Keller M W, Spotnitz W D, Matthew T L, Glasheen W P, Watson D D, Kaul S
Department of Surgery, University of Virginia School of Medicine, Charlottesville.
J Am Coll Cardiol. 1990 Nov;16(5):1267-79. doi: 10.1016/0735-1097(90)90565-7.
To test the hypothesis that myocardial contrast echocardiography can be used to quantitate regional myocardial flow in the arrested heart at the time of delivery of cardioplegic solution, data were acquired in 13 dogs on cardiopulmonary bypass. Different degrees of stenosis were placed in random order on the left anterior descending coronary artery. For each stenosis, myocardial contrast echocardiography was performed by injecting sonicated albumin microbubbles into the cross-clamped aortic root at the time of delivery of cardioplegic solution. The resultant echocardiographic images were analyzed on an off-line computer. Background-subtracted time-intensity plots were generated, and an exponential function, f(t) = Ce-alpha t + De- beta t, was applied to each plot. Variables that reflected the total number of microbubbles entering the coronary artery bed, such as the area under the curve and the peak height of the curve, correlated best with radiolabeled microsphere-measured myocardial flow (r = 0.92 and r = 0.91, respectively). Variables that reflected the appearance of contrast microbubbles in the myocardium, such as the initial slope and the slope at 1 s, also had a good correlation with myocardial flow (r = 0.84 and r = 0.89, respectively). Variables that reflected the washout of contrast medium from the myocardium, such as the slope of the descending portion of the curve, had only a fair correlation with myocardial flow (r = 0.65). In six dogs, the technique of injecting contrast medium into the cross-clamped aortic root was also examined. Although continuous infusion of contrast medium produced smaller perturbations in mean aortic and distal left anterior descending artery pressures compared with a bolus injection (p less than 0.01), the correlation between the variables of the time-intensity curves and flow was equally close with both techniques. It is concluded that it is possible to quantitate myocardial flow by using myocardial contrast echocardiography at the time of delivery of cardioplegic solution in dogs on cardiopulmonary bypass. The implementation of this technique in humans might be useful in guiding the sequence of graft placement and thereby improving myocardial preservation during coronary artery bypass operations.
为了验证在给予心脏停搏液时心肌对比超声心动图可用于定量停跳心脏局部心肌血流这一假设，对13只接受体外循环的犬进行了数据采集。在左前降支冠状动脉上随机顺序放置不同程度的狭窄。对于每个狭窄，在给予心脏停搏液时，通过向夹闭的主动脉根部注射超声处理的白蛋白微泡来进行心肌对比超声心动图检查。将所得的超声心动图图像在离线计算机上进行分析。生成背景扣除后的时间 - 强度曲线，并将指数函数f(t)=Ce -αt + De -βt应用于每条曲线。反映进入冠状动脉床的微泡总数的变量，如曲线下面积和曲线峰值高度，与放射性标记微球测量的心肌血流相关性最好（分别为r = 0.92和r = 0.91）。反映心肌中对比微泡出现情况的变量，如初始斜率和1秒时的斜率，也与心肌血流有良好的相关性（分别为r = 0.84和r = 0.89）。反映造影剂从心肌中清除情况的变量，如曲线下降部分的斜率，与心肌血流的相关性一般（r = 0.65）。在6只犬中，还研究了向夹闭的主动脉根部注射造影剂的技术。尽管与推注相比，持续输注造影剂对平均主动脉压和左前降支远端动脉压产生的扰动较小（p < 0.01），但两种技术下时间 - 强度曲线变量与血流之间的相关性同样密切。得出结论，在接受体外循环的犬给予心脏停搏液时，使用心肌对比超声心动图可以定量心肌血流。该技术在人类中的应用可能有助于指导移植血管放置顺序，从而在冠状动脉搭桥手术中改善心肌保护。
