Experimental Studies On The Influence Of Hypothermic Ventricular Fibrillating During Cardiopulmonary Bypass On Myocardial Structure, Function And Energetic Metabolism

Cardiosurgery made great progress during techniq past time.There are many kinds of surgery now. But the success of open-heart surgery mainly depend on the effect of myocardial preservation. Many experimental and clinical investigation had been designed to research the myocardial preservation .Numerous techniques have been advocated over the years to preserve the myocardium.A lot of kinds of myocardial preservation to be chosen.But none of them are perfect.For a long time ,cardioplegia has became increasingly popular.It was considered to be the best method to proserve the myocardium.But its harmful effects are gradually realized by cardiac surgeon.The techniqueof VF is still practiced by surgeons who feel comfortable with the technique.Surgeon who practice the technique claim several advantages over cardioplegia :the cumulative cross-clamp times are less than with cardioplegia,the myocardium is intermittently perfused with oxygenated blood, the lower accident of cardiac arrhymia owing to hyperkalemia. Further studies revealed that moderate systemic hypothermia lowers the incresedmetabolic rate and oxygen consumption owing to VF and also prevents a significant build-up of lactate in the myocardium.So it is a operative myocardial preversation. But there isn't a isolated experiment to judge the myocardial preservation effects of VF at different temperature and time limit. Base on the feline cardiopulmonary bypass(CPB) model, the changes of myocardial function, myocardial structure, energetic metabolism and mitochondria Na＋－K＋ATPase activity were observed to evaluate the cardioprotective effects of the twokinds of method of hypothermic electric-induced ventricular fibrillating and intermittent antegrade perfusion with cold crystalloid.CPB management145 felines,each weighted 3.0 ± 0.5kg, were randomly divided into8 groups with 21 in each. GroupⅠ: Pure CPB without ACC. Group Ⅱ: After ACC at 30℃, 4℃ crystalloid cardioplegia was perfused via aortic root; tropical hypothermia was obtained by pericardial ice mud application following arrest. Cold crystalloid myocardial protection solution was perfused via aortic root every 20-30min; at ACC 90min, aortic crossclamping was removed and reperfused 30 min. Group Ⅲ: Base on CPB without ACC, continue induced fibrillating with 60Hz,5V alternating current 90min at 30℃ and reperfused 30min. Group Ⅳ: Base on CPB without ACC, continue induced fibrillating with 60Hz,5V alternating current 90min at28℃ and reperfused 30min.Group Ⅴ: Base on CPB without ACC, continue induced fibrillating with 60Hz,5V alternating current 90min at26℃ and reperfused 30min.Group Ⅵ: Base on CPB without ACC, continue induced fibrillating with 60Hz,5V alternating current60min at 30℃ and reperfused 30min.Group Ⅶ: Base on CPB without ACC, continue induced fibrillating with 60Hz,5V alternating current 60min at28℃ and reperfused 30min.Group Ⅷ: Base on CPB without ACC, continue induced fibrillating with 60Hz,5V alternating current 60min at26℃ and reperfused 30min. Results1. The changes of cardiac performances Lvsp and dp/dt max significant decreased after reperfused 30min in Group Ⅱto Ⅷ and were significantly different from those in GroupⅠ. The most obviously decreasing was observed in them about dp/dt min and also significantly different fromthose in GroupⅠ. Lvedp values in GroupⅠwere the most significantly different from those in Group Ⅱ to Ⅷ and also sigificantly different between them.It meaned that the cardiac performances of hypothermic fibrillating heart and cold crystalloid cardioplegia heart were damaged.2. Electromicroscopic observationsNo significant abnormality was spotted in GroupⅠ,with nothing more than minimal swelling of the cells part of the mitochondrias. After 30min reperfusion, hypothermic fibrillating heart showed ischemic and hypoxic injuries at myocardial ultrastruture. Cell edema, mitochondria swelling or crista fracture or even cavitation and capillary endothelium swelling et al was observe...