OCT-Based Morphological Classification of Healed Coronary Plaques: Insights from Imaging of Fresh Thrombi at Different Stages of Healing and Implications for Post-Stenting Edge Dissections

<i>Background and Objectives</i>: In vivo data on healed coronary plaques (HCPs), the hallmark of previous plaque disruption, remains scarce. The study aimed to use optical coherence tomography (OCT) imaging to assess the prevalence, morphological features, and clinical significance of culprit HCPs in patients with acute coronary syndrome (ACS). <i>Materials and Methods</i>: A total of 87 ACS patients (74.3% non-ST-segment elevation ACS) who underwent pre-procedural OCT imaging of the culprit vessel at a single center were retrospectively analyzed. A pilot subgroup of patients with intracoronary thrombi at the culprit site, in various stages of organization and healing, enabled a detailed morphological characterization of HCP despite the absence of histological validation. Three distinct HCP imaging aspects were identified: type I-overlaying fibrous tissue, type II-overlaying lipid tissue, and type III-overlaying calcific tissue. HCP presence was subsequently assessed in the entire population. Clinical correlations included associations with post-stenting outcomes, particularly edge dissections (ED). <i>Results</i>: Culprit HCPs were identified in 78 patients (89.7%): type I-30.8%, type II-51.3%, and type III-17.9%. Regarding the underlying substrate and complication mechanism, type I HCP was associated with pathological intimal thickening (70.8%) and plaque erosion (75%), type II with lipid-rich plaque (80%) and plaque rupture (PR) (82.5%), and type III correlated with calcific plaque (92.9%, <i>p</i> < 0.0001) and both PR and calcified nodule (<i>p</i> < 0.0001). A unique signal-rich ring was observed at the HCP-tissue interface in both type II (77.5%) and type III (78.6%, <i>p</i> < 0.0001). There was a significant correlation between stent ED and HCP presence at landing zones (LZ) (HR 4.14, 95% CI: 1.79-9.55; <i>p</i> < 0.001). <i>Conclusions</i>: OCT analysis of intracoronary organizing fresh thrombi allowed detailed characterization of culprit HCPs and in vivo classification into three imaging types. This approach likely contributed to the high observed detection rate of HCP by enhancing recognition of subtle OCT features. HCP may create mechanical vulnerability if located at the stent LZ. Our improved HCP detection techniques may help optimize stent-related outcomes of OCT-guided procedures by choosing an HCP-free LZ or longer stents.