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Myocarditis
Published in Andreas P. Kalogeropoulos, Hal A. Skopicki, Javed Butler, Heart Failure, 2023
George Lazaros, Emilia Lazarou, Dimitris Tousoulis
An ECG should be obtained in all suspected cases of myocarditis. Although a non-specific tool, the ECG shows pathologic findings in most patients with acute myocarditis.14,15 Most patients present with non-specific repolarization abnormalities. ST-segment elevation may raise differential diagnostic issues with acute myocardial infarction.14 Newly appearing Q waves, abnormal QRS axis, and prolongation beyond 120 ms, a QTc greater than 440 ms, and ventricular ectopy have been associated with adverse outcome and a need for transplantation.41
Targeting the Nervous System
Published in Nathan Keighley, Miraculous Medicines and the Chemistry of Drug Design, 2020
The energy from a stimulus causes a temporary reversal of charge in the axon membrane, due to the opening of voltage-gated channels. As the action potential passes, the sodium-potassium pump is turned off, while sodium voltage-gated channels open, allowing Na+ to diffuse into the axon along their electrochemical gradient and potassium ion channels close. This causes a reversal of charge across the axon membrane and an action potential of +40 mV is generated. This wave of depolarisation proceeds along regions of the axon, causing sodium ion channels to open, and then close in a Mexican wave-like fashion. These channels then remain closed during a refractory period to ensure that the nerve impulses are discrete and unidirectional. Repolarisation occurs when the potassium ion channels open again and K+ diffuse back out of the axon and the sodium-potassium pump reactivates.
The patient with acute cardiovascular problems
Published in Peate Ian, Dutton Helen, Acute Nursing Care, 2020
T wave: once the cells of the ventricular myocardium have been depolarised, they begin the process of returning to their normal resting state. Depolarisation is achieved by a rapid influx of positive ions, these need to move back across the cell membrane to reach its resting state in the process of repolarisation. This repolarisation phase lasts longer than depolarisation, hence the T wave is wider than the corresponding QRS complex that precedes it. The ST segment sits on the isoelectric line.
Comparison of different QT correction methods for nonclinical safety assessment in ketamine-anesthetized Indian rhesus monkeys (Macaca mulatta)
Published in Toxicology Mechanisms and Methods, 2023
Laxit K. Bhatt, Chitrang R. Shah, Rajesh J. Patel, Shital D. Patel, Sudhir R. Patel, Vipul A. Patel, Jitendra H. Patel, Pankaj Dwivedi, Niraj A. Shah, Rajesh S. Sundar, Mukul R. Jain
QT interval is the measure of the length from the onset of the QRS complex to the end of the T wave in one cardiac cycle, representing ventricular depolarization and repolarization (Chaves et al. 2006). QT interval varies with heart rate (HR); an inversely proportional relationship wherein a shorter QT interval is recorded for faster heart rates and vice versa (Chaves et al. 2006; Guth 2007). This has prompted researchers to develop a QT correction formula that adjusts the impact of HR on QT interval. The corrected QT interval (QTc) has widespread clinical and pharmaceutical significance (Chaves et al. 2006; Guth 2007). Various QT correction formulas are available currently. They can be divided into three types: population correction methods, test specific/individual correction methods and Holter bin methods. The population correction method can be used at any time and is the most popular (Holzgrefe et al. 2014).
Activation of SK3 channel plays a pivotal role in modulation of trigeminal neuralgia
Published in Neurological Research, 2021
Jiaomei Zhao, Yue Zhang, Xiangbo Liu, Yong Rao, Jia Fu, Lu Hua, Cehua Ou
CyPPA is a selective SK3 activator, which can regulate the Ca2+ influx into the cell, mediate hyperpolarization and affect cell activity [23]. Mechanical allodynia testing was carried out using different dosages of CyPPA (20 μg, 50 μg, 100 μg), controlled by 0.1 ml normal saline and Apamin. We found that there was a dose-dependent increase of facial mechanical pain threshold during the period of 20–60 min after operation. The pain threshold was decreased by injection of Apamin, which can be reversed by injection CyPPA. It might be accounted by ion channel activation that triggered the membrane potential repolarization and even hyperpolarization, and limited action potential discharge frequency, so as to avoid the afferent of injurious stimuli. The gradual recovery of the pain threshold during the period of 80–120 min after operation was related to the membrane potential equilibrium caused by ion influx and the absence of action potential. However, the certain amount of drug reaching TG, the amplitude of action potential and discharge frequency caused by the drug needed to be further explored by patch clamp and other technologies.
Comparison of ventricular repolarization parameters of Covid-19 patients diagnosed with chest CT and RT-PCR
Published in Acta Cardiologica, 2021
Ersin Ibisoglu, Bedrettin Boyraz
Regarding the risk of developing arrhythmia, the repolarization phase provides important determination and is an important predictor of arrhythmia in cardiac electrophysiology. In terms of 12-lead ECG, the QT interval is also important and is largely determined by the duration of repolarization, which corresponds to the JT interval. Therefore, the JT interval is more effective than the QT in measuring ventricular repolarization [19]. Furthermore, the prediction of incident cardiovascular events was better with the JT interval than with the QT interval [20,21]; the QT interval, JT interval, and Tp-e measurements, which are the main predictors of ventricular arrhythmia, and the relationship between QT and JT intervals are useful parameters indicating whether patients are susceptible to ventricular arrhythmia [8,22,23].