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SMV-2018-19: Systém for ECG analysis
Plešinger, Filip ; Jurák, Pavel ; Halámek, Josef ; Viščor, Ivo
A subject of this contracional research is development of algorithms for automated ECG processing from 1-lead ECG holters. Namely, it consists of:\n- development of algorithm for QRS recognition with focus on robustness against noise\n- development of classification algorithm to recognize arrhythmias, the algorithm is based on analysis of RR intervals and other ECG descriptors. The algorithm implements machine learning (neural networks). The input is Information related to QRS complexes and other descriptors extracted from ECG. The output is category of classified ECG block (atrial fibrillation, AB-block, non-quality signal, premature atrial contractions, premature ventricular contractions, sinus rhythm, supraventricular tachycardia and ventricular tachycardia)\n- Implemetation of these algorithms as software for .NET platform in C# language. It is optimized for multi-thread computers (computing server of the customer).\n
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Hemodynamic modelling in the calf — A pilot study
Matějková, M. ; Jurák, Pavel ; Soukup, L. ; Halámek, Josef ; Viščor, Ivo ; Langer, P. ; Vondra, Vlastimil
With increasing age, the cardiovascular system loses its efficiency. The goal of this work was to investigate the hemodynamic system response to a head-up tilt test in two groups of different aged people. We used a model for describing this response in the right calf based on a non-invasive, non-occlusive, bioimpedance signal measurement technique. A decrease in the bioimpedance value in the calf during the head-up tilt test is associated with the accumulation of blood in the calf, which can be expressed by a model parameter. Subjects were examined in both a head-up tilt test and a supine position. 50 healthy non-smoking volunteers were divided into two groups according to age. The impedance signal during the tilt test for each subject was fitted by a model exponential function: Z0 model EF(t) =A exp(-t/B)+C, where Z0 model EF(t) is the calculated model of electrical impedance in the calf by an exponential function, A is the amplitude of impedance change, B is the time constant of the impedance decrease, C is the value of the steady state after the tilt test and t denotes time. A lower time constant B shows a faster filling of the vascular system in the investigated part. The Mann-Whitney test (p-value<;0.005) revealed that the time constant B for the older group was significantly lower than for the young group (145.24+/- 80.28 vs. 239.23+/-136.59 sec.). A lower time constant value means a faster response to blood filling in the lower limbs and directly reflects decreased vessel elasticity. This time constant was lower in the older group. The results show increased vessel stiffness in old age and could lead to a non-invasive evaluating the cardiovascular system state.
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Biventricular pacing optimization by means of the dyssynchrony parameter
Jurák, Pavel ; Leinveber, P. ; Halámek, Josef ; Plešinger, Filip ; Postránecká, T. ; Lipoldová, J. ; Novák, M.
To improve Cardiac Resynchronization Therapy (CRT), different interventricular delay (VVD) settings can be used. However, relatively small VVD induced hemodynamic changes cannot be measured by standard echocardiographic methods. The QRS complex duration (QRSd) is mostly the main criterion. Here we introduce a new dyssynchrony parameter (DYS) that is able to more accurately detect improved electrical synchrony. Methods: 12-lead 5 kHz ECG during 3-10 minute rest period was measured in 46 patients with CRT OFF and CRT ON with VVD 0 ms (CRT0) and -20 ms (CRT20). We detected QRSd and the dyssynchrony parameter DYS as the time difference between 500-1000 Hz averaged envelopes positions in the V1 and V6 leads in the QRS complex region. Results: 32 of 46 patients had a positive CRT response manifested by QRSd shortening and a DYS decrease. 28 of 32 patients had a positive LV pre-excitation effect: additional QRSd shortening of 4.7+/-.9 ms and a DYS decrease of 12.6+/-7.5 ms. The correlation coefficient of QRSd and DYS changes (CRT 0 vs CRT 20) was 0.23 and indicates information diversity. The DYS parameter differs from QRSd and provides a significantly higher response to VVdelay changes (p <; 0.001).
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Automatic Analysis of Heart Rate Variability Signals
Kubičková, Alena ; Halámek, Josef (referee) ; Lhotská, Lenka (referee) ; Kozumplík, Jiří (advisor)
This dissertation thesis is dedicated to the heart rate variability and methods of its evaluation. It mainly focuses on nonlinear methods and especially on the Poincaré plot. First it deals with the principle and nature of the heart rate variability, then the ways of its representation, linear and also nonlinear methods of its analysis and physiological and pathophysiological influence on heart rate variability changes. In particular, there is emphasis on the metabolic syndrome. In the next section of the thesis there are compared and evaluated different ways of representation of the heart rate variability and further are tested selected methods of heart rate variability analysis on unique data from patients with the metabolic syndrome and healthy subjects provided by the Institute of Scientific Instruments, Academy of Sciences of Czech Republic. In particular, they are used the Poincaré plot and its parameters SD1 and SD2, commonly used time domain and frequency domain parameters, parameters evaluating signal entropy and the Lyapunov exponent. SD1 and SD2 combining the advantages of time and frequency domain methods of heart rate variability analysis distinguish successfully between patients with the metabolic syndrome and healthy subjects.
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Establishing Mutual Links among Brain Structures
Klimeš, Petr ; Hlinka,, Jaroslav (referee) ; Krajča,, Vladimír (referee) ; Halámek, Josef (advisor)
The Human brain consists of mutually connected neuronal populations that build anatomically and functionally separated structures. To understand human brain activity and connectivity, it is crucial to describe how these structures are connected and how information is spread. Commonly used methods often work with data from scalp EEG, with a limited number of contacts, and are incapable of observing dynamic changes during cognitive processes or different behavioural states. In addition, connectivity studies almost never analyse pathological parts of the brain, which can have a crucial impact on pathology research and treatment. The aim of this work is connectivity analysis and its evolution in time during cognitive tasks using data from intracranial EEG. Physiological processes in cognitive stimulation and the local connectivity of pathology in the epileptic brain during wake and sleep were analysed. The results provide new insight into human brain physiology research. This was achieved by an innovative approach which combines connectivity methods with EEG spectral power calculation. The second part of this work focuses on seizure onset zone (SOZ) connectivity in the epileptic brain. The results describe the functional isolation of the SOZ from the surrounding tissue, which may contribute to clinical research and epilepsy treatment.
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Study of Electrophysiological Function of the Heart in Experimental Cardiology
Ronzhina, Marina ; Tyšler, Milan (referee) ; Halámek, Josef (referee) ; Kolářová, Jana (advisor)
Srdeční poruchy, jejichž příkladem je ischemie myokardu, infarkt, hypertrofie levé komory a myokarditida, jsou v experimentální kardiologii obvykle studovány na modelu izolovaného srdce. Kritéria pro detekci srdečních poruch však nejsou pro zvířecí modely standardizována, což komplikuje srovnání a interpretaci výsledků různých experimentálních studií. Obzvlášť složitá situace nastává při současném výskytu několika patologických jevů, jejichž vzájemná součinnost komplikuje rozpoznání jejich individuálních účinků. Korektní posouzení stavu srdce vyžaduje také zohlednění mnoha faktorů spojených s akvizicí dat. Tato práce je věnována kvantitativnímu hodnocení elektrofyziologických změn způsobených globální ischemií myokardu. Vliv ischemie byl hodnocen pro fyziologická srdce a srdce se zvětšenou levou komorou a dále pro srdce nabarvená napěťově-citlivým barvivem di-4-ANEPPS. Přestože jsou oba fenomény často zastoupeny v animálních studiích, nebyl dosud popsán jejich vliv na manifestaci ischemie v elektrogramech (EG), ani nebyl kvantifikován jejich vliv na přesnost detekčních algoritmů pro identifikaci ischemie. Práce shrnuje kvantitativní změny srdeční funkce vyvolané ischemií (v normálních podmínkách, při hypertrofii levé komory, a při administraci barviva) založené na hodnocení EG a VKG parametrů. Dále práce obsahuje rozbor důležitých aspektů akvizice záznamů, jako je umístění snímacích elektrod, způsob výpočtu deskriptorů z EG a VKG (s použitím výsledků manuálního rozměření záznamů, nebo bez něj) a identifikace okamžiku vývoje ischemie v preparátu. Nedílnou součást práce tvoří návrh, realizace a ověření metod pro automatickou detekci ischemie v experimentálních záznamech. Výsledky práce dokazují, že dosažení opakovatelných a věrohodných výsledků je podmíněno zohledněním všech výše uvedených faktorů souvisejících jak se stavem srdce, tak s metodikou záznamu a analýzy dat.
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Methods for the evaluation of heart rate and arterial blood pressure variability
Sedláčková, Gabriela ; Halámek, Josef (referee) ; Leinveber, Pavel (advisor)
The bachelor thesis deals with methods for description of heart rate variability and arterial blood pressure. An important mechanism for maintaining homoeostasis in the body is so called baroreflex feedback loop, which allows for a short-term regulation of blood pressure. The thesis contains description of methods which are currently used for baroreflex sensitivity evaluation. Analysis in time domain as well as in frequency domain was done using programs in Matlab environment. At the end of the thesis the influence of ventricular extrasystoles on output parameter is evaluated.
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Wavelet Based Filtering of Electrocardiograms
Smital, Lukáš ; Smékal, Zdeněk (referee) ; Halámek, Josef (referee) ; Kozumplík, Jiří (advisor)
This dissertation deals with possibilities of using wavelet transforms for elimination of broadband muscle noise in ECG signals. In this work, the characteristics of ECG signals and particularly the most frequently occurring type of interference are discussed firstly. The theory of wavelet transforms is also introduced and followed by design of the simple wavelet filter and the more sophisticated version with wiener filtering of wavelet coefficients. Next part is devoted to the design of our filter, which is based on wavelet wiener filtering and is complemented by algorithms that ensure full adaptability of its parameters when the properties of the input signal are changing. Suitable parameters of the proposed system are searched automatically and the algorithm is tested on the complete standard electrocardiograms database CSE, where it achieves significantly better results than other published methods.
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Model Study of Ultrasound Effects on Fetal Development
Jaroš, Josef ; Halámek, Josef (referee) ; Hrazdíra,, Ivo (referee) ; Rozman, Jiří (advisor)
The progress in ultrasound techniques goes hand in hand with increasing of diagnostic machine acoustic outputs. Ultrasound biological effects can adversely influence the development of human fetus. Recent studies of thermal effect on biological tissues are usually based on simulation of simple ultrasound transducers. The aim of this work is to build a flexible model of diagnostic system to simulate temperature increase during fetal development. Different types of ultrasound probes were used for generation of acoustic field with simulated piezoelectric element properties. Optimized linear and phased arrays were modeled with dynamic beam steering and focus. Computer simulations were concentrated on extreme conditions in obstetric ultrasonography and 3D tissue model was compared with real ultrasound probes measurements. To detect temperature increase, the bone tissue phantom was used. Results point out potential risks for fetus with diagnostic ultrasound probes. Based on the results of this work, practical recommendations increasing safety of obstetric examinations were drawn.
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