Assessment of myocardial perfusion abnormalities with contrast-enhanced two-dimensional echocardiography.

Abstract

A new echocardiographic contrast agent, gelatin-encapsulated microbubbles, that produces an intramyocardial contrast effect, was evaluated as a marker for the detection of regions of abnormal myocardial perfusion in nine open-chest dogs. The gleatin-encapsulated microbubbles were injected into the aortic root under control conditions and during circumflex coronary artery occlusion. Myocardial perfusion was simultaneously assessed with radioactive microspheres. Echocardiographic contrast enhancement (ECE) was measured in footlamberts (Ft-L) from the videoscreen of an off-line playback system, using a commercially available light meter. A single short-axis section of the left ventricle was divided into octants to analyze myocardial perfusion. The equivalent regions of the echocardiographic image were analyzed for contrast enhancement and wall motion. An ECE > 0.3 Ft-L was seen in all 120 octants analyzed before circumflex coronary artery occlusion and in 48 of 51 (94%) octants with > 50% of the normal zone flow during circumflex artery occlusion. An ECE .ltoreq. 0.3 Ft-L identified 19 of 21 octants (90%) with .ltoreq. 50% normal zone flow and all 13 octants with .ltoreq. 25% normal zone flow during coronary artery occlusion. In contrast, wall motion abnormalities (akinesis or dyskinesis) were seen in 13 of 51 octants (25%) with > 50% normal zone flow, and normal wall motion was seen in 2 of 21 octants (10%) with blood flow .ltoreq. 50% of normal zone flow during circumflex coronary artery occlusion. A linear correlation could not be demonstrated between ECE and the absolute level of myocardial blood flow. This was possibly due to the limitations imposed by imaging an open-chest animal preparation, variation in the number of gelatin-encapsulated microbubbles used for each injection and variations in the echocardiographic gain settings among experiments. Contrast-enhanced 2-dimensional echocardiography with gelatin-encapsulated microbubbles can accurately identify ischemic regions of the left ventricular myocardium. This technique is more accurate than wall motion analysis for detecting myocardoial ischemia.