Remodeling Index Compared to Actual Vascular Remodeling in Atherosclerotic Left Main Coronary Arteries as Assessed With Long-Term (≥12 Months) Serial Intravascular Ultrasound Original Research Article

Objectives We present the remodeling index (RI) versus serial intravascular ultrasound (IVUS) data. Background The RI, derived by comparing lesion external elastic membrane (EEM) cross-sectional area versus the reference at one time point, is used in various IVUS studies as a substitute of true remodeling (change in EEM over time), assuming that it represents true remodeling. Methods We studied 46 non-stenotic left main arteries using serial IVUS (follow-up 18 ± 8 months). Plaques were divided into subgroups according to the follow-up RI: follow-up RI >1 (n = 27) versus follow-up RI ≤1 (n = 19). Results Lesions with a follow-up RI >1 had an increase in lumen despite an increase in plaque because of an increase in EEM. Conversely, lesions with a follow-up RI ≤1 had a reduction in lumen as a result of both a plaque increase and EEM decrease. Overall, the follow-up RI correlated directly with changes in lesion site EEM (baseline-to-follow-up). Although there was no correlation between the follow-up RI and changes in reference EEM area, changes in reference EEM area did correlate directly with changes in lesion EEM area. In nearly 90% of lesions with a follow-up RI >1, there was a previously documented increase in EEM area. Using multivariate linear regression analysis, the follow-up RI was dependent on the baseline RI, the increase in lesion EEM area, and the decrease in reference EEM area. The follow-up RI was not dependent on changes in lesion plaque area. Conclusions The vast majority of left main lesions with a remodeling index >1 had evidence of a previous increase in lesion-site EEM area.