| Background and ObjectiveCoronary heart disease what short of coronary atherosclerotic heart disease wasknown as the first killer of human health. The incidence rate of coronary heart diseaseshowed an increasing and younger trend. Acute myocardial infarction may occurwhen the patients were in physical labor or stress situations. Quantitative, objectiveand correct assessment of the extent of dysfunctional but viable myocardium withacute myocardial infarction (AMI) has important therapeutic and prognosticimplications. The study aimed to observe the value of three-dimensional speckletracking imaging (3D-STI) combined with dobutamine stress echocardiography (DSE)in assessing viable myocardium of open-chest dogs with AMI.Methods18open-chest healthy Beagle dogs underwent left anterior descending (LAD)occlusion for90min followed by180min reperfusion. Dobutamine was administered continuously via vein at two different dose of5and10μg/kg/min over a period of5min. Images were acquired by3D-STI and conventional echocardiography exam atbaseline (before coronary artery ligation), after reperfusion (when reperfusionfinished) and after dobutamine administration (when every stage stopped). Finally, alldogs were killed by injecting10%KCl via vein. To assess viable, normal andinfarcted myocardium,2,3,5-triphenyltetrazolium chloride (TTC) staining wereapplied. Infarcted myocardial were dyed pale, viable myocardial were light red andnormal myocardial were brick red. Using Photoshop software, pale areascorresponding to lack of TTC stain were mapped for each segment and the areadivided by the total area of the segment and multiplied by100%to obtain the area ofinfarct (percent) for each segment. Segments with＞50%areas of infarct wereconsidered to be infarct, areas with=0%of infarct were considered to be normal, andareas with1-50%of infarct were considered to be viable. Based on TTC staining, thesegments were divided into the following groups on the background of thedistribution of infarct myocardium: infarcted group, viable group and normal group.Conventional echocardiography measurement indicators included: left ventricularejection fraction (LVEF) acquired by Simpson’s, wall motion score (WMS), wallmotion score index (WMSI).3D-STI measurement indicators included：each peak area strain (PAS), peaklongitudinal strain (PLS), peak circumferential strain (PCS), peak radial strain (PRS)of all segments of left ventricular; left ventricular systolic global peak area ofstrain(GPAS), left ventricular systolic global peak longitudinal of strain(GPLS), leftventricular systolic global peak circumferential of strain(GPCS), left ventricularsystolic global peak radial of strain(GPRS).Results1、General situationAs a result,1dog died of anesthesia accident and2dogs died of ventricularfibrillation after LAD ligation in18dogs. Finally,15dogs finished the experimentand entered into the statistical analysis. 2、Pathological stainingAs a result,171segments were normal,37segments were viable whereas32segments were infarcted among240segments in15dogs.3、Hemodynamic and global left ventricular functionCompared with the baseline, when reperfusion finished the GPAS, GPLS, GPCS,GPRS, LVEF, HR, and MAP all significantly decreased (P＜0.05), and WMSIsignificantly increased (P＜0.05).When dobutamine was administered from5μg/kg/min to10μg/kg/min, LVEF及GPAS, GPLS, GPCS, GPRS increased(P＜0.05), and WMSI and HR decreased(P＞0.05).A significant relation between GPAS(r=-0.828, P＜0.05), GPLS(r=-0.712, P＜0.05), GPCS(r=-0.717, P＜0.05), GPRS (r=0.665, P＜0.05)and LVEF could befound when reperfusion finished.4、Comparison of WMS and left ventricular regional three-dimensional strainparameters among normal group, viable group and infarcted group at the same statesAt baseline There was no significant difference in PRS, PAS, PLS, PCS andWMS among normal group, viable group and infarcted group at baseline(P＞0.05).After reperfusion and when dobutamine was administered In viable group andinfarcted group, WMS were higher than that in normal group(P＜0.05), PAS, PLS,PCS and PRS were lower than that in normal group(P＜0.05). When compared viablewith infarcted group, PAS, PLS, PCS and PRS in viable group all higher than that ininfarcted group (at10μg/kg/min of LDD, P＜0.05), but there was no significantdifference in WMS between them.5、Comparison of WMS and left ventricular regional three-dimensional strainparameters in normal group, viable group and infarcted group at different statesIn normal group: After reperfusion, PLS, PCS and PRS decreased significantly(P＜0.05), PAS showed no regular change(P＞0.05). When dobutamine wasadministered at5μg/kg/min, PAS, PLS, PCS and PRS showed no regular change(P＞0.05). When dobutamine was administered at10μg/kg/min, PAS, PLS, PCS, PRSincreased significantly and there was no significant difference with baseline(P＜0.05).The WMS showed no regular change at different states(P＞0.05). In viable group: After reperfusion, PAS, PLS, PCS and PRS decreasedsignificantly(P＜0.05), WMS increased significantly(P＜0.05). When dobutaminewas administered, PAS, PLS, PCS and PRS increased(at5μg/kg/min, P＞0.05; at10μg/kg/min, P＜0.05), but lower then that measured at baseline(P＜0.05), WMSdecreased (at5μg/kg/min, P＞0.05; at10μg/kg/min, P＜0.05), but higher then thatmeasured at baseline(P＜0.05).In infarcted group, After reperfusion, PAS, PLS, PCS and PRS decreasedsignificantly(P＜0.05), WMS increased significantly(P＜0.05). When dobutaminewas administered, PRS, PAS, PLS, PCS and WMS showed no regular change(P＞0.05).6、ROC curve analysis PAS, PLS, PCS, PRS and WMS detecting of infarctedmyocardium at LDD of10μg/kg/minAt LDD of10μg/kg/min, the AUC of PAS, PLS, PCS, PRS and WMS detectinginfarcted myocardium were94.7%,87.0%,84.4%,86.8%and81.4%. Moreover, PAShad the best ability to identify infarcted myocardium, the sensitivity and specificitywere higher than PLS, PCS, PRS and WMS.Conclusion3D-STI can analysis myocardial contraction, combined with DSE can analysis themyocardial contractile reserve, and they could be a sensitive and noninvasive meansto assess regional myocardial viability. |
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