Myocardial contrast two-dimensional echocardiography: experimental examination at different coronary flow levels.

Regional myocardial echo contrast appearance-disappearance after intracoronary contrast agent injection was examined with computerized two-dimensional contrast echocardiography in eight open chest dogs during successive variation of the coronary blood supply. A new sonication method applied to dextrose 50% produced an echo contrast agent with a microbubble size of 12 +/- 6 mu (mean +/- standard deviation), and 1 cc of this agent was injected into a coronary artery during the echocardiographic study of the left ventricle. Left anterior descending or circumflex coronary artery flow, measured by electromagnetic flowmeter, was successively reduced up to 90% with an extravascular hydraulic occluder, or else increased 40 to 60% through intravenous dipyridamole infusion (7 to 10 micrograms/kg per min). The corresponding myocardial echo time-intensity curves were analyzed for each of 12 segments of a midventricular short-axis cross section. Several potential indexes of myocardial perfusion were derived: peak echo contrast intensity, time from echo contrast appearance to peak intensity, half-life of echo contrast decay phase (T 1/2) and total duration of contrast appearance-disappearance. Except for peak intensity, all of these indexes provided significant (p less than 0.05) differentiation between control coronary flow (66 +/- 17 ml/min) and greater than 50% flow reductions (26 +/- 6 ml/min) or hyperemia (115 +/- 17 ml/min). Half-life values were 5.2 +/- 0.3 seconds for the control state, 9 +/- 2 seconds for the reduced coronary flow and 2 +/- 2 seconds for dipyridamole hyperemia.(ABSTRACT TRUNCATED AT 250 WORDS)