Papers by Peter Van Leeuwen
The American journal of physiology, 1999
The purpose of this study was to expand classic heart period analysis methods by techniques from ... more The purpose of this study was to expand classic heart period analysis methods by techniques from ethnomusicology that explicitly take complex musical rhythm principles into consideration. The methods used are based on the theory of African music, the theory of symbolic dynamics, and combinatorial theory. Heart period tachograms from 192 24-h electrocardiograms of 96 healthy subjects were transformed into binary symbol sequences that were interpretable as elementary rhythmic (percussive) patterns, the time lines in African music. Using a hierarchical rhythm pattern scheme closely related to the Derler Rhythm Classification (from jazz theory), we calculated the predominance and stability of pattern classes. The results show that during sleep certain classes, specific to individuals, occurred in a cyclically recurrent manner and many times more often than expected. Simultaneously, other classes disappeared more or less completely. Moreover, the most frequent classes obviously originate...
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2009
Heart rate dynamics assessed by different strategies of symbolization
2014 8th Conference of the European Study Group on Cardiovascular Oscillations (ESGCO), 2014
ABSTRACT The analysis of symbolic dynamics applied to the RR interval series is able to retrieve ... more ABSTRACT 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 symbolization of the first derivative. Each method was applied to the RR interval series and its difference of 17 healthy subjects obtained during head-up tilt testing. Dynamical properties were assessed by the occurrence of short sequences ('words') of length 3. The occurrence of words was grouped according to variations of the symbols in each word (0, 1, and 2 variations). Linear regression analysis showed that the occurrence of these words reflects changes of heart rate dynamics during graded head-up tilt. Hence, very short symbolic sequences are able to track changes of the cardiac autonomic regulation.
Proceedings of the National Academy of Sciences, 2009
Pregnant mothers often report a special awareness of and bonding with their unborn child. Little ... more 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 fetalmaternal heart rate synchronization under uncontrolled conditions with spontaneous maternal breathing. Here, we examine whether the occurrence of such epochs can be influenced by maternal respiratory arrhythmia induced by paced breathing at several different rates (10, 12, 15, and 20 cycles per minute). To test for such weak and nonstationary synchronizations among the fetal-maternal subsystems, we apply a multivariate synchronization analysis technique and test statistics based on twin surrogates. We find a clear increase in synchronization epochs mostly at high maternal respiratory rates in the original but not in the surrogate data. On the other hand, fewer epochs are found at low respiratory rates both in original and surrogate data. The results suggest that the fetal cardiac system seems to possess the capability to adjust its rate of activation in response to external-i.e., maternal-stimulation. Hence, the pregnant mothers' special awareness to the unborn child may also be reflected by fetal-maternal interaction of cardiac activity. Our approach opens up the chance to examine this interaction between independent but closely linked physiological systems.
The European Physical Journal Special Topics, 2013
The analysis of symbolic dynamics applied to physiological time series is able to retrieve inform... more 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. Yet the differences between the approaches are unknown. In this study three different transformation methods are investigated: (1) symbolization according to the deviation from the average time series, (2) symbolization according to several equidistant levels between the minimum and maximum of the time series, (3) binary symbolization of the first derivative of the time series. Furthermore, permutation entropy was used to quantify the symbolic series. Each method was applied to the cardiac interbeat interval series RR i and its difference ΔRRI of 17 healthy subjects obtained during head-up tilt testing. The symbolic dynamics of each method is analyzed by means of the occurrence of short sequences ("words") of length 3. The occurrence of words is grouped according to words without variations of the symbols (0V%), words with one variation (1V%), two like variations (2LV%) and two unlike variations (2UV%). Linear regression analysis showed that for method 1 0V%, 1V%, 2LV% and 2UV% changed with increasing tilt angle. For method 2 0V%, 2LV% and 2UV% changed with increasing tilt angle and method 3 showed changes for 0V% and 1V%. Furthermore, also the permutation entropy decreased with increasing tilt angle. In conclusion, all methods are capable of reflecting changes of the cardiac autonomic nervous system during head-up tilt. All methods show that a e-mail: [email protected]
Outcome of CT-guided vertebroplasty in outpatients with severe vertebral compression fractures
International Journal of Computer Assisted Radiology and Surgery, 2008
... vertebral compression fractures Markus Braun · Athour Gevargez · Silke Lange · Peter van Leeu... more ... vertebral compression fractures Markus Braun · Athour Gevargez · Silke Lange · Peter van Leeuwen · Dietrich HW Grönemeyer Received: 25 May 2007 / Accepted: 31 October 2007 / Published online: 29 February 2008 © CARS 2008 ...
BMC Physiology, 2002
The objective was to evaluate and to compare two completely different detection algorithms of int... more The objective was to evaluate and to compare two completely different detection algorithms of intermittent (short-term) cardiorespiratory coordination during night sleep. The first method is based on a combination of respiratory flow and electrocardiogram recordings and determines the relative phases of R waves between successive onsets of inspiration. Intermittent phase coordination is defined as phase recurrence with accuracy α over at least k heartbeats. The second, recently introduced method utilizes only binary coded variations of heart rate (acceleration = 1, deceleration = 0) and identifies binary pattern classes which can be assigned to respiratory sinus arrhythmia (RSA). It is hypothesized that RSA pattern class recurrence over at least k heartbeats is strongly related with the intermittent phase coordination defined above.
Pacing and Clinical Electrophysiology, 2008
We present a case of supraventricular tachycardia affecting one fetus in a twin pregnancy. Before... more 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 with a number of HRV measures. This case demonstrates that magnetocardiography not only enables identification of fetal arrhythmia, but also permits the investigation of the effects of antiarrhythmic treatment on the conductive system as well as on interaction with the autonomic nervous system. (PACE 2008; 31:1213-1217 fetal arrhythmia, magnetocardiography, flecainide, cardiac time intervals, heart rate variability
Biomedizinische Technik/Biomedical Engineering, 2000
Annals of Noninvasive Electrocardiology, 2005
The noninvasive detection of restenosis after percutaneous coronary intervention (PCI) remains a ... more The noninvasive detection of restenosis after percutaneous coronary intervention (PCI) remains a clinical challenge. Previous studies have shown that magnetocardiograms reveal obvious changes in patients with coronary artery disease (CAD) and normal electrocardiogram (ECG) at rest.
Nichtinvasive Lokalisation einer ventrikulären Ektopie anhand isolierter monomorpher Extrasystolen mittels Magnetokardiographie und Magnetresonanztomographie
Biomedizinische Technik, 1995
Die Magnetokardiographie - eine mögliche ergänzende Methode zur Früherkennung einer fetalen Gefährdung in Risikoschwangerschaften
Zeitschrift Fur Geburtshilfe Und Neonatologie, 2005
Fetal electrocardiographic measurements in the assessment of fetal heart rate variability in the antepartum period
Physiological Measurement, 2014
This study examines signal availability in fetal electrocardiogram (FECG) beat-to-beat acquisitio... more 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 of gestation) under uncontrolled conditions. Identification of R-peaks demonstrated a signal loss of 30% ± 24% with 3.6 ± 1.7 signal gaps per minute. Median duration of the gaps within a recording was 1.8 ± 0.2 s. Per hour of recording, 1.8 ± 2.1 episodes of 5 min of uninterrupted data were found. Signal availability improved with gestational age and was poorer in women with high body-mass index. Fetal HRV between weeks 36-42 was examined on the basis of 5 min RR-interval episodes obtained under controlled quiet conditions in 55 FECG compared to 46 high quality fetal magnetocardiograms. There were no differences in RR-interval duration, its standard deviation and low frequency power. However, various measures of short-term HRV were significantly higher in the FECG data: root mean square of successive differences (10.0 ± 1.8 versus 6.6 ± 3.0 ms, p < 0.001, high frequency spectral power (24 ± 12 versus 13 ± 13 ms(2), p < 0.001) and approximate entropy (0.86 ± 0.16 versus 0.73 ± 0.24, p = 0.007). We conclude that, in spite of considerable signal loss, FECG recordings can accurately estimate heart rate and its overall variance. However, measures that quantify short-term beat-to-beat HRV will be compromised due to possible recurring inappropriate detection of single R-peaks.
Frontiers in Physiology, 2015
Two diverse complexity metrics quantifying time irreversibility and local prediction, in connecti... more 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 orthostatic challenge. The metrics indicated the presence of two distinct types of nonlinear HP dynamics characterized by diverse ranges of time scales. These findings stress the need to render more specific the analysis of nonlinear components of HP dynamics by accounting for different temporal scales.
Die fetale Herzfrequenzvariabilität in der Magnetokardiographie (MKG) und der Cardiotokographie (CTG)
Die fetale Herzfrequenzvariation in der Magnetokardiografie und der Kardiotokografie-direkter Vergleich beider Verfahren
Circadian variations of heart rate, respiratory rate and pulse respiration ratio in routinely examined hospital patients
Die Bestimmung der Atemfrequenz aus der respiratorischen Sinusarrhythmie (RSA). Determination of Respiratory Rate on the Basis of Respiratory Sinus Arrhythmia
Biomedizinische Technik/Biomedical Engineering, 2000
Dimensional analysis of RR dynamic in 24 hour electrocardiograms
Acta Biotheoretica, 1992
Using dimensional analysis, we demonstrate that it is possible to quantify changes in the topolog... more Using dimensional analysis, we demonstrate that it is possible to quantify changes in the topological structure of cardiac dynamics over long periods of time. A method was developed to calculate a dimension-like measure (referred to here as apparent dimension) from a correlation algorithm within a data window of 500 heart beats which is moved in equidistant steps over the time series of the RR intervals over 24 hours. The correspondence between the apparent dimension and the correlation dimension was tested using artificial data sequences. Furthermore 24 hour electrocardiographic recordings of two healthy subjects and of a patient with acute myocardial infarction were examined. The reliability of the analysis could be demonstrated and changes in dimension reflecting physiological as well as pathophysiological changes were observed.
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Papers by Peter Van Leeuwen