Effects of fentanyl postconditioning, remote ischemia postconditioning and ischemia postconditioning on ventricular arrhythmia during myocardial ischemia and initial reperfusion in rats

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 methods 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 μg/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,Ischemia postconditioning 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),the 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 during initial period of reperfusion 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.Conclusions 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. Key words: Myocardial ischemia/reperfusion injury;  Cardioprotection;  Ischemia postconditioning;  Remote ischemia postconditioning;  Pharmacological postconditioning;  Opioid;  Arrhythmia