Myocardial contrast two-dimensional echocardiography: Dose-myocardial effect relations of intracoronary microbubbles

Abstract

It is controversial whether echocardiographic contrast agents prepared by sonication cause transient myocardial depression beyond that known to occur with contrast agents alone. In nine open chest dogs, contrast injections were made into the left anterior descending coronary artery during two-dimensional echocardiography. One hundred forty-four recordings were analyzed subsequently, by an observer who was unaware of other data, for percent depression of systolic wall thickening, duration of regional wall motion abnormalities, peak contrast enhancement and contrast washout. Two microbubble sizes were obtained by sonicating Renografin-76 (meglumine sodium diatrizoate): mean diameter 12 ± 3 (SEE) and 20 ± 6 μm. Four doses (range 0.5 to 3 ml) of each of four agents (12 and 20 μm bubbles in Renografin, nonsonicated Renografin and saline solution) were injected in random order.Significant relations were found between percent depression of systolic wall thickening, duration of regional wall motion abnormalities and contrast washout time versus microbubble size (p < 0.001) and microbubble dose (p < 0.01). Little increased contrast effect was found at larger doses or with larger microbubbles compared with the smaller doses and size studied. Injections of nonsonicated Renografin caused less depression of systolic wall thickening (p < 0.05), faster resolution of wall motion abnormalities (p < 0.05), less contrast (p < 0.001) and more rapid contrast washout (p < 0.601) than did 12 μm bubbles in Renografin. A significant correlation was found between the duration of regional wall motion abnormalities and contrast washout time (r = 0.93, p < 0.001).It is concluded that: 1) dose-effect curves can be obtained for intracoronary microbubbles; 2) transient depression of left ventricular function is due to both the carrier agent itself and the presence of microbubbles; 3) smaller microbubble doses and size cause adequate contrast with decreased depression of systolic wail thickening and fewer wall motion abnormalities; 4) there is a correlation between contrast washout time and the duration of wall motion abnormalities.