703-1 Detection of Coronary Stenoses and Quantification of Blood Flow Mismatch Using Myocardial Contrast Echocardiography During Coronary Hyperemia with FS-069, a New Intravenous Contrast Agent

Abstract

We hypothesized that coronary stenoses, which are not flow-limiting at rest, can be detected and the degree and spatial extent of blood flow mismatch can be quantified during pharmacologically-induced coronary hyperemia using FS-069, a new intravenous contrast agent. In 15 open-chest dogs, myocardial contrast echo (MCE) was performed using 1-2 ml of FS-069 injected intravenously and myocardial blood flow (MBF) was measured using radiolabeled microspheres at baseline and during dipyridamole (0.56 mg/kg) induced coronary hyperemia. In the presence of this drug, a stenosis was placed either on the left anterior descending (LAD) (n = 9) or the left circumflex (LC) (n = 6) coronary arteries and MCE and MBF assessment were repeated at each stage. MCE images, where contrast disparity between LAD and LC beds was maximal, were digitally-subtracted from pre-contrast images and mean videointensities in the LAD and LC beds were measured. There was a good correlation between the LAD/LC bed videointensity ratio and LAD/LC bed MBF ratio (y = 0.2x + 0.71, r = 0.77, p = 0.0001, SEE = 0.16, n = 45). In addition, the region showing hypoperfusion during LAD or LC stenosis was planimetered and expressed as a percent of the myocardial area in the short-axis slice. There was also a fair correlation between the hypoperfused bed size on MCE and the hypoperfused myocardium as determined by radiolabeled microspheres during LAD or LC stenosis (y = 0.8x + 3.3, r = 0.65, p < 0.001, SEE = 4.2, n = 15). We conclude that it is possible to detect coronary stenoses that are not flow limiting at rest with MCE using intravenous injection of FS-069 during pharmacologically-induced coronary vasodilation. The magnitude of blood flow mismatch and the spatial extent of relative hypoperfusion can also be quantified using this approach. Thus it is possible not only to detect the presence of coronary stenoses, but also to quantify their severity and the quantum of myocardium they supply using MCE from venous injection of 1-2 ml of this new contrast agent.