Prolongation of The Activation Time in Ischemic Myocardium is Associated with J-wave Generation in ECG and Ventricular Fibrillation

Abstract

J-wave pattern has been recognized as an arrhythmic risk marker, particularly in myocardial infarction patients. Mechanisms underlying J-wave development in ischemia remain unknown. In myocardial infarction model, we evaluated activation time delay as a prerequisite of J-wave appearance and predictor of ventricular fibrillation. Body surface ECGs and myocardial unipolar electrograms were recorded in 14 anesthetized pigs. 48 intramural leads were positioned across ventricular free walls and interventricular septum. Myocardial ischemia was induced by ligation of the left anterior descending coronary artery and the recordings were done during 40-minute coronary occlusion. The local activation times were determined as instants of dV/dt minimum during QRS complex in unipolar electrograms. During occlusion, ventricular local activation time prolonged in the middle portion of the left ventricular free wall, and basal and middle portions of septum, while J-waves appeared in precordial leads in 11 animals. In logistic regression and ROC curve analyses, activation time delay at a given time-point was associated with J-wave development, and a longer activation time was associated with ventricular fibrillation appearance. In experimental coronary occlusion, activation delay in ischemic myocardium was associated with generation of the J waves in the body surface ECG and predicted ventricular fibrillation.

Contribution of Depolarization and Repolarization Changes to J-Wave Generation and Ventricular Fibrillation in Ischemia

“…However, it was pointed out that not every ever observed J-wave necessarily predicts ventricular fibrillation or sudden cardiac death ( Bourier et al, 2018 ; Demidova et al, 2019 ). Our previous ( Azarov et al, 2019 ) and present studies demonstrated that both repolarization- and depolarization-related mechanisms are involved in J-wave generation in the ischemic conditions. However, only activation delay is associated with VF incidence.…”

“…Similarly, J-wave appeared under inhibition of sodium current (Meijborg et al, 2016). In the previous study (Azarov et al, 2019),…”

“…Similarly, J-wave appeared under inhibition of sodium current ( Meijborg et al, 2016 ). In the previous study ( Azarov et al, 2019 ), we directly showed an association between activation delay in the ischemic myocardium and J-wave development in the precordial leads. Clinical data ( Nakayama et al, 2013 , 2019 ) also suggest that conduction delay facilitates formation of J-waves in patients with myocardial ischemia.…”

“…The study conformed to the Guide for the Care and Use of Laboratory Animals, 8th Edition published by the National Academies Press (United States) 2011, the guidelines from Directive 2010/63/EU of the European Parliament on the protection of animals used for scientific purposes and was approved by the Ethical Committee of the Institute of Physiology of the Komi Science Centre, Ural Branch of Russian Academy of Sciences. Experimental procedures were described earlier (Azarov et al, 2019). Briefly, the animals were anesthetized with zoletil (Virbac S.A., Carros, France, 10-15 mg/kg, i.m.…”

“…A conduction block-related mechanism could be responsible for J-wave augmentation with cycle length shortening in acute myocardial infarction patients ( Nakayama et al, 2013 , 2019 ). Recently, in an in vivo model of acute myocardial infarction, we directly demonstrated an association between activation delay in the ischemic myocardium, J-wave, and VF occurrence ( Azarov et al, 2019 ). However, a role, if any, of repolarization abnormalities in these phenomena in ischemia has not yet been tested.…”