2ND-HARMONIC IMAGING OF AN INTRAVENOUSLY ADMINISTERED ECHOCARDIOGRAPHIC CONTRAST AGENT - VISUALIZATION OF CORONARY-ARTERIES AND MEASUREMENTOF CORONARY BLOOD-FLOW

Objectives. This study sought to evaluate the potential of second harm onic contrast echocardiography to assess coronary vasculature. Backgro und. Newer transpulmonary ultrasound contrast agents capable of resona nce phenomena detected by harmonic imaging may theoretically be able t o demonstrate blood flow in the myocardium. Methods. Transthoracic B-m ode images and Doppler were obtained using a prototype second harmonic ultrasound system after femoral vein injection of AF0145 (10 to 40 mg ) in 13 closed chest dogs (mean weight 25.6 kg). Coronary Doppler flow was simultaneously invasively measured using an intracoronary flow wi re and visually compared with transthoracic Doppler flow. ''Noninvasiv e'' coronary vasodilator reserve was determined by measuring the ratio of the Doppler time velocity integral after adenosine to the baseline value and compared with the ''invasive'' intracoronary determination. Results. Harmonic imaging showed heterogeneous opacification of the m yocardium characterized by linear branching structures consistent with intramyocardial coronary arteries, which were not clearly visible dur ing conventional ultrasound imaging. In nine dogs, transthoracic Doppl er was performed, and characteristic coronary Doppler flow was observe d, identical to the simultaneously observed intracoronary Doppler flow , Intracoronary adenosine (120 to 150 mu g) equally increased intracor onary and transthoracic Doppler how velocities. The calculated ''nonin vasive'' and ''invasive'' coronary vasodilator reserve ratios were sim ilar ([mean +/- SD] 3.3 +/- 1.0 and 3.6 +/- 1.2, p = NS), with excelle nt correlation (r = 0.95, p = 0.0012). Conclusions. These findings ind icate that noninvasive assessment of intramyocardial coronary vasculat ure and measurement of coronary blood flow reserve are possible using second harmonic contrast echocardiography.