Evaluation Of The Protective Effects Of Ischemic Postconditioning On Acute Ischemia-reperfused Canine Heart By Quantitative Tissue Velocity Imaging

Objective:To discuss the feasibility and accuracy of quantitative tissue velocity imaging (QTVI) to quantify myocardial function induced by acute ischemia and reperfusion, which will be a convenient and objective method applied for the clinic.To discuss the feasibility,security and availability of myocardial ischemic- postconditioning(IPostC),which will be a new and practical thinking for the clinic to reduce myocardial ischemia-reperfusion injury(MIRI).To discuss the relation between oxygen free radical(OFR) and myocardial ischemic-postconditioning.Methods:All animals were randomly assigned to one of three groups: control group (Con,n=7): the left anterior descending artery (LAD ) was reversibly occluded for 60 min followed by 3h of reperfusion; ischemic-preconditioning group (Pre-C, n=7):The LAD was occluded for 5 min followed by 5 min of reperfusion before the 60 min of prolonged occlusion; ischemic-postconditioning group (n=7):after 60 min of LAD occlusion, reperfusion was initiated for 30s followed by 30s of reocclusion, repeated for three cycles. Reperfusion was continued for a total of 3h in all experiments. All indexes were examinated at baseline, at the end of ischemia, and at 1, 2, 3h of reperfu- sion.The indexes of systolic function included systolic peak velocity (Vs),systolic peak displacement(Ds),fraction of shorten(FS) and ejective fraction of left ventricle(LVEF).Vs and Ds were measured on anterior wall of left ventricle and inferior wall, anterior septal and post wall, post septal and lateral wall using QTVI technique; LVEF was measured using Simpson's method and FS was measured with anatomical m-mode echocardiography. The infarct size was evaluated by blood-serum creatine kinase(CK) and patholog-ic stain using triphenyltetrazolium chloride(TTC). Venous blood samples were with- drawn at baseline and 3h of reperfusion for measuring CK. After the heart was harve- sted, the LAD was religated in the original position, and Evens blue dye was injected for staining the nonischemic region blue and thereby outline the area of risk(AR).The- n the AR was separated from the nonischemic zone and incubated in a 2% solution of TTC to differentiate the area of necrosis(AN) from the nonnecrotic AR.The AR was expressed as a percentage of the left ventricular mass (AR/LV), and AN, as a percent- age of the AR (AN/AR), and they were calculated by tissue weight.The indexes of OFR including blood-serum malondialdehyde(MDA) and super- oxide dismutase(SOD) were measured in each group at baseline, at the end of ischem- ia, and at 1, 2, and 3 h of reperfusion.Results:In all canines, Vs,Ds,EF and FS decreased significantly at the end of ischemia.At 3h of reperfusion, compared to the Con group,Vs,Ds,EF and FS were higher in the Post-C group and Pre-C group;Plasma CK and MDA were less,whereas SOD was more;the infarct size measured by TTC was smaller,and the Vs and Ds measured by QTVI well correlated with EF and FS.Conclusions:With convenient and objective feature,QTVI technique could evaluate systolic function exactly in acute myocardial ischemia-reperfusion injury(MIRI) in dogs.Similar to the ischemic-preconditioning,ischemic-postconditioning could decrease the area of necrosis and recover systolic function to reduce MIRI.This protection was possibly concerned with oxygen free radical.