The Importance of Proximal Non-obstructive Plaque for Predicting Risk of Future Acute Coronary Syndrome in Stable CAD: Prognostic Value of Coronary CT Angiography

Objective: To evaluate the prognostic value of proximal non-obstructive coronary plaques detected by coronary computed tomography angiography (CCTA) in predicting acute coronary syndrome (ACS) among patients with stable coronary artery disease (CAD). Methods: This retrospective cohort included patients with stable CAD who underwent CCTA at Adam Malik General Hospital, Medan, between January and December 2023. Of 458 patients with non-obstructive plaques, 416 met inclusion criteria and were followed for 18 months. Patients were classified into proximal involvement (left main, proximal left anterior descending artery, proximal left circumflex artery, or proximal right coronary artery) and non-proximal groups. The primary endpoint was occurrence of ACS (unstable angina, non-ST elevation myocardial infarction, or ST-elevation myocardial infarction). Logistic regression and Kaplan–Meier analyses were applied. Results: Among 416 patients, 208 (50 %) had proximal plaque involvement. These patients were older (58.1 vs. 51.9 years, p < 0.001), had higher rates of diabetes and dyslipidemia, and exhibited higher coronary artery calcium (CAC) scores (113.7 ± 144.1 vs. 43.5 ± 32.1, p < 0.001) and more moderate stenosis. During follow-up, ACS occurred in 20 patients (4.8 %), all from the proximal involvement group (p < 0.001). Multivariate analysis confirmed proximal plaques as an independent predictor of ACS (OR 6.51, 95 % CI 3.42–10.78, p < 0.001), along with stenosis severity, segment involvement score, and CAC score. Kaplan–Meier curves showed a significantly higher cumulative incidence of ACS in the proximal group. Conclusions: Proximal non-obstructive plaques strongly predict ACS in stable CAD. CCTA provides important prognostic information beyond stenosis severity, supporting its use for refined risk stratification and preventive strategies.