Abstract 1970: Tissue Characteristics at the Site of Gradual Progression of Coronary Plaques Assessed by Integrated Backscatter Intravascular Ultrasound
Background: The tissue characteristics at the site of gradual progression of coronary plaques have not been investigated in clinical settings. We developed a commercially-available Integrated Backscatter Intravascular Ultrasound (IB-IVUS) for tissue characterization of coronary plaques.
Methods: In an autopsy study, 45 coronary arteries with moderate or severe stenosis, but without thrombus, obtained from 25 cadavers were evaluated by IB-IVUS. In a clinical study, lesions with significant stenosis that caused stable angina (SA: n = 64 patients) and lesions that caused acute coronary syndrome (ACS: n = 22) were compared with plaques with moderate stenosis (MS: n = 143) that did not cause ACS during a two-year follow-up period.
Results: There was no significant difference in the % fibrous area (fibrous area/plaque area) (MS: 47 ± 14, SA: 47 ± 12%) and % lipid area (MS: 50 ± 16, SA: 52 ± 12) between the two groups. That is, gradual luminal narrowing was caused by the same percentage increment of fibrous area as lipid area. These parameters were similar in ACS. Remodeling index in SA was lower than in MS (1.00 ± 0.14, 1.16 ± 0.16, p < 0.01). This means shrinkage of plaques during gradual progression. In the autopsy study, 19 of 26 plaques (73%) with severe stenosis showed healed multiple plaque rupture. In the clinical study, multi-layer appearances that consisted of a fibrous area were seen in 66% of the plaques with gradual luminal narrowing (42 /64 segments).
Conclusion: This is the first clinical demonstration of tissue characteristics of plaques with gradual luminal narrowing. Gradual plaque progression results from multi-layer fibrous cap that is derived from repair after plaque rupture.