ECG Markers of Acute Melatonin Treatment in a Porcine Model of Acute Myocardial Ischemia.

In myocardial ischemia, melatonin confers antiarrhythmic action, but its electrocardiographic expression is unclear. We aimed to evaluate the effects of melatonin treatment on electrocardiogram (ECG) parameters reflecting major arrhythmogenic factors and to test the association of these parameters with ventricular fibrillation (VF) incidence. Myocardial ischemia was induced by 40 min coronary artery occlusion in 25 anesthetized pigs.

Melatonin Prevents Early but Not Delayed Ventricular Fibrillation in the Experimental Porcine Model of Acute Ischemia.

Antiarrhythmic effects of melatonin have been demonstrated ex vivo and in rodent models, but its action in a clinically relevant large mammalian model remains largely unknown. Objectives of the present study were to evaluate electrophysiological and antiarrhythmic effects of melatonin in a porcine model of acute myocardial infarction. Myocardial ischemia was induced by 40-min coronary occlusion in 25 anesthetized pigs.

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

: Activation delay in ischemic myocardium has been found to contribute to J-wave appearance and to predict ventricular fibrillation (VF) in experimental myocardial infarction. However, the role of ischemia-related repolarization abnormalities in J-wave generation remains unclear. : The objective of our study was to assess a contribution of myocardial repolarization changes to J-wave generation in the body surface ECG and VF in a porcine acute myocardial infarction model.

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

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.

Functional role of myocardial electrical remodeling in diabetic rabbits.

The objective of the study was to investigate the role of electrical remodeling of the ventricular myocardium in hemodynamic impairment and the development of arrhythmogenic substrate. Experiments were conducted with 11 healthy and 12 diabetic (alloxan model, 4 weeks) rabbits. Left ventricular pressure was monitored and unipolar electrograms were recorded from 64 epicardial leads.

The contribution of ventricular apicobasal and transmural repolarization patterns to the development of the T wave body surface potentials in frogs (Rana temporaria) and pike (Esox lucius).

The study aimed at the simultaneous determination of the transmural and apicobasal differences in the repolarization timing and the comparison of the contributions of these two repolarization gradients to the development of the body surface T wave potentials in animals with the single heart ventricle (fishes and amphibians). Unipolar potentials were measured on the body surface, epicardium and in the intramural (subepicardial, Epi; midmyocardial; and subendocardial, Endo) ventricular layers of 9 pike and 8 frogs. Activation times, repolarization times and activation-recovery intervals were determined.