QUANTIFICATION OF MYOCARDIAL PERFUSION WITH MYOCARDIAL CONTRAST ECHOCARDIOGRAPHY DURING LEFT ATRIAL INJECTION OF CONTRAST - IMPLICATIONS FOR VENOUS INJECTION

Background The purpose of this study was to determine whether myocardi al perfusion can be quantified with myocardial contrast echocardiograp hy using left atrial (LA) injection of contrast. Methods and Results B ased on a series of in vitro and in vivo experiments, the optimal dose of sonicated albumin microbubbles injected into the LA for establishi ng a linear relation between video intensity and blood volume in the a nterior myocardium was determined. In 10 open-chest dogs, myocardial b lood flow (MBF) was augmented by increasing myocardial blood volume (M BV) with an intravenous infusion of phenylephrine HCl. In the presence of this drug, left anterior descending artery stenosis was produced, followed by release of stenosis, to change MBF within the anterior myo cardium. MBV was calculated by dividing radiolabeled microsphere-deriv ed MBF by microbubble transit rate. There was close coupling between M BF and MBV in the anterior myocardium during LA injection of contrast (y=1.0x-0.03, SEE=1.07, r=.92, P<.001). An excellent correlation was a lso noted between background-subtracted peak video intensity and MBV ( y=0.24x+0.73, SEE=0.36, r=.88, P<.001), On multivariate analysis, back ground-subtracted peak video intensity correlated best with MBV. Concl usions Myocardial perfusion can be quantified from time-intensity curv es derived from the anterior myocardium after LA injection of contrast . Background-subtracted peak video intensity in this situation correla tes closely with MBV. When MBV and MBF are closely coupled, such as du ring inotropic stimulation of the heart, background-subtracted peak vi deo intensity also correlates closely with MBF. Since there are simila rities in the models of LA and venous injections, these data indicate that it may be feasible to quantify myocardial perfusion with myocardi al contrast echocardiography after venous injection of contrast.