Thin Calcification Predicts Lipid Component in Carotid Plaque-Relationship Between Lipid Distribution and Thin Calcification.

BACKGROUND: Accurately evaluating plaque characteristics is essential because lesions with lipid-rich plaque put patients at risk of thromboembolic complications from carotid artery stenting. Near-infrared spectroscopy (NIRS) is a diagnostic imaging modality that identifies lipid components from the near-infrared absorption pattern but does not reveal the distribution of calcification. The purpose of this study was to investigate the calcification characteristics of unstable carotid plaques, focusing on relationships between the calcification characteristics revealed by computed tomography angiography and the lipid core distribution derived from NIRS. METHODS: Participants in this retrospective analysis comprised 35 patients (29 men, 6 women; mean age, 76.0 years; range, 52-89 years) who underwent carotid artery stenting in our institute between January 2021 and December 2022. We evaluated the thickness and length of carotid calcifications at the minimal lumen level from preoperative computed tomography angiography and analyzed the relationship with maximum lipid core burden index (max-LCBI) from NIRS. RESULTS: Strong negative linear correlations were observed between the thickness of calcification and max-LCBI at Area (any segment in a target lesion) (r = -0.795, P < 0.001), max-LCBI at minimal lumen area (r = -0.795, P < 0.001) and lipid core burden index (LCBI) at lesion (rate of LCBI in entire plaque lesion) (r = -0.788, P < 0.001), respectively. Significant negative linear correlations were observed between distribution of calcification length and max-LCBI at area (r = -0.429, P = 0.01), max-LCBI at minimal lumen area (r = -0.373, P = 0.027), and LCBI at lesion (r = -0.443, P = 0.008). CONCLUSIONS: Thin and ubiquitous carotid calcification was associated with LCBI values derived from NIRS indicative of carotid lipid plaque distribution, implying the possibility of predicting lesion instability.

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.

Additive Effect of Multiple High-Risk Coronary Artery Segments on Patient Outcomes: LRP Study Sub-Analysis.

BACKGROUND: The Lipid Rich Plaque (LRP) Study established the association between high volume of lipidic content (maximum Lipid Core Burden Index [maxLCBI4mm] >400) in the coronary arteries and subsequent non-culprit major adverse cardiac events (NC-MACE). This analysis sought to assess the clinical impact of more than one lipid-rich plaque in the coronary tree. METHODS: The LRP patient population was divided into four cohorts: 1) patients with all segments with maxLCBI4mm = 0; 2) patients with all coronary segments maxLCBI4mm < 400, but >0; 3) patients with 1 segment maxLCBI4mm > 400; and 4) patients with 2+ coronary segments with maxLCBI4mm > 400. Baseline characteristics, plaque-level characteristics, and follow-up outcomes were described. RESULTS: Among 1550 patients, only 3.2 % had all segments with maxLCBI4mm = 0; 65.1 % had segments with maxLCBI4mm > 0 but <400; 22.5 % had one segment with maxLCBI4mm > 400; and 9.5 % had 2+ coronary segments with maxLCBI4mm > 400. Distribution within the coronary tree (one versus multiple arteries) did not differ. Overall, 1269 patients were allocated to follow-up (per study design). The composite of all-cause death, cardiac death, any revascularization, and NC-MACE was statistically higher in patients with 1 segment maxLCBI4mm > 400 and numerically even higher in patients with 2+ segments with maxLCBI4mm > 400. Patients with maxLCBI4mm = 0 had no events within two years. CONCLUSION: There is a stepwise increased risk of all-cause death, cardiac death, any revascularization, and NC-MACE according to the number of coronary segments with maxLCBI4mm > 400. In contrast, maxLCBI4mm = 0 results in a low event rate. CLINICAL TRIAL REGISTRATION: The Lipid-Rich Plaque Study (LRP), https://clinicaltrials.gov/ct2/show/NCT02033694, NCT02033694.

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.

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.

There is urgent need to treat atherosclerotic cardiovascular disease risk earlier, more intensively, and with greater precision: A review of current practice and recommendations for improved effectiveness.

Atherosclerotic cardiovascular disease (ASCVD) is epidemic throughout the world and is etiologic for such acute cardiovascular events as myocardial infarction, ischemic stroke, unstable angina, and death. ASCVD also impacts risk for dementia, chronic kidney disease peripheral arterial disease and mobility, impaired sexual response, and a host of other visceral impairments that adversely impact the quality and rate of progression of aging. The relationship between low-density lipoprotein cholesterol (LDL-C) and risk for ASCVD is one of the most highly established and investigated issues in the entirety of modern medicine. Elevated LDL-C is a necessary condition for atherogenesis induction. Basic scientific investigation, prospective longitudinal cohorts, and randomized clinical trials have all validated this association. Yet despite the enormous number of clinical trials which support the need for reducing the burden of atherogenic lipoprotein in blood, the percentage of high and very high-risk patients who achieve risk stratified LDL-C target reductions is low and has remained low for the last thirty years. Atherosclerosis is a preventable disease. As clinicians, the time has come for us to take primordial and primary prevention more serously. Despite a plethora of therapeutic approaches, the large majority of patients at risk for ASCVD are poorly or inadequately treated, leaving them vulnerable to disease progression, acute cardiovascular events, and poor aging due to loss of function in multiple visceral organs. Herein we discuss the need to greatly intensify efforts to reduce risk, decrease disease burden, and provide more comprehensive and earlier risk assessment to optimally prevent ASCVD and its complications. Evidence is presented to support that treatment should aim for far lower goals in cholesterol management, should take into account many more factors than commonly employed today and should begin significantly earlier in life.

Correlation between lipidic content and arterial-wall plaque burden: A Lipid Rich Plaque study sub-analysis.

BACKGROUND: Large plaque burden (PB) has been linked to adverse coronary events. We sought to assess the correlation between lipidic content and arterial PB within the Lipid Rich Plaque (LRP) study. METHODS: This analysis included 1269 patients and 5743 coronary segments with both evaluable Lipid Core Burden Index (maxLCBI4mm) and PB. Non-culprit major adverse cardiac events (NC-MACE; defined as a composite of cardiac death, cardiac arrest, non-fatal myocardial infarction, acute coronary syndrome, revascularization, and hospital readmission for angina with progressive stenosis) were assessed by hazard ratios (HR) at 2 years. RESULTS: NC-MACE for segment cohorts in the most vulnerable quadrant of maxLCBI4mm > 400 and PB >40% was the highest (HR, 3.78 [95% confidence interval (CI) 2.39-5.66]) with similar rates for just PB >40% (HR 1.31 [95% CI 0.81-2.02]) and just maxLCBI4mm > 400 (HR 1.11 [95% CI 0.10-5.38]). Fewer events occurred in the maxLCBI4mm ≤ 400 and PB ≤40% quadrant (HR 0.25 [95% CI 0.11-0.50]). CONCLUSIONS: Coronary segments with high lipid content but no measurable PB were still associated with events at 2 years. NC-MACE vulnerability increased as the lipidic content and PB increased, with the highest incidence within segments having maxLCBI4mm > 400 and plaque >40%. CLINICAL TRIAL REGISTRATION: The Lipid-Rich Plaque Study (LRP), NCT02033694, https://clinicaltrials.gov/ct2/show/NCT02033694.

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 (maxLCBI4mm). A predefined cutoff of maxLCBI4mm >100 was required for inclusion in the analysis. Forty-nine patients (HIIT=20, usual care=29) had maxLCBI4mm >100 at baseline. Change in maxLCBI4mm did not differ between groups (-1.2, 95% CI, -65.8 to 63.4, P=0.97). The estimated reduction in maxLCBI4mm 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 (VO2peak) and change in lipid content (Spearman's correlation -0.44, P=0.009). With an increase in VO2peak above 1 metabolic equivalent task, maxLCBI4mm was on average reduced by 142 (-8 to -262), whereas the change was -3.2 (154 to -255) with increased VO2peak 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 VO2peak 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.

Adoption of a new automated optical coherence tomography software to obtain a lipid plaque spread-out plot.

PURPOSE: Near infrared spectroscopy-Intravascular ultrasound (NIRS-IVUS) provide a fully automated Lipid Core Burden Index (LCBI). Optical coherence tomography (OCT) is potentially capable of measuring lipid longitudinal extension in a dedicated two-dimensional LCBI spread-out plot. The present study has been designed to validate an automated approach to assess OCT images, able of providing a dedicated LCBI spread-out plot. METHODS: We compared results obtained with conventional (manual) OCT, with those obtained with a novel automated OCT algorithm and with NIRS-IVUS in consecutive 40 patients. Our goal was to calculate the lipid core longitudinal extension in a dedicated two-dimensional LCBI spread-out plot. Three groups were identified according to the studied lesions: (1) culprit lesions in ACS patients (n = 16), (2) non-culprit lesions in ACS patients (n = 12) and (3) lesions in stable patients (n = 12). OCT (either manual and automated) and NIRS-IVUS assessment showed for culprit ACS plaques a more complex anatomy. RESULTS: A strong trend for increased LCBI was found in the culprit ACS group, regardless of the adopted imaging modality (either NIRS-IVUS or automated OCT). A fair correlation was obtained for the maximum 4 mm LCBI measured by NIRS-IVUS and automated OCT (r = 0.75). The sensitivity and specificity of automated OCT to detect significant LCBI (> 400) were 90.5 and 84.2 respectively. CONCLUSION: We developed an OCT automated approach that can provide a dedicated lipid plaque spread-out plot to address plaque vulnerability. The automated OCT software can promote and improve OCT clinical applications for the identification of patients at risk of hard events.

Lipid Core Burden Index Assessed by Near-Infrared Spectroscopy of Symptomatic Carotid Plaques: Association with Magnetic Resonance T1-Weighted Imaging.

INTRODUCTION: Vulnerable plaques are a strong predictor of cerebrovascular ischemic events, and high lipid core plaques (LCPs) are associated with an increased risk of embolic infarcts during carotid artery stenting (CAS). Recent developments in magnetic resonance (MR) plaque imaging have enabled noninvasive assessment of carotid plaque vulnerability, and the lipid component and intraplaque hemorrhage (IPH) are visible as high signal intensity areas on T1-weighted MR images. Recently, catheter-based near-infrared spectroscopy (NIRS) has been shown to accurately distinguish LCPs without IPH. This study aimed to determine whether the results of assessment of high LCPs by catheter-based NIRS correlate with the results of MR plaque imaging. METHODS: We recruited 82 consecutive symptomatic carotid artery stenosis patients who were treated with CAS under NIRS and MR plaque assessment. Maximum lipid core burden index (max-LCBI) at minimal luminal areas (MLA), defined as max-LCBIMLA, and max-LCBI for any 4-mm segment in a target lesion, defined as max-LCBIAREA, were assessed by NIRS. Correlations were investigated between max-LCBI and MR T1-weighted plaque signal intensity ratio (T1W-SIR) and MR time-of-flight signal intensity ratio (TOF-SIR) in the same regions as assessed by NIRS. RESULTS: Both T1W-SIRMLA and T1W-SIRAREA were significantly lower in the high LCP group (max-LCBI >504, p < 0.001 for both), while TOF-SIRMLA and TOF-SIRAREA were significantly higher in the high LCP group (p < 0.001 and p = 0.004, respectively). A significant linear correlation was present between max-LCBIMLA and both TIW-SIRMLA and TOF-SIRMLA (r = -0.610 and 0.452, respectively, p < 0.0001 for both). Furthermore, logistic regression analysis revealed that T1W-SIRMLA and TOF-SIRMLA were significantly associated with a high LCP assessed by NIRS (OR, 44.19 and 0.43; 95% CI: 6.55-298.19 and 0.19-0.96; p < 0.001 and = 0.039, respectively). CONCLUSIONS: A high LCP assessed by NIRS correlates with the signal intensity ratio of MR imaging in symptomatic patients with unstable carotid plaques.

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.

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.

Near-infrared spectroscopy-derived lipid core burden index predicts adverse cardiovascular outcome in patients with coronary artery disease during long-term follow-up.

Aims: Near-infrared spectroscopy (NIRS) is able to quantify cholesterol within coronary arteries by the lipid core burden index (LCBI). We studied the prognostic value of NIRS-derived LCBI in patients with coronary artery disease (CAD) for adverse cardiac outcome during long-term follow-up. Methods and results: During 2009-2013, NIRS was performed in a non-culprit artery of 275 patients undergoing coronary angiography for acute coronary syndrome (ACS) or stable angina. LCBI was quantified by an independent corelab for the region of interest (LCBIROI) and the 4 and 10 mm long segment with the maximum LCBI (MaxLCBI4mm and MaxLCBI10mm). The primary endpoint was major adverse cardiac events (MACE), defined as the composite of all-cause death, non-fatal ACS, or unplanned revascularization. Hazard ratios (HR) were adjusted for age, gender, clinical risk factors, and segment plaque burden based on intravascular ultrasound. During a median follow-up of 4.1 years, 79 patients (28.7%) had MACE. There was a statistically significant and independent continuous relationship between higher MaxLCBI4mm values and a higher risk of MACE. Each 100 units increase of MaxLCBI4mm was associated with a 19% increase in MACE [hazard ratios (HR) 1.19, 95% confidence intervals (95% CI): 1.07-1.32, P = 0.001]. Continuous MaxLCBI4mm remained independently associated with MACE after exclusion of target lesion-related events (HR 1.21, 95% CI: 1.08-1.35), as well as after exclusion of adverse events related to the NIRS-imaged coronary segment (HR 1.19, 95% CI: 1.06-1.34). Results for MaxLCBI10mm were comparable. Conclusion: NIRS-derived LCBI is associated with adverse cardiac outcome in CAD patients during long-term follow-up independent of clinical risk factors and plaque burden.

Determinants of high cardiovascular risk in relation to plaque-composition of a non-culprit coronary segment visualized by near-infrared spectroscopy in patients undergoing percutaneous coronary intervention.

AIM: The aim of this study was to determine the relationship between clinical and blood characteristics of a vascular inflammatory milieu and coronary plaque composition visualized by near-infrared spectroscopy (NIRS) in percutaneous coronary intervention (PCI) patients. METHODS AND RESULTS: Between April 2009 and January 2011, we performed NIRS in 208 patients who underwent PCI or invasive diagnostic coronary exploration for various indications. Imaging was performed of one non-intervened coronary segment after the initial procedure. Univariate and multivariate linear regression analyses were applied to evaluate the relationship between the acquired NIRS-derived lipid core burden index (LCBI) and clinical and blood (lipids and hs-C-reactive protein) characteristics. Patients with a history of hypercholesterolaemia [median 48 (inter-quartile range 21-101) vs. 38 (13-70), P = 0.043] and multi-vessel disease [55 (24-104) vs. 32 (12-71), P = 0.012] had higher LCBI levels. Men had higher LCBI than women [48 (21-95) vs. 27 (9-59), P = 0.003]. Hypercholesterolaemia and gender remained significant in multivariate regression analysis, whereas also a history of non-cardiac vascular disease and beta-blockers were positively associated with LCBI. Altogether 23.2% of the variability in LCBI could be explained by clinical and blood characteristics. CONCLUSION: Clinical characteristics reflecting patients with a high cardiovascular risk profile explained 23.2% of the variability in LCBI, whereas blood biomarkers added little. Further research is warranted to evaluate whether NIRS has the potential to provide additional prognostic information about patients' cardiovascular risk.

Detection by near-infrared spectroscopy of large lipid core plaques at culprit sites in patients with acute ST-segment elevation myocardial infarction.

OBJECTIVES: This study sought to describe near-infrared spectroscopy (NIRS) findings of culprit lesions in ST-segment elevation myocardial infarction (STEMI). BACKGROUND: Although autopsy studies demonstrate that most STEMI are caused by rupture of pre-existing lipid core plaque (LCP), it has not been possible to identify LCP in vivo. A novel intracoronary NIRS catheter has made it possible to detect LCP in patients. METHODS: We performed NIRS within the culprit vessels of 20 patients with acute STEMI and compared the STEMI culprit findings to findings in nonculprit segments of the artery and to findings in autopsy control segments. Culprit and control segments were analyzed for the maximum lipid core burden index in a 4-mm length of artery (maxLCBI(4mm)). RESULTS: MaxLCBI(4mm) was 5.8-fold higher in STEMI culprit segments than in 87 nonculprit segments of the STEMI culprit vessel (median [interquartile range (IQR)]: 523 [445 to 821] vs. 90 [6 to 265]; p < 0.001) and 87-fold higher than in 279 coronary autopsy segments free of large LCP by histology (median [IQR]: 523 [445 to 821] vs. 6 [0 to 88]; p < 0.001).Within the STEMI culprit artery, NIRS accurately distinguished culprit from nonculprit segments (receiver-operating characteristic analysis area under the curve = 0.90). A threshold of maxLCBI(4mm) >400 distinguished STEMI culprit segments from specimens free of large LCP by histology (sensitivity: 85%, specificity: 98%). CONCLUSIONS: The present study has demonstrated in vivo that a maxLCBI(4mm) >400, as detected by NIRS, is a signature of plaques causing STEMI.