| Summary: | Background: Studies have demonstrated that patients with non-obstructive coronary artery disease (NOCAD) have an increased risk of myocardial infarction and all-cause mortality, particularly due to coronary microvascular dysfunction (CMD). Moreover, the features of atherosclerotic plaque can affect myocardial blood flow (MBF); however, data on these findings remain limited. Therefore, this study aimed to assess the impact of quantitative coronary computed tomography angiography (CCTA)-derived atherosclerotic plaque features on myocardial perfusion and MBF in NOCAD patients measured using dynamic cadmium–zinc–telluride single-photon emission computed tomography (CZT-SPECT). Methods: Based on the CCTA results, a total of 49 NOCAD patients (stenosis <50%, 29 men, mean age 57.4 ± 9.0 years) were included in the study. In addition to estimating stenosis severity, the plaque volume (mm3) and burden (%) were measured using the coronary bed and separately by structural components (non-calcified, soft-tissue, fibrous, calcified). All patients underwent dynamic CZT-SPECT to assess stress and resting MBF and myocardial flow reserve (MFR). Results: Based on the MFR values, patients were divided into two groups: Group 1 consisted of patients with reduced MFR (<2.0, n = 20), and Group 2 consisted of those with normal MFR (≥2.0, n = 29). Not all patients had severe myocardial perfusion abnormalities, as determined by standard myocardial perfusion imaging indexes. Analysis of the CCTA data demonstrated that small volumes and burdens of atherosclerotic plaques were characteristic of patients. Stress was significantly correlated with total plaque volume (Spearman's rank correlation coefficient (ρ) = –0.402) and burden (ρ = –0.374), as well as non-calcified plaque volume (ρ = –0.341) and burden (ρ = –0.314). Rest significantly correlated with total plaque volume (ρ = –0.504) and burden (ρ = –0.432), and non-calcified plaque volume (ρ = –0.471) and burden (ρ = –0.433). Meanwhile, MFR and standard indexes of myocardial perfusion impairment did not exhibit significant associations with quantitative CCTA parameters. Multivariate logistic regression analysis revealed that only total plaque volume (odds ratio 1.01; 95% confidence interval 1.005–1.030; p < 0.001) was an independent predictor of reduced stress-related MBF of less than 1.5 mL/min/g. Conclusions: Total plaque volume, derived from quantitative CCTA data, represents an independent predictor of reduced stress-related MBF of less than 1.5 mL/min/g, as obtained using dynamic CZT-SPECT, even in the absence of obstructive coronary artery disease (CAD).
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