The effect of parameters of electrocardiograph measuring channel on recordings of micropotentials of the heart. Biology and Medicine

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1 eissn: The effect of parameters of electrocardiograph measuring channel on recordings of micropotentials of the heart Biology and Medicine Research Article Volume 6, Issue 2, Article ID: BM , 2014 Indexed by Scopus (Elsevier) Co-Publisher: OMICS Group,

2 The effect of parameters of electrocardiograph measuring channel on recordings of micropotentials of the heart Diana Konstantinovna Avdeeva 1 *, Veniamin Yur evich Kazakov 1, Nataliya Mihajlovna Natalinova 1, Ivan Vadimovich Maksimov 2, Marija Vjacheslavovna Balahonova 2 1 National Research Tomsk Polytechnic University, 30 Lenin Avenue, Tomsk, Russia. 2 RI Cardiology, 30 Kiyevskaya Street, Tomsk, Russia. *Corresponding author: National Research Tomsk Polytechnic University, 30 Lenin Avenue, Tomsk, Russia. Received: 4 th Sep 2014; Accepted: 17 th Oct 2014; Published: 2 nd Nov 2014 Abstract The paper presents the research findings on the total effect of different types of filters on the electrocardiogram (ECG) signal recorded by a high-resolution electrocardiograph based on nanoelectrodes without filters in the band from 0 to 150 Hz. A standard block diagram of one ECG channel includes both amplifiers and a number of filters: a high-pass filter, a filter of constant component, a low-pass filter, an anti-aliasing filter, a rejection filter, and others. The method of computer simulation was used to study the effect of the fine structure distortions (low-amplitude high-frequency fluctuations) of the heart biopotentials caused by the filter circuits. The simulation was performed using the LabVIEW software package. It is shown that the filters distort the shape and amplitude of the heart micropotentials, and introduce phase shifts or remove them from the output signal of the considered ECG. It is essential to consider signal filtering when applying the amplitude and time diagnostic criteria. In some cases, application of diagnostic criteria to the filtered signal can produce erroneous results. Keywords: ECG; measurement of the heart biopotentials; signal filtering; high-pass filter; low-pass filter; rejection filter; bandpass filter; micropotentials of the heart. Introduction Currently, electrocardiogram (ECG) is a commonly used method for detecting cardiac problems. The block diagrams of the hardware component of conventional electrocardiographs (measuring channel) typically consist of different types of filters [1]. A great number of methods for the cardiac signal processing have been developed to detect the symptoms of various pathologies. However, there is a problem of mismatch between the specific requirements for the cardiac signal processing method and the characteristics of the standardized measuring channel used to obtain cardiac signals. This paper aims to explore the total effect of the bandpass filter (BPF) and rejection filter (RF) on the ECG signal recorded by a high-resolution electrocardiograph based on nanoelectrodes without filters in the band from 0 to 150 Hz [2]. The problem is also essential to diagnose coronary heart disease (CHD) or ventricular fibrillation (precursor of sudden cardiac death SCD) in the early stages and requires the investigation of the cardiac signal low-amplitude fluctuations of a relatively high-frequency (more than 20 Hz). It is of great importance to develop the apparatus high-resolution ECG, which allows recording cardiac signals in order to detect their lowamplitude potentials: ventricular late potentials (VLP) and atrial late potentials (ALP). The papers [3,4] present the analysis of distortions and noise in the ECG signal caused by the converters of the analog component of the measuring channel, and show the optimization results of the ECG measuring channel parameters to record micropotentials of the heart. In this paper, we have investigated the effect of parameters of the filter circuits of the ECG measuring channel on the possibility to record micropotentials of the heart. Methods A standard block diagram of one ECG channel includes both amplifiers and a number of filters: a high-pass filter (HPF) a filter of constant component (cutoff frequency f Hz), a low-pass filter (LPF) an anti-aliasing filter Article ID: BM Page 1 of 5

3 (cutoff frequency f Hz), and others. In this case, the dynamic distortions caused by the filter circuits of the measuring channel can be significant. The method of computer simulation was used to study the effect of distortions of the fine structure (low-amplitude high-frequency fluctuations) of biopotentials of the heart caused by the filter circuits. The software models of the filter circuit were developed using LabVIEW containing a large number of well-tested software models of various filter types [5]. Results and Discussion Table 1 shows the filter circuit parameters considered in this research. The high-resolution signals recorded by the apparatus based on highly stable low-noise nanoelectrodes in the band from 0 to 150 Hz were used as test signals [6]. Figure 1 shows the ECG signal of patient P-44 with an isolated fragment characterizing ST segment. This ECG fragment contains the informative low- amplitude fluctuations of the signal. Further, only the above-mentioned ECG fragment is considered. Figure 2 shows the effect of the upper cutoff frequency f 2 of the fourth order Bessel BPF on the characteristics of the ECG signal of P-44 in the vicinity of QRS complex, f Hz. Line 1 refers to the original signal; lines 2, 3, and 4 refer to the cutoff frequencies f , 75, 100 Hz, respectively. It can be seen that the Bessel filters with all the cutoff frequencies f 2 suppress both the high-frequency noise of the measuring channel and the informative low-amplitude fluctuations [7-9]. Figure 3 shows the result of presence the rejection filter with a stopband from 49 to 50 Hz. The other conditions correspond to Figure 2. It should be noted that the rejection filter introduces additional low-amplitude fluctuations masking informative signs into the signal [10]. Figure 4 illustrates the effect of the filter type. The fourth order BPFs of the following types were used: Bessel, Butterworth, elliptic, Chebyshev (f Hz, f Hz). The fourth order Bessel RF is found in the measuring channel to suppress hum. The data analysis indicates that the signal amplitude distortions due to the time delays and bandpass flatness vary from 2 to 15% for different filter types and can be compared to the amplitudes of the heart VLP. The greatest distortions of the signal amplitude are observed when using Chebyshev and elliptic filters with the bandpass flatness. In this case, the fluctuation of their transient responses significantly contributes to the distortions. Filters Table 1: Parameters of the filters of measuring channel. Lower frequency cutoff (Hz) Upper frequency cutoff (Hz) Filter type Filter order BPF 0.01, , 75, 100 Bessel, Chebyshev, Butterworth, Elliptic 2, 4, 8 RF Butterworth, Chebyshev, Bessel 4 Figure 1: ECG signal of patient P-44. Article ID: BM Page 2 of 5

4 Research Article Biology and Medicine, 6(2), 2014 Figure 2: Effect of the upper cutoff frequency of the fourth order Bessel BPF on the ECG signal of patient P-44. Figure 3: Effect of the rejection filter on the ECG signal of patient P-44. Figure 4: Effect of the filter type on the ECG signal of patient P-44. Article ID: BM Page 3 of 5

Figure 5: Effect of the filter order on the ECG signal of patient P-44. Figure 5 shows the effect of the filter order. The Bessel BPFs (f 1 5 0.

5 Figure 5: Effect of the filter order on the ECG signal of patient P-44. Figure 5 shows the effect of the filter order. The Bessel BPFs (f Hz, f Hz) of the second, fourth, and eighth orders were used. The fourth order Bessel RF is found in the measuring channel to suppress hum. The data analysis shows that the distortions caused by the filters of different orders are almost identical if the other distortion conditions are equal. Therefore, the effect of the filter order is not as significant as the other characteristics of the filter circuit. Conclusions The flatness of the filter amplitude-frequency response in the passband and the nonlinearity of the phase-frequency response causes the cardiac signal disturbances of the same order of magnitude as the informative low-amplitude biopotentials of the heart. The filters used in the electrocardiographic apparatus distort the shape and amplitude of micropotentials, and introduce phase shifts or remove them from the signal. It is essential to consider signal filtering when applying the amplitude and time diagnostic criteria. In some cases, application of diagnostic criteria to the filtered signal can produce erroneous results. The BPF and RF should not be used in the measuring channels to record cardiac signals for detecting their low-amplitude potentials: VLP and ALP. Acknowledgment The research was financially supported by the Federal Target Program Research and development on priority directions of scientific technological complex of Russia in years, Project No Development of an experimental model of the hardware software complex for noninvasive recording of the heart micropotentials in a broadband without filtering and averaging in real time in order to detect the early signs of sudden cardiac death. The unique identifier of the contract: RFMEF157814X0032. References 1. Clifford GD, Azuaje F, McSharry PE (2006) Advanced Methods and Tools for ECG Data Analysis. Boston: Artech House Inc., p Biopotentials and Electrophysiology Measurement. Date Views ru.scribd.com/ doc/ /biopotential-measurement. 3. Kavcic B (2013) Electrodynamics of Human Heart. Seminar (1b-1 Year), II. Cycle Program, University of Ljubljana Faculty of Mathematics and Physics Department. 4. Yuzhakov MM (2012) Development and Research of Methods and Equipment with Nanovolt and Microvolt Levels for Electrophysiological Studies, Ph.D. Thesis, NRTPU, Tomsk. Article ID: BM Page 4 of 5

6 5. Zaitchenko KV, Zharinov OO, Kulin AN (1998) Osobennosti postroyeniya vkhodnykh kaskadov vysokochuvstvitel nykh usiliteley biopotentsialov. Voprosy radioelektroniki 1: Zaitchenko KV, Zharinov OO, Kulin AN (1999) Estimation of micropotentials of electrocardiograms for diagnostics of heart diseases. Medical & Biological Engineering & Computing 37: Trevis D (2005) LabVIEW for All. Moscow: Dmk Press, p Avdeeva DK, Lezhnina IA, Pen kov PG, Rybalka SA, Uvarov AA (2011) Experimental studies of high-sensitivity channel on nanoelectrodes for measuring human biopotential. Kontrol Diagnostika 11: Avdeeva DK, Rybalka SA, Yuzhakov MM (2012) Nanovolt and microvolt levels wideband signal method development for electrophysiological research. International Journal of Applied and Fundamental Research 11: Avdeyeva DK, Vylegzhanin ON, Grekhov IS, Kazakov VY, Kim VL, et al. (2009) Experimental results of electric activity of electronic ionic conduction junction. European Journal of Natural History 2: Citation: Avdeeva DK, Kazakov VY, Natalinova NM, Maksimov IV, Balahonova MV (2014) The effect of parameters of electrocardiograph measuring channel on recordings of micropotentials of the heart. Biol Med 6(2): BM Article ID: BM Page 5 of 5

Analysis of the effect of filtering elements on EEG and EMG recorded with high sensitivity channel based on nanoelectrodes. Biology and Medicine

eissn: 09748369 Analysis of the effect of filtering elements on EEG and EMG recorded with high sensitivity channel based on nanoelectrodes Biology and Medicine Research Article Volume 6, Issue 2, Article