Abstract 2546: Are Lesions that Appear Echolucent on Greyscale IVUS Imaging “Vulnerable”? A Virtual Histology Intravascular Ultrasound Analysis
Echolucent plaques identified by greyscale intravascular ultrasound (IVUS) have been reported to be prone to future thrombotic events.
Methods and Results: Clinically indicated IVUS data from pts with acute coronary syndrome were collected. We blindly reviewed greyscale-IVUS and matched VH-IVUS in non-stented segments in 89 arteries from 85 pts. Fifty-three greyscale-IVUS echolucent zones were detected in 43 arteries from 43 pts (white arrow, left figure⇓). Analyzed length measured 54.5±24.9mm, and the distance from ostium to the echolucent plaque was 19.3±12.6mm. At the maximum echolcent plaque, lumen area and plaque burden (plaque/vessel area) measured 7.0±3.4mm2 and 61±14%. Most echolucent zones (92%) were located middle of the plaque. All echolucent zones contained fibrous (green) and fibrofatty plaque (light green) (single arrow, right figure⇓). Thirty-three of 53 (62%) echolucent zones contained a confluent necrotic core (NC) (red) at the bottom (double arrow, right figure⇓). The NC area measured 1.4±1.2mm2 (16% of plaque area) while fibrous and fibrofatty plaque measured 4.5±3.0mm2 (58%) and 1.6±1.4mm2 (25%), respectively. Eight of 53 (15%) has superficial confluent NC and only 3 lesions were categorized as thin-cap fibroatheroma by qualitative VH-IVUS analysis.
Conclusions: Echolucent zones identified by greyscale IVUS are typically are not stenotic, do not appear to be “vulnerable” by VH-IVUS analysis, and are rarely classified as thin-capped fibroatheromas. Rather, most appear to contain fibrotic and fibrofatty plaque with confluent NC only at the base of such areas and not near the lumen surface.