Confirmation of the Intracoronary Near-Infrared Spectroscopy Threshold of Lipid-Rich Plaques That Underlie ST-Segment–Elevation Myocardial Infarction

Abstract

C oronary artery disease accounts for ≈1 in every 6 deaths in the United States, with acute ST-segment-elevation myocardial infarction (STEMI) contributing significantly to the overall morbidity associated with this disease. 1 Postmortem studies in patients dying of myocardial infarction consistently demonstrate that the majority of STEMIs are triggered by rupture of a thin-fibrous cap overlying a lipidrich necrotic core. 2-5Intracoronary near-infrared spectroscopy (NIRS) is a catheter-based imaging modality developed and validated to detect lipid-rich plaques (LRPs) in patients undergoing coronary angiography. 6,7 In an exploratory analysis in a small number of STEMI patients, NIRS demonstrated large, significant differences in the lipid content between culprit and nonculprit segments.8 A potential NIRS signature of STEMI culprit lesions was identified, defined by a maximum lipid core burden index within a 4-mm coronary section (maxL-CBI 4mm ) being >400. These initial observations were limited by a modest sample size, single-center enrollment, and post hoc selection of the maxLCBI 4mm ≥400 threshold. This study was designed a priori to confirm the ability of NIRS to discriminate STEMI culprit from nonculprit segments and to determine the sensitivity and specificity of the maxLCBI 4mm ≥400 threshold. Secondary aims were to evaluate the ability of the NIRS block chemogram to differentiate culprit from nonculprit segments and to evaluate the regional deposition of lipid within coronary segments adjacent to the angiographically defined culprit segment.© 2016 American Heart Association, Inc. Objective-In a previous exploratory analysis, intracoronary near-infrared spectroscopy (NIRS) found the majority of culprit lesions in ST-segment-elevation myocardial infarction (STEMI) to contain a maximum lipid core burden index in 4 mm (maxLCBI 4mm ) of >400. This initial study was limited by a small sample size, enrollment at a single center, and post hoc selection of the maxLCBI 4mm ≥400 threshold. This study was designed a priori to substantiate the ability of NIRS to discriminate STEMI culprit from nonculprit segments and to confirm the performance of the maxLCBI 4mm ≥400 threshold. Approach and Results-At 2 centers in the United States and Sweden, 75 STEMI patients underwent intracoronary NIRS imaging after establishing thrombolysis in myocardial infarction 3 flow, but before stenting. Blinded core laboratory analysis defined the culprit segment as the 10-mm segment distal to the proximal angiographic culprit margin. The remaining vessel was divided into contiguous 10-mm nonculprit segments.

Invasive or non-invasive imaging for detecting high-risk coronary lesions?

“…Madder et al used NIRS-IVUS to study 20 culprit lesions in patients presented with a STEMI and showed that an increased lipid component (lipid core burden index in a 4-mm segment, LCBI 4 mm > 400) was able to differentiate the culprit from the non-ruptured plaques with a high accuracy (AUC: 0.90) [79]. These findings were echoed in a larger study that demonstrated a sensitivity of 64% and a specificity of 85% for LCBI 4 mm > 400 in identifying culprit lesions that caused STEMI [80]. The same research group replicated the above study in patients who presented with a NSTEMI or unstable angina and showed that larger lipid cores were present in the culprit lesions of these patients as well, but in this setting, LCBI 4 mm > 400 had a lower sensitivity and specificity (63.6% and 94.0% for NSTEMI and 38.5% and 89.8% for culprit lesion causing unstable angina, respectively) [81].…”

Current Advances in the Diagnostic Imaging of Atherosclerosis: Insights into the Pathophysiology of Vulnerable Plaque

“…Demonstrating more reliable characterization of plaque composition, fused IVUS-NIRS imaging underwent histopathological validation in recent studies [72,73]. For instance, the detection of superficial thinning as the IVUS signature of a fibroatheroma is frequently prevented by the presence of calcification; NIRS can detect lipid regardless of substantial calcification [74]. The improved efficacy of fusion of IVUS and NIRS, compared to their separate use, was also proven by some other IVUS-NIRS studies [74,75].…”

“…For instance, the detection of superficial thinning as the IVUS signature of a fibroatheroma is frequently prevented by the presence of calcification; NIRS can detect lipid regardless of substantial calcification [74]. The improved efficacy of fusion of IVUS and NIRS, compared to their separate use, was also proven by some other IVUS-NIRS studies [74,75]. Because the culprit lesions in patients with non-ST or ST-elevation myocardial infarction (STEMI) have specific morphological characteristics [76], the IVUS-NIRS application was shown to be capable of accurately differentiating STEMI culprit from non-culprit segments [74,75].…”

Coronary Atherosclerotic Vulnerable Plaque: Current Perspectives

“…86 Studies using NIRS have shown that large lipid content, rather than plaque burden, is associated with thin cap fibroatheroma features. 25,87 Larger lipid core burden has been shown to accurately differentiate between culprit and nonculprit lesion in ST-elevation MI patients 88 and has been associated with higher risk for periprocedural myocardial infarction. 89 Interestingly, combination with IVUS may allow for concomitant appreciation of both plaque structure and composition, 90 comparing favorably with OCT. 87 Despite recent studies linking lipid-rich, NIRS-defined nonculprit plaque presence with a 4-fold risk for adverse events (all-cause mortality, nonfatal ACS, stroke, and unplanned revascularizationexcluding those definitely related to the initial culprit lesion) 91 within the first year of follow-up, it cannot be inferred whether these were actually triggered by the detected vulnerable plaque (thus being amenable to preventive stenting) or by other, not assessed lesions (NIRS was only performed over a vessel segment).…”