P and T wave analysis in ECG signals using Bayesian methods

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Chapter 1 Introduction to Cardiac Electrophysiology Contents 1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.2 Cardiology basis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.2.1 Heart anatomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.2.2 Heart operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1.3 Electrocardiography . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.3.1 ECG measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 1.3.2 ECG interpretation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 1.4 Literature review of ECG signal processing methods . . . . . . . . 24 1.4.1 Preprocessing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 1.4.2 QRS detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 1.4.3 P and T wave delineation . . . . . . . . . . . . . . . . . . . . . . . . . 29 1.1 Introduction Before attempting any ECG signal processing, it is important to first understand the physiological basis of the ECG, to review measurement conventions of the standard ECG, and to review how a clinician uses ECGs for patient care. Understanding the basis of a normal ECG requires appreciation of four aspects: • physiology of the specific structures of the heart, • electrophysiology of the heat and the origin of the ECG, • ECG measurement and registration, • ECG interpretation in clinical context. Around these four topics, we will discuss in the first two sections how the wave of electrical current propagates through the heart muscle, the physiology of the specific structures of the heart through which the electrical wave travels, how that leads to a measurable signal on the 7
8 Chapter 1 - Introduction to Cardiac Electrophysiology surface of the body, producing the normal ECG, and last how a cardiologist interprets the ECG. It should be noted that, through decades of investigation, much detail is available about the electrophysiologic activity of the heart and the introduction in this thesis is therefore only a highly abbreviated summary. Some of the material and figures in this chapter are taken from [Mar90, CAM06, CR90, CPD09], to which the reader is referred for a more detailed overview of this subject. As mentioned in the general introduction, the detection/estimation and delineation of each wave component of the ECG signal is a crucial step for ECG interpretation. In the last section of this chapter, a brief review of ECG signal processing methods proposed in the literature is given, with the emphasis on wave detection and delineation. 1.2 Cardiology basis The heart is a muscle that is rhythmically driven to contract and hence drive the circulation of blood throughout the body. Before every normal heartbeat, or systole, a wave of electrical current passes through the entire heart, which triggers myocardial contraction. The pattern of electrical propagation is not random, but spreads over the structure of the heart in a coordinated pattern which leads to an effective, coordinated systole. This results in a measurable change in potential difference on the body surface of the subject. The resultant amplified (and filtered) signal is known as an ECG. To understand the origin of the ECG, one should begin with the heart structure and its functioning. 1.2.1 Heart anatomy The heart consists of four chambers (see Fig. 1.1: two atrial chambers (atrium) in the upper heart and two ventricular chambers (ventricles) in the lower part.). The atrium are the receiving chambers and the ventricles are the discharging chambers. The heart is mainly constituted by a specialized type of striated muscle, with properties that functions somewhat differently than skeletal muscle. Heart cells are connected by gap junctions that allow ions to flow from one cell to another, allowing for rapid spreading of depolarization. A collection of heart cells connected in this way constitutes a syncytium. The heart is composed of two syncytiums: an atrial syncytium and a ventricular syncytium. The muscle, which is like a wall around the heart, is called the myocardium. The two ventricles are separated by the ventricular septum, which is thick muscular toward the bottom, and thick fibrous at the top. Under the myocardium is the endocardium, which lines the chambers of the heart, and which is mainly composed of epithelial cells. The pericardium is a double-walled sac that contains the heart and the roots of the great vessels. The outer wall of the pericardium is composed of dense connective tissue. The portion of the inner wall of the pericardium that is in contact with the heart (but not in contact with the great vessels) is the epicardium. The epicardium contains the blood vessels supplying blood to heart muscle (the coronary arteries) as well as nerve fibers. The veins of the body terminate in two great vessels that empty into the right atrium: the
Page 1 and 2: InstitutNationalPolytechniquedeToul
Page 3 and 4: 2 Armengaud, Sylvie Eichen, Marie-J
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162 Conclusions and Perspectives
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Appendix A Sampling distributions f
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167 Waveform coefficients. The samp
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Appendix B Sampling distributions f
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171 that can be summarized as [ ∝
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Appendix C Sampling distributions f
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175 Inserting (2.5) for p(x|θ) and
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Appendix D Proposal distributions f
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Appendix E T waveform estimation us
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181 that the noise variance σ 2 w,
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Bibliography [AAC81] [AAC + 04] [Al
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BIBLIOGRAPHY 185 [CM08] [CPD09] [CR
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BIBLIOGRAPHY 187 [Har78] [HB97] [he
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BIBLIOGRAPHY 189 [MHI + 05] A. Mayb
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BIBLIOGRAPHY 191 [SGN05] [SLKG02] [
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P and T wave analysis in ECG signals using Bayesian methods

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