Postconditioning markedly attenuates ventricular arrhythmias after ischemia-reperfusion

Background: Brief periods of reocclusion (postconditioning) during early reperfusion reduce myocardial infarct size. Whether postconditioning has all effect on lethal ventricular arrhythmias independent of infarction in an in-vivo regional ischemia model is unknown. The purpose of this study was to determine if postconditioning limited reperfusion arrhythmias in a necrosis-free model. Methods: Anesthetized rats were subjected to 5 minutes of proximal coronary artery occlusion; they were randomized to a control group (n = 15) that underwent reperfusion alone or a postconditioning group (n = 15) that received four cycles of 20 seconds reperfusion, 20 seconds reocclusion before final reperfusion. Results: During the final reperfusion phase, venticular arrhythmias occurred in 14 of 15 control rats and 8 of 15 postconditioning rats (P=.017). Venticular tachycardia occurred in 10 of 15 control rats vs 4 of 15 postconditioning rats (P =.028). Control rats demonstrated 1.3 runs of venticular tachycardia per minute vs 0.4 runs in postconditioning rats (P =.026). The average duration of venticular tachycardia runs was 8.8 +/- 3.2 seconds in the control group vs 5.0 +/- 3.9 seconds in postconditioning rats (P = NS). Conclusion: This in-vivo study showed that postconditioning markedly attenuates venticular arrhythmia after regional ischemia in a noninfarct model.