SMALLER INTRAVENOUS PERFLUOROCARBON-CONTAINING MICROBUBBLES PRODUCE GREATER MYOCARDIAL CONTRAST WITH INTERMITTENT HARMONIC IMAGING AND BETTER DELINEATION OF RISK AREA DURING ACUTE MYOCARDIAL-ISCHEMIA

The purpose of this article was to determine wether applying negative or positive pressure to perfluorocarbon-containing microbubbles before intravenous injection would improve the myocardial contrast when usin g newer imaging techniques such as harmonic and intermittent imaging. Perfluorocarbon-containing microbubbles were exposed to sustained nega tive or positive pressure before intravenous injection in 10 dogs. Mic robubble size distribution and concentration were measured after each exposure. Peak myocardial video-intensity with intermittent harmonic i maging with each sample was compared. A Microbubbles exposed to -200 m m Hg pressure before intravenous injection produced both the highest c oncentration of microbubbles and greater numbers of microbubbles less than 4 mu m. Peak myocardial videointensity did not correlate with mic robubble concentration or size but did correlate with the absolute num ber of microbubbles < 4 mu m (mean r value 0.76, range 0.61 to 0.90). Risk area was best visualized with perfluorocarbon-containing microbub ble samples containing the smallest microbubbles. We conclude that the myocardial contrast observed with perfluorocarbon-containing microbub bles can be enhanced by applying negative pressure before injection. T he mechanism for this improved contrast appears to be related to creat ion of smaller microbubbles.