Detection of cholesterol crystals by optical coherence tomography.

AIMS

The aim of this study was to determine the ability of optical frequency domain imaging (OFDI)/optical coherence tomography (OCT) imaging systems to visualise the presence of cholesterol crystals (CCR) in human atherosclerotic coronary arteries.

METHODS AND RESULTS

We performed ex vivo imaging of human coronary arteries by OFDI/OCT. A total of 559 cross-sectional images from 45 autopsy cases were co-registered with histology; 117 histologic sections showed presence of necrotic core with cholesterol clefts (CC). We modified a previously used OFDI/OCT definition for identification of CCRs which we now define as a linear and discrete high-intensity signal (bright area) within the plaque with sharp borders between it and adjacent low-/intermediate-intensity tissue. Additionally, the high-intensity signal is not a spot but a well-defined area distinguishing it from macrophages which lack sharp borders. OFDI/OCT imaging identified the presence of CCR in 30 of the 117 histologic sections. The sensitivity and specificity of OFDI/OCT for detection of CCR was 25.6% and 100.0%, respectively. By multivariate analysis, significant predictors to visualise CCR by OCT/OFDI were 1) an overlying fibrous plaque, and 2) the presence of stacked CC, defined as CC arranged one on top of another with >3 layers of CC. The prevalence of complicated plaques (i.e., plaque haemorrhage and late necrotic core) was significantly higher in detectable CCR by OFDI/OCT as compared to undetectable CCR.

CONCLUSIONS

The presence of stacked CCs is required to detect CCR by OFDI/OCT. Detection of CCR by OCT/OFDI may help us to identify the late stages of atherosclerotic coronary plaque progression and improve risk stratification.