Myocardial contrast echocardiography: examination of intracoronary injections, microbubble diameters, and video-intensity decay.

Contrast echocardiographic assessment of blood flow within the myocardium requires standardization of contrast agents and echo image analysis. Sonicated contrast solutions containing small and relatively stable microbubble ultrasound reflectors were injected into coronary arteries of five dogs, and a newly developed computer assisted densitometric analysis of myocardial echo intensity decay was examined. The sonicated solutions included sorbitol 70%, dextrose 70%, and dextrose 50%, and myocardial contrast echo data were analyzed by applying an exponential decay index (T-1/2) to the digitized time intensity curves obtained with videodensitometric techniques. In 30 intracoronary injections selected for further analysis, sonicated sorbitol 70% demonstrated the most physiologic myocardial transit time with the smallest variability (6.0 +/- 2.0 seconds). Sonicated dextrose 70% and dextrose 50% solutions exhibited significantly prolonged and more variable transit times (11.4 +/- 4.0 seconds and 13.9 +/- 5.0 seconds). The results of this study suggest that appropriate echo contrast solutions with small microbubble diameters are critical to satisfactory echocardiographic assessment of myocardial blood flow, and that objective analysis of contrast two-dimensional echocardiographic images can be achieved with computer-assisted videodensity algorithms featuring standardized echo analysis of the time intensity data.