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Electrocardiography and arrhythmias
Published in Neil Herring, David J. Paterson, Levick's Introduction to Cardiovascular Physiology, 2018
Neil Herring, David J. Paterson
VT is a dangerous arrhythmia that originates within the ventricle, usually when there is an abnormal structural substrate (such as ischaemia or infarction, dilated cardiomyopathy, hypertrophic cardiomyopathy or arrhythmogenic right ventricular cardiomyopathy) or an abnormal electrophysiological substrate (such as LQT syndrome, or Na+ channel [SCN5A] mutations causing Brugada syndrome). The ECG shows a characteristic regular broad complex tachycardia (Figure 5.18). The atria are not involved in the circuit although they can be activated retrogradely through the AV node in up to 10% of cases. Occasionally, P waves can be observed on the ECG but they are completely dissociated from the broad complex rhythm. Sometimes, a P wave may conduct through the AV node to give a narrow complex capture beat, or collide with the VT circuit to form a fusion beat. At slower rates, VT may cause palpitations but if the rate is more rapid so that cardiac output falls significantly, then symptoms such as breathlessness and chest pain can occur. If the rate is more rapid still, then VT can lower blood pressure and reduce cerebral perfusion, so that loss of consciousness may occur, or cardiac output may fall to nothing and a cardiac arrest ensue. VT can also change from a single re-entry circuit into multiple wavelets and fibrillation if wavebreak occurs. VT should therefore be treated with emergency cardioversion either pharmacologically or, if there is any haemodynamic compromise, electrically.
Classification of normal sinus rhythm, abnormal arrhythmia and congestive heart failure ECG signals using LSTM and hybrid CNN-SVM deep neural networks
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Ahmet Çınar, Seda Arslan Tuncer
Current arrhythmia classification techniques report low accuracy for several classes of arrhythmias due to class conflict and class imbalance problems. Arrhythmias are divided into five classes: ANSI/AAMI EC57: non-ectopic beat (N), supraventricular ectopic beat (S), ventricular ectopic beat (V), fusion beat (F) and unknown beat (Q) according to 2012 (AAMI 2012). Algorithms used for arrhythmia classification include preprocessing, feature extraction, and classification. Classification becomes complicated when class conflict and class imbalance problems occur together.