ASSESSING DIFFUSE CORONARY ATHEROSCLEROSIS IN SUBJECTS WITH IMPAIRED CORONARY FLOW RESERVE BUT NO ANGIOGRAPHIC CRITICAL STENOSIS. A TRANSTHORACIC ENHANCED COLOR DOPPLER ECHOCARDIOGRAPHYC STUDY

Background: Coronary atherosclerosis is in general diffuse even in the presence of a mild stenosis. Enhanced Doppler transthoracic echo (E-Doppler TTE) is highly feasible and reliable in assessing coronary flow reserve (CFR) in the distal left anterior descending coronary artery (LAD) and also in detecting a coronary stenosis both mild and critical as a localized accelerated flow (ASF) in the epicardial conduit. Thus we hypothesized in patients with impaired CFR (<2.0) but no critical stenosis that E-Doppler TTE can detect DA, an overlooked cause of impaired CFR, as a minor focal or diffuse accelerated stenotic flow. Methods: Twenty-four consecutive patients (pts) were recruited. CFR, assessed in the distal LAD, was calculated as the ratio of peak flow velocity during i.v. adenosine (140mcg/Kg/m) to resting flow velocity. Color-guided Pulsed wave Doppler recording of flow velocities was obtained in the proximal, mid and distal portions of the LAD . An ACS, predictive of mild coronary stenosis as previously validated versus intracoronary ultrasound (IVUS), was present when the max flow velocity was 23% higher than the reference flow velocity measured proximally or distally to this portion, or when the velocity was uniformly high (> 50 cm/s) in the absence of anaemia and LVH. Results: In all patients flow velocities were obtained in the entire LAD. Among them, 12 pts (50%) showed at least one localized mild ASF (61±30%) (9 pts) or a uniformly high flow (3 pts) (group 1), while 12 (50%) did not (group 2). CFR was 1.5±0.3 in group 1 and 1.5±0.4 in group 2 (p=ns). Coronary angiography/IVUS showed that 11/12 pts in group 1 and 2/12 pts in group 2 had mild lumen narrowing and/ or diffuse intimal irregularities or a severe plaque burden (>70%) of the LAD (p<0.001). Thus, an accelerated stenotic flow predicted LAD diffuse atherosclerosis with a sensitivity of 85% (11/13) (95% CI 54% to 98%) and specificity of 91% (10/11) (95%CI 59% to 99%). Conclusion: Non-invasive flow velocity assessment in the entire LAD by E-Doppler TTE has high potential in assessing diffuse atherosclerosis in pts with a severe CFR reduction but no critical stenosis, distinguishing diffuse atherosclerosis from pure microvascular causes of CFR impairment.