Intravascular ultrasound analysis of arterial remodeling in the double-injury swine coronary artery model of restenosis.

Background: Vascular remodeling is a major component of atherosclerotic and restenotic processes. The aim of this study was to evaluate remodeling at two different axial loci in a restenotic (double-injury) coronary artery model in the hypercholesterolemic minipig.

Methods: The cross-sectional area (CSA) of the lumen, artery and neointima following a single stenotic injury (SI) and second restenotic injury (RI) was measured by serial intravascular ultrasound (IVUS). IVUS CSAs were determined before, immediately after and 4 weeks after each injury. Analyses were performed at two selected axial loci, defined as: 1) locus of the minimal luminal area (MLA) 4 weeks after SI (measured immediately prior to the RI); and 2) locus of the MLA at 4 weeks after RI. Loci were selected to mimic diverse approaches used in studies of remodeling.

Results: Restenotic remodeling, defined by locus 1, was unchanged 4 weeks following the RI and neointima formation accounted for the chronic lumen loss. In contrast, constrictive remodeling was the prominent arterial response defined by locus 2. Regardless of the MLA analysis, artery wall enlargement occurred in more than half of the pigs at 4 weeks following the SI. Balloon/artery ratios were comparable during the two injuries and could not account for observed differences in remodeling. Remodeling results obtained by comparison of artery CSA to a reference CSA differed from serial IVUS analysis.

Conclusions: In the presence of a pre-established stenosis, vascular remodeling depends on the axial locus of interest. In contrast, remodeling following injury of a naïve artery is independent of defined axial locations used here and is predominantly one of outward remodeling.