计算机辅助心肌造影负荷超声定量评价心肌灌注及局部收缩功能

Quantitative evaluation of myocardial perfusion and regional systolic function by myocardial contrast stress echocardiography with computer-assisted technique in ischemic myocardium of rabbits

目的探讨计算机辅助心肌造影负荷超声（MCSE）定量评价心肌灌注和局部收缩功能的应用价值。方法采用急性阻断再灌注左室支建立兔模型，根据阻断和再灌注时间分为两组：阻断30min后再灌注60min（Ⅰ组）和阻断120min后再灌注60min（Ⅱ组）。分别在基础状态、阻断、再灌注和多巴酚丁胺负荷（5、10、15和20μg·kg^-1·min^-1）行心肌造影超声心动图，造影图像经自制计算机辅助软件处理后，自动标出每个节段的标化造影剂密度（CI），根据标化CI值，彩色编码标记为：0～-20像素（pix）黄色、-21～-40pix蓝色、-41～-70pix绿色以及〈-70pix红色。分别计算出阻断时和再灌注后红色编码区面积，并与荧光微球染色和氯化三苯基四氮唑染色面积对照分析。同时测量各阶段危险心肌的收缩期室壁增厚率（WT）。结果（1）阻断时，危险心肌的WT降到零点或呈负值，CI明显低于基础状态，红色编码区面积与荧光染色危险心肌面积呈正相关（r=0．91，P〈0．01）。（2）再灌注和多巴酚丁胺5μg·kg^-1·min^-1后，各组危险心肌的WT和标化CI仍减低。以标化CI-70pix为截断值，识别梗死节段的敏感性为95％，特异性为87％。红色编码面积与氯化三苯基四氮唑染色梗死心肌面积呈正相关（r=0．89，P〈0．01）。（3）随着多巴酚丁胺剂量的增加，Ⅰ组的标化CI恢复至基础状态，WT逐渐增加超过基础水平，但Ⅱ组仍保持较低水平。结论计算机辅助心肌造影负荷超声可以定量评价心肌灌注和局部收缩功能，是识别顿抑和梗死心肌安全可行的方法。

Objective To evaluate the feasibility and value of determining myocardial perfusion and regional systolic function by myocardial contrast stress echocardiography （MCSE） with computer-assisted technique in a rabbit model of ischemia/reperfusion injury. Methods Rabbits underwent 30-（ Group Ⅰ , n =15） and 120-（Group Ⅱ , n = 15） minute left ventricular branch of the left circumflex coronary artery occlusion followed by 60-minute reperfusion, dobutamine at increasing doses （5, 10, 15 and 20 μg · kg^-1 · min^-1） was then infused after reperfusion for 15 min. Bolus myocardial contrast agent was injected and MCSE performed at baseline, at the end of coronary occlusion and reperfusion, at the end of each dobutamine infusion. Images were analyzed by computer-assisted technique and myocardial calibrated contrast intensity （CI） of each segment was measured and a color-coded map was then obtained automatically （yellow： from 0 to - 20 pix, blue： from - 21 to - 40 pix, green： from - 41 to - 70 pix, red： 〈 -70 pix）. The area at risk and infarct area obtained by red-coded map were compared with ex vivo results determined by fluorescent microsphere and triphenyl-tetrazolium chloride （TYC） staining. Percentage wall thickening （WT） of each risk segment at each stage were also measured. Results （ 1 ） During occlusion, WT in the areas at risk decreased to zero or negative and the calibrated CI values were significantly lower than those at baseline. Area at risk obtained by red-coded map correlated well with that obtained by fluorescent staining （r =0. 91, P 〈 0. 01 ）. （2） After reperfusion and 5 μg · kg^-1 · min^-1 dobutamine administration, WT and calibrated CI in all rabbits remained depressed. Calibrated CI at -70 pix was an optimal cutoff point to identify infarcted segments （ sensitivity 95%, specificity 87% ）. The correlation between the infarct size by red-coded image and TTC was 0.89 （ P 〈0. 01 ）. （ 3 ） Calibrated CI and WT significantly improved in Group Ⅰ rabbits while these parameters remained unchanged in Group Ⅱ rabbits after increasing doses of dobutamine post ischemia. Conclusions Myocardial contrast stress echocardiography in combination with computer-assisted analysis technique are valuable techniques to quaotitatively assess myocardi＇al perfusion and regional systolic＇ function and exactly identify stunned mvocardium and infarcted myocardium.