Abstract 4755: Serial Changes in Coronary Vessel Remodeling During Plaque Progression Are Related to Alterations in Plaque Composition as Seen on Integrated Backscatter Intravascular Ultrasound

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Background: Studies have demonstrated that coronary arteries with initial atherosclerosis show outward (positive) remodeling in order to maintain luminal diameter. However, serial changes in coronary vessel remodeling and its relation to alterations in plaque composition have not been investigated. Recently, assessment of plaque composition has become possible using an integrated backscatter intravascular ultrasound system (IB-IVUS). Using IB-IVUS, we examined whether the progression of coronary vessel remodeling is associated with changes in plaque components. Methods: One hundred sixty non-culprit, intermediate lesions were identified in 88 patients. Seventy-eight plaques demonstrated plaque progression at follow up examination and were included in this study. Plaque progression was defined as a >5% increase in plaque volume. A total of 20 IB-IVUS images were recorded at 0.5 mm intervals along a 10 mm length of plaque. Total vessel volume (TVV) on conventional IVUS, total lipid volume (TLV) and total fibrous volume (TFV) on IB-IVUS were measured at each site. Six months later, a follow up IVUS examination was performed of the same coronary segment imaged at baseline. Serial changes in vessel remodeling (vessel remodeling index: VRI) were calculated as TVV at follow up examination/TVV at baseline examination. Progressive plaques were divided into two groups (compensation: 52 plaques, C-group VRI>1; no compensation or shrinkage: 26 plaques, S-group VRI≤1). Results: TLV and TFV at baseline examination were not significantly different between the two groups. However, ΔTLV (TLV at follow up examination - TLV at baseline examination) in the C-group was significantly higher compared to the S-group (10.0±8.6 vs. 2.7±7.0 mm 3 , P<0.01). Conversely, ΔTFV (TFV at follow up examination - TFV at baseline examination) in the C-group was significantly lower compared to the S-group (2.9±5.6 vs. 6.5±3.9 mm 3 , P<0.01). The VRI positively correlated with ΔTLV (r=0.34, P<0.01), but not with ΔTFV. Conclusions: Serial changes in coronary vessel remodeling are associated with alterations in the lipid component of progressively enlarging plaques.