Regional myocardial blood flow and ventricular arrhythmias following one-stage and two-stage coronary artery occlusion in anesthetized dogs

Experiments were performed in 29 anesthetized dogs to compare effects of one-stage and two-stage coronary artery occlusion on ventricular arrhythmias and regional myocardial blood flow (MBF). Two periods of arrhythmias were observed and both were associated with evidence suggesting reentry; i.e., activity in ischemic zone electrograms which bridged the diastolic intervals preceding ventricular ectopic beats. Early ventricular arrhythmias followed progressive deterioration of conduction in the ischemic zone, whereas later arrhythmias occurred unexpectedly with the sudden appearance of bridging activity. One-stage occlusion produced a higher incidence of ventricular arrhythmias and ventricular fibrillation than two-stage occlusion. However, there was no difference in central ischemic zone blood flow, indicating that the protective effect of two-stage occlusion was not due to greater blood flow in this region. These results suggest that factors other than the degree of MBF reduction are important determinants of the incidence and severity of ventricular arrhythmias following coronary artery occlusion.