Impact of changes in tissue properties of neointimal tissue of in-stent lesion during excimer laser coronary angioplasty (ELCA) evaluated by integrated-backscatter intravascular ultrasound (IB-IVUS).

Abstract

Excimer laser coronary angioplasty (ELCA) plays an important role in modifying plaque composition, yet its impact on neointimal tissue (NIT) in in-stent restenosis lesions has remained unclear. While integrated backscatter intravascular ultrasound (IB-IVUS) can characterize plaque composition in de novo lesions, its ability to reflect tissue characteristics in NIT is limited due to the distinct structural and acoustic properties of neointimal tissue. This study aimed to investigate the effects of ELCA on NIT using IB-IVUS. We examined 49 in-stent lesions in 49 patients. IB-IVUS analysis focused on a 10 mm segment centered on the minimum lumen area (MLA), with data collected every 1 mm. Color maps were generated based on IB-IVUS backscatter values and included the following classifications: Red (typically calcification in de novo lesions), Yellow (dense fibrosis), Green (fibrosis), Blue (lipid pool), and Purple (lipid pool with attenuation). These classifications are based on tissue characteristics as defined in de novo settings and may differ in in-stent neointimal tissue. We compared Color-Ave (average color-coded area across 11 cross-sections, mm²) and %Color-Ave (relative to neointimal tissue area), before and after ELCA. IB-related values, including mean (Ave-IB) and variance (Variance-IB), were automatically obtained. Following ELCA, Purple-Ave and %Purple-Ave significantly decreased (from 0.95±1.28 mm² to 0.77±1.13 mm², and from 13.5±12.8% to 11.2±11.1%, both p=0.002). %Green-Ave increased significantly (from 53.6±14.1% to 55.5±12.7%, p=0.016), although Green-Ave remained unchanged. No significant changes were observed in Red-, Yellow-, and Blue-code areas. Similar trends were observed in MLA- and volume-based analyses. Ave-IB increased (p=0.028), while Variance-IB decreased (p=0.005). Changes in IB-related values were associated with their pre-ELCA levels. ELCA appears to ablate tissue with high IB-related values, leading to reduced tissue heterogeneity, even in NIT where tissue characterization by IB-IVUS is inherently limited.