THE DOPPLER KINETICS OF MICROBUBBLE ECHO CONTRAST

The right and left heart kinetics of a saccharide-based microbubble ec ho contrast agent were measured in 11 anesthetized dogs using Doppler intensity as a measure of microbubble concentration while controlling for the dose administered, weight of the subject and cardiac output, A two-phase Doppler time-intensity curve was noted in all vascular regi ons, A brief first pass effect (phase 1) was found to depend on the co ntrast dose, cardiac output and subject size, This was followed by a m uch longer nearly steady-state elevation in the Doppler intensity comp ared with baseline (phase 2), The kinetics of phase 2 were found to be the same in all vascular distributions and independent of cardiac out put. The phase 2 kinetics depend on the contrast dose, subject size an d elimination characteristics of the contrast agent, The clinically im portant conclusions are: (1) the magnitude of Doppler enhancement and duration of the contrast effect can be predicted using the simple form ulas presented; (2) the flow-dependent portion of the arterial contras t effect is effectively over only a few seconds after intravenous inje ction; and (3) the kinetics of phase 2 are the same throughout the bod y.