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Detection of ECG T-wave Alternans Using Maxima of Continuous-Time Wavelet Transform Ridges

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Prognostic utility of microvolt T-wave alternans (TWA) has been established since its clinical acceptance as marker for malignant ventricular arrhythmias, leading to sudden cardiac death. Accurate detection of TWA from surface ECG is a challenge because of invisible nature of the phenomenon. A novel TWA detection scheme based upon analysis of continuous time wavelet ridges (CTWR) of consecutive ventricular repolarization complexes is presented. The CTWR is computed using maxima of wavelet energy coefficients of continuous wavelet transform. Variety of simulated alternans waveforms, wavelet functions, frequency bands and noise levels are used to test the algorithm. The study concludes that CTWR can successfully characterize the alternation of cardiac repolarization and detect TWA phenomenon. Streszczenie. Diagnostyka sygnału TWA odgrywa du˙za˛ role˛ w badaniach jako marker arytmii powoduja˛cej zawał serca. Sygnał TWA jest wykrywany jako składowa sygnału elektrokardiogramu. W artykule opisano wykorzystanie cia˛głej transformaty falkowej do analizy tego sygnału. (Detekcja składowej TWA sygnału EKG bazuja˛ca na wykorzystaniu cia˛głej transformaty falkowej) Keywords: Continuous-Time Wavelet Transform, Detection, Electrocardiography (ECG), T-wave Alternans Słowa kluczowe: transformata falkowa, elektrokardiogram, sygnał TWA Introduction Electrocardiography (ECG) is an important clinical tool for diagnosis of cardiac diseases. It is commonly measured by placing the surface electrodes on a subject’s chest and recording the cardiac cellular potential variations. The measured voltages, graphically plotted as a function of time, represent sequential depolarization (P-wave and QRS complex) and repolarization (T-wave) of cardiac chambers. A single such heart beat is shown in Fig. 1(a). 0 0.1 0.2 0.3 0.4 0.5 0.6 -1 0 1 2 (a) ECG (mV) 0 1 2 3 4 5 -1 0 1 2 (b) ECG (mV) 0 1 2 3 4 5 -1 0 1 2 (c) time(sec) ECG (mv) P Q R S T[...]

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