The protective effect of preconditioning on reperfusion-induced arrhythmia is lost by treatment with superoxide dismutase.

The purpose of this study was to investigate the relation between free radicals and the effect of preconditioning on reperfusion arrhythmias using the isolated working rat heart model. Rats were divided into 3 groups: control, preconditioned without superoxide dismutase (SOD) and preconditioned with SOD (n = 8 each group). The incidence of reperfusion-induced ventricular fibrillation (Vf) in the preconditioned without SOD group was reduced from 100% to 13% (p < 0.005 vs control). This protective effect of preconditioning was not observed in the SOD-treated group (incidence of Vf increased from 13% to 75%, p < 0.025). The protective effect of preconditioning on reperfusion arrhythmias is related to the presence of oxygen free radicals which occur during the reperfusion period of the preconditioning phase.