Detection of Coronary Stenoses at Rest With Myocardial Contrast Echocardiography

Abstract

Background-We hypothesized that autoregulatory changes in arteriolar blood volume (aBV) that develop distal to a stenosis can be measured with myocardial contrast echocardiography, allowing coronary stenosis detection at rest without recourse to stress. Methods and Results-Patients with varying degrees of coronary artery stenosis on quantitative angiography underwent high-mechanical-index myocardial contrast echocardiography at 15 Hz to allow measurement of phasic changes in aBV in large intramyocardial vessels using either Definity (group 1; nϭ22) or Imagent (group 2; nϭ22 A systolic/diastolic aBV signal ratio of Ͼ0.34 provided a sensitivity and specificity of 80% and 71%, respectively, for the detection of Ͼ75% coronary stenosis in group 1 patients, whereas a ratio of Ͼ0.43 provided a sensitivity and specificity of 89% and 74%, respectively, for the detection of Ͼ75% stenosis in group 2 patients. Conclusions-Both the presence and severity of a physiologically significant coronary stenosis can be detected at rest by measuring the increase in aBV on myocardial contrast echocardiography that occurs distally to the stenosis without recourse to any form of stress.

Assessment of tissue perfusion by contrast-enhanced ultrasound

“…In cardiac imaging, CEUS has an established role in left ventricle opacification and endocardial border definition to assess myocardial function and ejection fraction [55][56][57]. The quantification of myocardial perfusion through reperfusion kinetics [57,58] is accurate in the detection of coronary artery stenosis [59], and provides similar results to SPECT and stress echocardiography [60].…”

Myocardial Contrast Echocardiography

“…Because the larger intramyocardial arterioles do not participate in autoregulation, the diastolic signal from them remains unchanged. It was first shown in an animal model 84 ( Figure 9A) and then in humans 85 ( Figure 9B) that the systolic-to-diastolic aBV signal ratio measured at rest increases in the presence of a noncritical stenosis and that the degree of increase is proportional to coronary stenosis severity. Thus, by exploiting the microcirculatory compensatory mechanisms that are evoked to maintain a constant perfusion pressure distal to a stenosis, we can detect the presence of stenosis even at rest using a novel adaptation of MCE.…”

“…However, if imaging is performed with a very short interval between destructive ultrasound pulses, the signal obtained is derived only from vessels that fill in this short period of time, as neither capillaries nor venules have adequate time to fill. 84,85 Thus, this approach can be used to image the blood volume of relatively larger intramyocardial vessels.…”

Stress Echo Without the Stress

“…In the setting of a flow-limiting coronary stenosis, the arterioles vasodilate at rest as part of coronary autoregulation. Therefore, Wei et al 17 hypothesize that the retrograde systolic flow component would be larger in the presence of a flow-limiting coronary stenosis. By calculating the systolic to diastolic (S/D) ratio of aBV, the same authors were able to predict the severity of an artificially induced coronary stenosis in the dog model without the need for exercise or pharmacological stress.…”

“…1 Wei et al 17 are to be congratulated for advancing the art of MCE by incorporating the science of coronary microvascular physiology with the unique ability of MCE to specifically image coronary aBV.…”