多巴酚丁胺-美托洛尔负荷超声心动图检测心肌缺血的实验研究

Dobutamine-metoprolol stress echocardiography in detecting myocardial ischemia: experimental study

目的通过定量组织速度成像(QTVI)技术分析多巴酚丁胺-美托洛尔负荷超声心动图(DMSE)在心肌缺血检测中的价值及机制。方法采用Ameroid环套扎冠状动脉左回旋支建立22只小型猪慢性心肌缺血模型,于造模术前行常规超声心动图及DMSE检查,术后3周复查DMSE,并与冠状动脉造影(CAG)及放射性核素心肌灌注条件下行单电子发射计算机断层摄影(SPECT)检查结果进行比较,确定缺血节段;计算DMSE检查中多巴酚丁胺及美托洛尔各剂量级别的室壁运动计分指数(WMSI),采用QTVI测定各剂量级别缺血节段心内膜及心外膜下心肌收缩期峰速度(Vs-end、Vs-epi),并计算心肌速度梯度(MVG)。结果19只模型猪存活并完成各项检测,造模后12只实验猪DSE阳性,15只实验猪DMSE阳性。造模前Vs-end、Vs-epi、MVG均随多巴酚丁胺剂量的增大而升高(P<0.05),并在美托洛尔静脉注射后下降(P<0.05);造模后Vs-end、MVG随多巴酚丁胺剂量的增大及美托洛尔的注射无明显改变,而Vs-epi在达负荷心率时明显高于基础状态(P<0.05),并在美托洛尔静脉注射后降低(P<0.05)。结论DMSE可提高DSE对冠心病检测的敏感性,其机理在于美托洛尔静脉注射后能快速阻断β受体,缓解心外高动力状态,从而有利于揭示多巴酚丁胺诱导的局限于心内膜下的心肌缺血。

Objective To study the value and mechanism of Dobutamine-Metoprolol stress echocardiography (DMSE) in detecting coronary disease by quantitative tissue velocity imaging (QTVI). Methods The left circumflex coronary arteries in 22 swines were obstructed with Ameroid occlusions to establish chronic myocardial ischemia model. All the swines received routine echocardiography and DMSE before the operation. 3 weeks later coronary angiography (CAG) and myocardial perfusion tomography were performed and DMSE was repeated. We compared the above results to confirm the ischemia segments. Wall motion score index (WMSI) in different dosage during DMSE was accessed. The endocardial velocity (V_ s-end ), epicardial velocitiy (V_ s-epi ) and myocardial velocity gradient (MVG) were detected using QTVI. Results There were 19 swines established the chronic myocardial ischemia model and finished all the data successfully. The sensitivity value of DSE for detecting myocardial ischemia was 12/19 (63.2%), while that of DMSE was 15/19 (78.9%). Before the operation, V_ s-end , V_ s-epi , and MVG demonstrated a dose-responsive increase during dobutamine injection and significant decrease after metoprolol injection. After the operation, V_ s-end and MVG failed to respond to either dobutamine or metroprolol injection, while V_ s-epi demonstrated a significant increase in stress heart rate compared with the baseline, and decreased obviously after metoprolol injection. Conclusions DMSE can improve the sensitivity of DSE in detecting myocardial ischemia. The mechanism is that metroprolol injection can depress the hyperdynamic constriction in the epicardial layer so as to reveal the endocardial ischemia induced by dobutamine.