Abstract: Objective: To investigate the effects of fentanyl postconditioning, remote ischemia postconditioning and ischemia postconditoning on ventricular arrhythmias during myocardial ischemia and initial reperfusion in rats. Methods: Seventy-three anesthetized male SD rats (weighed 250 g to 350 g) were randomly allocated into nine groups: sham group (group S, n=5), control group (group C, n=7), fentanyl postconditioning group (group F, n=9); remote postconditioning group (group R, n=9), ischemia postconditioning group (group P, n=8); combined fentanyl postconditioning and remote postconditioning group (group F-R, n=9); combined fentanyl postconditioning and ischemia postconditioning group (group F-P, n=8); combined remote postconditioning and ischemia postconditioning group (group R-P, n=9); and combined all three method group (group F-R-P n=9). Thoracotomy was performed in the rats, and the left anterior descending coronary artery (LAD) was encircled with a suture to make a snare. Except for the group S, in the other groups, LAD was ligated for 30 min (ischemia) followed by a 60 min reperfusion (LAD open) in vivo. In group C, no additional intervention was performed. In groups F, F-R, F-P and F-R-P, fentanyl 30 ug/kg was slowly injected intravenously at 15 min after LAD ligation. In groups R, F-R, R-P and F-R-P, the bilateral hind limbs underwent a 10 min ischemia which started at 15 min after LAD ligation with tourniquet. In groups P, F-P, R-P and F-R-P, 30 min after LAD ligation, IPOC was done with successive three cycles of a 20 s LAD open followed by a 20 s LAD re-occlusion. During the periods of ischemia and the first 30 min of reperfusion,the arrhythmias score (AS), incidences and durations of ventricular tachycardia (VT) and fibrillation (VF) were recorded. Results: There were no significant differences in the AS, incidences and durations of VT and VF during the periods of ischemia among groups C, F, R, P, F-R, F-P, R-P and F-R-P. The medians of AS in groups C, F, R, P, F-R, F-P, R-P and F-R-P were 4, 2, 2, 1, 2, 1, 1 and 2, respectively. During initial period of reperfusion, compared with group C, incidence of ventricular arrhythmia was significantly decreased in other groups; duration of both VT and AS did not significantly changed in groups F and R, but duration of VT was shorter in group F-R. As compared to groups F, R and F-R, duration of VT during initial period of reperfusion was significantly shorter, and AS was lower in groups P, F-P, R-P and F-R-P. Conclusion: As compared with fentanyl postconditioning and remote postconditioning, ischemia postconditioning was more effective in anti-arrhythmia during initial period of reperfusion. Combined fentanyl postconditioning and remote postconditioning can produce an enhanced anti-arrhythmic effect during the myocardial ischemia-reperfusion process.
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