速度向量成像技术评价兔心尖部心肌梗死后左心室扭转功能的动态研究

Time course studies on left ventricular torsion evolution in rabbit apical myocardial infarction using velocity vector imaging

目的应用速度向量成像技术评价兔心尖部心肌梗死后左心室扭转运动的动态演变特点。方法用新西兰大白兔复制心肌梗死模型,于手术前1 d及术后8周内不同时间点采集心脏动态图像进行速度向量成像（velocity vector imaging,VVI）分析,记录左心室扭转参数。结果心肌梗死组术后1周内,心底水平左心室旋转角度、速度及解旋速度较术前有减低趋势但无统计学意义（P〉0.05）,术后2-8周较术前明显减低（P〈0.05）。术后1 d心尖水平左心室旋转角度、速度及解旋速度均显著低于术前测值（P〈0.05）,并随心肌梗死时间延长逐渐减低,至术后4周达高峰。心肌梗死后8周内,左心室解旋达峰时间延长,等容舒张期内左心室解旋角度占整个解旋角度的百分比减少（P〈0.05）。左心室整体扭转参数的改变趋势与心尖水平相似。结论心尖部心肌梗死后左心室心尖水平旋转呈进行性减低,其减低程度较心底水平明显,且出现时间早。左心室整体扭转和解旋功能受损主要由心尖部旋转和解旋减低引起。

Objective To evaluate the dynamic evolutions of left ventricular （LV） torsion using velocity vector imaging （VVI） in rabbits after apical myocardial infarction （MI）. Methods MI model was induced by occlusion of coronary artery in New Zealand white rabbits. Dynamic cardiac images of LV were collected in 1 d before and within 8 weeks after MI. All of these images were analyzed off-line using VVI software and torsion-related parameters were recorded. Results Rotate angle, rotate velocity and recoiling velocity of basal LV tended to decrease within 1 week post MI then significantly decreased in 2 to 8 weeks after surgery （P 〈 but without obvious difference （P 〉 0.05 ）, and 0.05）. In 1 d after surgery, rotate angle, rotate velocity and recoiling velocity of apical LV were greatly lower than those before surgery （ P 〈 0.05 ）, and then gradually decreased post MI and reached the lowest after 4 weeks （ P 〈 00. 05 ）. Time to peak untwisting velocity of LV gradually prolonged and the percentage of isovolumic untwisting to entire untwisting decreased within 8 weeks post MI （P 〈 0.05 ）. Similar to rotational changes of apical LV, twist angle, twist velocity, and untwisting velocity of LV were also decreased after MI （P 〈 0.05 ）. The trend of LV rotation parameters was coincidence with that of apical LV. Conclusion Apical rotation is gradually decreased post apical MI, with the rotational change of apical LV greater and occuring earlier than that of basal LV. The impairment of systolic twist and diastolic untwisting after MI might be mainly caused by rotational changes of apical LV.