Visualization of subendocardial myocardial ischemia with myocardial contrast echocardiography in humans.

Abstract

Previous studies indicate the degree of myocardial echo contrast enhancement may be related to regional myocardial perfusion. In this study, myocardial contrast echocardiography was used to characterize changes in the transmural myocardial blood flow distribution that were provoked by rapid atrial pacing in 11 patients with one-vessel coronary artery disease. Ten patients without coronary artery disease served as controls. Myocardial contrast echocardiography was performed by intracoronary injection of 2 ml hand-agitated amidotrizoate sodium meglumine (Urografin-76) and by imaging a short-axis view of the left ventricle with twodimensional echocardiography before and during injection of the contrast agent. The twodimensional echocardiographic images at end diastole, before and after injection of the contrast agent, were digitized off-line into a 512 x 512 pixel matrix with 256 gray levels/pixel to quantify the degree of the enhancement of the peak gray level after injection. Transmural myocardial blood flow distribution was evaluated by measuring the ratio of the enhanced gray level in the endocardial half (endo) to that in the epicardial half (epi) (endo:epi gray level ratio) in the anteroseptal, posterolateral, and inferior segments before and just after rapid atrial pacing in each patient. In patients without coronary artery disease, there were no differences in the endo:epi gray level ratio between any of the three segments both before and after pacing. Mean values of the three segments were 0.95±0.08 before pacing and 0.90±0.13 after pacing, respectively. In contrast, in patients with coronary artery disease, the endo:epi gray level ratio for the segment supplied with stenotic coronary artery decreased after pacing (0.40±+0.21 vs. 0.93+0.18, p <0.01), probably reflecting subendocardial myocardial ischemia, whereas that for the segment supplied with nonstenotic coronary artery remained unchanged (0.88+±0.20 vs. 0.99±0.23, NS). Thus, changes in transmural myocardial blood flow distribution with rapid pacing, which may be due to transient subendocardial ischemia, are visualized with myocardial contrast echocardiography. (Circulation 1989;79:233-244) M y yocardial ischemia is clinically anticipated from ST segment depression in an electrocardiogram because reduction in coronary blood flow causes a shift in transmural myocardial blood flow distribution toward epicardial site, producing myocardial ischemia predominantly in the subendocardial layer.1'2 The changes in transmural myocardial blood flow distribution during

Assessment of Transmural Distribution of Myocardial Perfusion With Contrast Echocardiography

“…There has been controversy regarding the ability of MCE to determine the MBF-EER, 12,[22][23][24][25] some of which may be due to differences in methodologies. For instance, some investigators used microbubbles made by sonicating radio-opaque dyes, 23 which tend to produce larger bubbles that transiently block the microcirculation, whereas others 20 used flow tracers that behave like red blood cells within the microcirculation.…”

“…For instance, some investigators used microbubbles made by sonicating radio-opaque dyes, 23 which tend to produce larger bubbles that transiently block the microcirculation, whereas others 20 used flow tracers that behave like red blood cells within the microcirculation. 26 -28 Some studies were performed in patients in whom the presence of selective reduction in endocardial MBF could not be independently confirmed.…”

“…26 -28 Some studies were performed in patients in whom the presence of selective reduction in endocardial MBF could not be independently confirmed. 23,24 In other studies with animals, the limited lateral resolution of ultrasound was a confounding problem in the lateral wall supplied by a stenotic left circumflex coronary artery. 22,25 In these experiments, although decreases in peak VI were noted in the presence of reduction in endocardial MBF during coronary hyperemia, no correlation between VI and endocardial MBF was demonstrated.…”

Evaluation of Transmural Myocardial Perfusion by Ultra-Harmonic Myocardial Contrast Echocardiography in Reperfused Acute Myocardial Infarction

“…Experimental studies indicate that intravenous MCE can be used to assess the transmural distribution of myocardial perfusion because of its higher temporal and spatial resolution. 14,[17][18][19] Recent technical advances in MCE with intravenous drip infusion of contrast microbubbles enable assessment of the transmural distribution of myocardial perfusion in patients with significant coronary arterial stenosis. 20 In addition, recent clinical reports suggest that MCE may be able to differentiate stunning from necrosis and predict recovery of LV function.…”

Evaluation of contrast agents for delineation of vessel wall boundary by intracoronary ultrasound after coronary angioplasty in human

“…Recently, animal studies have demonstrated that contrast medium can improve image quality and the accuracy of measurement of the coronary arteries [9,10]. Intracoronary administration of echogenic contrast agents has been widely used for evaluation of myocardial perfusion in humans [11][12][13][14][15], and these studies have proven the safety of such agents. Therefore, contrast-enhanced ICUS should be a useful procedure, but suitable agents to use in humans are not well documented.…”