心肌声学造影定量心肌血流判断存活心肌的实验研究

Assessment of myocardial viability with myocardial contrast echocardiography:an experimental study

目的 评价经静脉心肌声学造影 (MCE)判断存活心肌的可行性。方法 建立急性心肌梗死犬模型 ,经外周静脉持续滴注微泡造影剂 ,通过计算A·β值测定心肌相对血流量。以放射性微球法测定的心肌血流量 (MBF)为标准 ,了解A·β值测定MBF的准确性。通过A·β值估测心肌存活与否 ,病理检查验证其可靠性。结果 放射性微球法所测的正常区、缺血区、坏死区的MBF分别为 ( 1 5± 0 3)、( 0 7± 0 3)、( 0 3± 0 2 )ml·min-1·g-1;MCE测得的A·β值分别为 5 2 46± 15 0 9、2 4 36±3 89、3 74± 3 80 ;正常区、缺血区、坏死区的MBF和A·β值“标化”后分别为 1 0± 0 0、0 44± 0 17、0 17± 0 11和 1 0± 0 0、0 48± 0 0 9、0 0 7± 0 0 8,二者的相关性良好 (r=0 81,P =0 0 0 1)。MCE对坏死心肌的判定结果与病理结果吻合。结论 心肌声学造影可用于活体状态下评价存活心肌 ,“标化”后的A·β值 <0 2 3提示心肌坏死。

Objective To assess the feasibility of myocardial contrast echocardiography(MCE) in the evaluation of myocardial viability. Methods Seven dogs were ligated at the proximal of left anterior descending coronary artery to result in acute myocardial infarction model four hours after the coronary ligature. Microbubbles were administered as a constant venous infusion, and MCE was performed with the use of different pulse intervals. The video intensity versus pulsing interval plots derived from each myocardial pixel were fitted to an exponential function: y=A(1-e -β t ), where A reflected microvascular cross-sectional area (or myocardial blood volume), and β reflected mean myocardial microbubble velocity. The product of A·β represented myocardiol blood flow (MBF). Radiolabeled microsphere-derived MBF was used as 'golden standard' to compare A·β ,and pathological technology was used to verify the reliability of MCE in the determining of myocardial viability.Results Radiolabeled microsphere-derived MBF in the regions of normal, ischemia and infarction was (1.5±0.3)?(0.7±0.3)?(0.3±0.2) ml·min -1 ·g -1 respectively, and the product of A·β in those regions was 52.46±15.09?24.36±3.89?3.74±3.80 respectively. The normalized MBF in the corresponding regions was [1?(0.44±0.17)?(0.17±0.11)]ml·min -1 ·g -1 , and the normalized A·β was 1?0.48±0.09?0.07±0.08.There was a good correlation between normalized MBF and the normalized A·β (r=0.81, P=0.001). Myocardial viability determined by MCE was coincided with pathological-determined. Conclusions MCE could be used to determine myocardial viability in the beating heart less then 0.23 of the normalized A·β may represent myocardial necrosis.