Is the rate of disappearance of echo contrast from the interventricular septum a measure of left anterior descending coronary artery stenosis?

Although myocardial contrast echo has been used recently in human studies, no study is available at the present time which relates contrast echo findings to the degree of coronary artery stenosis. The present study is the first attempt to determine whether a quantitative relationship exists between regional myocardial echo contrast disappearance rate ('washout') and the severity of coronary artery stenosis. Manual injection of sonicated iopamidol (Iopamiro 370) into the left main coronary artery with simultaneous cross-sectional echo registration provided the myocardial echo-contrast images. From the digitized images, an echo contrast time-intensity curve was constructed for the proximal basal interventricular septum (region I) and the mid-distal portion of the interventricular septum (region II). From these curves, T50 was calculated after Fourier transformation and mono-exponential curve fitting. The percentage stenosis area (%A) of the left descending coronary artery (LAD) was calculated from routine coronary arteriograms using a computer-based system. Thirty patients (22 men, 8 women; mean age 58 +/- 10 years) were included in the study. Group I (n = 7) had normal LAD, group II (n = 18) had LAD stenosis of varying degrees. Five patients were not suitable for quantitative evaluation. A curvilinear relation was found between T50 and %A. (T50 = 3.0 x e0.01%A; r = 0.78; P less than 0.05). Patients with asynergy had significantly longer T50 (8.2 +/- 2.5 s) than did patients without asynergy (4.2 +/- 1.5 s) (P less than 0.05). All patients with greater than 75% LAD %A had prolonged T50. T50 might be useful index for studying regional myocardial perfusion during cardiac catheterization.