A Study of Ventricular Arrhythmias Associated with Acute Myocardial Infarction in the Canine Heart

A study was designed to correlate changes in bipolar epicardial electrograms recorded from normal and acutely infarcted myocardium with the onset of ventricular arrhythmias. Electrodes were sewn to selected sites on the left ventricle, and after control electrograms and ECG's were recorded, the left anterior descending coronary artery was doubly ligated close to its origin. Electrograms recorded from within the infarct initially manifested diminished amplitude and increased duration of the deflection which reflected depolarization. The appearance of ventricular arrhythmias during phase 1 of Harris was associated with the appearance in electrograms recorded from within the infarct of continuous electrical activity which extended beyond the T wave of the preceding beat and preceded the onset of the arrhythmia. During the continuous electrical activity, it was not possible to delineate which deflections of the electrogram reflected depolarization or repolarization and it was suggested that the continuous electrical activity was localized fibrillation. For three experiments in which no arrhythmias occurred during phase 1 of Harris and for all animals which survived into phase 2 of Harris, the absence of ventricular arrhythmias was correlated with the absence of continuous electrical activity or locallized fibrillation recorded from within the area of the infarct.