New noninvasive method for coronary flow reserve assessment - Contrast-enhanced transthoracic second harmonic echo Doppler

Background-We tested the hypothesis that blood flow velocity could be recor ded in the left anterior descending coronary artery (LAD) during transthora cic echocardiography by use of second harmonic echo Doppler modality along with contrast enhancement (intravenous Levovist) at rest and after pharmaco logically induced maximal vasodilation to assess coronary flow reserve (CFR ) with a totally noninvasive approach. Methods and Results-Fifty-six consecutive patients undergoing coronary angi ography underwent transthoracic contrast-enhanced pulsed-wave Doppler recor ding of blood flow velocity in the LAD by use of harmonic color Doppler as a guide at rest and after maximal vasodilation by dipyridamole infusion. Co ntrast enhancement with the harmonic mode greatly improved the success rate of recording adequate pulsed-wave Doppler signal in the LAD. CFR was (mean +/-SD) 1.54+/-0.7 in patients with (group 1) and 2.79+/-0.9 in patients wit hout (group 2) significant LAD stenosis (lumen narrowing >70%) (P<0.001); s ensitivity and specificity in detecting significant LAD stenosis were 86% a nd 90%, respectively. There was close agreement between CFRs determined by this new method and intracoronary Doppler flow wire. Conclusions-Contrast-enhanced transthoracic echo Doppler with the harmonic mode is a feasible and promising technique for assessing CFR in a totally n oninvasive way.