Dissertations / Theses on the topic 'Electrocardiography'
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1
Namprempre, Chanathip. "Electrocardiography in DICOM." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/42751.
Abstract:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (p. 69).
by Chanathip Namprempre.
M.Eng.
2
Lopez, Rincon Alejandro. "Le problème inverse en l'électrocardiographie." Thesis, Bordeaux 1, 2013. http://www.theses.fr/2013BOR15261/document.
Abstract:
Dans le problème inverse d’électrocardiographie, le cible est faire la reconstruction de l’activité électrophysiologique dans le cœur sans mesurer directement dans sa surface (sans interventions avec cathéter). Il est important remarque que en l’actualité la solution numérique du problème inverse est résolu avec le modèle quasi-statique. Ce modèle ne considère pas la dynamique du cœur et peut produire des erreurs dans la reconstruction de la solution sur la surface du cœur. Dans cette thèse, différents méthodologies était investigue pour résoudre le problème inverse d’électrocardiographie comme intelligence artificielle, et modèles dynamiques limites. Aussi, les effets de différents opérateurs en utilisant méthodes d’éléments de frontière , et méthodes d’élément finis était investigueIn the inverse problem of electrocardiography, the target is to make the reconstruction of electrophysiological activity in the heart without measuring directly in its surface (without interventions with catheter). It is important to note that the current numerical solution of the inverse problem is solved with the quasi-static model. This model does not consider the dynamics of the heart and can cause errors in the reconstruction of the solution on the surface of the heart. This thesis investigates different methodologies was to solve the inverse problem of electrocardiography as artificial intelligence and dynamic models limits. Also, the effects of different operators using boundary element methods, finite element methods, and was investigates
3
Rusnak, I. T. "Differentiated electrocardiography to improve diagnostics." Thesis, БДМУ, 2017. http://dspace.bsmu.edu.ua:8080/xmlui/handle/123456789/17086.
4
Fox, Alice J. Sophia Women's & Children's Health Faculty of Medicine UNSW. "Non-invasive procedure for fetal electrocardiography." Awarded by:University of New South Wales. Women's & Children's Health, 2007. http://handle.unsw.edu.au/1959.4/41240.
Abstract:
Antenatal fetal surveillance is a field of increasing importance in modern obstetrics. Measurements extracted (such as fetal heart rate) from antenatal fetal monitoring techniques have the potential to reduce the social, personal and financial burdens of fetal death on families, health care systems and the community. Techniques to monitor the fetus through pregnancy have been developed with the aim of providing information to enable the clinician to diagnose fetal wellbeing, characterise development and detect abnormality. An early diagnosis before delivery may increase the effectiveness of the appropriate treatment. Over the years, various research efforts have been carried out in the field of fetal electrocardiography by attaching surface electrodes to the maternal body. Unfortunately the desired fetal heartbeat signals at the electrode output are buried in an additive mixture of undesired interference disturbances. In this thesis, a non-invasive fetal electrocardiogram machine has been designed, constructed and implemented. This machine is composed of three modified electrocardiogram circuits and an external soundcard. Data was acquired from four surface electrodes placed on the maternal body. Eleven pregnant subjects, with a gestation age between the 30th and 40th weeks of pregnancy, were used to investigate the validity of this machine. Fetal R-waves were detected in 72.7 percent of subjects. The development of a non-invasive machine, capable of detecting and recording valuable anatomic and electrophysiological information of a fetus, represents an important tool in clinical and investigative obstetrics.
5
Howell, Stephen John Lamb. "Simultaneous ambulatory cassette electroencephalography and electrocardiography." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316986.
6
Farina, Dmytro. "Forward and inverse problems of electrocardiography clinical investigation." Karlsruhe : Univ.-Verl. Karlsruhe, 2008. http://d-nb.info/988009609/34.
7
Crowcombe, James Edward. "Larval zebrafish electrocardiography electrodynmaic modelling and sensor design." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7545/.
Abstract:
This thesis presents the first model of the electrical activity of the larval zebrafish heart as well as the design and fabrication of novel electrode arrays that were created to measure the electrocardiogram. The model consists of realistic 3D geometry of a 3 day’s post fertilisation zebrafish heart and body with a bidomain electrical model that uses the Fitzhugh-Nagumo equations as the ionic model. The model is able to replicate experimentally observed conduction velocities and action potentials by using region specific parameters and simulate electrocardiograms that are comparable to measurements. The electrode arrays are constructed from flexible polyimide films with gold microelectrodes. These devices have the potential to improve the measurement of the electrocardiogram for drug screening applications as an alternative to the use of micropipette electrodes. Gold plating and PEDOT:PSS coating techniques were applied to the devices to successfully reduce electrode impedance with the effectiveness of each technique categorised using impedance spectroscopy. The devices were tested in vivo with larval zebrafish with limited success and so in vitro tests were conducted using an artificial current source.
8
Mukalaf, A. "Adaptive cancellation techniques for noise reduction in electrocardiography." Thesis, Keele University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380184.
9
Gao, George Qi. "Computerised detection and classification of five cardiac conditions thesis submitted in partial fulfilment of the degree of Master of Engineering, Auckland University of Technology, May 2003." Full thesis. Abstract, 2003.
10
DeLong, David James. "Spectral analysis of heart rate variability : acquisition/analysis software development /." Online version of thesis, 1992. http://hdl.handle.net/1850/10858.
11
Li, Yelei. "Heartbeat detection, classification and coupling analysis using Electrocardiography data." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1405084050.
12
Aydin, Umit. "Solution Of Inverse Problem Of Electrocardiography Using State Space Models." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12611027/index.pdf.
Abstract:
Heart is a vital organ that pumps blood to whole body. Synchronous contraction of the heart muscles assures that the required blood flow is supplied to organs. But sometimes the synchrony between those muscles is distorted, which results in reduced cardiac output that might lead to severe diseases, and even death. The most common of heart diseases are myocardial infarction and arrhythmias. The contraction of heart muscles is controlled by the electrical activity of the heart, therefore determination of that electrical activity could give us the information regarding the severeness and type of the disease. In order to diagnose heart diseases, classical 12 lead electrocardiogram (ECG) is the standard clinical tool. Although many cardiac diseases could be diagnosed with the 12 lead ECG, measurements from sparse electrode locations limit the interpretations. The main objective of this thesis is to determine the cardiac electrical activity from dense body surface measurements. This problem is called the inverse problem of electrocardiography. The high resolution maps of epicardial potentials could supply the physician the information that could not be obtained with any other method. But the calculation of those epicardial potentials are not easythe problem is severely ill-posed due to the discretization and attenuation within the thorax. To overcome this ill-posedness, the solution should be constrained using prior information on the epicardial potential distributions. In this thesis, spatial and spatio-temporal Bayesian maximum a posteriori estimation (MAP), Tikhonov regularization and Kalman filter and Kalman smoother approaches are used to overcome the ill-posedness that is associated with the inverse problem of ECG. As part of the Kalman filter approach, the state transition matrix (STM) that determines the evolution of epicardial potentials over time is also estimated, both from the true epicardial potentials and previous estimates of the epicardial potentials. An activation time based approach was developed to overcome the computational complexity of the STM estimation problem. Another objective of this thesis is to study the effects of geometric errors to the solutions, and modify the inverse solution algorithms to minimize these effects. Geometric errors are simulated by changing the size and the location of the heart in the mathematical torso model. These errors are modeled as additive Gaussian noise in the inverse problem formulation. Residual-based and expectation maximization methods are implemented to estimate the measurement and process noise variances, as well as the geometric noise.
13
Bircan, Ali. "Solution Of Inverse Electrocardiography Problem Using Minimum Relative Entropy Method." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612574/index.pdf.
Abstract:
The interpretation of heart's electrical activity is very important in clinical medicine since contraction of cardiac muscles is initiated by the electrical activity of the heart. The electrocardiogram (ECG) is a diagnostic tool that measures and records the electrical activity of the heart. The conventional 12 lead ECG is a clinical tool that provides information about the heart status. However, it has limited information about functionality of heart due to limited number of recordings. A better alternative approach for understanding cardiac electrical activity is the incorporation of body surface potential measurements with torso geometry and the estimation of the equivalent cardiac sources. The problem of the estimating the cardiac sources from the torso potentials and the body geometry is called the inverse problem of electrocardiography. The aim of this thesis is reconstructing accurate high resolution maps of epicardial potential representing the electrical activity of the heart from the body surface measurements. However, accurate estimation of the epicardial potentials is not an easy problem due to ill-posed nature of the inverse problem. In this thesis, the linear inverse ECG problem is solved using different optimization techniques such as Conic Quadratic Programming, multiple constrained convex optimization, Linearly Constrained Tikhonov Regularization and Minimum Relative Entropy (MRE) method. The prior information used in MRE method is the lower and upper bounds of epicardial potentials and a prior expected value of epicardial potentials. The results are compared with Tikhonov Regularization and with the true potentials.
14
Perumalla, Calvin A. "Machine Learning and Adaptive Signal Processing Methods for Electrocardiography Applications." Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6926.
Abstract:
This dissertation is directed towards improving the state of art cardiac monitoring methods and automatic diagnosis of cardiac anomalies through modern engineering approaches such as adaptive signal processing, and machine learning methods. The dissertation will describe the invention and associated methods of a cardiac rhythm monitor dubbed the Integrated Vectorcardiogram (iVCG). In addition, novel machine learning approaches are discussed to improve diagnoses and prediction accuracy of cardiac diseases.
It is estimated that around 17 million people in the world die from cardiac related events each year. It has also been shown that many of such deaths can be averted with long-term continuous monitoring and actuation. Hence, there is a growing need for better cardiac monitoring solutions. Leveraging the improvements in computational power, communication bandwidth, energy efficiency and electronic chip size in recent years, the Integrated Vectorcardiogram (iVCG) was invented as an answer to this problem. The iVCG is a miniaturized, integrated version of the Vectorcardiogram that was invented in the 1930s. The Vectorcardiogram provides full diagnostic quality cardiac information equivalent to that of the gold standard, 12-lead ECG, which is restricted to in-office use due to its bulky, obtrusive form. With the iVCG, it is possible to provide continuous, long-term, full diagnostic quality information, while being portable and unobtrusive to the patient. Moreover, it is possible to leverage this ‘Big Data’ and create machine learning algorithms to deliver better patient outcomes in the form of patient specific machine diagnosis and timely alerts.
First, we present a proof-of-concept investigation for a miniaturized vectorcardiogram, the iVCG system for ambulatory on-body applications that continuously monitors the electrical activity of the heart in three dimensions. We investigate the minimum distance between a pair of leads in the X, Y and Z axes such that the signals are distinguishable from the noise. The target dimensions for our prototype iVCG are 3x3x2 cm and based on our experimental results we show that it is possible to achieve these dimensions.
Following this, we present a solution to the problem of transforming the three VCG component signals to the familiar 12-lead ECG for the convenience of cardiologists. The least squares (LS) method is employed on the VCG signals and the reference (training) 12-lead ECG to obtain a 12x3 transformation matrix to generate the real-time ECG signals from the VCG signals.
The iVCG is portable and worn on the chest of the patient and although a physician or trained technician will initially install it in the appropriate position, it is prone to subsequent rotation and displacement errors introduced by the patient placement of the device. We characterize these errors and present a software solution to correct the effect of the errors on the iVCG signals.
We also describe the design of machine learning methods to improve automatic diagnosis and prediction of various heart conditions. Methods very similar to the ones described in this dissertation can be used on the long term, full diagnostic quality ‘Big Data’ such that the iVCG will be able to provide further insights into the health of patients.
The iVCG system is potentially breakthrough and disruptive technology allowing long term and continuous remote monitoring of patient’s electrical heart activity. The implications are profound and include 1) providing a less expensive device compared to the 12-lead ECG system (the “gold standard”); 2) providing continuous, remote tele-monitoring of patients; 3) the replacement of current Holter shortterm monitoring system; 4) Improved and economic ICU cardiac monitoring; 5) The ability for patients to be sent home earlier from a hospital since physicians will have continuous remote monitoring of the patients.
15
MacNeil, Toinette. "An LP approach to solving the inverse problem of electrocardiography." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0021/MQ57220.pdf.
16
Guldenring, Daniel. "Theory and applications of linear lead transformations in computerised electrocardiography." Thesis, Ulster University, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.665848.
17
Hilal, Mohammed Azeez. "Domain decomposition like methods for solving an electrocardiography inverse problem." Thesis, Nantes, 2016. http://www.theses.fr/2016NANT4060.
Abstract:
L’objectif de cette thèse est d’étudier un problème électrocardiographique (ECG), modélisant l’activité électrique cardiaque en utilisant un modèle bidomaine stationnaire. Deux types de modélisation sont considérées : la modélisation basée sur un modèle mathématique directe et la modélisation basée sur un problème inverse de Cauchy. Dans le premier cas, le problème directe est résolu en utilisant la méthode de décomposition de domaine et l’approximation par la méthode des éléments finis. Dans le deuxième cas le problème inverse de Cauchy de l’ECG a été reformulé en un problème de point fixe. Puis, un résultat d’existence et l’unicité du point fixe basé sur les degrés topologique de Leray-Schauder a été démontré. Ensuite, quelques algorithmes itératifs régularisant et stables basés sur les techniques de décomposition de domaine ont été développés. Enfin, l’efficacité et la précision des résultats obtenus a été discutésThe aim of the this thesis is to study an electrocardiography (ECG) problem, modeling the cardiac electrical activity by using the stationary bidomain model. Tow types of modeling are considered :The modeling based on direct mathematical model and the modeling based on an inverse Cauchy problem. In the first case, the direct problem is solved by using domain decomposition methods and the approximation by finite elements method. For the inverse Cauchy problem of ECG, it was reformulated into a fixed point problem. In the second case, the existence and uniqueness of fixed point based on the topological degree of Leray-Schauder is showed. Then, some regularizing and stable iterative algorithms based on the techniques of domain decomposition method was developed. Finally, the efficiency and the accurate of the obtained results was discussed
18
Tie, Hii Hui Clinical School St Vincents UNSW. "Cellular mechanisms of QT prolongation and proarrhythmia induced by non-antiarrhythmic drugs." Awarded by:University of New South Wales. Clinical School - St. Vincents, 2002. http://handle.unsw.edu.au/1959.4/19035.
Abstract:
A variety of drugs prolong cardiac repolarization (manifested as QT prolongation on ECG), although the major example are the so-called class III antiarrhythmics. However, antiarrhythmic drugs which prolong cardiac repolarization are not harmless, as they may also be proarrhythmic, inducing a potentially fatal arrhythmia known as torsade de pointes (TdP). Recently, it has become apparent that a wide variety of non-antiarrhythmic agents may also, as an entirely undesired side-effect, provoke TdP. TdP is also characteristic of the congenital long QT syndrome, one form of which is caused by mutations in the HERG gene which encodes the major repolarizing potassium channel, IKr. Furthermore, HERG appears to be the main molecular target for drugs which cause QT prolongation. This thesis investigates the cellular mechanism for QT prolongation, proarrhythmia and sudden death associated with several commonly prescribed non-antiarrhythmic drugs. Specifically, we studied the effects of an antimalarial agent, halofantrine, and five psychoactive agents, thioridazine, chlorpromazine, clozapine, amitriptyline and mianserin on the HERG channel. A better understanding of the way these drugs interact with HERG could facilitate the development of safer drugs. We used the whole-cell voltage clamp technique to study currents produced by stable transfection of HERG into Chinese hamster ovary cells (CHO-K1). Our HERG-transfected cells possessed a potassium channel with biophysical properties similar to HERG-transfected cells previously reported (e.g. Xenopus oocytes, human embryonic kidney cells 293) and also to human IKr. HERG currents were potently inhibited by E-4031, a defining pharmacological signature of IKr. Therefore, these cells provide an appropriate model for the study of this important current in isolation. Halofantrine is a widely used antimalarial agent which has been associated with QT prolongation, TdP and sudden death. Halofantrine blocked HERG tail currents potently with an IC50 of 196.9 nM. Channel inhibition was time-, voltage- and use-dependent. Halofantrine did not alter channel activation or deactivation kinetics but inactivation was accelerated and there was a 20 mV hyperpolarizing shift in the mid-activation potential of steady state inactivation. Block increased with increasing depolarizing pulse duration and was enhanced by pulses that render channels inactivated. This is the first report of HERG channel blockade by halofantrine and is the likely cellular mechanism for its proarrhythmic potential. Our data indicate preferential binding of halofantrine to the open and inactivated channel states. Cardiovascular mortality in psychiatric patients is high. Reports of sudden unexplained death in those taking antipsychotic drugs have raised concerns that part of this excess may be due to drug-induced arrhythmias. We found that thioridazine and chlorpromazine blocked HERG channels (IC50 1.07 ????M and 1.47????M respectively) at clinically relevant concentrations and this is likely the cellular mechanism for their ability to prolong QT interval and induce TdP. To date, HERG block by chlorpromazine has not been reported and the state dependence of channel blockade by these phenothiazines has not been studied. Our results indicate that both drugs preferentially bind to closed HERG channels on the basis that block was not time-, voltage- or use-dependent, did not alter channel activation or deactivation kinetics and was unaffected by the depolarizing pulse duration. Clozapine is the prototype of the newer atypical antipsychotic drugs and is more efficacious and better tolerated than the traditional agents. Serious cardiotoxicity have occurred in clozapine-treated patients including sudden death. We found that clozapine produced a tonic block on HERG channels indicating preferential binding to the closed channel state. The IC50 for block was 2.62 ????M. This is close to the therapeutic concentration of the drug (0.6 to 2 ????M) and concentrations above 10 ????M have been reported during overdoses. Although there have been no specific reports of QT prolongation or TdP in clozapine-treated patients, our data raises the possibility of proarrhythmia as another potential explanation for sudden death during clozapine treatment. Amitriptyline, a commonly prescribed tricyclic antidepressant, can induce a variety of cardiac rhythm disturbances. Most reports have attributed these effects to its Na+ channel blocking ability. We found that amitriptyline blocked HERG channels with an IC50 of 10 ????M. Such high concentrations can be achieved during overdoses. Thus HERG channel blockade likely underlies amitriptyline????s QT-prolonging effect. Channel inhibition by amitriptyline exhibited positive voltage- and use-dependence and increased progressively with further prolongation of depolarization during an envelope of tails protocol, indicating preferential binding to an activated (open/inactivated) state of the channel. In contrast to the tricyclics, the tetracyclic antidepressant, mianserin, is much safer and only very rarely associated with cardiac complications. HERG channel blockade by mianserin was the least potent among the 5 psychoactive drugs we studied, with an IC50 of 14.78 ????M, which is 30- to 40-fold higher than therapeutic plasma concentrations of the drug. This probably, in part, accounts for the lack of reports of QT prolongation or TdP with mianserin. Mianserin displayed preferential affinity for an activated state of HERG channels on the basis of voltage-dependent block, a hyperpolarizing shift in the voltage of half-maximal activation and an increase in block at low external potassium concentration. Our results show that HERG block is a common feature of many non-cardiac drugs and that this underlies their potential for QT prolongation and TdP. Although the proarrhythmic risk varies according to potency of HERG block (e.g. mianserin is a weak blocker and does not induce TdP), other factors such as drug metabolism, protein binding and myocardial concentrations are also important since the risk of proarrhythmia during clinical use differ significantly even among the more potent HERG blockers. The preferential binding of these drugs to different channel states together with their diverse chemical structures suggest the presence of multiple distinct binding sites for drugs on HERG channels. There is increasing awareness that many non-antiarrhythmic drugs can prolong the QT interval and provoke TdP. Cardiac safety is now a major issue in new drug development. Our model of HERG K+ channels stably expressed in a mammalian cell line (CHO-K1) provides a useful tool for screening, at the preclinical stage, the proarrhythmic potential of novel drugs intended for human use.
19
Budgett, David Mortimer. "Remote sensing of the epicardium." Thesis, Imperial College London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363025.
20
Romosios, Apostolos. "Comparison of algorithms to extract the fetal electrocardiogram signal from the maternal signal." Thesis, University of Nottingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272657.
21
Chishti, Parveen. "Automated techniques for ECG waveform fiducial point recognition." Thesis, University of Glasgow, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390780.
22
Hedén, Bo. "Analysis of electrocardiograms using artificial neural networks." Lund : Dept. of Clinical Physiology, Lund University, 1997. http://catalog.hathitrust.org/api/volumes/oclc/39751585.html.
23
Farina, Dmytro [Verfasser]. "Forward and inverse problems of electrocardiography : clinical investigation / von Dmytro Farina." Karlsruhe : Univ.-Verl. Karlsruhe, 2008. http://d-nb.info/988009609/34.
24
Huwez, F. U. "Electrocardiography of the left ventricle in coronary artery disease and hypertrophy." Thesis, University of Glasgow, 1990. http://theses.gla.ac.uk/5665/.
Abstract:
This thesis describes a series of studies which were undertaken to improve the diagnostic accuracy of the electrocardiogram (ECG), given the availability of computer assisted measurement techniques. Scalar 12 lead electrocardiograms have been recorded from over 200 cardiac patients recruited specifically for this study. Over 1,500 additional ECGs were available from normal and abnormal test populations. The ECG measurements were correlated with clinical, echocardiographic, radionuclide, coronary angiographic and contrast angiographic data of the left ventricle in order to meet the aims of the study. The history of electrocardiography was reviewed both with respect to the technique itself and the evolution of equipment through to present day computer assisted technology for recording and measurement of ECG waveforms. In addition, the development of echocardiography, nuclear cardiology and cardiac catheterization was also reviewed with particular attention being given to recent developments in technology which have allowed a reappraisal of gold standards against which the ECG can be compared. With more specific relevance to the aim of this study, the development of ECG criteria mainly with respect to post mortem examinations was reviewed so that a contrast could be drawn with present day techniques. In particular, emphasis was laid on the twin areas of left ventricular hypertrophy and ischemic heart disease. Evaluation of left ventricular function from the scalar electrocardiogram was undertaken in two ways. First of all the latest ECG scoring system of Selvester was assessed, from which left ventricular ejection fraction could be calculated. Secondly, indirect evidence of left atrial overload from the electrocardiogram was also studied. It was shown that left ventricular function could be predicted qualitatively with reasonable accuracy in the early post infarct period (third day) using the 54 criteria/32 points scoring system.
25
Kwan, Siu-ki, and 關兆奇. "Development of high performance implantable cardioverter defibrillatorbased statistical analysis of electrocardiography." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B38320289.
26
Rader, Florian. "Quantitative Electrocardiography for Prediction of Postoperative Atrial Fibrillation after Cardiac Surgery." Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1260380041.
27
Мороз, В. О. "Електрокардіографія - фізичний метод діагностики." Thesis, Сумський державний університет, 2013. http://essuir.sumdu.edu.ua/handle/123456789/41029.
Abstract:
Розвиток медицини безпосередньо пов’язаний з розвитком фізики,
техніки, комп’ютерних технологій. Фізика озброює медичних
працівників знаннями фізичних методів діагностики захворювань та
лікування хворих.
28
Kwan, Siu-ki. "Development of high performance implantable cardioverter defibrillator based statistical analysis of electrocardiography." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B38320289.
29
Guclu, Alperen. "Comparison Of Five Regularization Methods For The Solution Of Inverse Electrocardiography Problem." Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615552/index.pdf.
Abstract:
Understanding heart&rsquos electrical activity is very important because coronary problems -such as heart attacks, arrhythmia and stroke- are the leading cause of death in the world. Forward and inverse problems of electrocardiography (ECG) are methods that provide detailed information about the electrical activity of the heart. Forward problem of electrocardiography is the estimation of body surface potentials from equivalent cardiac sources. Inverse problem of electrocardiography can be described as estimation of the electrical sources in the heart using the potential measurements obtained from the body surface. Due to spatial smoothing and attenuation that occur within the thorax, inverse ECG problem is ill-posed and the transfer matrix is ill-conditioned. Thus, regularization is needed to find a stable and accurate solution. In this thesis, epicardial potentials used as equivalent cardiac sources to represent electrical activity of the heart and performances of five different regularization methods are compared. These regularization methods are Tikhonov regularization, truncated singular value decomposition, least squares QR factorization, truncated total least squares, and Lanczos truncated total least squares. Results are assessed qualitatively using correlation coefficient (CC) and relative difference measurement star (RDMS) measures. In addition, real and reconstructed surface potential distributions are compared qualitatively. Body surface potential measurements are simulated with different levels of measurement noise. Geometric errors are also included by changing the size and the location of the heart in the mathematical torso model. According to our test results, the performances of the regularization methods in solving the inverse ECG problem depend on the form and amount of the noise.
30
Poulikakos, Dimitrios. "Electrocardiography for risk stratification of sudden cardiac death in chronic kidney disease." Thesis, St George's, University of London, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.703279.
Abstract:
Sudden cardiac death accounts for one fourth of deaths in prevalent dialysis patients yet risk stratification for targeted preventive treatment remains an unmet clinical need. This thesis belongs to the field of non-invasive electrophysiology and its goal is to investigate if electrocardiographic monitoring during dialysis can provide subject specific profiles of selected indices of repolarisation and cardiac autonomic modulation derived with computerised analysis of the surface electrocardiogram that would be suitable for risk stratification purposes for sudden cardiac death in dialysis patients. To this end the following objectives were set: a) test the intrasubject reproducibility of selected repolarisation descriptors and of spectral parameters of heart rate variability (HRV) during 5 dialysis sessions, b) investigate their relationship with clinical and laboratory parameters associated with increased cardiovascular risk, c) examine the interrelationship between cardiac autonomic regulation and repolarisation indices, and d) follow up the study population for major arrhythmic events. The thesis is organised in a manner that allows selected chapters based on published articles to be read in their own right. A literature review on the epidemiology and possible underlying mechanisms of ventricular arrhythmias in chronic kidney disease is presented in Chapter 2. Chapter 3 deals with aspects of the study design and methodology. Chapter 4 includes the results on intrasubject stability of selected repolarisation descriptors. Chapter 5 reports on repolarisation descriptors in patients that suffered major arrhythmic events after a follow up period of 18 months. Chapter 6 reports on sex dependent association between HRV and pulse pressure and Chapter 7 reports an association between HRV and bone mineral abnormalities. T.he interrelationship between HRV and the studied repolarisation indices is investigated in Chapter 8. In Chapter 9 the future research plan is briefly outlined and Chapter 10 summarises and concludes the thesis.
31
Long, Meijing, and 龍梅菁. "Prevalence of electrocardiographic abnormalities and the relationship bewtween alcohol use and electrocardiographic-left ventricularhypertrophy in older Chinese people: theGuangzhou biobank cohort study." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45789642.
32
Still, A. M. (Aino-Maija). "Prevalence and characteristics of ectopic atrial tachycardia and inappropriate sinus tachycardia." Doctoral thesis, University of Oulu, 2004. http://urn.fi/urn:isbn:9514273818.
Abstract:
Abstract
This research was designed to assess the prevalence, characteristics, natural course and autonomic regulation of ectopic atrial tachycardia (EAT) and inappropriate sinus tachycardia (IST) and the response of IST to adenosine.
The prevalence of EAT, as estimated from the electrocardiograms (ECG) of males applying for a pilot's licence, was 0.34%. During a mean follow-up time of 8 years among 10 asymptomatic subjects and 7 years among 17 symptomatic patients, a majority of the subjects showed a reduction of the heart rate (HR), either with restoration of sinus rhythm (SR) (37%) or with a change in P wave morphology (37%).
The prevalence of IST in a random sample of 604 middle-aged subjects was 1.16%. The systolic and diastolic ambulatory blood pressures were higher among the subjects with IST than subjects with SR (P < 0.001). The other laboratory, echocardiographic and personality measurements, with the exception of the hostility score (P < 0.001), revealed no differences between the groups. During a mean follow-up of 6 years, none of the subjects with IST developed any evidence of structural heart disease despite ongoing palpitations, and there was no significant reduction of the 24-hour average HR.
In an analysis of R-R interval variability from 24-hour ECG recordings in 12 patients with incessant EAT, 12 subjects with IST and 24 subjects with SR, the time- and frequency-domain measures of HR variability did not differ between the subjects with EAT and IST. However, the short-term fractal HR behaviour differed between EAT and IST.
In studies of the effects of adenosine in 18 patients with IST and 18 subjects with SR, adenosine prolonged significantly the sinus interval (P < 0.001) in the control subjects, but did not cause any significant changes of atrial cycle length in the patients with IST.
Conclusions: 1. EAT has a tendency towards gradual degeneration over time. 2. The prevalence of IST is higher than previously assumed, but the overall prognosis is good. 3. EAT and IST seem to be under similar autonomic regulation as the sinus node, but the firing of ectopic atrial foci shows more random behaviour. 4. The usual negative chronotropic effect of adenosine is impaired in subjects with IST.
33
Jim, Man-hong. "New electrocardiographic and angiographic observations in acute inferior myocardial infarction and their prognostic impacts." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B39558423.
34
邱文輝 and Man-fai Yau. "Automatic on-line classification of ECG morphology for ambulatory monitoring." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1988. http://hub.hku.hk/bib/B31209038.
35
Mason, Laura Laura. "Signal processing methods for non-invasive respiration monitoring." Thesis, University of Oxford, 2002. http://ora.ox.ac.uk/objects/uuid:68b60700-1cf5-4587-8896-4e18a70c5193.
Abstract:
This thesis investigates the feasibility of using a set of non-invasive biomedical signals to monitor respiration. The signals of interest being the electrocardiogram (EGG), photoplethysmography (PPG) and impedance plethysmography (IP) signals. The work has two main aims; the first being to estimate breathing rates from the signals, the second being to detect apnoeas from the signals. The fusion of information from different signals is used throughout in developing algorithms that give more accurate respiratory information than that obtained using one signal alone. Respiratory waveforms are derived from the signals, and the accuracy of detecting individual breaths from the waveforms is assessed and compared objectively. Results from evaluations on two separate databases show there is no waveform that gives sufficient accuracy to consider using it alone. A novel fusion method is developed which uses measurements from all three signals. This fusion method is based on weighting the estimates from each signal, according to the innovation from a Kalman filter model, applied to each respiratory waveform separately. The fused estimates give a higher overall correlation with respect to the reference breathing rate values than any of the breathing estimates derived from a single waveform. The detection of both central and obstructive sleep apnoea from the signals is investigated. It is shown that the accuracy of detecting central apnoeas from the IP signal using a timedomain method, often used in practice, can be improved by combining it with information from the frequency-domain. When discriminating between obstructive sleep apnoeic and non-apnoeic data it is seen that combining features from two signals results in a superior classification accuracy than is possible by using features from just one signal. The proposed classification system using just one of these signals, the EGG, is shown to give a performance accuracy comparable to that found in the literature. In conclusion this thesis shows that by fusing information from a number of non-invasive biomedical signals, estimations of breathing rates can be found with correlation 0.8. This is superior to estimation using only the impedance pneumography signal (correlation 0.64) which is currently used to monitor respiration. The fusion approach could potentially be applied to improve other non-invasive physiological monitoring systems.
36
di, Bernardo Diego. "Computer modelling of cardiac repolarisation for the analysis of the electrocardiogram." Thesis, University of Newcastle Upon Tyne, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364809.
37
Lewis, Jonathan David. "The development of a clinical ambulatory body surface potential mapping recorder for the diagnosis of myocardial ischaemia." Thesis, University of Sussex, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309442.
38
Crihalmeanu, Simona Gabriela. "Representative ways to analyze and survey changes in long-term electrocardiographic recordings." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1623.
Abstract:
Thesis (M.S.)--West Virginia University, 2000.Title from document title page. Document formatted into pages; contains viii, 195 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 77-81).
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Yau, Man-fai. "Automatic on-line classification of ECG morphology for ambulatory monitoring /." [Hong Kong] : University of Hong Kong, 1988. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12433962.
40
Onal, Murat. "Evaulation Of Spatial And Spatio-temporal Regularization Approaches In Inverse Problem Of Electrocardiography." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/2/12610045/index.pdf.
Abstract:
Conventional electrocardiography (ECG) is an essential tool for investigating cardiac disorders such as arrhythmias or myocardial infarction. It consists of interpretation of potentials recorded at the body surface that occur due to the electrical activity of the heart. However, electrical signals originated at the heart suffer from attenuation and smoothing within the thorax, therefore ECG signal measured on the body surface lacks some important details. The goal of forward and inverse ECG problems is to recover these lost details by estimating the heart’
s electrical activity non-invasively from body surface potential measurements. In the forward problem, one calculates the body surface potential distribution (i.e. torso potentials) using an appropriate source model for the equivalent cardiac sources. In the inverse problem of ECG, one estimates cardiac electrical activity based on measured torso potentials and a geometric model of the torso. Due to attenuation and spatial smoothing that occur within the thorax, inverse ECG problem is ill-posed and the forward model matrix is badly conditioned. Thus, small disturbances in the measurements lead to amplified errors in inverse solutions. It is difficult to solve this problem for effective cardiac imaging due to the ill-posed nature and high dimensionality of the problem. Tikhonov regularization, Truncated Singular Value Decomposition (TSVD) and Bayesian MAP estimation are some of the methods proposed in literature to cope with the ill-posedness of the problem. The most common approach in these methods is to ignore temporal relations of epicardial potentials and to solve the inverse problem at every time instant independently (column sequential approach). This is the fastest and the easiest approach
however, it does not include temporal correlations. The goal of this thesis is to include temporal constraints as well as spatial constraints in solving the inverse ECG problem. For this purpose, two methods are used. In the first method, we solved the augmented problem directly. Alternatively, we solve the problem with column sequential approach after applying temporal whitening. The performance of each method is evaluated.
41
SULAS, ELEONORA. "Development of a Novel Dataset and Tools for Non-Invasive Fetal Electrocardiography Research." Doctoral thesis, Università degli Studi di Cagliari, 2020. http://hdl.handle.net/11584/284403.
Abstract:
This PhD thesis presents the development of a novel open multi-modal dataset
for advanced studies on fetal cardiological assessment, along with a set of signal
processing tools for its exploitation. The Non-Invasive Fetal Electrocardiography
(ECG) Analysis (NInFEA) dataset features multi-channel electrophysiological
recordings characterized by high sampling frequency and digital resolution,
maternal respiration signal, synchronized fetal trans-abdominal pulsed-wave
Doppler (PWD) recordings and clinical annotations provided by expert
clinicians at the time of the signal collection. To the best of our knowledge,
there are no similar dataset available.
The signal processing tools targeted both the PWD and the non-invasive
fetal ECG, exploiting the recorded dataset. About the former, the study focuses
on the processing aimed at the preparation of the signal for the automatic
measurement of relevant morphological features, already adopted in the
clinical practice for cardiac assessment. To this aim, a relevant step is the automatic
identification of the complete and measurable cardiac cycles in the PWD
videos: a rigorous methodology was deployed for the analysis of the different
processing steps involved in the automatic delineation of the PWD envelope,
then implementing different approaches for the supervised classification of the
cardiac cycles, discriminating between complete and measurable vs. malformed
or incomplete ones. Finally, preliminary measurement algorithms were also developed
in order to extract clinically relevant parameters from the PWD.
About the fetal ECG, this thesis concentrated on the systematic analysis of
the adaptive filters performance for non-invasive fetal ECG extraction processing,
identified as the reference tool throughout the thesis. Then, two studies
are reported: one on the wavelet-based denoising of the extracted fetal ECG
and another one on the fetal ECG quality assessment from the analysis of the
raw abdominal recordings.
Overall, the thesis represents an important milestone in the field, by promoting
the open-data approach and introducing automated analysis tools that
could be easily integrated in future medical devices.
42
Cheng, Pak-ho. "P wave characteristics and QRS duration in patients after Fontan-type procedures." Click to view the E-thesis via HKUTO, 2010. http://sunzi.lib.hku.hk/hkuto/record/B43781627.
43
Hedberg, Pär. "Left ventricular systolic dysfunction in 75-year-old men and women : a community-based study of prevalence, screening and mitral annulus motion for diagnosis and prognostics /." Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5793.
44
Jim, Man-hong, and 詹民康. "New electrocardiographic and angiographic observations in acute inferior myocardial infarction and their prognostic impacts." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39558423.
45
Morales, Eduardo. "Spatio-temporal ECG analysis for localization of arrhythmias using precordial ECG leads and 128-lead system." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Botelho, Roberto Vieira. "Valor preditivo da tele-eletrocardiografia no infarto agudo do miocárdio." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/5/5144/tde-29012009-134020/.
Abstract:
O presente estudo procurou avaliar, prospectivamente, a segurança do sistema de tele-eletrocardiografia para a liberação de pacientes que se apresentem a postos de saúde com queixa de dor torácica. Avaliamos a incidência de infarto do miocárdio dessa população ao longo de seis meses. Como objetivo secundário, correlacionamos, retrospectivamente, a razão das probabilidades entre diferentes indicadores clínicos e eletrocardiográficos e a ocorrência do infarto do miocárdio. Entre junho e dezembro de 2006, 32444 pacientes foram atendidos em postos de saúde pública, carentes de cardiologistas e tiveram o seu tele-eletrocardiograma transmitido até uma central de telemedicina, através de linha telefônica fixa. Selecionaram-se 1535 pacientes atendidos devido a dor torácica, que tinham mais de 50 anos e apresentavam exame clínico, laboratorial (troponina I ou creatino fosfoquinase fração MB-CKMB) e tele-eletrocardiográfico normais além de consentirem em repetir o tele-eletrocardiograma após um e seis meses. Todos os pacientes foram seguidos durante seis meses. Não houve eventos durante o primeiro mês. No segundo mês houve 12(0,8%) infartos; no terceiro mês, 18(1,2%); no quarto mês, 38(2,4%) e no sexto, 18(1,2%). Ao longo dos seis meses houve 15(1%) óbitos, sendo 9(0,6%) de origem cardíaca; 9 (0,6%)acidentes vasculares encefálicos e 86(5,6%) infartos agudos do miocárdio. Entre as variáveis que se correlacionaram, independentemente, com maior chance de infarto agudo do miocárdio, encontrou-se a obesidade grau I [p=0,009 RC 4,5 IC 95%(1,5-13,8)], a dislipidemia [p< 0,0001 RC 3,4 IC 95%(2,0-5,8)], a baixa amplitude da onda T em V2 [p<0,001 RC 2,9 IC 95%(2,4-3,5)] e o sobrepeso [p=0,019 RC 2,6 IC 95%(1,2-5,7)]. Cada 0,5mm de redução na amplitude da onda T aumentou em quase três vezes a chance de ocorrência do infarto agudo do miocárdio durante seis meses. O tabagismo apresentou forte tendência [p=0,057 RC 1,7 IC 95%(1,0-2,8)] à regressão logística binária e foi significante após análise por árvore de decisão. Estes resultados permitiram as seguintes conclusões: o sistema de tele-eletrocardiografia oferece alta segurança ao estratificar o risco de pacientes com exame clínico, laboratorial e tele-eletrocardiográfico normais, queixando-se de dor torácica. Identificou-se, ao longo dos seis meses, a população de maior chance de apresentar o evento através de variáveis clínicas (obesidade, dislipidemia, tabagismo e sobrepeso) e tele-eletrocardiográficas (amplitude da onda T em V2), que determinaram, independentemente, a ocorrência de infarto agudo do miocárdioThe present study aimed at prospectively evaluating the reliability of teleeletrocardiography for the discharge of chest pain patients who present themselves at remote medical centers. The incidence of acute myocardial infarction among this population was evaluated during a period of six months. As a secondary objective, the correlation between different clinical and electrocardiographic features and the occurrence of myocardial infarction was retrospectively checked. Between June and December of 2006, 32.444 patients were treated in public medical centers which lacked the assistance of cardiologists. Those patients had their electrocardiogram transmitted to a telemedicine center over a fixed-wired telephone line. Among them 1535 patients who had been assisted due to chest pain were selected. Those patients were all older than 50 years and showed normal clinical and laboratorial (troponine I or creatine phosphokinase MB-CKMB fraction) exams, as well as normal tele-electrocardiograms. They also agreed to repeat the teleelectrocardiogram in a six-month period. All patients were followed up to the sixth-month. In the second month, there were 12 (0,8%) infarctions; in the third month there were 18 (1,2%) infarctions; in the fourth month there were 38 (2,4%) infarctions, and in the sixth month there were 18 (1,2%) infarctions. Over that six month period, there were 15 (1%) deaths, 9 (0,6%) of which were related to cardiac causes; 9 (0,6%) strokes, and 86 (5,6%) acute myocardial infarctions. Among the variables which independently correlated with greater risk of acute myocardial infarction, we found grade I obesity [p=0,009 RC 4,5 IC95%(1,5-13,8)]; dyslipidemia [p<0,0001 RC 3,4 IC 95%(2,0-5,8)]; low T-wave amplitude in V2 [p<0,001 RC 2,9 IC 95%(2,4-3,5)], and overweight [p=0,019 RC 2,6 IC 95%(1,2-5,7)]. Each 0,5mm reduction in the T-wave raised almost three times the chance for the occurrence of acute myocardial infarction in a sixmonth period. Smoking showed a strong tendency [p=0,057 RC 1,7 IC 95%(1,0-2,8)] to binary logistic regression and was significant after decision tree analysis. These results lead to the following conclusions: the teleelectrocardiographic system offers high level of safety and reliability due to its capacity to stratify chest pain patient risk. Over these six months the study identified the population who showed greater chances of presenting the event through clinical (obesity, dyslipidemia, smoking and overweight) and teleelectrocardiography (amplitude of T-wave in V2) variables, which independently, determined the occurrence of acute myocardial infarction
47
Sarikaya, Sedat. "Combination Of Conventional Regularization Methods And Genetic Algorithms For Solving The Inverse Problem Of Electrocardiography." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/2/12611669/index.pdf.
Abstract:
Distribution of electrical potentials over the surface of the heart, i.e., the epicardial potentials, is a valuable tool to understand whether there is a defect in the heart. However, it is not easy to detect these potentials non-invasively. Instead, body surface potentials, which occur as a result of the electrical activity of the heart, are measured to diagnose heart defects. However the source electrical signals loose some critical details because of the attenuation and smoothing they encounter due to body tissues such as lungs, fat, etc. Direct measurement of these epicardial potentials requires invasive procedures. Alternatively, one can reconstruct the epicardial potentials non-invasively from the body surface potentialsthis method is called the inverse problem of electrocardiography (ECG). The goal of this study is to solve the inverse problem of ECG using several well-known regularization methods and using their combinations with genetic algorihm (GA) and finally compare the performances of these methods. The results show that GA can be combined with the conventional regularization methods and their combination improves the regularization of ill-posed inverse ECG problem. In several studies, the results show that their combination provide a good scheme for solving the ECG inverse problem and the performance of regularization methods can be improved further. We also suggest that GA can be initiated succesfully with a training set of epicardial potentials, and with the optimum, over- and under-regularized Tikhonov regularization solutions.
48
Pan, Xiang. "Deep Transfer Learning Applied to Time-series Classification for Predicting Heart Failure Worsening Using Electrocardiography." Digital WPI, 2020. https://digitalcommons.wpi.edu/etd-dissertations/615.
Abstract:
Computational ECG (electrocardiogram) analysis enables accurate and faster diagnosis and early prediction of heart failure related symptoms (heart failure worsening). Machine learning, particularly deep learning, has been applied for ECG data successfully. The previous applications, however, either mainly focused on classifying occurrent, known patterns of on-going heart failure or heart failure related diseases such arrhythmia, which have undesirable predictability beforehand, or emphasizing on data from pre-processed public database data. In this dissertation, we developed an approach, however, does not fully capitalize on the potential of deep learning, which directly learns important features from raw input data without relying on a priori knowledge. Here, we present a deep transfer learning pipeline which combines an image-based pretrained deep neural network model with manifold learning to predict the precursors of heart failure (heart failure-worsening and recurrent heart failure related re-hospitalization) using raw ECG time series from wearable devices. In this dissertation, we used the unprocessed real-life ECG data from the SENTINEL-HF study by Dovancescu, et al. to predict the precursors of heart failure worsening. To extract rich features from ECG time series, we took a deep transfer learning approach where 1D time-series of five heartbeats were transformed to 2D images by Gramian Angular Summation Field (GASF) and then the pretrained models, VGG19 were used for feature extraction. Then, we applied UMAP (Uniform Manifold Approximation and Projection) to capture the manifold of the standardized feature space and reduce the dimension, followed by SVM (Support Vector Machine) training. Using our pipeline, we demonstrated that our classifier was able to predict heart failure worsening with 92.1% accuracy, 92.9% precision, 92.6% recall and F1 score of 0.93 bypassing the detection of known abnormal ECG patterns. In conclusion, we demonstrate the feasibility of early alerts of heart failure by predicting the precursor of heart failure worsening based on raw ECG signals. We expected that our approached provided an innovative method to assess the recovery and successfulness for the treatment patient received during the first hospitalization, to predict whether recurrent heart failure is likely to occur, and to evaluate whether the patient should be discharged.
49
Arnold, Michael Leonard. "Correlation Of Lead I With Standard 12-Lead Electrocardiography: A Potential Tool For Cardiac Screening." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/347311.
Abstract:
Background: Heart disease remains the leading cause of morbidity and mortality worldwide. Typical symptoms of heart disease are lacking in nearly one-third of patients with acute myocardial infarction (AMI). Simplified ECG assessment via lead I by various handheld and smartphone-based electrocardiogram (ECG) devices may be used for rapid screening without the traditional delays, privacy concerns, or costs of 12-lead ECG recording in patients who are asymptomatic or have atypical symptoms. The purpose of this DNP project was to compare ECG data from lead I to the standard 12-lead ECG to determine its potential efficacy as an early screening tool for AMI. Methods: This project compared ECGs in 84 patients with cardiac diagnoses, 66 (78.6%) had acute myocardial infarction with abnormal 12-lead ECGs and 18 (22.6 %) were without AMI or abnormal findings on the standard 12-lead ECG. ST-segment and T-wave amplitude and characteristics were compared between infarction territories. Results: Lead I in those with abnormal ECGs had a mean ST-segment deviation from baseline of 1.0 ± 0.7 mm, which was significantly different than those with normal ECGs (mean 0.1 ± 0.3 mm)(p = .000). The mean T-wave amplitude in patients with abnormal ECGs was 0.7 ± 1.3 mm, which was a significant reduction compared to those with normal ECGs group of 2.2 ± 1.5 mm (p = .000). Conclusion: ST-segment deviations and reduction in T-wave amplitude are significant indicators of acute myocardial infarction in lead I ECG, the same vector used in handheld single-lead ECG devices.
50
BALDAZZI, GIULIA. "Advanced signal processing and machine learning tools for non-invasive foetal electrocardiography and intracardiac electrophysiology." Doctoral thesis, Università degli studi di Genova, 2022. http://hdl.handle.net/11567/1082764.
Abstract:
In the last decades, bioengineering research promoted the improvement in human health and wellbeing through the development, optimization and evaluation of innovative technologies and medical devices for both diagnosis and therapy. In this context, the exploitation of biomedical technology advances plays a key role in the study and treatment of heart disorders.
This PhD thesis focuses on two main application areas: on one hand, foetal cardiac physiology and electrocardiography and, on the other, intracardiac electrophysiology, substrate mapping and radiofrequency ablation. There, it aims at providing new instruments and insights to improve the knowledge and go beyond the current state of the art by the development of novel signal processing and machine learning tools that aim at supporting the diagnosis and treatment of cardiac diseases.
Non-invasive foetal ECG (fECG) is a long-standing niche research topic characterized by the continuous demand of improved solutions to solve the problem of recovering high-quality fECG signals from non-invasive trans-abdominal recordings. This PhD thesis focused on the development of algorithms for non-invasive fECG extraction and enhancement. Specifically, in collaboration with the Prof. Hau-Tieng Wu (Department of Mathematics and Statistical Science, Duke University, Durham, NC, USA), a novel algorithm for the extraction of morphologically preserved multi-channel fECG signals was conceived. Furthermore, wavelet denoising was deeply investigated for the post-processing of the fECG recordings, to quantitatively evaluate the noise-removal and morphology-preservation effects of different wavelet denoising approaches, expressly tailored for this application domain.
Intracardiac electrophysiology is a branch of interventional cardiology aimed at the diagnosis and treatment of arrhythmias by catheter-based techniques exploiting electroanatomic substrate mapping and ablation. In this exciting scenario, this PhD thesis focused on post-ischemic ventricular tachycardia, which is a life-threatening arrhythmia. Being the electrophysiological studies and ablations very time-consuming and operator-dependent, the first applied-research goal was the development of an effective tool able to support clinical experts in the recognition of the ablation targets during clinical procedures. Moreover, a detailed spectral characterization of post-ischaemic signals was performed, thus paving the way to the development of novel approaches in terms of advanced signal analysis, automatic recognition of the arrhythmogenic substrates, study of the substrate and, in general, to a deeper understanding of the arrhythmogenic mechanisms.
Beyond the scientific content, this PhD thesis gives an important contribution from an industrial perspective in both fields. In fact, automated signal processing tools for the non-invasive fECG signals can improve the detection capabilities of current tools, to be clinically exploited for low-cost antenatal screening. At the same time, novel methods for ablation targets recognition in cardiac electrophysiology could be embedded in future medical electroanatomic mapping systems as plug-in to enhance current computer-aided methods.