CORONARY-BYPASS GRAFTING WITH BIOLOGICAL GRAFTS IN A CANINE MODEL

Background Poor patency rates have limited the success of biological v ascular grafts in the coronary artery position. Recently, two bovine i nternal mammary arterial grafts have been developed for possible use a s coronary artery bypass graft (CABG) conduits: (1) Denaflex grafts (B axter Healthcare Co, 3-mm ID) treated with polyepoxy compounds and wit h heparin ionically bound to the luminal surface and (2) Bioflow graft s (Bio-Vascular, Inc, 3-mm ID) treated with dialdehyde starch. Methods and Results Thirty dogs underwent CABG with either a Denaflex (n=20) or Bioflow (n=10) graft to the left circumflex coronary artery (LCx). The left main coronary artery (n=12) or proximal LCx (n=18) was then l igated. Six-month patency (Kaplan-Meier) for Denaflex grafts was 44+/- 13% (+/-SEM), compared with 12+/-11% for Bioflow grafts, but this diff erence did not reach statistical significance (P=.56). Among grafts op en at 14 days, however, there were no occlusions among six Denaflex gr afts versus five occlusions among seven Bioflow grafts. At 6 months, a ll six surviving Denaflex grafts appeared normal, while the only remai ning patent Bioflow graft was angiographically dilated and had diffuse luminal irregularities. At 1 year, three Denaflex grafts angiographic ally had no dilation, stenosis, or luminal irregularities. Macroscopic ally, all explanted long-term (6 to 12 months) Denaflex grafts had a s mooth, clean luminal surface, whereas the only patent Bioflow graft ha d multifocal thrombi. Microscopically, all Denaflex grafts had minimal degenerative changes, but the Bioflow graft had transmural linear cra cks and medial deterioration. Conclusions These data suggest that long -term (>6 month) patency is possible with small-caliber, low-flow biol ogical grafts in the canine coronary position, although both types of grafts are prone to early occlusion. If these early failures are exclu ded, the Denaflex graft appears to be associated with better long-term patency and an absence of degenerative changes.