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Electrocardiogram
Published in Kayvan Najarian, Robert Splinter, Biomedical Signal and Image Processing, 2016
Kayvan Najarian, Robert Splinter
As mentioned earlier, the A-V node is slower than the S-A node, and, as a result of various illnesses, the conduction from S-A node to A-V node can be interrupted. This is called AV block. Under these circumstances, the atria will contract faster than the ventricles and the pump function will be severely compromised. As discussed earlier, if the P wave precedes the QRS complex with a PR interval of 0.12 s, the AV conduction is normal. If the PR interval is fixed but shorter than normal, either the origin of the impulse is closer to the ventricles or the AV conduction is utilizing an (abnormal) bypass tract leading to preexcitation of the ventricles. The latter is called the Wolff–Parkinson–White (WPW) syndrome and is discussed later. The PR interval may also be variable, such as in a wandering atrial pacemaker and multifocal atrial tachycardia. An example of the ECG recorded during a third-degree AV block is shown in Figure 9.13.
Cardiac dysrhythmia management in the radiology department
Published in William H. Bush, Karl N. Krecke, Bernard F. King, Michael A. Bettmann, Radiology Life Support (Rad-LS), 2017
The rate is usually 150–250 beats/min, both atrial and ventricular. The rhythm is perfectly regular. P waves are present, but may be very difficult to identify, and may not have the normal rounded shape, since they do not originate in the SA node. If a PR interval can be measured, it is usually within normal limits. The QRS complex is normal, except in the presence of an accessory pathway.
Machine Learning-Based Rapid Prediction of Sudden Cardiac Death (SCD) Using Precise Statistical Features of Heart Rate Variability for Single Lead ECG Signal
Published in Sourav Banerjee, Chinmay Chakraborty, Kousik Dasgupta, Green Computing and Predictive Analytics for Healthcare, 2020
An ECG is a graphic representation of the electrical activity of the hearts condition system recorded over a period of time. Under normal conditions, ECG tracing has a very predictable direction, duration and amplitude. The ECG is also used to monitor the heart’s response to therapeutic intervention [17]. The normal ECG configuration is composed of waves, complexes, segment and intervals which are directly related to different phases of action potential. Each phase is distinguished by an alteration of sodium, potassium and calcium ions. The quick movement of positive ions of sodium causes depolarization [18]. After moving the depolarization wave, the heart muscle cells return to their rest state to start resting negative potential. Two or more waveforms together are called a complex. A flat, straight or isoelectric line is called a segment. A waveform or complex connected to a segment is called an interval. All ECG tracings above the baseline are described as positive deflections. Waveforms below the baseline are negative deflections [19]. The ECG over a single cardiac cycle has a characteristic morphology comprising a P wave, a QRS complex and a T wave. The P-wave is the first deflection of the ECG. It results from depolarization of the atria. Atrial re-polarization occurs during ventricular depolarization and is obscured, which is shown in Figure 4.1. The QRS complex corresponds to the ventricular depolarization [20]. The T-wave represents ventricular rapid re-polarization. The PR interval represents the time for an impulse to travel from the atria to the ventricles. The Q-T interval represents ventricular depolarization and re-polarization [21]. The PQ interval expresses the time consumed from atrial depolarization to the onset of ventricular depolarization. The ST interval coincides with the slow and rapid re-polarization of ventricular muscle. The Q-T interval corresponds to the duration of the ventricular action potential and re-polarization. The R-R interval represents one cardiac cycle and it is used to calculate the heartrate [21,22]. The typical shape of the ECG signal and its essential waves and characteristic point is represented in Figure 4.2.
Machine learning-based automatic sleep apnoea and severity level classification using ECG and SpO2 signals
Published in Journal of Medical Engineering & Technology, 2022
Gizeaddis Lamesgin Simegn, Hundessa Daba Nemomssa, Mikiyas Petros Ayalew
The QRS complex represents is the combination of three graphical deflections of an ECG and represents the ventricular depolarisation. It is used to obtain clinical information from ECG signal including RR interval, QT interval and PR interval. Detection of QRS is critical for ECG-based heart disease diagnosis. In this study, the Pan-Tompkins algorithm-based QRS detection method has been adopted [23]. This algorithm uses three steps to detect a QRS including filtering, transformation and decision rule. In the first step, a band pass filter with cut-off frequencies of 5 and 15 Hz is used to emphasise the QRS and hindering false peaks or noises. Then a derivate is used to obtain slope information followed by squaring function which further attenuates other ECG features leaving the QRS complexes as an outstanding positive peaks regardless of the polarity. Then a moving window function results a large amplitude pulse for each QRS and decreasing amplitude of noise spikes. At the end, an adaptive thresholding method is used to select peaks with relatively bigger amplitudes, which are candidate R peaks.
Spectral feature and optimization- based actor-critic neural network for arrhythmia classification using ECG signal
Published in Journal of Experimental & Theoretical Artificial Intelligence, 2020
Anoop Vylala, Bipin Plakkottu Radhakrishnan
The PR interval denotes the time interval between the P wave of the point and the R wave of the point. In other words, the PR interval is the time duration between the P wave of the point and the R wave of the successive point. The mean of the total number of points is determined to present the PR feature of the ECG signal.