Quantitative assessment of left ventricular perfusion defects using real-time three-dimensional myocardial contrast echocardiography

Quantitative assessment of perfusion defects with myocardial contrast echocardiography can be a valuable tool in the evaluation of patients with coronary artery disease. However, the use of 2-dimensional echocardiography for this purpose is limited to a restricted number of imaging planes. Real-time 3-dimensional echocardiography (RT3D) is a novel technique that provides instantaneous volumetric images. The aim of this study was to validate the use of RT3D for the quantitative assessment of myocardial perfusion defects in a model of acute coronary occlusion. To this end, 20 sheep underwent acute ligation of the left anterior descending (n = 14) or the posterior branch of the circumflex (n = 6) artery under general anesthesia. The RT3D images were obtained after left atrial injection of the contrast agent EchoGen (perflenapent emulsion; 0.8-1 mL). Evans blue dye was injected into the occluded coronary artery for subsequent anatomic identification of underperfused myocardium. The mass of the entire left ventricle and of the underperfused myocardial region were measured after death. Blinded off-line calculation of left ventricular (LV) mass and perfusion-defect mass from RT3D images were performed using an interactive aided-manual tracing technique. Total LV mass ranged from 68 to 141 g (mean +/- SD: 92 +/- 24 g). The mass of the perfusion defect ranged from 0 to 43 g (mean SD: 16 +/- 9 g) or 0 to 36% of total LV mass (meant +/- SD: 18% +/- 9%). The RT3D estimation of total LV mass strongly correlated with the anatomic measurement (r = 0.91; y = -2.54 + 1.04x; standard error of the estimate [SEE] = 11.9 g). The RT3D calculation of the mass of underperfused myocardium also strongly correlated with the anatomic measurement, both in absolute terms (r = 0.96; y = 2.01 + 0.87x; SEE = 2.2 g) and when expressed as percentage of total LV mass (r - 0.96; y = 0.11 + 1.02x; SEE = 2.8%). Hence, RT3D with myocardial contrast opacification accurately predicts the amount of underperfused myocardium in an animal model of acute coronary occlusion. This technique may therefore be useful for the quantitative assessment of myocardial perfusion defects in patients with coronary artery disease.