NIRS-IVUS Assessment of OCT-Derived Healed Coronary Plaques

Healed plaque (HP) is associated with rapid plaque growth and luminal narrowing. Thin-cap fibroatheroma (TCFA) is recognized as a precursor lesion to plaque rupture. The aim of the present study was to compare the lipid size among optical coherence tomography (OCT)-derived HP, TCFA, and thick-cap fibroatheroma (ThCFA) using near-infrared spectroscopy-intravascular ultrasound (NIRS-IVUS).

The present study included 173 patients with acute myocardial infarction (AMI) who underwent percutaneous coronary intervention. Non-culprit lesions with angiographically intermediate stenosis were assessed by both OCT and NIRS-IVUS.

The frequency of TCFA, HP, and ThCFA was 35 (20%), 53 (30%), and 85 (49%), respectively. Minimum lumen area was not significantly different between TCFA and HP, but was smaller in TCFA and HP than in ThCFA (4.6 [interquartile range {IQR}: 3.5-6.4] mm² vs. 4.3 [3.4-5.3] mm² vs. 6.5 [4.8-8.6] mm², P＜0.001). Plaque burden was not significantly different between TCFA and HP, but was larger in TCFA and HP than in ThCFA (72 [IQR: 66-80] % vs. 75 [67-80] % vs. 62 [54-69] %, P＜0.001). Maximum lipid core burden index in 4mm (maxLCBI_4mm) was largest in TCFA, followed by HP and ThCFA (493 [IQR: 443-606] vs. 446 [347-520] vs. 231 [161-302], P＜0.001). The frequency of lipid rich plaque with maxLCBI_4mm ＞400 was highest in TCFA, followed by HP and ThCFA (89% vs. 60% vs. 7%, P＜0.001).

Based on NIRS-IVUS findings, non-culprit coronary HP in AMI was associated with vulnerable plaque characteristics, but not as much as TCFA.