Histological assessment of a novel restorative coronary artery bypass graft in a chronic ovine model

Background: Although prosthetic conduits for coronary artery bypass grafting (CABG) are increasingly needed because of the limited availability and patency of autologous conduits, no alternatives have succeeded. Methods: Sixteen sheep underwent CABG. Thirteen received a bioabsorbable polymer graft with an incorporated nitinol microskeleton (Xeltis coronary artery bypass graft [XABG]), and three received autologous saphenous vein grafts (SVG). Pathological evaluation was conducted at 12 months. Results: In the XABG group, two sheep died perioperatively; two were sacrificed at 3 months (1 occluded, 1 patent) and two at 6 months (both patent). Two more died from occlusion at 9–10 months, and five survived with patent grafts at 12 months. All SVGs remained patent for 12 months. Histology demonstrated near-complete luminal endothelialization in XABG, with increased polymer adsorption and matrix deposition. The cross-sectional area of the SVG lumen was significantly larger than XABGs (48.2 mm² vs 12.9 mm², p = 0.0018), consistent with a reduced angiographic flow velocity in SVG. The neointimal area was greater in SVGs than XABGs (19.6 vs. 6.7 mm², p = 0.0005), especially at the distal ends of SVGs due to thrombus formation. Conclusion: XABG demonstrated 1-year feasibility with consistent endothelialization and polymer absorption. While SVGs had better patency, they showed greater diametrical irregularity and subsequent neointimal proliferation.