Noninvasive assessment of coronary flow reserve with transthoracic signal-enhanced Doppler echocardiography

Objectives: The feasibility of noninvasive assessment of coronary flow reserve (CFR) in the distal left anterior descending artery (LAD) with echocardiography-enhanced transthoracic pulsed wave Doppler guided by high-resolution transthoracic color Doppler (TTCD) was investigated. The results were compared with the degree of coronary diameter stenosis obtained during cardiac catheterization. Background: Assessment of CFR has proven to be useful in the selection of patients undergoing invasive treatment of coronary artery disease and in estimating their prognosis. However, CPR could only be determined invasively in everyday practice during catheterization procedures. Recent development of high-resolution TTCD allows transthoracic visualization of distal LAD and supra-apical intramyocardial perforator branches and noninvasive measurement of CPR with pulsed wave Doppler technique. Methods: CFR was determined by measuring the ratio of pulsed wave Doppler time velocity integral during adenosine-induced hyperemia (140 mu g/kg/min intravenously) to baseline value. If the baseline Doppler signal of LAD flow was insufficient, an echocardiography (echo) enhancer (Levovist) was used. Forty-five patients were examined by TTCD (7-MHz B-mode, 5-MHz color Doppler, and 3.5-MHz pulsed wave Doppler) after coronary angiography had been performed. Group 1 consisted of 15 patients without heart disease, group 2 of 15 patients with 50% to 85% isolated LAD diameter stenosis, and group 3 of 15 patients with >85% LAD diameter stenosis. Results: Peripheral LAD coronary how at baseline condition was assessed in 40 (88%) patients with TTCD. CFR could be quantified in 36 (80%) of the 45 patients: in 18 patients without echo enhancer, and in 18 patients with echo-enhancing agent. CPR could not be assessed in 9 (20%) patients. CFR In the various groups was as follows:: group 1, 3.15 +/- 0.57; group 2, 2.23 +/- 0.20 (vs group 1: P < .01); and group 3, 1.64 +/- 0.30 (vs group 2: P < .02). Conclusion: CFR in the LAD can be determined in 80% of patients with pulsed wave Doppler guided by high-resolution TTCD combined with intravenously administer-ed echo-enhancing agent.