Clinical Significance of the Presence or Absence of Lipid-Rich Plaque Underneath Intact Fibrous Cap Plaque in Acute Coronary Syndrome

Background-Although most coronary thromboses occur on the surface of lipid-rich plaque (LRP) with plaque rupture (PR), previous pathological and optical coherence tomography studies demonstrated diversity in the morphological characteristics of culprit plaque underlying the thrombus, including lesions with intact fibrous cap (IFC). We investigated the clinical significance of IFC in relation to the presence or absence of LRP observed via optical coherence tomography in culprit lesions of acute coronary syndrome. Methods and Results-We investigated 510 patients with acute coronary syndrome who underwent optical coherence tomography for the culprit lesion. Optical coherence tomography analysis included the presence or absence of PR, which were categorized into the PR group and the IFC group, respectively. The IFC group was further categorized on the basis of the presence of LRP. Incidence of major adverse cardiac events (MACEs), including cardiac death, myocardial infarction, and clinically driven remote revascularizations, was compared. Culprit lesions were categorized into 328 PRs and 182 IFCs. MACEs occurred in 85 patients (16.7%) during the median follow-up duration of 621 days. LRP was detected in 325 lesions (99%) with PR, whereas 60 (33.0%) of the lesions with IFC did not show LRP. Kaplan-Meier analysis revealed significantly lower MACEs in the IFC group compared with the PR group. Furthermore, the IFC group without LRP showed significantly lower MACEs compared with the IFC group with LRP. Multivariate Cox proportional hazards analysis demonstrated that IFC without LRP was an independent predictor of better prognosis. Conclusions-Exclusion of LRP underneath IFC culprit lesions in acute coronary syndrome may predict a lower risk of future MACEs.