Large lipid-rich coronary plaques detected by near-infrared spectroscopy at non-stented sites in the target artery identify patients likely to experience future major adverse cardiovascular events

The Ability of Near-Infrared Spectroscopy to Identify Vulnerable Patients and Plaques: A Systematic Review and Meta-Analysis

Previous studies have analyzed the efficacy of near-infrared spectroscopy-derived lipid core burden index (LCBI) in quantifying and identifying high-risk plaques and patients at increased risk of future major adverse cardiac outcomes/major adverse cardiovascular and cerebrovascular events. A maxLCBI4mm of 400 or greater seems to be an effective threshold for classifying at-risk plaques. This meta-analysis provides a more precise odds ratio with a narrow standard deviation that can be used to guide future studies.

Sex differences in diagnostic modalities of atherosclerosis in the macrocirculation

Asymptomatic atherosclerosis begins early in life and may progress in a sex-specific manner to become the major cause of cardiovascular morbidity and death. As diagnostic tools to evaluate atherosclerosis in the macrocirculation, we discuss imaging methods (in terms of computed tomography, positron emission tomography, intravascular ultrasound, magnetic resonance imaging, and optical coherence tomography), along with derived scores (Agatston, Gensini, Leaman, Syntax), and also hemodynamic indices of vascular stiffness (including flow-mediated dilation, shear stress, pulse pressure, augmentation index, arterial distensibility), assessment of plaque properties (composition, erosion, rupture), stenosis measures such as fractional flow reserve. Moreover, biomarkers including matrix metalloproteinases, vascular endothelial growth factors and miRNAs, as well as the impact of machine learning support, are described. Special attention is given to age-related aspects and sex-specific characteristics, along with clinical implications. Knowledge gaps are identified and directions for future research formulated.

Effects of Lipid Lowering Therapies on Vulnerable Plaque Features: An Updated Narrative Review of the Literature

The clinical evidence on the efficacy of lipid lowering therapy in patients with coronary artery disease (CAD) is unequivocally established. However, the effects of these therapies on plaque composition and stability are less clear. The use of intracoronary imaging (ICI) technologies has emerged as a complement to conventional angiography to further characterize plaque morphology and detect high-risk plaque features related to cardiovascular events. Along with clinical outcomes studies, parallel imaging trials employing serial evaluations with intravascular ultrasound (IVUS) have shown that pharmacological treatment has the capacity to either slow disease progression or promote plaque regression, depending on the degree of lipid lowering achieved. Subsequently, the introduction of high-intensity lipid lowering therapy led to much lower levels of low-density lipoprotein cholesterol (LDL-C) levels than achieved in the past, resulting in greater clinical benefit. However, the degree of atheroma regression showed in concomitant imaging trials appeared more modest as compared to the magnitude of clinical benefit accrued from high-intensity statin therapy. Recently, new randomized trials have investigated the additional effects of achieving very low levels of LDL-C on high-risk plaque features-such as fibrous cap thickness and large lipid accumulation-beyond its size. This paper provides an overview of the currently available evidence of the effects of moderate to high-intensity lipid lowering therapy on high-risk plaque features as assessed by different ICI modalities, reviews data supporting the use of these trials, and analyse the future perspectives in this field.

The association between circulating lipoprotein subfractions and lipid content in coronary atheromatous plaques assessed by near-infrared spectroscopy

Background

Lipid content in coronary atheromatous plaques, measured by near-infrared spectroscopy (NIRS), can predict the risk of future coronary events. Biomarkers that reflect lipid content in coronary plaques may therefore improve coronary artery disease (CAD) risk assessment.

Purpose

We aimed to investigate the association between circulating lipoprotein subfractions and lipid content in coronary atheromatous plaques in statin-treated patients with stable CAD undergoing percutaneous coronary intervention.

Methods

56 patients with stable CAD underwent three-vessel imaging with NIRS when feasible. The coronary artery segment with the highest lipid content, defined as the maximum lipid core burden index within any 4 mm length across the entire lesion (maxLCBI_4mm), was defined as target segment. Lipoprotein subfractions and Lipoprotein a (Lp(a)) were analyzed in fasting serum samples by nuclear magnetic resonance spectroscopy and by standard in-hospital procedures, respectively. Penalized linear regression analyses were used to identify the best predictors of maxLCBI_4mm. The uncertainty of the lasso estimates was assessed as the percentage presence of a variable in resampled datasets by bootstrapping.

Results

Only modest evidence was found for an association between lipoprotein subfractions and maxLCBI_4mm. The lipoprotein subfractions with strongest potential as predictors according to the percentage presence in resampled datasets were Lp(a) (78.1 % presence) and free cholesterol in the smallest high-density lipoprotein (HDL) subfractions (74.3 % presence). When including established cardiovascular disease (CVD) risk factors in the regression model, none of the lipoprotein subfractions were considered potential predictors of maxLCBI_4mm.

Conclusion

In this study, serum levels of Lp(a) and free cholesterol in the smallest HDL subfractions showed the strongest potential as predictors for lipid content in coronary atheromatous plaques. Although the evidence is modest, our study suggests that measurement of lipoprotein subfractions may provide additional information with respect to coronary plaque composition compared to traditional lipid measurements, but not in addition to established risk factors. Further and larger studies are needed to assess the potential of circulating lipoprotein subfractions as meaningful biomarkers both for lipid content in coronary atheromatous plaques and as CVD risk markers.

Associations between circulating microRNAs and lipid-rich coronary plaques measured with near-infrared spectroscopy

Lipid-rich coronary atherosclerotic plaques often cause myocardial infarction (MI), and circulating biomarkers that reflect lipid content may predict risk of MI. We investigated the association between circulating microRNAs (miRs) are lipid-rich coronary plaques in 47 statin-treated patients (44 males) with stable coronary artery disease undergoing percutaneous coronary intervention. We assessed lipid content in non-culprit coronary artery lesions with near-infrared spectroscopy and selected the 4 mm segment with the highest measured lipid core burden index (maxLCBI_4mm). Lipid-rich plaques were predefined as a lesion with maxLCBI_4mm ≥ 324.7. We analyzed 177 circulating miRs with quantitative polymerase chain reaction in plasma samples. The associations between miRs and lipid-rich plaques were analyzed with elastic net. miR-133b was the miR most strongly associated with lipid-rich coronary plaques, with an estimated 18% increase in odds of lipid-rich plaques per unit increase in miR-133b. Assessing the uncertainty by bootstrapping, miR-133b was present in 82.6% of the resampled dataset. Inclusion of established cardiovascular risk factors did not attenuate the association. No evidence was found for an association between the other analyzed miRs and lipid-rich coronary plaques. Even though the evidence for an association was modest, miR-133b could be a potential biomarker of vulnerable coronary plaques and risk of future MI. However, the prognostic value and clinical relevance of miR-133b needs to be assessed in larger cohorts.

Hyperspectral imaging of lipids in biological tissues using near-infrared and shortwave infrared transmission mode: A pilot study

Label-free hyperspectral imaging (HSI) of lipids was demonstrated in the near-infrared (NIR) and shortwave infrared (SWIR) regions (950-1800 nm) using porcine tissue. HSI was performed in the transmission light-pass configuration, using a NIR-SWIR camera coupled with a liquid crystal tunable filter. The transmittance spectra of the regions of interest (ROIs), which correspond to the lipid and muscle areas in the specimen, were utilized for the spectrum unmixing. The transmittance spectra in ROIs were compared with those recorded by a spectrophotometer using samples of adipose and muscle. The lipid optical absorption bands at 1210 and 1730 nm were first used for the unmixing and mapping. Then, we performed the continuous multiband unmixing over the entire available spectral range, thereby, considering a combination of characteristic absorption bands of lipids, proteins, and water. The enhanced protocol demonstrates the ability to visualize small adipose inclusions of 1-10 μm size.

Near-Infrared Spectroscopy-Guided Percutaneous Coronary Intervention: Practical Applications and Available Evidence

Intracoronary near-infrared spectroscopy (NIRS) has been extensively validated against the gold standard of histopathology to identify lipid-rich plaque. NIRS is currently in clinical use as a combined multimodality imaging catheter with intravascular ultrasonography. When used before PCI, NIRS has clinical utility in determining the mechanism underlying acute coronary syndromes and can be used to guide stent length selection and identify the risk of periprocedural myocardial infarction. When used after PCI, NIRS can identify vulnerable patients at increased risk of future patient-level cardiovascular events and can detect vulnerable plaques at increased risk of future site-specific coronary events.

The Ability of Near-Infrared Spectroscopy to Identify Vulnerable Patients and Plaques: A Systematic Review and Meta-Analysis

Previous studies have analyzed the efficacy of near-infrared spectroscopy-derived lipid core burden index (LCBI) in quantifying and identifying high-risk plaques and patients at increased risk of future major adverse cardiac outcomes/major adverse cardiovascular and cerebrovascular events. A maxLCBI_4mm of 400 or greater seems to be an effective threshold for classifying at-risk plaques. This meta-analysis provides a more precise odds ratio with a narrow standard deviation that can be used to guide future studies.

Optical coherence tomography-derived lipid core burden index and clinical outcomes: results from the CLIMA registry

AIMS

The aim of this study was to assess the morphological characteristics and prognostic implications of the optical coherence tomography (OCT)-derived lipid core burden index (LCBI).

METHODS AND RESULTS

OCT-LCBI was assessed in 1003 patients with 1-year follow-up from the CLIMA multicentre registry using a validated software able to automatically obtain a maximum OCT-LCBI in 4 mm (maxOCT-LCBI4mm). Primary composite clinical endpoint included cardiac death, myocardial infarction, and target-vessel revascularization. A secondary analysis using clinical outcomes of CLIMA study was performed. Patients with a maxOCT-LCBI4mm ≥ 400 showed higher prevalence of fibrous cap thickness (FCT) <75 μm [odds ratio (OR) 1.43, 95% confidence interval (CI) 1.03-1.99; P = 0.034], lipid pool arc >180° (OR 3.93, 95%CI 2.97-5.21; P < 0.001), minimum lumen area <3.5 mm2 (OR 1.5, 95%CI 1.16-1.94; P = 0.002), macrophage infiltration (OR 2.38, 95%CI 1.81-3.13; P < 0.001), and intra-plaque intimal vasculature (OR 1.34, 95%CI 1.05-1.72; P = 0.021). A maxOCT-LCBI4mm ≥400 predicted the primary endpoint [adjusted hazard ratio (HR) 1.86, 95%CI 1.1-3.2; P = 0.019] as well as the CLIMA endpoint (HR 2.56, 95%CI 1.24-5.29; P = 0.011). Patients with high lipid content and thin FCT < 75 µm were at higher risk for adverse events (HR 4.88, 95%CI 2.44-9.72; P < 0.001).

CONCLUSIONS

A high maxOCT-LCBI4mm was related to poor outcome and vulnerable plaque features. This study represents a step further in the automated assessment of the coronary plaque risk profile.

High intensity interval training induces beneficial effects on coronary atheromatous plaques - a randomized trial

BACKGROUND

Coronary atheroma volume is associated with risk of coronary events in coronary artery disease (CAD). Exercise training is a cornerstone in primary and secondary prevention of CAD, but the effect of exercise on coronary atheromatous plaques is largely unknown.

PURPOSE

We assessed the effect of six months supervised high intensity interval training (HIIT) on coronary plaque geometry using intravascular ultrasound in patients with stable CAD following percutaneous coronary intervention (PCI).

METHODS

Sixty patients were randomized to two sessions of weekly supervised HIIT at 85-95% of peak heart rate (n = 30) or to follow contemporary preventive guidelines (control group, n = 30). The study endpoints were change in percent atheroma volume (PAV) and total atheroma volume (TAV) normalized for segment length (TAVnorm) at six-month follow-up.

RESULTS

The change in average PAV for matched coronary segments from baseline to follow-up showed a significant between-group difference (-1.4, 95% CI: -2.7 to -0.1, p = 0.036). There was a significant reduction in the HIIT group (-1.2, 95% CI: -2.1 to -0.2, p = 0.017) while not in the control group (0.2, 95% CI: -0.7 to 1.1, p = 0.616). TAVnorm was reduced (-9 mm3, 95% CI: -14.7 to -3.4, p = 0.002) after HIIT, with a significant between-group difference (-12.0 mm3, 95% CI: -19.9 to -4.2, p = 0.003).

CONCLUSION

In patients with established CAD, a regression of atheroma volume was observed in those undergoing six months of supervised HIIT compared with patients following contemporary preventive guidelines. Our study indicates that high intensity interval training counteracts atherosclerotic coronary disease progression and reduces atheroma volume in residual coronary atheromatous plaques following PCI.

Epicardial Adipose Tissue Thickness Is Related to Plaque Composition in Coronary Artery Disease

(1) Background: Currently, limited data are available regarding the relationship between epicardial fat and plaque composition. The aim of this study was to assess the relationship between visceral fat surrounding the heart and the lipid core burden in patients with coronary artery diseases; (2) Methods: Overall, 331 patients undergoing coronary angiography with combined near-infrared spectroscopy and intravascular ultrasound imaging were evaluated for epicardial adipose tissue (EAT) thickness using transthoracic echocardiography. Patients were divided into thick EAT and thin EAT groups according to the median value; (3) Results: There was a positive correlation between EAT thickness and maxLCBI4mm, and maxLCBI4mm was significantly higher in the thick EAT group compared to the thin EAT group (437 vs. 293, p < 0.001). EAT thickness was an independent predictor of maxLCBI4mm ≥ 400 along with age, low-density lipoprotein-cholesterol level, acute coronary syndrome presentation, and plaque burden in a multiple linear regression model. Receiver operating characteristic curve analysis showed that EAT thickness was a predictor for maxLCBI4mm ≥ 400; (4) Conclusions: In the present study, EAT thickness is related to the lipid core burden assessed by NIRS-IVUS in patients with CAD which suggests that EAT may affect the stability of the plaques in coronary arteries.

The critical issue linking lipids and inflammation: Clinical utility of stopping oxidative stress

The formation of an atheroma begins when lipoproteins become trapped in the intima. Entrapped lipoproteins become oxidized and activate the innate immune system. This immunity represents the primary association between lipids and inflammation. When the trapping continues, the link between lipids and inflammation becomes chronic and detrimental, resulting in atherosclerosis. When entrapment ceases, the association between lipids and inflammation is temporary and healthy, and the atherogenic process halts. Therefore, the link between lipids and inflammation depends upon lipoprotein retention in the intima. The entrapment is due to electrostatic forces uniting apolipoprotein B to polysaccharide chains on intimal proteoglycans. The genetic transformation of contractile smooth muscle cells in the media into migratory secretory smooth muscle cells produces the intimal proteoglycans. The protein, platelet-derived growth factor produced by activated platelets, is the primary stimulus for this genetic change. Oxidative stress is the main stimulus to activate platelets. Therefore, minimizing oxidative stress would significantly reduce the retention of lipoproteins. Less entrapment decreases the association between lipids and inflammation. More importantly, it would halt atherogenesis. This review will analyze oxidative stress as the critical link between lipids, inflammation, and the pathogenesis of atherosclerosis. Through this perspective, we will discuss stopping oxidative stress to disrupt a harmful association between lipids and inflammation. Numerous therapeutic options will be discussed to mitigate oxidative stress. This paper will add a new meaning to the Morse code distress signal SOS-stopping oxidative stress.

Additive effects of ezetimibe, evolocumab, and alirocumab on plaque burden and lipid content as assessed by intravascular ultrasound: A PRISMA-compliant meta-analysis

BACKGROUND

The additive effects of ezetimibe, evolocumab or alirocumab on lipid level, plaque volume, and plaque composition using intravascular ultrasound (IVUS) remain unclear.

METHODS

According to the Preferred Reporting Items for Systematic reviews and Meta-Analyses statement, we performed a systematic review and meta-analysis of trials assessing the effects of ezetimibe, evolocumab, and alirocumab on coronary atherosclerosis using IVUS. The primary outcome was change in total atheroma volume (TAV), and the secondary outcomes were changes and differences in plaque composition and lipid content.

RESULTS

Data were collected from 9 trials, involving 917 patients who received ezetimibe, evolocumab or alirocumab in addition to a statin and 919 patients who received statins alone. The pooled estimate demonstrated a significant reduction in TAV with the addition of ezetimibe and favorable effects of evolocumab and alirocumab on TAV. Subgroup analysis also supported favorable effects of evolocumab and alirocumab on TAV, according to baseline TAV, gender, type 2 diabetes mellitus, and prior stain use. Addition of proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor to statin therapy resulted in significant reductions in low-density lipoprotein cholesterol (LDL-C), total cholesterol (TC), and triglycerides (TG), but not in high-density lipoprotein cholesterol (HDL-C). The pooled estimate also showed significant favorable effects of ezetimibe on LDL-C, TC, and TG, but an insignificant effect on HDL-C. Patients who received ezetimibe showed similar changes in the necrotic core, fibro-fatty plaque, fibrous plaque, and dense calcification compared with patients not treated with ezetimibe.

CONCLUSIONS

The addition of ezetimibe to statin therapy may further reduce plaque and lipid burdens but may not modify plaque composition. Although current evidence supports a similar impact from the addition of PCSK9 inhibitors to statin therapy, more evidence is needed to confirm such an effect.

Association between High Lipid Burden of Target Lesion and Slow TIMI Flow in Coronary Interventions

Decreased thrombolysis in myocardial infarction (TIMI) flow is associated with poor clinical outcomes. However, its predictors are not fully known. A combination of near-infrared spectroscopy (NIRS) and intravascular ultrasound (IVUS) could be used to detect lesions at high risk of slow TIMI flow. This study evaluated 636 consecutive patients undergoing target-lesion NIRS-IVUS imaging prior to percutaneous coronary intervention (PCI). The maximal lipid core burden index over 4-mm segments (maxLCBI4mm) per target vessel was calculated. The primary endpoint was the association between maxLCBI4mm and post-interventional TIMI flow. A high lipid core burden index (LCBI) cut-off point was determined using receiver-operating characteristic analysis. Decreased TIMI flow (TIMI less than 3) occurred in 90 patients and normal TIMI flow in 546 patients. The decreased TIMI flow group showed significantly higher incidence of cardiovascular events (5.6% vs. 1.5%, log-rank p = 0.010) in three months of composite events including cardiac death, myocardial infarction, stent thrombosis, and target lesion revascularization. In multivariable analysis, a high LCBI (≥354) was independently associated with slow TIMI flow (OR, 2.59 (95% CI, 1.33–5.04), p = 0.005). High LCBI measured using NIRS-IVUS imaging was an independent predictor of decreased post-PCI TIMI flow. Performing PCI for high-LCBI lesions may necessitate adjunctive measures to prevent suboptimal post-PCI reperfusion.

High-Risk Coronary Plaque Features: A Narrative Review

Advances in coronary plaque imaging over the last few decades have led to an increased interest in the identification of novel high-risk plaque features that are associated with cardiovascular events. Existing practices focus on risk stratification and lipid monitoring for primary and secondary prevention of cardiac events, which is limited by a lack of assessment and treatment of vulnerable plaque. In this review, we summarize the multitude of studies that have identified plaque, haemodynamic and patient factors associated with risk of acute coronary syndrome. Future progress in multi-modal imaging strategies and in our understanding of high-risk plaque features could expand treatment options for coronary disease and improve patient outcomes.

CENIT (Impact of Cardiac Exercise Training on Lipid Content in Coronary Atheromatous Plaques Evaluated by Near‐Infrared Spectroscopy): A Randomized Trial

Background

The effect of physical exercise on lipid content of coronary artery plaques is unknown. With near infrared spectroscopy we measured the effect of high intensity interval training (HIIT) on lipid content in coronary plaques in patients with stable coronary artery disease following percutaneous coronary intervention.

Methods and Results

In CENIT (Impact of Cardiac Exercise Training on Lipid Content in Coronary Atheromatous Plaques Evaluated by Near‐Infrared Spectroscopy) 60 patients were randomized to 6 months supervised HIIT or to a control group. The primary end point was change in lipid content measured as maximum lipid core burden index at 4 mm (maxLCBI_4mm). A predefined cutoff of maxLCBI_4mm >100 was required for inclusion in the analysis. Forty‐nine patients (HIIT=20, usual care=29) had maxLCBI_4mm >100 at baseline. Change in maxLCBI_4mm did not differ between groups (−1.2, 95% CI, −65.8 to 63.4, P=0.97). The estimated reduction in maxLCBI_4mm was −47.7 (95% CI, −100.3 to 5.0, P=0.075) and −46.5 (95% CI, −87.5 to −5.4, P=0.027) after HIIT and in controls, respectively. A negative correlation was observed between change in peak oxygen uptake (VO_2peak) and change in lipid content (Spearman’s correlation −0.44, P=0.009). With an increase in VO_2peak above 1 metabolic equivalent task, maxLCBI_4mm was on average reduced by 142 (−8 to −262), whereas the change was −3.2 (154 to −255) with increased VO_2peak below 1 metabolic equivalent task.

Conclusions

Six months of HIIT following percutaneous coronary intervention did not reduce lipid content in coronary plaques compared with usual care. A moderate negative correlation between increase in VO_2peak and change in lipid content generates the hypothesis that exercise with a subsequent increase in fitness may reduce lipid content in coronary atheromatous plaques.

Registration

URL: https://www.clinicaltrials.gov; Unique identifier: NCT02494947.

Near-infrared spectroscopy predicts events in men and women: Results from the Lipid Rich Plaque study

Background

The Lipid Rich Plaque (LRP) study demonstrated that near-infrared spectroscopy imaging of non-obstructive lesions identified patients and segments at higher risk for subsequent non-culprit major adverse cardiac events (NC-MACE). Whether this is true for both men and women is not known. In this post hoc analysis of the LRP study, we sought to investigate whether the maximum 4-mm Lipid Core Burden Index (maxLCBI_4mm) was of similar predictive value in men and women for NC-MACE.

Methods

Patients with an evaluable maxLCBI_4mm were stratified on the basis of sex at birth. A Cox proportional-hazards model was used to assess the predictive value of maxLCBI_4mm on future NC-MACE at the patient and plaque levels. The primary endpoint was cumulative incidence of NC-MACE at 24 months.

Results

Among 1271 patients, 388 (30.5%) were women. Women were older and had a higher cardiovascular risk profile. Cumulative incidence of NC-MACE at 24 months was 10.3% for women and 7.6% for men (log-rank p = 0.11). When comparing maxLCBI_4mm > 400 to maxLCBI_4mm ≤ 400, the hazard ratio (HR) for future NC-MACE was not significantly different between sexes: 2.10 (95% confidence interval [CI]: 1.28–3.44; p = 0.003) for men and 2.24 (95% CI: 1.18–4.28; p = 0.014) for women (p = 0.87). At the plaque level, the HR comparing maxLCBI_4mm > 400 to maxLCBI_4mm ≤ 400 was 3.49 (95% CI: 1.60–7.60, p = 0.002) for men and 4.79 (95% CI: 2.02–11.38, p < 0.001) for women, which was not significantly different (p = 0.57).

Conclusions

The maxLCBI_4mm was of similar predictive value for NC-MACE within 24 months in men and women.

Discrepancy between plaque vulnerability and functional severity of angiographically intermediate coronary artery lesions

This study sought to investigate the relationship between physiological severity and plaque vulnerability of intermediate coronary artery stenoses as assessed by fractional flow reserve (FFR) and near-infrared spectroscopy-intravascular ultrasound (NIRS-IVUS). We included vessels where both FFR and NIRS-IVUS were performed. A positive FFR was defined as FFR ≤ 0.80. Lipid core burden index of the entire target vessel (TV-LCBI), maximum LCBI in 4 mm (maxLCBI_4mm), and maximum plaque burden (PB) were evaluated using NIRS-IVUS. A vulnerable plaque was defined as a lipid-rich plaque (maxLCBI4_mm ≥ 400) with large PB (≥ 70%). A total of 59 vessels of 45 patients were included. Median FFR value was 0.75 [interquartile 0.72, 0.82]. An FFR value of ≤ 0.80 was observed in 42 vessels (71%). TV-LCBI (correlation coefficient [CC] = - 0.331, p = 0.011), lesion length (CC = - 0.350, p = 0.007), and PB (CC = - 0.230, p = 0.080) negatively correlated with FFR value, while maxLCBI_4mm did not (CC = - 0.156, p = 0.24). The prevalence of vulnerable plaques (26.2% vs. 29.4%, p > 0.99) and mean TV-LCBI, maxLCBI_4mm, and PB values were not significantly different between the vessels with FFR ≤ 0.80 and those with FFR > 0.80. In multivariable logistic models, diabetes mellitus (p = 0.003) and hemoglobin A1c (p = 0.012) were associated with the presence of a vulnerable plaque. In conclusion, the results of the present study suggested that FFR may reflect total lipid burden but not necessarily plaque vulnerability. In patients with coronary artery disease and a high likelihood of rapid atherosclerosis progression, such as diabetes mellitus patients, assessing plaque vulnerability in addition to the functional severity of coronary artery lesions may help stratify better the risk of future events.

Detection of Vulnerable Coronary Plaques Using Invasive and Non-Invasive Imaging Modalities

Acute coronary syndrome (ACS) mostly arises from so-called vulnerable coronary plaques, particularly prone for rupture. Vulnerable plaques comprise a specific type of plaque, called the thin-cap fibroatheroma (TFCA). A TCFA is characterized by a large lipid-rich necrotic core, a thin fibrous cap, inflammation, neovascularization, intraplaque hemorrhage, microcalcifications or spotty calcifications, and positive remodeling. Vulnerable plaques are often not visible during coronary angiography. However, different plaque features can be visualized with the use of intracoronary imaging techniques, such as intravascular ultrasound (IVUS), potentially with the addition of near-infrared spectroscopy (NIRS), or optical coherence tomography (OCT). Non-invasive imaging techniques, such as computed tomography coronary angiography (CTCA), cardiovascular magnetic resonance (CMR) imaging, and nuclear imaging, can be used as an alternative for these invasive imaging techniques. These invasive and non-invasive imaging modalities can be implemented for screening to guide primary or secondary prevention therapies, leading to a more patient-tailored diagnostic and treatment strategy. Systemic pharmaceutical treatment with lipid-lowering or anti-inflammatory medication leads to plaque stabilization and reduction of cardiovascular events. Additionally, ongoing studies are investigating whether modification of vulnerable plaque features with local invasive treatment options leads to plaque stabilization and subsequent cardiovascular risk reduction.

Extent of lipid core plaque in patients with Achilles tendon xanthoma undergoing percutaneous coronary intervention for coronary artery disease

BACKGROUND

It has been reported that Achilles tendon xanthoma (ATX), being one of the important diagnostic criteria for familial hypercholesterolemia, is independently associated with the severity of coronary artery disease (CAD). The aim of this study was to investigate plaque vulnerability in CAD patients with ATX.

METHODS

Patients with CAD who underwent percutaneous coronary intervention (PCI) with near-infrared spectroscopy-intravascular ultrasound (NIRS-IVUS) guidance were enrolled. Soft X-ray radiography of the Achilles tendon was performed, and a maximum thickness of 9 mm or more was regarded as ATX. Using NIRS-IVUS, the degree of lipid core plaque (LCP) was evaluated by calculating the maximum value of lipid core burden index (LCBI) for any of the 4-mm segments (maxLCBI_4mm) in the target lesion and non-target vessel.

RESULTS

In a total of 156 patients, 14 patients (9.0%) had ATX. MaxLCBI_4mm in the ATX group was significantly greater in the target lesion (p<0.001) and in the non-target vessel (p=0.032) compared to the non-ATX group. When patients were divided into tertiles according to Achilles tendon thickness, maxLCBI_4mm was progressively increased in favor of thickness, although there was only a tendency in the target lesion (p=0.062), and no statistical significance in the non-target vessel (p=0.189). Multiple linear regression analysis determined ATX as an independent predictor for maxLCBI_4mm in the target lesion and non-target vessel.

CONCLUSIONS

ATX was associated with the degree of LCP in CAD patients requiring PCI. High-risk patients with lipid-rich vulnerable plaque can possibly be detected by evaluating Achilles tendon thickness.

Long-term changes after carotid stenting assessed by intravascular ultrasound and near-infrared spectroscopy

BACKGROUND

Long-term effect of carotid stenting (CAS) on the stabilization of the plaque is almost unrecognized. Vascular healing and remodeling might seal the atherosclerotic plaque with neointimal hyperplasia decreasing the vulnerability. We aimed to assess long-term change in the lipid signal, stent and luminal dimensions and restenosis after CAS with the intravascular ultrasound (IVUS) and near-infrared spectroscopy (NIRS) imaging.

METHODS

We performed follow-up angiography and NIRS-IVUS imaging of 58 carotid stents in 52 patients. Median time from CAS to the follow-up examination was 31 months (range, 5-56). The lipid signal of the stented segment was calculated from a NIRS-derived chemogram (a spectroscopic map) as the lipid core burden index (LCBI, a dimensionless number from 0 to 1,000). Planimetric and volumetric measurements from IVUS were performed to assess change in minimal stent area (MSA), minimal luminal area (MLA), stent and luminal volume, late stent expansion and percentage in-stent restenosis (ISR) volume.

RESULTS

During the follow-up period, the mean (±SD) LCBI significantly decreased from 32±56 to 17±27 (P=0.002). The mean stent volume significantly increased from 717±302 to 1,019±429 mm3 (P<0.001) with mean stent expansion 43%±24%. The mean luminal volume increased from 717±302 to 760±359 mm3 (P=0.025) due to ISR encroaching 26%±15% of the stent volume.

CONCLUSIONS

Lipid signal decreased during the follow-up period suggesting stabilization of the plaque. Late stent expansion was balanced with neointimal hyperplasia.

TRIAL REGISTRATION

The trial is registered under clinicaltrials.gov NCT03141580.

Lipid-rich plaques detected by near-infrared spectroscopy predict coronary events irrespective of age: A Lipid Rich Plaque sub-study

BACKGROUND AND AIMS

In this Lipid Rich Plaque (LRP) sub-study, 1551 patients undergoing coronary angiography for acute coronary syndromes or stable angina were examined with near-infrared spectroscopy (NIRS) and intravascular ultrasound (IVUS). We aimed to assess the correlation of patient age with the presence of high-risk plaques, defined as maximum 4-mm Lipid Core Burden Index (maxLCBI_4mm) >400 and plaque burden >70%, and 2-year incidence of non-culprit major adverse cardiovascular events (NC-MACE).

METHODS

The study population was divided into four groups according to age: <50 years (122), 50-64 years (700), 65-74 years (502), and ≥75 years (227). The primary outcome was NC-MACE from index procedure to event or the end of the study. Cox regression and mixed-effects Cox regression models were used to assess the effect of age on the association between LCBI and NC-MACE at the patient and plaque levels.

RESULTS

Average maxLCBI_4mm and percentage of patients with at least one segment with maxLCBI_4mm > 400 were similar across the four age groups at both the patient and coronary segment levels. Having at least one segment with maxLCBI_4mm > 400 was strongly associated with NC-MACE, and that association did not differ significantly across age subgroups. Although less common (prevalence of 0.8%-1.3%), a similar trend toward greater NC-MACE rates was seen in patients with plaque burden >70% at the maximum LCBI site across age subgroups.

CONCLUSIONS

Lipid-rich plaques were as frequent in older as in younger patients and predicted a higher incidence of NC-MACE over 2-year follow-up irrespective of age.

Vulnerable plaques and patients: state-of-the-art

Despite advanced understanding of the biology of atherosclerosis, coronary heart disease remains the leading cause of death worldwide. Progress has been challenging as half of the individuals who suffer sudden cardiac death do not experience premonitory symptoms. Furthermore, it is well-recognized that also a plaque that does not cause a haemodynamically significant stenosis can trigger a sudden cardiac event, yet the majority of ruptured or eroded plaques remain clinically silent. In the past 30 years since the term 'vulnerable plaque' was introduced, there have been major advances in the understanding of plaque pathogenesis and pathophysiology, shifting from pursuing features of 'vulnerability' of a specific lesion to the more comprehensive goal of identifying patient 'cardiovascular vulnerability'. It has been also recognized that aside a thin-capped, lipid-rich plaque associated with plaque rupture, acute coronary syndromes (ACS) are also caused by plaque erosion underlying between 25% and 60% of ACS nowadays, by calcified nodule or by functional coronary alterations. While there have been advances in preventive strategies and in pharmacotherapy, with improved agents to reduce cholesterol, thrombosis, and inflammation, events continue to occur in patients receiving optimal medical treatment. Although at present the positive predictive value of imaging precursors of the culprit plaques remains too low for clinical relevance, improving coronary plaque imaging may be instrumental in guiding pharmacotherapy intensity and could facilitate optimal allocation of novel, more aggressive, and costly treatment strategies. Recent technical and diagnostic advances justify continuation of interdisciplinary research efforts to improve cardiovascular prognosis by both systemic and 'local' diagnostics and therapies. The present state-of-the-art document aims to present and critically appraise the latest evidence, developments, and future perspectives in detection, prevention, and treatment of 'high-risk' plaques occurring in 'vulnerable' patients.

Target Lesion Lipid Content Detected by Near-Infrared Spectroscopy After Stenting and the Risk of Subsequent Target Lesion Failure

[Figure: see text].

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

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 (maxLCBI4mm)] on NIRS in de-novo culprit and non-culprit segments were analyzed.

RESULTS

The ACS culprit lesions had a significantly higher maxLCBI4mm (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 maxLCBI4mm ≥ 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 maxLCBI4mm ≥ 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.

Identification of vulnerable plaques and patients by intracoronary near-infrared spectroscopy and ultrasound (PROSPECT II): a prospective natural history study

BACKGROUND

Near-infrared spectroscopy (NIRS) and intravascular ultrasound are promising imaging modalities to identify non-obstructive plaques likely to cause coronary-related events. We aimed to assess whether combined NIRS and intravascular ultrasound can identify high-risk plaques and patients that are at risk for future major adverse cardiac events (MACEs).

METHODS

PROSPECT II is an investigator-sponsored, multicentre, prospective natural history study done at 14 university hospitals and two community hospitals in Denmark, Norway, and Sweden. We recruited patients of any age with recent (within past 4 weeks) myocardial infarction. After treatment of all flow-limiting coronary lesions, three-vessel imaging was done with a combined NIRS and intravascular ultrasound catheter. Untreated lesions (also known as non-culprit lesions) were identified by intravascular ultrasound and their lipid content was assessed by NIRS. The primary outcome was the covariate-adjusted rate of MACEs (the composite of cardiac death, myocardial infarction, unstable angina, or progressive angina) arising from untreated non-culprit lesions during follow-up. The relations between plaques with high lipid content, large plaque burden, and small lumen areas and patient-level and lesion-level events were determined. This trial is registered with ClinicalTrials.gov, NCT02171065.

FINDINGS

Between June 10, 2014, and Dec 20, 2017, 3629 non-culprit lesions were characterised in 898 patients (153 [17%] women, 745 [83%] men; median age 63 [IQR 55-70] years). Median follow-up was 3·7 (IQR 3·0-4·4) years. Adverse events within 4 years occurred in 112 (13·2%, 95% CI 11·0-15·6) of 898 patients, with 66 (8·0%, 95% CI 6·2-10·0) arising from 78 untreated non-culprit lesions (mean baseline angiographic diameter stenosis 46·9% [SD 15·9]). Highly lipidic lesions (851 [24%] of 3500 lesions, present in 520 [59%] of 884 patients) were an independent predictor of patient-level non-culprit lesion-related MACEs (adjusted odds ratio 2·27, 95% CI 1·25-4·13) and non-culprit lesion-specific MACEs (7·83, 4·12-14·89). Large plaque burden (787 [22%] of 3629 lesions, present in 530 [59%] of 898 patients) was also an independent predictor of non-culprit lesion-related MACEs. Lesions with both large plaque burden by intravascular ultrasound and large lipid-rich cores by NIRS had a 4-year non-culprit lesion-related MACE rate of 7·0% (95% CI 4·0-10·0). Patients in whom one or more such lesions were identified had a 4-year non-culprit lesion-related MACE rate of 13·2% (95% CI 9·4-17·6).

INTERPRETATION

Combined NIRS and intravascular ultrasound detects angiographically non-obstructive lesions with a high lipid content and large plaque burden that are at increased risk for future adverse cardiac outcomes.

FUNDING

Abbott Vascular, Infraredx, and The Medicines Company.

Quantitative Validation of the Coronary Angioscopic Yellow Plaque with Lipid Core Burden Index Assessed by Intracoronary Near-Infrared Spectroscopy

Aim: We aimed to validate the subjective and qualitative angioscopic findings by the objective and quantitative near-infrared spectroscopic (NIRS) assessment to compensate each other’s drawbacks.

Methods: This is a single-center prospective observational study. Patients undergoing a planned follow-up coronary angiography after percutaneous coronary intervention were prospectively enrolled from January 2018 to April 2019. The major three vessels were examined by NIRS-intravascular ultrasound, followed by coronary angioscopic evaluation. Yellow color grade on angioscopy was classified into four grades (0, white; 1, slight yellow; 2, yellow; and 3, intensive yellow) at a location of maximal lipid core burden index over 4 mm [LCBI (4)] on NIRS in each vessel.

Results: A total of 95 lesions in 44 patients (72.6±6.7 years, 75% male) were analyzed. LCBI (4) was significantly different among different yellow color grades by coronary angioscopy (ANOVA, p ＜0.001). Positive correlation was found between angioscopic yellow color grade and LCBI (4) (beta coefficient 164.8, 95% confidence interval 122.9–206.7; p ＜0.001). The best cutoff value of LCBI (4) to predict the presence of yellow plaque (yellow color grade ≥ 2) was 448 (sensitivity 79.3%, specificity 69.7%, C-statistic 0.800, 95% confidence interval 0.713–0.887, p ＜0.001).

Conclusion: The qualitative angioscopic assessment was objectively validated by the quantitative NIRS evaluation, which would be helpful for the reinterpretation of the existing evidences of both imaging modalities.

The role of intracoronary imaging in translational research

Atherosclerotic cardiovascular disease is a key public health concern worldwide and leading cause of morbidity, mortality and health economic costs. Understanding atherosclerotic plaque microstructure in relation to molecular mechanisms that underpin its initiation and progression is needed to provide the best chance of combating this disease. Evolving vessel wall-based, endovascular coronary imaging modalities, including intravascular ultrasound (IVUS), optical coherence tomography (OCT) and near-infrared spectroscopy (NIRS), used in isolation or as hybrid modalities, have been advanced to allow comprehensive visualization of the pathological substrate of coronary atherosclerosis and accurately measure temporal changes in both the vessel wall and plaque characteristics. This has helped further our appreciation of the natural history of coronary artery disease (CAD) and the risk for major adverse cardiovascular events (MACE), evaluate the responsiveness to conventional and experimental therapeutic interventions, and assist in guiding percutaneous coronary intervention (PCI). Here we review the use of different imaging modalities for these purposes and the lessons they have provided thus far.

Impact of clinical presentations on lipid core plaque assessed by near-infrared spectroscopy intravascular ultrasound

Near-infrared spectroscopy-intravascular ultrasound (NIRS-IVUS) studies have demonstrated that lipid core plaque (LCP) is frequently observed in the culprit segment of myocardial infarction (MI). However, little is known about the impact of clinical presentations such as chronic coronary syndrome (CCS) and acute coronary syndrome (ACS) including unstable angina (UA), non ST-segment elevation MI (NSTEMI), and ST-segment elevation MI (STEMI) on LCP. The present prospective single-center registry included a total of 178 patients who underwent percutaneous coronary intervention under NIRS-IVUS guidance. Patients were divided into CCS and ACS groups, and ACS patients were further sub-divided into the 3 groups according to the clinical presentation. The primary endpoint was coronary LCP in the target lesion assessed by NIRS-IVUS with maximal lipid core burden index over any 4 mm segment (maxLCBI_4mm). The study population included 124 and 54 patients with CCS and ACS. MaxLCBI_4mm in the target lesion was significantly higher in the ACS group than in the CCS group (503 [284-672] vs. 406 [250-557], p = 0.046). Among ACS patients, MaxLCBI_4mm in the target lesion was also significantly different in those with UA (n = 18), NSTEMI (n = 21), and STEMI (n = 15) (288 [162-524] vs. 518 [358-745] vs. 646 [394-848], p = 0.021). In conclusion, LCP assessed by NIRS-IVUS, a surrogate of coronary plaque vulnerability, was significantly different according to the clinical presentations such as CCS, UA, NSTEMI, and STEMI.

Clinical use of intracoronary imaging. Part 2: acute coronary syndromes, ambiguous coronary angiography findings, and guiding interventional decision-making: an expert consensus document of the European Association of Percutaneous Cardiovascular Interventions

This consensus document is the second of two reports summarizing the views of an expert panel organized by the European Association of Percutaneous Cardiovascular Interventions (EAPCI) on the clinical use of intracoronary imaging including intravascular ultrasound (IVUS), optical coherence tomography (OCT), and near infrared spectroscopy (NIRS)-IVUS. Beyond guidance of stent selection and optimization of deployment, invasive imaging facilitates angiographic interpretation and may guide treatment in acute coronary syndrome. Intravascular imaging can provide additional important diagnostic information when confronted with angiographically ambiguous lesions and allows assessment of plaque morphology enabling identification of vulnerability characteristics. This second document focuses on useful imaging features to identify culprit and vulnerable coronary plaque, which offers the interventional cardiologist guidance on when to adopt an intracoronary imaging-guided approach to the treatment of coronary artery disease and provides an appraisal of intravascular imaging-derived metrics to define the haemodynamic significance of coronary lesions.

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

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.

Intracoronary near-infrared spectroscopy-role and clinical applications

Intracoronary near-infrared spectroscopy (NIRS) has been developed and validated for the detection of lipid-rich plaque in the coronary arteries. A combined NIRS and intravascular ultrasound catheter is currently in clinical use and has an emerging role in evaluating plaques both before and after percutaneous coronary intervention. NIRS has recently been shown to positively identify both vulnerable patients and vulnerable plaques. This review focuses on the principles and image interpretation of intracoronary NIRS, as well as its clinical applications, limitations, and future directions.

Near-Infrared Spectroscopy Intravascular Ultrasound Imaging: State of the Art

Acute coronary syndromes (ACS) secondary to coronary vessel plaques represent a major cause of cardiovascular morbidity and mortality worldwide. Advancements in imaging technology over the last 3 decades have continuously enabled the study of coronary plaques via invasive imaging methods like intravascular ultrasound (IVUS) and optical coherence tomography (OCT). The introduction of near-infrared spectroscopy (NIRS) as a modality that could detect the lipid (cholesterol) content of atherosclerotic plaques in the early nineties, opened the potential of studying “vulnerable” or rupture-prone, lipid-rich coronary plaques in ACS patients. Most recently, the ability of NIRS-IVUS to identify patients at risk of future adverse events was shown in a prospective multicenter trial, the Lipid-Rich-plaque Study. Intracoronary NIRS-IVUS imaging offers a unique method of coronary lipid-plaque characterization and could become a valuable clinical diagnostic and treatment monitoring tool.

OCT-NIRS Imaging for Detection of Coronary Plaque Structure and Vulnerability

A combination optical coherence tomography and near-infrared spectroscopy (OCT-NIRS) coronary imaging system is being developed to improve the care of coronary patients. While stenting has improved, complications continue to occur at the stented site and new events are caused by unrecognized vulnerable plaques. An OCT-NIRS device has potential to improve secondary prevention by optimizing stenting and by identifying vulnerable patients and vulnerable plaques. OCT is already in widespread use world-wide to optimize coronary artery stenting. It provides automated lumen detection and can identify features of coronary plaques not accurately identified by angiography or intravascular ultrasound. The ILUMIEN IV study, to be completed in 2022, will determine if OCT-guided stenting will yield better clinical outcomes than angiographic guidance alone. While the superb spatial resolution of OCT enables the identification of many plaque structural features, the detection by OCT of lipids, an important component of vulnerable plaques, is limited by suboptimal specificity and interobserver agreement. In contrast, NIRS has been extensively validated for lipid-rich plaque detection against the gold-standard of histology and is the only FDA-approved method to identify coronary lipids. Studies in patients have demonstrated that NIRS detects lipid in culprit lesions causing coronary events. In 2019, the positive results of the prospective Lipid-Rich Plaque Study led to FDA approval of NIRS for detection of high-risk plaques and patients. The complementarity of OCT for plaque structure and NIRS for plaque composition led to the sequential performance of NIRS and OCT imaging in patients. NIRS identified lipid while OCT determined the thickness of the cap over the lipid pool. The positive results obtained with OCT and NIRS imaging led to development of a prototype combined OCT-NIRS catheter that can provide co-registered OCT and NIRS data in a single pullback. The data will provide structural and chemical information likely to improve stenting and deliver more accurate identification of vulnerable plaques and vulnerable patients. More precise diagnosis will then lead to OCT-NIRS guided treatment trials to improve secondary prevention. Success in secondary prevention will then facilitate development of improved primary prevention with invasive imaging and effective treatment of patients identified by non-invasive methods.

Cardiovascular Prevention: Migrating From a Binary to a Ternary Classification

Migrating from a binary approach to risk assessment to a ternary model of disease identification allows for individualized, optimal disease management. Redefining the disease/inflammatory approach has been proven to identify, stabilize, and regress atherosclerosis while adding understanding to the progression of vascular disease. Our previously published results show the beneficial effect of comprehensive, evidence-based management on subclinical atherosclerosis and vulnerable plaque. We argue that this approach does not mitigate the value of utilizing standard risk factor identification, but rather augments it for the benefit of the individual patient.

Relation of Plasma Xanthine Oxidoreductase Activity to Coronary Lipid Core Plaques Assessed by Near-Infrared Spectroscopy Intravascular Ultrasound in Patients With Stable Coronary Artery Disease

Previous studies reported that elevated serum uric acid level was associated with greater coronary lipid plaque. Xanthine oxidoreductase (XOR) is a rate-limiting enzyme in purine metabolism and is believed to play important roles in coronary atherosclerosis. However, the relation between XOR and coronary lipid plaque is unclear. Patients with stable coronary artery disease who underwent elective percutaneous coronary intervention under near-infrared spectroscopy intravascular ultrasound (NIRS-IVUS) guidance were prospectively included. They were divided into 3 groups according to plasma XOR activities based on a previous report: low, normal, and high. Quantitative coronary angiography and gray-scale IVUS were analyzed. The primary end point was coronary lipid plaques in a nontarget vessel assessed by NIRS-IVUS with lipid core burden index (LCBI) and maximum LCBI in 4 mm (maxLCBI_4mm). Out of 68 patients, 26, 31, and 11 patients were classified as low, normal, and high XOR activity groups. Quantitative coronary angiography demonstrated that the high XOR activity group had longer lesion length, smaller minimum lumen diameter, and higher percentage of diameter stenosis in a nontarget vessel among the 3 groups. Gray-scale IVUS analysis also showed smaller lumen area in the high XOR activity group than the others. LCBI (102.1 ± 56.5 vs 65.6 ± 48.5 vs 55.6 ± 37.8, p = 0.04) and maxLCBI_4mm (474.4 ± 171.6 vs 347.4 ± 181.6, 294.0 ± 155.9, p = 0.04) in a nontarget vessel were significantly higher in the high XOR group than in the normal and low groups. In conclusion, elevated XOR activity was associated with coronary lipid-rich plaque in a nontarget vessel in patients with stable coronary artery disease.

Coronary Atherosclerosis Imaging

Identifying patients at increased risk of coronary artery disease, before the atherosclerotic complications become clinically evident, is the aim of cardiovascular prevention. Imaging techniques provide direct assessment of coronary atherosclerotic burden and pathological characteristics of atherosclerotic lesions which may predict the progression of disease. Atherosclerosis imaging has been traditionally based on the evaluation of coronary luminal narrowing and stenosis. However, the degree of arterial obstruction is a poor predictor of subsequent acute events. More recent techniques focus on the high-resolution visualization of the arterial wall and the coronary plaques. Most acute coronary events are triggered by plaque rupture or erosion. Hence, atherosclerotic plaque imaging has generally focused on the detection of vulnerable plaque prone to rupture. However, atherosclerosis is a dynamic process and the plaque morphology and composition may change over time. Most vulnerable plaques undergo progressive transformation from high-risk to more stable and heavily calcified lesions, while others undergo subclinical rupture and healing. Although extensive plaque calcification is often associated with stable atherosclerosis, the extent of coronary artery calcification strongly correlates with the degree of atherosclerosis and with the rate of future cardiac events. Inflammation has a central role in atherogenesis, from plaque formation to rupture, hence in the development of acute coronary events. Morphologic plaque assessment, both invasive and non-invasive, gives limited information as to the current activity of the atherosclerotic disease. The addition of nuclear imaging, based on radioactive tracers targeted to the inflammatory components of the plaques, provides a highly sensitive assessment of coronary disease activity, thus distinguishing those patients who have stable disease from those with active plaque inflammation.

Identification of patients and plaques vulnerable to future coronary events with near-infrared spectroscopy intravascular ultrasound imaging: a prospective, cohort study

BACKGROUND

Near-infrared spectroscopy (NIRS) intravascular ultrasound imaging can detect lipid-rich plaques (LRPs). LRPs are associated with acute coronary syndromes or myocardial infarction, which can result in revascularisation or cardiac death. In this study, we aimed to establish the relationship between LRPs detected by NIRS-intravascular ultrasound imaging at unstented sites and subsequent coronary events from new culprit lesions.

METHODS

In this prospective, cohort study (LRP), patients from 44 medical centres were enrolled in Italy, Latvia, Netherlands, Slovakia, UK, and the USA. Patients with suspected coronary artery disease who underwent cardiac catheterisation with possible ad hoc percutaneous coronary intervention were eligible to be enrolled. Enrolled patients underwent scanning of non-culprit segments using NIRS-intravascular ultrasound imaging. The study had two hierarchal primary hypotheses, patient and plaque, each testing the association between maximum 4 mm Lipid Core Burden Index (maxLCBI_4mm) and non-culprit major adverse cardiovascular events (NC-MACE). Enrolled patients with large LRPs (≥250 maxLCBI_4mm) and a randomly selected half of patients with small LRPs (<250 maxLCBI_4mm) were followed up for 24 months. This study is registered with ClinicalTrials.gov, NCT02033694.

FINDINGS

Between Feb 21, 2014, and March 30, 2016, 1563 patients were enrolled. NIRS-intravascular ultrasound device-related events were seen in six (0·4%) patients. 1271 patients (mean age 64 years, SD 10, 883 [69%] men, 388 [31%]women) with analysable maxLCBI_4mm were allocated to follow-up. The 2-year cumulative incidence of NC-MACE was 9% (n=103). Both hierarchical primary hypotheses were met. On a patient level, the unadjusted hazard ratio (HR) for NC-MACE was 1·21 (95% CI 1·09-1·35; p=0·0004) for each 100-unit increase maxLCBI_4mm) and adjusted HR 1·18 (1·05-1·32; p=0·0043). In patients with a maxLCBI_4mm more than 400, the unadjusted HR for NC-MACE was 2·18 (1·48-3·22; p<0·0001) and adjusted HR was 1·89 (1·26-2·83; p=0·0021). At the plaque level, the unadjusted HR was 1·45 (1·30-1·60; p<0·0001) for each 100-unit increase in maxLCBI_4mm. For segments with a maxLCBI_4mm more than 400, the unadjusted HR for NC-MACE was 4·22 (2·39-7·45; p<0·0001) and adjusted HR was 3·39 (1·85-6·20; p<0·0001).

INTERPRETATION

NIRS imaging of non-obstructive territories in patients undergoing cardiac catheterisation and possible percutaneous coronary intervention was safe and can aid in identifying patients and segments at higher risk for subsequent NC-MACE. NIRS-intravascular ultrasound imaging adds to the armamentarium as the first diagnostic tool able to detect vulnerable patients and plaques in clinical practice.

FUNDING

Infraredx.

Clinical use of intracoronary imaging. Part 2: acute coronary syndromes, ambiguous coronary angiography findings, and guiding interventional decision-making: an expert consensus document of the European Association of Percutaneous Cardiovascular Interventions

This consensus document is the second of two reports summarizing the views of an expert panel organized by the European Association of Percutaneous Cardiovascular Interventions (EAPCI) on the clinical use of intracoronary imaging including intravascular ultrasound (IVUS), optical coherence tomography (OCT), and near infrared spectroscopy (NIRS)-IVUS. Beyond guidance of stent selection and optimization of deployment, invasive imaging facilitates angiographic interpretation and may guide treatment in acute coronary syndrome. Intravascular imaging can provide additional important diagnostic information when confronted with angiographically ambiguous lesions and allows assessment of plaque morphology enabling identification of vulnerability characteristics. This second document focuses on useful imaging features to identify culprit and vulnerable coronary plaque, which offers the interventional cardiologist guidance on when to adopt an intracoronary imaging-guided approach to the treatment of coronary artery disease and provides an appraisal of intravascular imaging-derived metrics to define the haemodynamic significance of coronary lesions.

Comparative Quantification of Arterial Lipid by Intravascular Photoacoustic-Ultrasound Imaging and Near-Infrared Spectroscopy-Intravascular Ultrasound

Intravascular photoacoustic-ultrasound (IVPA-US) imaging and near-infrared spectroscopy-intravascular ultrasound (NIRS-IVUS) are two hybrid modalities that detect arterial lipid, with comparison necessary to understand the relative advantages of each. We performed in vivo and ex vivo IVPA-US imaging of the iliac arteries of Ossabaw swine with metabolic syndrome (MetS) and lean swine to investigate sensitivity for early-stage atherosclerosis. We repeated imaging ex vivo with NIRS-IVUS for comparison to IVPA-US and histology. Both modalities showed significantly greater lipid in MetS vs. lean swine, but only IVPA-US localized the lipid as perivascular. To investigate late-stage atherosclerosis, we performed ex vivo IVPA-US imaging of a human coronary artery with comparison to NIRS-IVUS and histology. Two advanced fibroatheromas were identified, with agreement between IVPA-measured lipid area and NIRS-derived lipid content. As confirmed histologically, IVPA-US has sensitivity to detect lipid content similar to NIRS-IVUS and provides additional depth resolution, enabling quantification and localization of lipid cores within plaques.

Intracoronary near-infrared spectroscopy and the risk of future cardiovascular events

Objectives

The objectives of this study were to investigate if findings by intracoronary near-infrared spectroscopy (NIRS) and intravascular ultrasound (IVUS) are associated with future cardiovascular events and if NIRS can differentiate culprit from non-culprit segments in patients with coronary artery disease.

Methods

The study included 144 patients with coronary artery disease undergoing percutaneous coronary intervention and combined NIRS-IVUS imaging at two Swedish hospitals. The NIRS-derived lipid core burden index (LCBI), the 4 mm segment with maximum LCBI (MaxLCBI4mm) and the IVUS-derived maximum plaque burden (MaxPB) were analysed within the culprit segment and continuous 10 mm non-culprit segments of the index culprit vessels. The association with future major adverse cardiovascular and cerebrovascular events (MACCE), defined as all-cause mortality, acute coronary syndrome requiring revascularisation and cerebrovascular events during follow-up was evaluated using multivariable Cox regressions. A receiver operating characteristic (ROC) analysis was performed to test the ability of NIRS to discriminate culprit against non-culprit segments.

Results

A non-culprit maxLCBI4mm ≥400 (HR: 3.67, 95% CI 1.46 to 9.23, p=0.006) and a non-culprit LCBI ≥ median (HR: 3.08, 95% CI 1.11 to 8.56, p=0.031) were both significantly associated with MACCE, whereas a non-culprit MaxPB ≥70% (HR: 0.61, 95% CI 0.08 to 4.59, p=0.63) was not. The culprit segments had larger lipid cores compared with non-culprit segments (MaxLCBI4mm 425 vs 74, p<0.001), and the ROC analysis showed that NIRS can differentiate culprit against non-culprit segments (c-statistics: 0.85, 95% CI 0.81 to 0.89).

Conclusion

A maxLCBI4mm ≥400 and LCBI ≥ median, assessed by NIRS in non-culprit segments of a culprit artery, were significantly associated with patient-level MACCE. NIRS furthermore adequately discriminated culprit against non-culprit segments in patients with coronary disease.

Intraluminal Ultrasonic Palpation Imaging Technique Revisited for Anisotropic Characterization of Healthy and Atherosclerotic Coronary Arteries: A Feasibility Study

Accurate mechanical characterization of coronary atherosclerotic lesions remains essential for the in vivo detection of vulnerable plaques. Using intravascular ultrasound strain measurements and based on the mechanical response of a circular and concentric vascular model, E. I. Céspedes, C. L. de Korte and A. F. van der Steen developed an elasticity-palpography technique in 2000 to estimate the apparent stress-strain modulus palpogram of the thick subendoluminal arterial wall layer. More recently, this approach was improved by our group to consider the real anatomic shape of the vulnerable plaque. Even though these two studies highlighted original and promising approaches for improving the detection of vulnerable plaques, they did not overcome a main limitation related to the anisotropic mechanical behavior of the vascular tissue. The present study was therefore designed to extend these previous approaches by considering the orthotropic mechanical properties of the arterial wall and lesion constituents. Based on the continuum mechanics theory prescribing the strain field, an elastic anisotropy index was defined. This new anisotropic elasticity-palpography technique was successfully applied to characterize ten coronary plaque and one healthy vessel geometries of patients imaged in vivo with intravascular ultrasound. The results revealed that the anisotropy index-palpograms were estimated with a good accuracy (with a mean relative error of 26.8 ± 48.8%) compared with ground true solutions.