Abstract
Objective:
Recently, it has been reported that ischemic postconditioning, a brief episode of ischemia-reperfusion performed after prolonged ischemia, can reduce ischemic myocardial injury. However, the effects of ischemic postconditioning on ischemia/reperfusion injury remain unclear. We investigated the effects of brief ischemia-reperfusion before (ischemic preconditioning) and after (ischemic postconditioning) prolonged ischemia on myocardial ischemia/reperfusion injury, especially reperfusion arrhythmias.
Methods:
Adult male Sprague-Dawley rats weighing about 400-500 g were used. The isolated heart was perfused using a working heart method (Krebs-Henseleit bicarbonate buffer). In the control group, after stabilization, diastolic global ischemia for 15 minutes was produced by a one-way ball valve with electrical pacing (330 bpm, 2.0 V). After ischemia, the heart was reperfused for 20 minutes. In the preconditioning and postconditioning groups, 5-minute global ischemia was produced before and after ischemia for 15 minutes with a 1 minute interval. An electrocardiogram was performed and left ventricular pressure (LVP, +dP/dt, -dP/dt) and CK activity in coronary effluent were measured during the protocol.
Results:
Ischemic preconditioning did not affect the incidence or duration of reperfusion ventricular arrhythmias. Ischemic postconditioning could terminate reperfusion ventricular arrhythmias completely and reduced the duration of reperfusion ventricular arrhythmias significantly (P < 0.01). Furthermore, the recovery ratio of +dP/dt at 20 minutes after initial reperfusion was significantly higher in the postconditioning group than in the other groups.
Conclusion:
These results suggest that ischemic postconditioning can terminate reperfusion arrhythmias with no reduction of cardiac function, and may be useful for correcting stunned myocardium.
