Abstract Background/Introduction Coronary flow reserve (CFR) reflects the coronary arteries’ ability to augment blood flow in response to increased demand, with impairment serving as an early marker of coronary artery disease (CAD). Prior studies suggest that CFR reduction may precede visible plaque development, highlighting its potential role in detecting early atherosclerosis. However, the relationship between CFR and high-risk plaque features in non-obstructive CAD remains poorly understood. Purpose This study aims to investigate this association, providing insights into how functional assessments correlate with anatomical plaque characteristics and cardiovascular risk. Methods Twenty-two patients with non-obstructive CAD were prospectively recruited and underwent same-day cardiac computed tomography angiography (CTCA) and invasive pressure-wire assessment of proximal left anterior descending artery (pLAD). Quantitative and qualitative plaque analysis were performed using semi-automated software (Autoplaque, v2.5). Percent atheroma volume (PAV) was calculated as (total plaque volume/ vessel volume) x 100%. Results The mean CFR in the cohort was 2.50 (range: 1.56 – 4.21). The average pLAD length was 16.69 mm with a vessel volume of 222.26mm3. Mean total PAV was 27.92%, with 20.39% non-calcified PAV, 1.00% low-density non-calcified PAV, and 7.62% calcified PAV. Plaque composition analysis demonstrated a mean necrotic core volume of 3.15%, fibrous fatty plaque volume of 23.60%, fibrous plaque volume of 50.21%, and dense calcium volume of 22.98%. There was poor correlation between CFR and total PAV (r= -0.15, 95% CI: -0.54 to 0.29, P= 0.51) as well as plaque subtypes (necrotic core: r= 0.27, 95% CI: 0.17 to 0.62, P= 0.07; fibrous fatty: r= -0.19, 95% CI: -0.57 to 0.25, P= 0.39; fibrous volume: r= =0.19, 95% CI: -0.56 to 0.25, P= 0.40; dense calcium: r=0.22, 95% CI: -0.22 to 0.59, P=0.32). Conclusion In this study of patients with non-obstructive CAD, CFR demonstrated poor correlation with total plaque burden and high-risk plaque features. These findings suggest that functional coronary haemodynamics may not directly reflect anatomical plaque characteristics in non-obstructive CAD, underscoring the complex interplay between coronary physiology and atherosclerotic plaque compositions. One limitation of this study is the small sample size. Further research is needed to clarify alternative mechanisms influencing CFR in this population.
Chan et al. (Sat,) studied this question.