Nonuniform epicardial depolarizations during coronary occlusion in dogs

Epicardial electrograms were recorded before and after occlusion of the left anterior descending coronary artery. The greatest difference between the post-occlusion and pre-occlusion depolarization times were determined. These times were referred to as the normalized times of greatest disparity, delta tmax. It was found that following both one- and two-stage occlusion of the LAD there was a significant increase in delta tmax in the ischemic area of the myocardium. This indicates increased asynchrony of depolarization. However, no significant change in depolarization times occurred in the unaffected area. In one-stage occlusion with an increase in delta t max there was a linear correlation with the development of ventricular arrhythmias, especially ventricular premature beats and tachycardia. Thus, there is evidence which links the increase in depolarization times with the mechanism of reentry and ventricular arrhythmias.