Contrast-enhanced transthoracic second harmonic echo Doppler with adenosine - A noninvasive, rapid and effective method for coronary flow reserve assessment

OBJECTIVES The purpose of this study is to evaluate the feasibility in detecting blood flow in the left anterior descending coronary artery (LAD) using transthoracic color Doppler (CD) imaging (in both second harmonic and fundamental mode) along with contrast enhancement and to verify ii this new noninvasive method along with adenosine is safe, rapid and effective in assessing coronary flow reserve (CFR). BACKGROUND Feasibility of contrast-enhanced transthoracic Doppler recording (in both second harmonic and fundamental mode) of blood flow velocity in the LAD has not been assessed. Adenosine has a greater vasodilator potency and more favorable kinetics than dipyridamole and thus it can be more suitable for assessing CFR in conjunction with this method. METHODS Sixty-one patients with angiographically patent LAD underwent CD (both in fundamental and harmonic mode) as well as color-guided pulsed wave (PW) Doppler recording of blood flow velocity in the distal LAD before and after intravenous contrast injection. fl second group of patients (n = 77), undergoing coronary angiography, was submitted tu transthoracic contrast-enhanced PW Doppler recording of blood flow velocity in the LAD using harmonic CD as a guide, at rest and during adenosine-induced hyperemia. RESULTS Harmonic CD along with echo contrast consistently improved blood flow detection in the LAD; the success rate in detecting Row of optimal quality was 88% with this approach, whereas it was 11% and 16% with. CD in fundamental mode, respectively, before and after contrast. Pulsed wave Doppler results paralleled those of harmonic CD (p < 0.001 contrast harmonic vs. fundamental). In the second group of patients coronary angiography revealed 0% to <40% stenosis in 24 patients (group I), greater than or equal to 40% to less than or equal to 75% in 17 patients (group II) and >75% stenosis in 34 patients (group III). There was a significant difference in CFR among the three groups of patients; CFR for peak diastolic velocity was (mean +/- SD): 2.88 +/- 0.7 (group I), 2.09 +/- 0.5 (group II) and 1.51 +/- 0.5 cm/s (group II) (p < 0.05 group I vs. both group II and group III; p < 0.05 group IT vs, group III). The whole examination took less than 10 min. CONCLUSIONS Contrast-enhanced second harmonic Doppler recording of blood velocity in the LAD is highly feasible and in combination with adenosine it is a rapid, safe and effective method for assessing CFR ratio. (C) 1999 by the American College of Cardiology.