Endothelial Shear Stress and Coronary Plaque Characteristics in Humans

Abstract

BACKGROUND—Despite the exposure of the entire vasculature to the atherogenic effects of systemic risk factors, atherosclerotic plaques preferentially develop at sites with disturbed flow. This study aimed at exploring in vivo the relationship between local endothelial shear stress (ESS) and coronary plaque characteristics in humans using computational fluid dynamics and frequency-domain optical coherence tomography. METHODS AND RESULTS—Three-dimensional coronary artery reconstruction was performed in 21 patients (24 arteries) presenting with acute coronary syndrome using frequency-domain optical coherence tomography and coronary angiography. Each coronary artery was divided into sequential 3-mm segments and analyzed for the assessment of local ESS and plaque characteristics. A total of 146 nonculprit segments were evaluated. Compared with segments with higher ESS [≥1 Pascal (Pa)], those with low ESS (<1 Pa) showed higher prevalence of lipid-rich plaques (37.5% versus 20.0%; P=0.019) and thin-cap fibroatheroma (12.5% versus 2.0%; P=0.037). Overall, lipid plaques in segments with low ESS had thinner fibrous cap (115 μm [63–166] versus 170 μm [107–219]; P=0.004) and higher macrophage density (normalized standard deviation: 8.4% [4.8–12.6] versus 6.2% [4.2–8.8]; P=0.017). Segments with low ESS showed more superficial calcifications (minimum calcification depth: 93 μm [50–140] versus 152 μm [105–258]; P=0.049) and tended to have higher prevalence of spotty calcifications (26.0% versus 12.0%; P=0.076). CONCLUSIONS—Coronary regions exposed to low ESS are associated with larger lipid burden, thinner fibrous cap, and higher prevalence of thin-cap fibroatheroma in humans. Frequency-domain optical coherence tomography–based assessment of ESS and wall characteristics may be useful in identifying vulnerable coronary regions.