Non-culprit plaque healing on serial OCT imaging and future outcome in patients with acute coronary syndromes

Background and aims: Histologic studies indicated that healed plaque, characterized by a multilayered pattern, is indicative of prior atherothrombosis and subsequent healing. However, longitudinal in vivo data on healed plaque formation in non-culprit plaques are limited. This study aimed to investigate serial changes and clinical significance of new layered pattern formation in non-culprit plaques in patients with acute coronary syndromes (ACS) using serial optical coherence tomography (OCT) imaging. Methods: ACS patients who underwent two OCTs at baseline and 1-year follow-up were included. Serial changes in morphologic characteristics of non-culprit plaques were evaluated. New layered pattern was defined as a new signal-rich layer on the plaque surface at follow-up that was not present at baseline. Results: Among 553 non-culprit plaques observed in 222 patients, 82 (14.8 %) exhibited a new layered pattern at follow-up. Thin-cap fibroatheroma, macrophage, and thrombus were identified as independent predictors of the new layered pattern. Plaques with new layered pattern formation showed a greater significant reduction in luminal area and lipid content, as well as a greater increase in fibrous cap thickness compared to those without. The incidence of 6-year non-culprit-related major adverse cardiac events was higher in patients with new layered pattern than in those without (25.4 % vs. 10.8 %, p = 0.011), mainly due to clinically driven coronary revascularization. Conclusions: Plaque destabilization and subsequent healing frequently occur in non-culprit plaques after ACS. The formation of a new layered pattern may contribute to temporary plaque stabilization, but results in luminal stenosis and worse clinical outcomes.