Carnitine is a vital biologic substance transporting fatty acids into myocytes and facilitates fatty acids
-oxidation for energy production.There is little findings about its cardio protective effects on cardiac arrhythmias during ischemia / reperfusion. So in this study, effects of L-Carnitine on cardiac arrhythmias in the ischemic reperfused isolated rat hearts were investigated.Male Sprague-Dawley rats (270-330g) divided into 4 groups randomly and were anesthetized by Sodium Pentobarbital (50-60 mg/kg-ip). The hearts were removed and quickly mounted on a Langendorff apparatus and were perfused by a modified Krebs-Henseleit solution under constant pressure at 37 C. In control group (n=6), the hearts were perfused only by normal Krebs -Henseleit solution at stabilization, 30 min regional ischemia and 30 min reperfusion time, while in the treated groups (n=6 in each group), the hearts during ischemia / reperfusion were perfused with 0.5,2.5 and 5mM/L of L-Carnitine - enriched Krebs-Henseleit solution. ECG was recorded during the experiment. During ischemia and reperfusion, cardiac arrhythmias were analyzed based on Lambeth Convention. At the ischemic phase, number, duration and incidence of Ventricular Tachycardia (VT) were decreased with doses of 2.5 and 5mM/L L-Carnitine (p<0.05).L-Carnitine in doses of 2.5 and 5mM/L reduced the number of VT considerably (p<0.05) at the reperfusion phase. But duration of VT was not decreased significantly. Total Ventricular Ectopic Beats (VEBs: Single + Salvos + VT) also were reduced in treated groups by 0.5-5mM/L of L-Carnitine (p<0.05). However, single VEBs and duration of Reversible Ventricular Fibrilation (Rev VF) were decreased only by 5mM/L L-Carnitine. There were no significant differences between control and treated groups in the time to onset of Rev VF and incidences of VF and VT at the reperfusion phase.Considering these results, we conclude that L-carnitine has a protective effect against ischemia reperfusion injuries as a reduction of cardiac arrhythmias.