In vivo imaging of vulnerable plaque with intravascular modalities: its advantages and limitations

Abstract

In vivo imaging of plaque instability has been considered to have a great potential to predict future coronary events and evaluate the stabilization effect of novel anti-atherosclerotic medical therapies. Currently, there are several intravascular imaging modalities which enable to visualize plaque components associated with its vulnerability. These include virtual histology intravascular ultrasound (VH-IVUS), integrated backscatter IVUS (IB-IVUS), optical coherence tomography (OCT), near-infrared spectroscopy and coronary angioscopy. Recent studies have shown that these tools are applicable for risk stratification of cardiovascular events as well as drug efficacy assessment. However, several limitation exists in each modality. The current review paper will outline advantages and limitation of VH-IVUS, IB-IVUS, OCT, NIRS and coronary angioscopy imaging.

Keywords: Vulnerable plaque; integrated backscatter intravascular ultrasound (IB-IVUS), coronary angioscopy; intravascular imaging; near-infrared spectroscopy (NIRS); optical coherence tomography (OCT); virtual-histology intravascular ultrasound (VH-IVUS).

Figure 1

The recurrence of ACS due to progression of lipid-rich plaque containing cholesterol crystal (28). (A) A 60-year-old man with ST-segment elevation myocardial infarction received DES implantation at the middle segment of LAD (dotted line). There was a mild residual stenosis in LAD (red arrow). [1–4] correspond to OCT images in (B). (B) OCT imaging visualized the presence of lipid-rich plaque (L) harbouring cholesterol crystal (white triangle). (C) One year later, non-ST-segment elevation myocardial infarction occurred due to the progression of lipid-rich lesions with cholesterol crystal despite statin therapy (red arrow). ACS, acute coronary syndrome; DES, drug-eluting stent; LAD, left anterior descending artery; OCT, optical coherence tomography.

Figure 2

Limitation of OCT imaging for correct diagnosis of plaque erosion (35). (A) A 93-year-old woman was hospitalized due to anterior STEMI. Coronary angiography identified TIMI grade II flow with severe stenosis within LAD. [1-4] correspond to OCT images in (B and C). (B,C) The surface of culprit lesion was invisible due to its overlying thrombus (*) [2-4]. (D) After retrieving red thrombus with thrombectomy catheter, TIMI grade III flow was achieved without any residual stenosis. 1’-4’ correspond to OCT images in (E and F). (E) On OCT imaging after thrombectomy, an intact fibrous cap and signal attenuation were observed [1’-4’]. This lesion was accompanied by adjacent focal signal-rich region (3’: white arrows), suggesting the small lipidic plaque with superficial macrophages. IVUS, intravascular ultrasound; LAD, left anterior descending artery; OCT, optical coherence tomography; STEMI, ST-segment elevation myocardial infarction; TIMI, thrombolysis in myocardial infarction.

Figure 3

Progression of non-obstructive lesion harbouring high Max4 mmLCBI. (A) 70-year old gentleman received diagnostic coronary angiography due to suspected anginal chest symptom. There was a mild stenosis at the proximal segment of RCA (red arrow). (B) NIRS imaging identified high Max4 mmLCBI (=882) at the corresponding lesion (red arrow). (C) One year later, ACS occurred due to the progression of the lesion with high Max4 mmLCBI (red arrow). ACS, acute coronary syndrome; LCBI, lipid core burden index; NIRS, near-infrared spectroscopy; RCA, right coronary artery.