Usefulness of myocardial contrast echocardiography in predicting collateral blood flow in the presence of a persistently occluded acute myocardial infarction-related coronary artery.
ABSTRACT Adequate collateral blood flow at rest can sustain myocardial viability despite persistent occlusion of the infarct-related artery (IRA) in acute myocardial infarction (AMI). This has therapeutic and prognostic implications. Studies addressing the value of intravenous myocardial contrast echocardiography (MCE) to detect collateral blood flow after AMI in humans are limited. Accordingly, 70 consecutive patients with AMI underwent low-power intravenous MCE using a Sonovue infusion 7 to 10 days after thrombolysis. Myocardial perfusion detected by MCE was analyzed (qualitatively and quantitatively) in the akinetic segments in 20 patients (29%) with an occluded IRA who subsequently underwent revascularization. Contractile reserve, which is a marker of myocardial viability, was assessed with low-dose dobutamine 12 weeks after mechanical revascularization. Of the 102 akinetic segments (32%), 37 (36%) showed contractile reserve. Contractile reserve was present in 24 of the 29 segments (83%) with homogenous contrast opacification and absent in 60 of the 73 segments (82%) with reduced/absent opacification. Quantitative peak contrast intensity, microbubble velocity, and myocardial blood flow were significantly higher (p <0.0001) in the segments with contractile reserve than in those without contractile reserve. Multiple logistic regression analysis using electrocardiographic, biochemical, and myocardial contrast echocardiographic markers of collateral blood flow showed that MCE (odds ratio 26.0, 95% confidence interval 6.3 to 108.0, p <0.001) was the only independent predictor of collateral blood flow as demonstrated by the presence of contractile reserve. MCE may thus be used as a reliable bedside technique for the accurate evaluation of collateral blood flow in the presence of an occluded IRA after AMI.
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ABSTRACT: Ultrasound can cause microbubble destruction. If microbubbles are administered as a continuous infusion, then their destruction within the myocardium and measurement of their myocardial reappearance rate at steady state will provide a measure of mean myocardial microbubble velocity. Conversely, measurement of their myocardial concentration at steady state will provide an assessment of microvascular cross-sectional area. Myocardial blood flow (MBF) can then be calculated from the product of the two. Ex vivo and in vitro experiments were performed in which either flow was held constant and pulsing interval (interval between microbubble destruction and replenishment) was altered, or vice versa. In vivo experiments were performed in 21 dogs. In group 1 dogs (n=7), MBF was mechanically altered in a model in which coronary blood volume was constant. In group 2 dogs (n=5), MBF was altered by direct coronary infusions of vasodilators. In group 3 dogs (n=9), non-flow-limiting coronary stenoses were created, and MBF was measured before and after the venous administration of a coronary vasodilator. In all experiments, microbubbles were delivered as a constant infusion, and myocardial contrast echocardiography was performed using different pulsing intervals. The myocardial video intensity versus pulsing interval plots were fitted to an exponential function: y=A(1-e[-betat]), where A is the plateau video intensity reflecting the microvascular cross-sectional area, and beta reflects the rate of rise of video intensity and, hence, microbubble velocity. Excellent correlations were found between flow and beta, as well as flow and the product of A and beta. MBF can be quantified with myocardial contrast echocardiography during a venous infusion of microbubbles. This novel approach has potential for measuring tissue perfusion in any organ accessible to ultrasound.Circulation 03/1998; 97(5):473-83. · 15.20 Impact Factor
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ABSTRACT: Power pulse inversion echocardiography is a new technique by which contrast microbubbles can be visualised in real time within the myocardium, enabling simultaneous assessment of myocardial function and microvascular integrity, which is a prerequisite for myocardial viability. We aimed to determine whether microvascular integrity using power pulse inversion can be used to predict contractile reserve early after myocardial infarction. We studied 19 stable patients 5.1(1.6) days after presentation using low dose dobutamine stress echocardiography and power pulse inversion using slow bolus intravenous injections of Optison. A 16-segment left ventricular model was used to define wall thickening at baseline and following low dose dobutamine infusion (1, normal; 2, reduced; 3, absent), and contrast opacification (1, homogeneous; 2, heterogenous or reduced; 3, absent). The techniques were compared on a segment-by-segment basis to determine whether microvascular integrity (contrast opacification score of 1 or 2) could predict contractile reserve (any improvement during low dose dobutamine infusion) in segments that were akinetic at rest. Follow-up echocardiography was performed one month later. Ninety-four (31%) of the 304 segments were akinetic at rest, and 22 (23%) of these demonstrated contractile reserve. In 87 (92%) of the resting akinetic segments contrast opacification could be adequately determined, and of these 20 (23%) showed microvascular integrity. The negative and positive predictive value of microvascular integrity for determining contractile reserve was 90% and 65%, respectively, and 92% and 59% respectively for predicting recovery of function. Power pulse inversion can be used at rest to determine myocardial function and simultaneously to predict contractile reserve of akinetic segments in patients early after myocardial infarction. This technique has the potential to provide a bedside assessment of myocardial viability.European Heart Journal – Cardiovascular Imaging 07/2002; 3(2):95-9. · 2.39 Impact Factor
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ABSTRACT: To evaluate the influence of revascularization of a stenosis of the right coronary artery on right ventricular function. Prospective study. Single institutional study in a university hospital. 20 patients with different degrees of stenosis of the right coronary artery undergoing elective coronary artery bypass grafting. In 10 patients, bypass surgery included revascularization of a significant stenosis of the right coronary artery (group 1). In 10 other patients, the pathology of the right coronary artery was judged to be not significant, without indication for revascularization (group 2). Using the fast-response thermodilution pulmonary artery catheter, right ventricular function was estimated perioperatively. After termination of extracorporeal circulation, there was an increase in right ventricular volumes in group 2 (p < 0.05) and an initial decrease in group 1 (p < 0.05), with higher volumes in group 2 compared with group 1 (p < 0.05). The ejection fraction increased in group 1 (p < 0.05) and decreased in group 2 after operation (p < 0.05), with higher values in group 1 compared with group 2 (p < 0.05). In addition to these findings, the pressure-volume relationship showed a leftward and upward shift in group 1 and a rightward shift in group 2 postoperatively. These results indicate that right ventricular depression can occur after bypass grafting in patients with a moderate stenosis of the right coronary artery that is not revascularized. Revascularization of more severe stenosis of the right coronary artery appears to preserve postoperative right ventricular function.Journal of Cardiothoracic and Vascular Anesthesia 01/1996; 9(6):659-64. · 1.45 Impact Factor