Impact of vascular remodeling on the coronary plaque compositions: an investigation with in vivo tissue characterization using integrated backscatter-intravascular ultrasound.

Recent studies have indicated that positive remodeling is strongly associated with development of acute coronary syndrome (ACS). The aim of this study was to compare plaque composition of vascular remodeling patterns by an established in vivo tissue characterization method using integrated backscatter (IB)-intravascular ultrasound (IVUS). The study population consisted of 41 consecutive patients who received IVUS prior to percutaneous coronary intervention. Remodeling index (RI) was calculated as the external elastic membrane (EEM) area at the minimal lumen area (MLA) site divided by average EEM area at the proximal and distal reference sites. The patients were divided into two groups based on RI: positive remodeling (PR) defined as RI>1 and non-PR as RI<or=1. A total of 21 areas centered at MLA per lesion site were evaluated by IB-IVUS at 1mm intervals. The occupancy rate of four tissue types within atherosclerotic plaques was compared between the two groups. Percent lipid volume in the PR group (n=20) was significantly greater than the non-PR group (n=21) (40.5+/-14.8% vs. 26.4+/-15.9%, p<0.001). In contrast, % fibrous volume in the PR group was significantly lower than the non-PR group (49.9+/-9.4% vs. 56.1+/-9.6%, p=0.042). Percent dense fibrous volume and % calcified volume were slightly but significantly lower in the PR group compared with the non-PR group (dense fibrous: 6.8+/-5.0% vs. 11.6+/-8.4%, p=0.034, calcified: 2.6+/-2.0% vs. 5.1+/-4.4%, p=0.026). In conclusions, PR lesions contain more lipid-rich and less hard plaque components compared with non-PR lesions, which may account for the higher incidence of ACS and plaque vulnerability.