Comparison of near-infrared spectroscopy and optical coherence tomography for detection of lipid.

OBJECTIVES: To compare intracoronary near-infrared spectroscopy (NIRS) and optical coherence tomography (OCT) for the detection of lipid, to identify NIRS signals to differentiate superficial lipid, and to characterize the plaque with yellow block (YB) chemograms on NIRS.

BACKGROUND: Intracoronary NIRS has been developed to detect lipid core plaque (LCP).

METHODS: We investigated a total of 17 patients who underwent both OCT and NIRS. NIRS analysis included plaque lipid core burden index (LCBI), LCP length, and the presence of YB on the block chemogram. OCT analysis included maximum lipid arc (LA), the length of lipid (LL), lipid index, and the thinnest fibrous cap thickness (FCT).

RESULTS: Twenty-five plaques with >40% plaque burden were analyzed. LCP, showing LCBI > 0, was observed in 20 plaques (80%) and YB was detected in seven plaques (28%). Plaque LCBI showed modest correlations with maximum LA and lipid index by OCT (r(2) = 0.319, P = 0.003 and r(2) = 0. 404, P = 0.001, respectively). Lipid length showed a significant correlation between NIRS and OCT measurements (r(2) = 0.581, P < 0.001). There was no significant difference in NIRS parameters between superficial and deep lipid. Plaques with YB compared with those without YB showed a larger LA, longer LL, and thinner FCT (185 ± 29° vs. 105 ± 76°, P = 0.014; 8.5 ± 3.3 mm vs. 3.3 ± 2.7 mm, P = 0.001; 112 ± 42 vs. 166 ± 61 µm, P = 0.033).

CONCLUSIONS: NIRS and OCT parameters showed modest linear correlations in the measurement of lipid. The accurate depth of lipid in the vessel wall could not be identified by quantitative NIRS parameters. YB chemograms represented more vulnerable features on OCT.