Plaque morphology assessed by optical coherence tomography in the culprit lesions of the first episode of acute myocardial infarction in patients with low low-density lipoprotein cholesterol level

•Plaque erosion is the second major pathological substrate of acute coronary syndrome (ACS).•Plaque erosion is characterized with intact fibrous cap on optical coherence tomography.•Patients with low low-density lipoprotein cholesterol showed more intact fibrous cap at the culprit lesion.•Intact fibrous cap plaque might be the major cause of ACS after failed primary prevention. There remains a residual risk for acute myocardial infarction (AMI) even with low low-density lipoprotein cholesterol (LDL-C) levels. This study aimed to characterize the culprit lesion morphology of AMI by optical coherence tomography (OCT) in patients with low LDL-C. Four-hundred and nine culprit lesions of 409 patients with their first presentation of AMI imaged by OCT were investigated. OCT analysis included the presence of plaque rupture and thin-capped fibroatheroma (TCFA). Fibrous cap thickness and lipid length were also measured. Intravascular ultrasound (IVUS) was performed in 368 (90.0%) patients. OCT and IVUS findings were compared between patients with LDL-C