Anti-arrhythmic Effect of Melatonin in Reperfusion-induced Arrhythmia

ABSTRACT

BACKGROUND: Recently, a few studies demonstrated that melatonin reduced the severity of myocardial reperfusion injuries, such as reperfusion arrhythmias. However, it is uncertain whether the melatonin reduces reperfusion arrhythmias in thus anesthetized animals because results were obtained using isolated hearts. Thus, to see whether melatonin reduces reperfusion arrhythmias in anesthetized animals, we examined the effect of melatonin on the incidence of reperfusion arrhythmias in an anesthetized-cat model of regional ischemia. METHOD: Adult mongrel male cats(n=30, 2.9~4.2 kg) were anesthetized under positive-pressure artificial ventilation with room air. The animals of the control group(n=15) were subjected to 20-minute left anterior descending coronary artery(LAD) occlusion followed by abrupt reperfusion. The animals in experimental group(n=15) were divided into two. Group I(n=6) was pretreated with melatonin, 1 mg/kg, before occluding the LAD. Group II(n=9) was pretreated with melatonin, 10 mg/kg. The animals in experimental group were subjected to ischemia/reperfusion insult following drug treatment melatonin was applied intra-peritoneally for 3 minutes just before LAD coronary artery ligation. The Fisher's exact test was used to compare the data from different animal groups. p<0.05 was considered significant. RESULTS: The incidence of ventricular fibrillation(VF) during the reperfusion phase in group II(pretreated with melatonin, 10 mg) was significantly smaller than that in the control group(p-value = 0.0029). However, no statistically significant difference of VF incidence was found between group I(pretreated with melatonin, 1 mg) and the control group. CONCLUSION: Employing an anesthetized-cat model of regional cardiac ischemia, we investigated the dose-dependant effects of melatonin on reperfusion-induced arrhythmia. The cats pretreated with 10 mg/kg of melatonin before ischemia had a significantly reduced incidence of lethal reperfusion-induced arrhythmia, but there was no difference between the cats pretreated with 1 mg/kg of melatonin before ischemia and the control group.