Coronary lipid-rich plaque characteristics in Japanese patients with acute coronary syndrome and stable angina: A near infrared spectroscopy and intravascular ultrasound study

Abstract

Background: Asians have a much lower incidence of adverse coronary events than Caucasians. We sought to evaluate the characteristics of coronary lipid-rich plaques (LRP) in Asian patients with acute coronary syndrome (ACS) and stable angina (SA). We also aimed to identify surrogate markers for the extent of LRP.

Methods: We evaluated 207 patients (ACS, n = 75; SA, n = 132) who underwent percutaneous coronary intervention under near infrared spectroscopy intravascular ultrasound (NIRS-IVUS). Plaque characteristics and the extent of LRP [defined as a long segment with a 4-mm maximum lipid-core burden index (maxLCBI_4mm)] on NIRS in de-novo culprit and non-culprit segments were analyzed.

Results: The ACS culprit lesions had a significantly higher maxLCBI_4mm (median [interquartile range (IQR)]: 533 [385-745] vs. 361 [174-527], p < 0.001) than the SA culprit lesions. On multivariate logistic analysis, a large LRP (defined as maxLCBI_4mm ≥ 400) was the strongest independent predictor of the ACS culprit segment (odds ratio, 3.87; 95% confidence interval, 1.95-8.02). In non-culprit segments, 19.8% of patients had at least one large LRP without a small lumen. No significant correlation was found between the extent of LRP and systematic biomarkers (hs-CRP, IL-6, TNF-α), whereas the extent of LRP was positively correlated with IVUS plaque burden (r = 0.24, p < 0.001).

Conclusions: We confirmed that NIRS-IVUS plaque assessment could be useful to differentiate ACS from SA culprit lesions, and that a threshold maxLCBI_4mm ≥ 400 was clinically suitable in Japanese patients. No surrogate maker for a high-risk LRP was found; consequently, direct intravascular evaluation of plaque characteristics remains important.

Keywords: ACS, acute coronary syndrome; Asian; CI, confidence interval; CKD, chronic kidney disease; IL-6, interleukin-6; IQR, interquartile range; IVUS, intravascular ultrasound; Intracoronary imaging; LCBI; LCBI, lipid core burden index; LDL-C, low-density lipoprotein cholesterol; LRP, lipid-rich plaque; Lipid core burden index; MDA-LDL, malondialdehyde-modified LDL; MLA, minimum lumen area; NIRS; NIRS, near infrared spectroscopy; NSTE-ACS, non-ST elevation acute coronary syndrome; OR, odds ratio; PCI, percutaneous coronary intervention; PCSK9, proprotein convertase subtilisin / kexin type 9; SA, stable angina; STEMI, ST-elevation myocardial infarction; TNF-α, tumor necrosis factor-α; Vulnerable plaque; hs-CRP, high-sensitive C reactive protein.

Fig. 1

A representative case of NIRS-IVUS-detected LRP in a culprit lesion and non-culprit lesion. The findings of a 72-year-old man with unstable angina pectoris are shown. On the coronary angiogram, severe coronary stenosis was detected at the LAD proximal portion (B), and mild coronary stenosis was observed at LMT distal portion (A). A Culprit segment was defined as the segment that was stented by comparing pre- and post-PCI IVUS. A non-culprit segment was defined as the segment proximal to that of the culprit segment. Red brackets indicate the culprit segment, and yellow brackets indicate the non-culprit segment. On IVUS examination, an attenuated plaque was observed in the culprit segment and non-culprit segment (PB 76%, MLA 5.8 mm² (A), PB 89%, MLA 1.4 mm² (B), respectively). NIRS chemogram demonstrated an LRP (maxLCBI_4mm 470) at the culprit segment and (maxLCBI_4mm 422) the non-culprit segment. PCI, percutaneous coronary intervention; NIRS-IVUS, near infrared spectroscopy and intravascular ultrasound; LCBI, lipid core burden index; PB, plaque burden; MLA, minimum lumen area; LRP, lipid rich plaque; LAD, left descending artery; LMT, left main trunk artery. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 2

Receiver-operating characteristic curve for the discrimination of ACS culprit segments by NIRS and IVUS. MaxLCBI_4mm by NIRS, and PB at MLA by IVUS significantly discriminate ACS culprit from SA culprit lesion (p < 0.001, p = 0.001, respectively). ACS, acute coronary syndrome; NIRS, near infrared spectroscopy; IVUS, intravascular ultrasound; LCBI, lipid core burden index; PB, plaque burden; MLA, minimum lumen area; SA, stable angina pectoris.