EFFECTS OF ISCHEMIC PRECONDITIONING ON VENTRICULAR ARRHYTHMIAS DURINGISCHEMIA AND REPERFUSION USING A RETROGRADE BLOOD-FLOW MODEL IN DOGS

We examined the effects of ischemic preconditioning on ventricular arr hythmias during ischemia and reperfusion from the electrophysiologic p oint of view by using the retrograde blood flow (RBF) model, which cau ses severe ischemia. A total of 51 anesthetized dogs were divided into 3 groups. Group 1 (10-min simple occlusion) consisted of 15 dogs; gro up 2 (10-min RBF) consisted of 20 dogs; and group 3 (10-min RBF with p reconditioning) consisted of 16 dogs. Preconditioning consisted of 5 c ycles of 2 min of ischemia (RBF) and 5 min of reperfusion. In the sube picardium, myocardial blood flow (MBF) in group 2 was significantly lo wer than in group 1 or group 3 [group 2 (4.7 +/- 2.3 ml/min per 100 g) vs group 1 (35.0 +/- 5.8) or group 3 (22.0 +/- 4.6); p < 0.03 and p < 0.05 respectively]. However, there were no differences in MBF in the subendocardium between the 3 groups. The incidence of conduction block in the subepicardium was significantly higher in group 2 than in grou p I or group 3 [group 2 (85%) vs group 1 (33%); p < 0.01; vs group 3 ( 38%), p < 0.01]. There were no differences in the incidence of conduct ion block in the subendocardium between the 3 groups. During IO-min is chemia, the incidences of ventricular fibrillation (VF) were 7% in gro up 1, 35% in group 2, and 6% in group 3 (group 2 vs group 1, p < 0.05; and group 2 vs group 3, p < 0.05). During 10-min reperfusion, the inc idences of VF were 29% in group 1, 77% in group 2, and 33% in group 3 (group 2 vs group 1, p < 0.05; and group 2 vs group 3, p < 0.05). Vent ricular arrhythmias were reduced during both 10-min ischemia and 10-mi n reperfusion as a result of the improvement in the conduction compone nts by ischemic preconditioning which increased MBF in the subepicardi um.