Microtherapy, Bochum, Germany, to obtain recordings of magnetocardiograms (MCGs) in cardiac patients and...

We investigated the viability of a 2-channel low temperature biomagnetometer system implementing 2nd order gradiometers in an unshielded environment. We examined 2 fetuses (30th, 38th week of gestation) in and outside a shielded room as well as 3 (weeks 32, 36, 37) in the unshielded environment of an obstetrics department. Reference fetal magnetoca...

We report our recent work to set up a multi-channel high temperature superconducting (HTS) radio-frequency (rf) SQUID gradiometer and to perform adult and fetal magnetocardiography (MCG). We have compared the adult MCG measurement results using a magnetometer and different gradiometers in a standard magnetically shielded room. The special requireme...

The aim of this work was to compare three methods of determining cardiac magnetic field map orientation in the diagnosis of coronary artery disease (CAD). In 27 healthy subjects and 13 CAD patients, magnetocardiograms were registered at rest using a 61-channel biomagnetometer. Orientation was determined during QT interval using: 1) locations of cen...

An important clinical application of fetal magnetocardiography (FMCG) is the identification and classification of fetal arrhythmias. However, separation of fetal and maternal signals can be challenging due to cardiac conduction disturbances and changes in signal morphology. In twin pregnancy, the presence of an additional cardiac signal further com...

Magnetocardiography enables the precise determination of fetal cardiac time intervals (CTI) from approximately the 18th week to term. It has been shown that in healthy singleton pregnancies fetal development and growth is reflected in the changes in CTI and in fetuses with growth retardation, in particular fetal cardiac conduction times are shorten...

Ischemic heart disease (IHD) is still the leading cause of death in adults worldwide. MCG has the potential to analyze spatial and temporal aspects of cardiac electrogenesis in the context of IHD. This work gives an overview of recent developments in this field. In 3 studies, the group around Steinberg, Park and Tolstrup evaluated 49264 and 127 IHD...

An elevated arterial pressure with left ventricular hypertrophy (LVH) is one of the major causes of global mortality. The present study aimed to analyze the value of MCG in the detection of LVH in patients with and without coronary artery disease (CAD). The study included 212 subjects: 109 CAD patients (81 male, 61.6 ± 10 years), 24 with LVH and 10...

Fetal heart rate complexity was examined on the basis of RR interval time series obtained in the second and third trimester of pregnancy. In each fetal RR interval time series, short term beat-to-beat heart rate changes were coded in 8 bit binary sequences. Redundancies of the 2(8) different binary patterns were reduced by two different procedures....

Introduction Historical BackgroundElectrophysiologyForward Solutions IntroductionSingle Current Dipole in an Infinite Homogeneous Conductive MediumCurrent Dipole in a Realistic TorsoExtended Source ModelsSummaryInverse Solutions IntroductionModel Data Using the Current Dipole as Source ModelModel Data Using Distributed Sources as Source Model: Imag...

In fetal surveillance, fetal heart rate changes are assessed using cardiotocography (CTG). Standard procedures used in the quantification of heart rate variability (HRV) are seldom applied as CTG does not deliver beat interval durations with the same accuracy as the electrocardiogram (ECG). Thus little is known about the interdependency of standard...