Haemodynamic and blood viscosity profiles of culprit vs. non-culprit coronary vessels: Insights from NIRS-IVUS and CFD analysis.

To clarify the relationship between haemodynamic milieu and lipid core plaques among culprit and non-culprit coronary vessels. A total of 45 vessels from 20 patients with acute coronary syndrome who underwent invasive coronary angiography were prospectively enrolled for additional near-infrared spectroscopy intravascular ultrasound (NIRS-IVUS) imaging to quantify lipid plaque content. Haemodynamics assessments between culprit (n = 19, one excluded due to suboptimal angiography) and non-culprit (n = 25) vessels were performed using three-dimensional arterial reconstructions derived from fused NIRS-IVUS and quantitative coronary angiography imaging. Culprit vessels were characterised by a higher probability of lipid core containing coronary plaques (0.00 [interquartile range, IQR: 0.00-0.278] vs. 0.00 [0.00-0.119], p ≪ 0.05). The greatest haemodynamics differentiation between the two groups, in descending order, was observed in transverse endothelial shear stress (transESS), oscillatory shear index (OSI), and elevated blood viscosity (EBV). In mixed logistic regression, after adjusting for other haemodynamic metrics, culprit vessels exhibited decreasing odds of moderate-to-high OSI (odds ratio [OR] 0.484, 95% confidence interval [CI] 0.304-0.770, p = 0.002 and OR 0.578, 95% CI 0.339-0.985, p = 0.044, respectively), as was moderate transESS (OR 0.440, 95% CI 0.276-0.702, p < 0.001), but increasing odds of moderate-to-high EBV (OR 2.030, 95% CI 1.180-3.491, p = 0.010 and OR 4.373, 95% CI 2.017-9.479, p < 0.001, respectively). This study observed elevated blood viscosity within culprit vessels, as a potentially underexplored feature of plaque vulnerability. Our findings suggest that blood viscosity is associated with vessel-specific differences in lipid core plaque, though the small sample size means these findings should be considered hypothesis-generating.