Sex-related differences in coronary and carotid vessel geometry, plaque composition and shear stress obtained from imaging

Atherosclerosis manifests itself differently in men and women with respect to plaque initiation, progression and plaque composition. The observed delay in plaque progression in women is thought to be related to the hormonal status of women. Also features associated with the vulnerability of plaques to rupture seem to be less frequently present in women compared to men. Current invasive and non-invasive imaging modalities allow for visualization of plaque size, composition and high risk vulnerable plaque features. Moreover, image based modeling gives access to local shear stress and shear stress-related plaque growth. In this review, current knowledge on sex-related differences in plaque size, composition, high risk plaque features and shear stress related plaque growth in carotid and coronary arteries obtained from imaging are summarized.

Label-Free Fiber-Optic Raman Spectroscopy for Intravascular Coronary Atherosclerosis and Plaque Detection

The rupture of atherosclerotic plaques remains one of the leading causes of morbidity and mortality worldwide. The plaques have certain pathological characteristics including a fibrous cap, inflammation, and extensive lipid deposition in a lipid core. Various invasive and noninvasive imaging techniques can interrogate structural aspects of atheroma; however, the composition of the lipid core in coronary atherosclerosis and plaques cannot be accurately detected. Fiber-optic Raman spectroscopy has the capability of in vivo rapid and accurate biomarker detection as an emerging omics technology. Previous studies demonstrated that an intravascular Raman spectroscopic technique may assess and manage the therapeutic and medication strategies intraoperatively. The Raman spectral information identified plaque depositions consisting of lipids, triglycerides, and cholesterol esters as the major components by comparing normal region and early plaque formation region with histology. By focusing on the composition of plaques, we could identify the subgroups of plaques accurately and rapidly by Raman spectroscopy. Collectively, this fiber-optic Raman spectroscopy opens up new opportunities for coronary atherosclerosis and plaque detection, which would assist optimal surgical strategy and instant postoperative decision-making. In this paper, we will review the advancement of label-free fiber-optic Raman probe spectroscopy and its applications of coronary atherosclerosis and atherosclerotic plaque detection.

Characterization of plaque phenotypes exhibiting an elevated pericoronary adipose tissue attenuation: insights from the REASSURE-NIRS registry

Inflammation has been considered to promote atheroma instability. Coronary computed tomography angiography (CCTA) visualizes pericoronary adipose tissue (PCAT) attenuation, which reflects coronary artery inflammation. While PCAT attenuation has been reported to predict future coronary events, plaque phenotypes exhibiting high PCAT attenuation remains to be fully elucidated. The current study aims to characterize coronary atheroma with a greater vascular inflammation. We retrospectively analyzed culprit lesions in 69 CAD patients receiving PCI from the REASSURE-NIRS registry (NCT04864171). Culprit lesions were evaluated by both CCTA and near-infrared spectroscopy/intravascular ultrasound (NIRS/IVUS) imaging prior to PCI. PCAT attenuation at proximal RCA (PCATRCA) and NIRS/IVUS-derived plaque measures were compared in patients with PCATRCA attenuation ≥ and < -78.3 HU (median). Lesions with PCATRCA attenuation ≥ -78.3 HU exhibited a greater frequency of maxLCBI4mm ≥ 400 (66% vs. 26%, p < 0.01), plaque burden ≥ 70% (94% vs. 74%, p = 0.02) and spotty calcification (49% vs. 6%, p < 0.01). Whereas positive remodeling (63% vs. 41%, p = 0.07) did not differ between two groups. On multivariable analysis, maxLCBI4mm ≥ 400 (OR = 4.07; 95%CI 1.12-14.74, p = 0.03), plaque burden ≥ 70% (OR = 7.87; 95%CI 1.01-61.26, p = 0.04), and spotty calcification (OR = 14.33; 95%CI 2.37-86.73, p < 0.01) independently predicted high PCATRCA attenuation. Of note, while the presence of only one plaque feature did not necessarily elevate PCATRCA attenuation (p = 0.22), lesions harboring two or more features were significantly associated with higher PCATRCA attenuation. More vulnerable plaque phenotypes were observed in patients with high PCATRCA attenuation. Our findings suggest PCATRCA attenuation as the presence of profound disease substrate, which potentially benefits from anti-inflammatory agents.

[18F]ZCDD083: A PFKFB3-Targeted PET Tracer for Atherosclerotic Plaque Imaging

PFKFB3, a glycolysis-related enzyme upregulated in inflammatory conditions and angiogenesis, is an emerging target for diagnosis and therapy of atherosclerosis. The fluorinated phenoxindazole [¹⁸F]ZCDD083 was synthesized, radiolabeled in 17 ± 5% radiochemical yield and >99% radiochemical purity, and formulated for preclinical PET/CT imaging in mice. In vivo stability analysis showed no significant metabolite formation. Biodistribution studies showed high blood pool activity and slow hepatobiliary clearance. Significant activity was detected in the lung 2 h postinjection (pi) (11.0 ± 1.5%ID/g), while at 6 h pi no pulmonary background was observed. Ex vivo autoradiography at 6 h pi showed significant high uptake of [¹⁸F]ZCDD083 in the arch region and brachiocephalic artery of atherosclerotic mice, and no uptake in control mice, matching plaques distribution seen by lipid staining along with PFKFB3 expression seen by immunofluorescent staining. In vivo PET scans showed higher aortic region uptake of [¹⁸F]ZCDD083 in atherosclerotic ApoE^-/-Fbn1^C1039G+/- than in control mice (0.78 ± 0.05 vs 0.44 ± 0.09%ID/g). [¹⁸F]ZCDD083 was detected in aortic arch and brachiocephalic artery of ApoE^-/- (with moderate atherosclerosis) and ApoE^-/-Fbn1^C1039G+/- (with severe, advanced atherosclerosis) mice, suggesting this tracer may be useful for the noninvasive detection of atherosclerotic plaques in vivo.

The role of near-infrared spectroscopy in the detection of vulnerable atherosclerotic plaques

Coronary artery disease is the leading cause of mortality worldwide. Most acute coronary syndromes are caused by a rupture of a vulnerable atherosclerotic plaque which can be characterized by a lipid-rich necrotic core with an overlying thin fibrous cap. Many vulnerable plaques can cause angiographically mild stenoses due to positive remodelling, which is why the extent of coronary artery disease may be seriously underestimated. In recent years, we have witnessed a paradigm shift in interventional cardiology. We no longer focus solely on the degree of stenosis; rather, we seek to determine the true extent of atherosclerotic disease. We seek to identify high-risk plaques for improvement in risk stratification of patients and prevention. Several imaging methods have been developed for this purpose. Intracoronary near-infrared spectroscopy is one of the most promising. Here, we discuss the possible applications of this diagnostic method and provide a comprehensive overview of the current knowledge.

Intracoronary Imaging in the Detection of Vulnerable Plaques

Coronary artery disease is the result of atherosclerotic changes to the coronary arterial wall, comprising endothelial dysfunction, vascular inflammation and deposition of lipid-rich macrophage foam cells. Certain high-risk atherosclerotic plaques are vulnerable to disruption, leading to rupture, thrombosis and the clinical sequelae of acute coronary syndrome. Though recognised as the gold standard for evaluating the presence, distribution and severity of atherosclerotic lesions, invasive coronary angiography is incapable of identifying non-stenotic, vulnerable plaques that are responsible for adverse cardiovascular events. The recognition of such limitations has impelled the development of intracoronary imaging technologies, including intravascular ultrasound, optical coherence tomography and near-infrared spectroscopy, which enable the detailed evaluation of the coronary wall and atherosclerotic plaques in clinical practice. This review discusses the present status of invasive imaging technologies; summarises up-to-date, evidence-based clinical guidelines; and addresses questions that remain unanswered with regard to the future of intracoronary plaque imaging.

Adjunctive intra-coronary imaging for the assessment of coronary artery disease

Atherosclerotic coronary artery disease remains a leading cause of worldwide morbidity and mortality. Invasive angiography currently remains the gold standard method of diagnosing and treating coronary disease; however, more sophisticated adjunctive interventional technologies have been developed to combat the inter and intra-observer variability frequently encountered in the assessment of lesion severity. Intravascular imaging now plays a key role in optimising percutaneous coronary interventions and provides invaluable information as part of the interventional cardiologist's diagnostic arsenal. The principles, technical aspects and uses of two modalities of intracoronary imaging, intravascular ultrasound and optical coherence tomography, are discussed. We additionally provide examples of cases where the adjunctive intracoronary imaging was superior to angiography alone in successfully identifying and treating acute coronary syndromes.

Role of near-infrared spectroscopy in intravascular coronary imaging

Near-infrared spectroscopy is an intracoronary imaging modality that has been validated in preclinical and clinical studies to help quantify the lipid content of the coronary plaque and provide information regarding its vulnerability. It has the potential to develop into a valuable tool for the risk stratification of a vulnerable plaque and, furthermore, a vulnerable patient. In addition, in the future this technology may help in the development of novel therapies that impact vascular biology.

In vivo comparison between cardiac allograft vasculopathy and native atherosclerosis using near-infrared spectroscopy and intravascular ultrasound

AIMS

The aim was to compare cardiac allograft vasculopathy to native atherosclerosis by near-infrared spectroscopy-intravascular ultrasound (NIRS-IVUS).

METHODS AND RESULTS

Twenty-seven atherosclerotic (non-transplant) patients and 28 heart transplant recipients undergoing routine surveillance coronary angiography underwent NIRS-IVUS imaging of the left anterior descending coronary artery. In each proximal, middle, and distal coronary artery segment, the maxLCBI4mm [4-mm long segment with maximum lipid core burden index (LCBI)] and corresponding IVUS parameters were compared. MaxLCBI4mm was significantly greater among atherosclerotic patients than the transplant patients in both proximal and middle coronary artery segments, but not in the distal segment. There was a positive linear correlation between maxLCBI4mm and maximum plaque burden in both groups, but atherosclerotic patients demonstrated a smaller maxLCBI4mm than transplant recipients among segments with plaque burden <40%. Among segments with a maximum plaque burden ≥40%, native-atherosclerosis patients had a greater maxLCBI4mm compared with transplant patients (P = 0.015). Calcification was present in 72.9% of native atherosclerosis and 14.7% of transplant segments (P< 0.001). Among the 165 analysed segments, prevalence of lipid-rich plaque (LRP) with superficial attenuation (30.9 vs. 1.2%, P < 0.001) or calcified LRP (13.6 vs. 2.4%, P = 0.03) was significantly greater in native atherosclerosis compared with transplant patients. Conversely, the proportion of segments with non-LRP (46.4 vs. 11.1%, P < 0.001) was higher in transplant patients.

CONCLUSION

NIRS-IVUS imaging demonstrated early and accelerated lipid accumulation with smaller plaque burden and less calcium in patients after heart transplant when compared with patients with native atherosclerosis.