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

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. The maxLCBI 4mm of culprit segments (median [interquartile range]: 543 [273–756]) was 4.4-fold greater than nonculprit segments (median [interquartile range]: 123 [0–307]; P 4mm differentiated culprit from nonculprit segments with high accuracy (c-statistic=0.83; P 4mm ≥400 identified STEMI culprit segments with a sensitivity of 64% and specificity of 85%. Conclusions— This study substantiates the ability of NIRS to accurately differentiate STEMI culprit from nonculprit segments and confirms that a threshold maxLCBI 4mm ≥400 is detected by NIRS in the majority of STEMI culprits.