BACKGROUNDCoronary microcirculation reserve is an important field in the research of coronary artery disease, but it is difficult to identify clinically. Currently it is widely accepted that myocardial contrast echocardiography (MCE) is a safe, inexpensive method and has comparatively high image resolution. The present study used quantitative low-dose adenosine stress real-time (RT)-MCE to estimate myocardial perfusion and the coronary stenosis.

METHODSForty-nine left ventricular (LV) segments from 14 unselected patients were divided into three groups according to the coronary angiography or CT angiography results: group 1 (n = 20, 41%) without significant stenosis (< 70%), group 2 (n = 12, 24%) with successful percutaneous coronary intervention (PCI), and group 3 (n = 17, 35%) with significant stenosis (> 70%). RT-MCE was performed in these patients with low-dose adenosine stress and continuous infusion of Sonovue. The replenishing curves were drawn according to the contrast density measured at the end-diastolic frame of every cardiac circle by ACQ software.

RESULTSForty-nine LV segments with satisfactory image quality were picked for quantitative contrast echo analysis. The replenishing curves were analyzed at baseline and after stress. Perfusion of group 3 did not decrease significantly at baseline, and showed no improvement during adenosine stress and was significantly different from groups 1 and 2 (P < 0.05). The A·β and β increased more significantly in group 1 than in groups 2 and 3 (P < 0.05). In a receiver operating characteristic (ROC) curve analysis, A·β under adenosine stress < 1.74 dB/s had a sensitivity and specificity of 71% for diagnosis of coronary artery stenosis, reduced adenosine-induced rise (percentage of A·β < 81%) had a sensitivity and specificity of 83% and 79% for the diagnosis of low-reserve, and β < 54% had a sensitivity of 86% and specificity of 79%.

CONCLUSIONSRest perfusion of severely stenosed arteries may be normal, but adenosine stress can detect the impaired perfusion reserve. Low-dose adenosine stress RT-MCE provides good accuracy for the evaluation of coronary perfusion reserve and hence coronary stenosis.