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

Objectives: The feasibility of noninvasive assessment of coronary flow rese rve (CFR) in the distal left anterior descending artery (LAD) with echocard iography-enhanced transthoracic pulsed wave Doppler guided by high-resoluti on transthoracic color Doppler (TTCD) was investigated. The results were co mpared with the degree of coronary diameter stenosis obtained during cardia c catheterization. Background: Assessment of CFR has proven to be useful in the selection of p atients undergoing invasive treatment of coronary artery disease and in est imating their prognosis. However, CPR could only be determined invasively i n everyday practice during catheterization procedures. Recent development o f high-resolution TTCD allows transthoracic visualization of distal LAD and supra-apical intramyocardial perforator branches and noninvasive measureme nt of CPR with pulsed wave Doppler technique. Methods: CFR was determined by measuring the ratio of pulsed wave Doppler t ime velocity integral during adenosine-induced hyperemia (140 mu g/kg/min i ntravenously) 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 Doppl er, and 3.5-MHz pulsed wave Doppler) after coronary angiography had been pe rformed. 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 ech o-enhancing agent. CPR could not be assessed in 9 (20%) patients. CFR In th e 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 < .0 2). Conclusion: CFR in the LAD can be determined in 80% of patients with pulsed wave Doppler guided by high-resolution TTCD combined with intravenously ad minister-ed echo-enhancing agent.