The relationship between segmental wall shear stress and lipid core plaque derived from near-infrared spectroscopy

Wall shear stress (WSS) has an important role in the natural history of coronary atherosclerosis. The aim of this study is to investigate the relationship between WSS and the lipid content of atherosclerotic plaques as assessed by near-infrared spectroscopy (NIRS).

We performed serial NIRS and intravascular ultrasound (IVUS) upon Doppler coronary flow guidewire of coronary plaques at baseline and after 12-18 months in 28 patients with <30% angiographic stenosis, who presented with coronary artery disease. Segmental WSS, plaque burden and NIRS-derived lipid rich plaque (LRP) were evaluated at both time-points in 482 consecutive 2-mm coronary segments.

Segments with LRP at baseline (n = 106) had a higher average WSS (1.4 ± 0.6 N/m²), compared to those without LRP (n = 376) (1.2 ± 0.6 N/m², p<0.001). In segments without baseline LRP, WSS was higher in those who subsequently developed new LRP (n = 35) than those who did not (n = 341) (1.4 ± 0.8 vs. 1.1 ± 0.6 N/m², p=0.002). Conversely, in segments with baseline LRP, WSS was lower in those who had regression of lipid content (n = 41) than those who did not (n = 65) (1.2 ± 0.4 vs. 1.6 ± 0.7 N/m², p=0.007). Segments with the highest tertile of WSS displayed greater progression of LCBI irrespective of baseline lipid content (p<0.001). Multivariate analysis revealed that baseline WSS (p=0.017), PAV (p<0.001) and LCBI (p<0.001) were all independent predictors of change in LCBI over time.

Coronary segments with high WSS associate with progression of lipid content over time, which may indicate transformation to a more vulnerable phenotype.