P5630Morphometric and qualitative differences in neointimal tissue six months after implantation of bioresorbable scaffolds versus conventional everolimus eluting stents in ISAR-Absorb MI trial
Authors: Rai H , Alfonso F , Maeng M , Bradaric C , Wiebe J , Cuesta J , Christiansen E H , Bohner J , Hoppmann P , Colleran R , Schneider S , Laugwitz K L , Kastrati A , Byrne R A 
Published: October 2019

Abstract

Background
Bioresorbable scaffolds (BRS) are novel devices designed to overcome the long-term limitations of permanent metallic stent implantation. Optical coherence tomography (OCT) surveillance can provide important insights on the process of vessel wall healing at follow-up.

Purpose
We sought to compare OCT-assessed healing at 6 months after implantation of everolimus-eluting BRS and everolimus-eluting metallic stents (EES) in patients treated for acute myocardial infarction (AMI).

Methods
ISAR-Absorb MI is a multicentre, 2:1 randomized trial comparing outcomes of patients with AMI stented with BRS or conventional EES. Angiographic surveillance was planned for all patients at 6–8 months follow-up. Patients who had OCT surveillance at follow-up were included for the present analysis. Analysis of contiguous OCT cross-sections- 1 mm apart was performed at a centralized core laboratory. Tissue characterisation using a 256-level grey-scale signal intensity (GSI) analysis was also performed for all neointimal regions of interest (ROI) with thickness of 100 to 400 μm. ROI's were classified as mature using a standard cut-off GSI score of 109.7. Generalised linear mixed model (GLMM) was used as appropriate. Statistical analysis was performed using R software. Data is presented as numbers, percentages or median (Interquartile range, IQR).

Results
Median follow-up interval was 216 days. 70 patients in the BRS arm and 33 patients in the EES arm were available for analysis. Stented length was 19.8 mm (13.6, 24.5) and 22.3 mm (16.7, 26.4) in BRS and EES arms respectively (p=0.73). Minimum lumen area [5.13 (3.95, 6.71) vs. 4.83 (3.63, 6.92) mm2] and minimum stent area [5.78 (4.88, 7.34) vs. 6.36 (4.70, 7.45) mm2] were comparable between BRS and EES.
2,262 frames (1,529 in BRS, 733 in EES) with 20,033 struts (12,704 in BRS, 7,329 in EES) were assessed. Overall strut coverage was better with BRS compared to EES (97.5% vs. 91.1% respectively, p<0.001). Malapposed (1.1% vs. 0.5%, p=0.54) and uncovered struts (7.3% vs. 1.3%, p<0.001) were more common with EES. Neointimal coverage was comparable amongst both stent groups [85.5 (61.9, 124.1) vs. 71.5 (33.4, 133.0) μm in BRS and EES groups respectively, p=0.50].
GSI analysis in 95 cases (65 cases, 2,233 ROIs in BRS; 30 cases, 1,210 ROIs in EES) showed that immature ROIs were numerically more common in the EES group as compared to the BRS group (75.4 vs. 57.0% respectively; p=0.35).
Two-year clinical follow-up and analysis of correlation of clinical outcomes with OCT findings will also be available for presentation at ESC Congress 2019.

Conclusions
In selected patients undergoing OCT imaging at 6–8 months after implantation of BRS and conventional EES for AMI, we observed generally favourable healing characteristics with high rates of strut coverage, low rates of strut malapposition and fewer areas of immature neointimal areas with BRS in comparison to EES.

Acknowledgement/Funding
The study was predominantly funded by Deutsches Herzzentrum München and in part by a grant from Abbott Vascular