Contrasting incidence, inducibility, and transmural sites of origin of ventricular arrhythmias during acute coronary occlusion and reperfusion.

The incidence, inducibility, and sites of origin of ventricular arrhythmias were studied in 16 open-chest dogs. The dogs were placed on cardiopulmonary bypass. Electrograms from ischemic endocardium and epicardium and normal epicardium were recorded with bipolar composite electrodes. Burst pacing was used to induce arrhythmias. Dogs were studied in the control state, 15 minutes after left anterior descending coronary artery occlusion, and during reperfusion performed after 20 minutes of occlusion. Ventricular fibrillation was seen more commonly (in 8 of 14 dogs) during reperfusion than during occlusion (in 4 of 13 dogs). Continuous fragmented electrical activity was first recorded on the ischemic zone epicardium in six of eight episodes during occlusion arrhythmias and on the endocardium in 25 of 33 episodes during reperfusion. These data may relate to the effects of varying degrees of ischemia and reperfusion on conduction characteristics of the respective layers.