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Feature-based approaches
Published in Elizabeth Ann Maharaj, Pierpaolo D'Urso, Jorge Caiado, Time Series Clustering and Classification, 2019
Elizabeth Ann Maharaj, Pierpaolo D'Urso, Jorge Caiado
A typical waveform from a single heart beat is shown in Figure 9.1. Any ECG signal imparts two pieces of information. The first is the duration of the electrical wave crossing the heart which in turn works out whether the electrical activity is normal, slow, or irregular, and the second is the amount of electrical activity passing through the heart muscle which determines whether parts of the heart are too large or overworked. Normally, the frequency range of an ECG signal is of 0.05-100 Hz and its dynamic range is of 1 - 10 mV. The ECG is characterized by five peaks and valleys labeled by the letters P, Q, R, S, T. In some cases another peak, the one to the extreme right in Figure 9.1. and referred to U is also present. The performance of an ECG analysing system depends mainly on the accurate and reliable detection of the QRS complex, as well as the T- and P-waves. The P-wave represents the activation of the upper chambers of the heart, the atria, while the QRS complex and the T-wave represent the excitation of the lower chambers of the heart, the ventricles. The QRS complex is the most prominent part of the waveform within the ECG signal. Since it reflects the electrical activity within the heart during ventricular contraction, the time of its occurrence as well as its shape provide some information about the current state of the heart.
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 electrocardiogram records the complex electrical events that occur in the heart with each cardiac cycle by assuming that the body can be regarded as a giant conductor of electrical currents. Any two points on the body surface can be connected to positive and negative ‘leads,’ with current flowing towards the positive electrode producing an upward deflection on the ECG trace. The 12-lead ECG ‘looks’ at the electrical activity in 12 different directions, any one of which could be used to evaluate the rhythm. The ‘standard limb-leads’ are conveniently selectable on most cardiac monitors by using only three leads connected to the patient. By convention, the resulting complexes are labeled the P wave, the QRS complex and the T wave. (see Fig. 6.1). Atrial depolarization produces the P wave, which is normally upright in lead II. The PR interval represents the normally slower conduction through the AV node, and should not exceed 0.2 s. The QRS complex represents ventricular depolarization, with the Q wave (the first negative deflection) not always visible. As viewed in lead II, the R wave is the next positive (upward) deflection, followed by a negative S wave. Because ventricular depolarization is a rapid event, the normal QRS is narrow and should not exceed 0.1 s. Atrial repolarization is obscured by the QRS complex. The ST segment represents the time from complete depolarization of the ventricles to the beginning of repolarization. Since no net electrical activity is occurring during this recovery phase of the cardiac cycle, the ST segment is normally flat. With ischemia or injury, the ST segment may be elevated or depressed. Ventricular repolarization results in the T wave, which is usually upright in lead II.
Electrocardiogram
Published in Kayvan Najarian, Robert Splinter, Biomedical Signal and Image Processing, 2016
Kayvan Najarian, Robert Splinter
Another characteristic of ventricular disturbance is the premature ventricular contraction. A premature ventricular contraction is one that occurs abnormally early. If the origin of the disturbance is in the ventricular muscle, the QRS complex has a very abnormal form and lasts longer than 0.1 s. Usually the P wave is not associated with it. The arrhythmogenic complex produced by this supraventricular arrhythmia lasts less than 0.1 s.
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.
IoT-enabled cloud-based real-time remote ECG monitoring system
Published in Journal of Medical Engineering & Technology, 2021
Manju Lata Sahu, Mithilesh Atulkar, Mitul Kumar Ahirwal, Afsar Ahamad
The rhythmic activity of ECG signal is used for calculation of the HR and the peaks of the sections of the cardiac cycle. It is also used in the investigation of the abnormal heart rhythms and helps in the diagnosis of a cardiac condition or ailments if heart hurts or produces any other irregular signs. The acquired ECG signal can be segmented as P wave, T wave and QRS complex [29]. Different time intervals such as PR, QRS, QT and ST are obtained as shown in Figure 3. QRS complex is considered as the most important feature of the ECG signal to derive the heart information and cardiac cycle from its features. The time duration of different ECG wave, intervals and segments are presented in Table 2. The process of ECG peak detection and abnormality detection is shown in Figure 4.
Adaptive multi-phase approach for solving the realistic vehicle routing problems in logistics with innovative comparison method for evaluation based on real GPS data
Published in Transportation Letters, 2022
Emir Žunić, Sead Delalić, Dženana Đonko
The similarity of the QRS complex detection problem on the ECG signal and the detection of this type of anomalies in GPS coordinates was observed, as is shown in Figure 5. In the left figure, the X-axis represents time, while the Y-axis represents above defined distances. The ECG is a graphical representation of cardiac activity. The signal is divided into specific parts that represent significant points for cardiac activities and are indicated by the letters: P, Q, R, S, T, U. The QRS complex is part of the ECG signal that can detect heartbeats and are of great importance for detection a large number of heart diseases. The peak of the R signal represents the point at which the signal has a higher amplitude than the rest of the PQRSTU signal.