DETECTION OF PERFUSION DEFECTS DURING CORONARY-OCCLUSION AND MYOCARDIAL REPERFUSION AFTER THROMBOLYSIS BY INTRAVENOUS ADMINISTRATION OF THEECHO-ENHANCING AGENT BR1

The purpose of this study was to detect myocardial perfusion defects a s a result of coronary occlusion and myocardial reperfusion after thro mbolysis with intravenous (IV) administration of the echo contrast age nt BR1 (Bracco Research, Switzerland), which consists of microbubbles (median diameter 2.5 mu m) containing sulfur exafluoride in a phosphol ipidic shell. To generate a coronary thrombosis, a copper coil was adv anced into the left circumflex coronary artery in eight anesthetized d ogs with opened chest cavities. Coronary occlusion occurred 18 +/- 10 minutes after the insertion of the coil and was documented both by an electromagnetic flow meter (as zero blood flow) and by radiolabeled mi crospheres (as myocardial perfusion defect). After 2 hours of occlusio n, streptokinase was infused IV; reperfusion was documented by both th e flow meter and microspheres. Left ventricular cavity enhancement was apparent after all contrast injections. Peak cavity intensity did not increase with dose and was not affected by signal processing (suggest ing signal saturation), whereas the duration of contrast effect signif icantly increased with the dose (from 26 +/- 16 to 147 +/- 74 seconds) . Myocardial contrast intensity also increased after contrast (from 15 +/- 12 to 21 +/- 18 gray level/pixel, p < 0.001). Contrast echo detec ted myocardial perfusion defects (corresponding to 17% +/- 11% of LV c ross-sectional area) in all the injections performed during coronary o cclusion and detected myocardial reperfusion with a sensitivity of 50% versus microspheres. The extent of perfusion defects by contrast echo showed a good correlation with microspheres (r = 0.73). Myocardial re perfusion was not detected by changes in heart rate, aortic pressure, pulmonary arterial pressure, cardiac output, left ventricular fraction al area change, or wall-motion score index. Hemodynamic parameters wer e not affected by contrast injections. Thus, the IV administration of BR1 allows us to accurately detect myocardial perfusion defects during coronary occlusion and, to a lesser extent, myocardial reperfusion af ter thrombolysis.