Combined IVUS and NIRS detection of fibroatheromas: histopathological validation in human coronary arteries

Objectives: This study assessed grayscale intravascular ultrasound (IVUS) and near-infrared spectroscopy (NIRS) detection of a histological fibroatheroma (FA).

Background: NIRS-detected, lipid-rich plaques (LRPs) and IVUS-detected attenuated plaques are considered to be vulnerable.

Methods: IVUS-attenuated plaque and NIRS-LRP (yellow or tan block chemogram) were compared with histopathology in 1,943 sections of 103 coronary arteries from 56 autopsied hearts.

Results: IVUS-superficial attenuation and NIRS-LRP showed a similar high specificity of approximately 95%, whereas IVUS-superficial attenuation alone had a poor sensitivity (vs. NIRS-LRP) in detecting FAs (36% vs. 47%; p = 0.001). Compared with FA sections with superficial attenuation, FA sections without superficial attenuation had a smaller plaque burden (57.1% vs. 67.7%), a larger arc of calcium (79.7° vs. 16.8°), and a lower prevalence of a ≥20% histological necrotic core (28% vs. 50%) or late FA (14% vs. 37%; all p < 0.05). Compared with FA sections with NIRS-LRP, FA sections without NIRS-LRP showed a smaller plaque burden (58.0% vs. 63.3%) and a lower prevalence of a ≥20% necrotic core (27% vs. 46%). Conversely, non-FAs with NIRS-LRP (vs. non-FAs without LRP) showed a larger plaque burden (55.1% vs. 46.3%), a greater prevalence of a ≥20% histological lipid pool (34% vs. 5%), and mostly pathological intimal thickening (50%) or fibrocalcific plaque (33%). When sections showed either IVUS attenuation or NIRS-LRP, the sensitivity for predicting a FA was significantly higher compared with IVUS attenuation alone (63% vs. 36%; p < 0.001) or NIRS-LRP alone (63% vs. 47%; p < 0.001). When sections showed both IVUS attenuation and NIRS-LRP, the positive predictive value improved compared with IVUS attenuation alone (84% vs. 66%; p < 0.001) or NIRS-LRP alone (84% vs. 65%; p < 0.001).

Conclusions: NIRS-LRP was more accurate than IVUS for predicting plaque containing a necrotic core or a large lipid pool, and the combination was more accurate than either alone.