Detection by near-infrared spectroscopy of large lipid cores at culprit sites in patients with non-ST-segment elevation myocardial infarction and unstable angina.

OBJECTIVE: This study was performed to assess the lipid burden of culprit lesions in non-ST-segment elevation myocardial infarction (non-STEMI) and unstable angina (UA). BACKGROUND: A recent intracoronary near-infrared spectroscopy (NIRS) study showed 85% of STEMI culprit lesions have a maximum lipid core burden index in 4-mm (maxLCBI(4mm)) ≥ 400. Whether culprit lesions in non-STEMI and UA are characterized by a similarly large lipid burden is unknown. METHODS: We studied 81 non-STEMI and UA patients undergoing culprit vessel NIRS imaging before stenting. Culprit segments were compared to all nonoverlapping 10-mm nonculprit segments for maxLCBI(4mm). Culprit segments in non-STEMI and UA were compared for the frequency of maxLCBI(4mm) ≥ 400. RESULTS: Among 81 patients (53.1% non-STEMI, 46.9% UA), non-STEMI culprit segments had a 3.4-fold greater maxLCBI(4mm) than nonculprits (448 ± 229 vs 132 ± 154, P < 0.001) and UA culprit segments had a 2.6-fold higher maxLCBI(4mm) than nonculprits (381 ± 239 vs 146 ± 175, P < 0.001). NIRS detected a maxLCBI(4mm) ≥ 400 in 63.6% of culprit segments in NSTEMI and in 38.5% of culprit segments in UA (P = 0.02). Against a background of nonculprit segments, maxLCBI(4mm) ≥ 400 had a sensitivity of 63.6% and specificity of 94.0% for culprit segments in NSTEMI and a sensitivity of 38.5% and specificity of 89.8% for culprit segments in UA. CONCLUSIONS: Large lipid cores similar to those recently detected by NIRS at STEMI culprit sites were frequently observed at culprit sites in patients with non-STEMI and UA. These findings support ongoing prospective trials designed to determine if NIRS can provide site-specific prediction of future acute coronary events.