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A Review on Biomedical Signals with Fundamentals of Digital Signal Processing
Published in Mitul Kumar Ahirwal, Narendra D. Londhe, Anil Kumar, Artificial Intelligence Applications for Health Care, 2022
Mangesh Ramaji Kose, Mitul Kumar Ahirwal, Mithilesh Atulkar
There are different configurations of an ECG recording machine; having 3, 6, or 12 electrodes for monitoring the heart condition. In the standard 12-lead ECG instrument, 10 electrodes are placed on different body parts as shown in Figure 2.3 [3–5]. In Figure 2.4, different heart locations are shown with their role in providing the waveform shape of ECG signal. Ionic activities are controlled by sinoatrial (SA) node in heart. In SA node, the process of depolarization takes place and also spreads across the atrium. Atrial depolarization gives the shape of P wave with duration of approx 80 ms. Depolarization goes down up to ventricles from atrioventricular (AV) node. Depolarization of left and right ventricles gives the shape to QRS complex with duration of approx 80 to 100 ms. Then repolarization of atria and QRS complex are overlapped, therefore atrial repolarization remains hidden in QRS complex. Ventricular repolarization for duration of around 160 ms results in generation of T wave. The U wave in ECG signal is generated because of repolarization of papillary muscle, which can be ignored [5,6]. Characterization of heart diseases can be easily done on the basis of intervals of different waves in ECG signal.
Designing a Low-Cost ECG Sensor and Monitor: Practical Considerations and Measures
Published in Daniel Tze Huei Lai, Rezaul Begg, Marimuthu Palaniswami, Healthcare Sensor Networks, 2016
Ahsan H. Khandoker, Brian A. Walker
“An electrocardiogram (ECG) is a graphic tracing of the electric current generated by the heart muscle during a heartbeat” (Low et al. 2006, p. 66). This current generates electric potentials on the surface of the skin. Figure 13.2 shows the deflection components making up the ECG signal (Low 2006). The QRS complex is sometimes subdivided into Q, R and S waves and is called a complex because of the usual presence of all three of these waves. The first or second positive waves above the baseline are known as the R waves. A negative wave following an R wave is known as an S wave, and a negative wave which precedes an R wave is known as a Q wave (Das 2006). The U wave is sometimes present in the ECG signal and is usually less than one-third of the T wave amplitude. The U wave represents the last phase of ventricular repolarization and is best seen when the heart rate is slow (Huff 2005).
AI-Based Approach for Person Identification Using ECG Biometric
Published in Gaurav Jaswal, Vivek Kanhangad, Raghavendra Ramachandra, AI and Deep Learning in Biometric Security, 2021
Amit Kaul, A.S. Arora, Sushil Chauhan
An ECG waveform consists of P-QRS-T waves; a small U wave may also be sometimes present. Each of these characteristic points in ECG is related to electrical activity in human heart during one cardiac cycle. The P-wave represents the atrial depolarisation, resulting in response to SA node triggering; PR interval indicates the AV node delay; the QRS complex characterizes the depolarisation of the ventricles, and finally the ventricular repolarisation is depicted by the T-wave.
Automatic atrial fibrillation detection from short ECG signals: A hybrid deep learning approach
Published in IISE Transactions on Healthcare Systems Engineering, 2022
Xiaodan Wu, Zeyu Sui, Chao-Hsien Chu, Guanjie Huang
During normal cardiac electrical activity, P-wave, QRS complex wave and T-wave appear successively in the ECG signals, and sometimes U-wave can also be seen. However, during the onset of AF, RR intervals will become irregular, and the P wave will also disappear, replaced by a series of continuous, fast, and irregular atrial excitation waves (Harris et al., 2012; Hennig et al., 2006). In this paper, RR intervals of ECG signals are extracted for comparative experiments of machine learning algorithms.
Predicting the cardiac toxicity of drugs using a novel multiscale exposure–response simulator
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2018
Francisco Sahli Costabal, Jiang Yao, Ellen Kuhl
Figure 9 summarizes the electrocardiogram recordings for the baseline case at 0x in Figure 5 and drug treatment with dofetilide at concentrations of 1x, 5.7x, and 30x in Figures 6–8. The baseline electrocardiogram displays a regular periodic activation pattern with characteristic QRS complexes and T waves, which repeat themselves identically every 1000 ms at a heart rate of 60.15 beats per minute. The dofetilide 1x electrocardiogram displays a regular periodic activation pattern similar to the baseline case. A dofetilide concentration of 1x moderately prolongs the plateau of the single-cell action potential in Figure 4, which translates into a prolongation of the QT interval of 55% compared to baseline. This agrees well with the delayed repolarization patterns in Figure 6. Although this is a quite significant prolongation, the heart maintains its normal sinus rhythm, which repeats itself identically every 1000 ms at a similar heart rate as the baseline case. The dofetilide 5.7x electrocardiogram displays a regular depolarization during the first 50 ms. With increasing drug concentration, the plateau of the single-cell action potential in Figure 4 increases, which translates into an increase of the QT interval in the electrocardiogram. A concentration of 5.7x prolongs the initial QT interval by 102% compared to baseline. This significantly prolonged QT interval makes the heart vulnerable to the spontaneous formation of ventricular fibrillation. During the first and second cycle, the T wave is followed by a marked U wave, a classical indicator for early afterdepolarizations or prolonged repolarization of myocardial midwall cells. After the first two cycles, at about 1500 ms, the dofetilide 5.7x electrocardiogram spontaneously transitions into a sequence of rapid, widened irregular QRS complexes, a characteristic hallmark of torsades de pointes, which agrees well with the observed excitation patterns in Figures 7. The dofetilide 30x electrocardiogram displays a regular depolarization during the first 50 ms. A concentration of 30x prolongs the initial QT interval by 132% compared to baseline. After the first T wave, the electrocardiogram shows a complete loss of coordinated excitation with irregular uncoordinated patterns that bear no resemblance with the regular sinus rhythm of the baseline case. This agrees well with the uncoordinated small local excitation patterns in Figures 8.
Comparison of NASA-TLX scale, modified Cooper–Harper scale and mean inter-beat interval as measures of pilot mental workload during simulated flight tasks
Published in Ergonomics, 2019
Heikki Mansikka, Kai Virtanen, Don Harris
Variations in arousal, effort and general activation level cause physiological changes. This has motivated the use of various physiological measures as indices of MWL. The major advantage of physiological measures is their ability to provide continuous, real time monitoring of the operator state (Jorna 1993). Another advantage is their objectivity, which also increases their utility in scenarios where it is reasonable to expect that subjective opinions are not accurate (Gopher and Donchin 1986). Although MWL cannot be measured directly, the heart’s responses to the neurological modulation provide an indirect method for its measurement; nerve activity causes electronic impulse transmissions in and around the heart, which can be recorded and interpreted with an electrocardiograph (ECG). A normal ECG consists of a P-wave, a QRS complex, followed by a T-wave and U-wave, each representing different de- and repolarization phases within the heart’s muscular cells. Once the QRS complexes are detected from the ECG, the normal-to-normal (NN) inter-beat interval (IBI) and differences between the NN intervals can be determined. When NN intervals are analysed, a decreased NN interval or a lowered mean of the IBIs between successive heart beats can be used as indirect indicators of increased MWL. IBI and IBI interval differences have been successfully used to measure task demand variations both in a flight simulator and in actual flight (Roscoe 1975; Aasman, Mulder, and Mulder 1987; Jorna 1993; Roscoe 1993; Wilson 1993; Svensson et al. 1997; Ylönen et al. 1997; Veltman and Gaillard 1998; Svensson, Angelborg-Thanderz, and Wilson 1999; Svensson and Wilson 2002; Dahlstrom and Nahlinder 2009; Mansikka et al. 2016a, 2016b). It is a common practice to use the R-wave peak as a reference point in measurements as it is typically the strongest wave and can, therefore, be easily detected even in noisy conditions. To emphasize the reference point used, the literature typically uses terms R-wave to R-wave (RR) interval and RR interval difference (or IBI and IBI difference) (Opmeer 1973; ChuDuc, NguyenPhan, and NguyenViet 2013). Out of the different methods available, this study used time domain methods to analyse RR intervals and RR interval differences. The time domain analysis techniques are based on the statistical analysis of the series of successive RR intervals. In its simplest form, the statistical analysis is used to determine IBI. It was expected that the simplicity of the method would encourage a broader audience to utilise the methods used in this study.