| Objective:To evaluate objectively the myocardial protective effect of beating heart with mildhypothermia and CPB during open-heart operation,the comparing study on the myocardialprotective effect of MVR between beating heart with mild hypothermia and arrested heartwith cold blood cardioplegia perfusion have been launched.Methods:20 rhutimatic heart disease were randomly allocated to two groups:beating heart group,10cases of MVR on beating heart with mild hypothermia and CPB;arrested heart group , 10cases of MVR on arrested heart with CBCand CPB.The samples of plasma were obtained at total 12 times points during CPB andpost-operation,which were surveyed the contents of ET and ANP.The samples ofmyocardium were obtained at total 3 times points during CPB through which myocardialultrastructure were observed and analysed in two groups.4Results:1.The range of ET and ANP fluctuated more dramatically and significantly in arrested heart group than that in beating heart group.The contents of plasma ET in beating heart group were lower than those in the arrested heart group's from 15 minutes after arrested to 12 hours after opened (P<0.05). The levels of ANP in beating heart group were higher than those in arrested heart groups (P<0.05) during arrested times. While the levels of ANP in arrested heart group were higher than those in beating heart group from the beginning of open to 24th hour after opening (P<0.05). There were positive correlation between ET and ANP of both two groups(r=0.78297,P<0.01).2.Routine observation under electron microscopy:There were hardly significant differences between pre-operation, during-operation andpost-operation in beating heart groups. However, there is an increasing injury tendencyamong each phase in arrested heart group.The Miotochondria Score of arrested heart group was higher than that of beating heartgroup in different phase time.3.The stereological studies of myocardial ultrastructure: All the ultrastructure of pre-operation indexes have no difference in both groups;(1)Dmit5and Amit in arrested heart group were higher than those in beating heart group in intraoperation and post-operation,but Vmit, Nami, and δ mit were significantly lower than those in beating group(p<0.05).(2)During CPB Vm and δ w were significantly lower in arrested heart group than in beating heart group(p<0.05). (p<0.05). D w and A w of post-operation were higher in AH groups than in BH groups, but Vw and δw of post-operation were significantly lower in AH groups than in BH groups(P<0.05);(3)There were no significantly difference both Vmyo and δmyo in both groups between preoperation and intraoperation(p<0.05),while Vmyo and δmyo of postoperations were significantly lower in AHgroups than Augroups.(P<0.05). Conclusion:The open-heart surgery with beating heart is a good myocardial protective method closed to physiological condition, which may be attributed to the reduction of ischemic-reperfusion injury. The heart is better preserved in beating heart surgery, which has good myocardial protective effect.
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