Abstract
Background: It is well known that coronary plaques that show backward attenuation of ultrasound signal (AT) often cause distal flow disturbance during percutaneous coronary intervention (PCI). However, tissue characteristics of such plaques have not been precisely investigated. We previously developed an Integrated Backscatter Intravascular Ultrasound (IB-IVUS) for tissue characterization of coronary plaques. The aim of this study is to clarify the relationship among tissue components of coronary plaques, AT and distal embolization after stent deployment by use of IB-IVUS. Methods: In the pathological study, images were acquired from 221 segments of 18 coronary arteries from 13 cadavers obtained at autopsy. Twenty-three segments that showed AT (10%) were enrolled in this study. A total of 47 regions of interest (ROI) on histological images were compared with IB-IVUS color coded maps. Micro calcifications and cholesterol clefts were evaluated by von Kossa, Masson Trichrome and Hematoxylin-Eosin staining. Percentage of cholesterol clefts area (area of cholesterol cleft/area of ROI) and micro calcification area were calculated by a personal computer. In the clinical study, fourteen lesions which underwent elective stent deployment were enrolled. We evaluated the degrees of distal embolization by measuring serum troponin I (TnI) level before and after PCI and compared with IB-IVUS parameters. We defined the area of AT as the area where IB value is -6dB less than lipid pool. Results: In the pathological study, the attenuation of IB values of cholesterol cleft and micro calcification were3.58 ± 1.56 dB/0.1 mm and 3.51 ± 1.74 dB/0.1 mm, respectively. As the % cholesterol cleft area and % micro calcification area increased, the attenuation of IB values increased (r = 0.59 and 0.62, P < 0.001 and 0.001, respectively). Elevation of serum TnI have strong correlation to AT volume at the target lesions compared to the % lipid volume (lipid volume/plaque volume) (r = 0.92 and 0.56, P < 0.001 and 0.001, respectively). Conclusion: This is the first demonstration of the relationship among the attenuation of IB values, tissue component and distal embolizaion after PCI. This study provides new clinical insights to prevent and predict distal flow disturbance during PCI.
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