ackground Healed plaques, morphologically characterized by a layered phenotype, are frequently found in subjects with sudden cardiac death. However, in vivo data are lacking. Objectives The purpose of this study was to determine the prevalence, morphological characteristics, and clinical significance of healed culprit plaques in patients with acute coronary syndromes (ACS) using optical coherence tomography (OCT). Methods A total of 376 ACS patients (252 ST-segment elevation myocardial infarction [MI] and 124 non–ST-segment elevation acute coronary syndrome) who had undergone pre-intervention OCT imaging of the culprit lesion were enrolled. Patients were stratified according to the presence of layered phenotype, defined ...