Background: Despite being a relatively widely-used non-invasive parameter of endothelial dysfunction, little is known regarding the relationship between flow-mediated dilatation (FMD) and coronary plaque vulnerability in patients with coronary artery disease (CAD).
Methods: 111 CAD patients (age; 68.9 ± 9.3) who underwent both coronary intervention and FMD were enrolled. Spectral analyses of intravascular ultrasound radiofrequency data for both culprit and non-culprit lesions were performed using Virtual Histology software. Plaque burden was described based on fibrotic, fibro-fatty, dense calcium, and necrotic core (NC) components, and thin-cap fibroatheroma (TCFA) was defined as focal NC rich (> 10%) plaques touching the lumen with a percent-plaque volume exceeding 40%.
Results: Averaged %FMD was 2.86 ± 2.03% (median 2.27%, 25th 1.40%, 75th 4.20%). NC volumes were negatively correlated with log%FMD for both culprit and non-culprit lesions (P = 0.001, r = 0.31 and P = 0.03, r = 0.21, respectively). We divided the patients into three tertiles according to %FMD; 38 were lower (≤ 1.75%), 41 were middle (> 1.75%, but ≤ 3.5%), and 32 were upper tertile (> 3.5%). The prevalence rate of TCFA increased with decreasing %FMD tertile and the incidence of major adverse cardiac events was significantly higher in lower %FMD tertile. Multivariate logistic regression analyses showed that the most powerful predictive factor for TCFA was log%FMD (P < 0.0001), and ROC curve analysis identified %FMD of < 2.81% (AUC = 0.82, sensitivity: 91.2%, specificity: 66.7%) as the optimal cut-off point for predicting the presence of TCFA.
Conclusions: Impaired endothelial function in brachial arteries may be associated with whole coronary plaque vulnerability and poor clinical outcome in patients with CAD.
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