Modification of the descending thoracic aortic anastomotic site using biodegradable felt: Study in a canine model with or without basic fibroblast growth factor

ObjectivesWe investigated the outcomes of reinforcing anastomotic sites using (1) nonbiodegradable polytetrafluoroethylene (PTFE) felt, (2) biodegradable polyglycolic acid (PGA) felt, and (3) PGA felt with basic fibroblast growth factor (bFGF) in a canine descending thoracic aortic replacement model.MethodsThirty-seven beagles underwent descending thoracic aorta replacement using a prosthetic graft with one of the above-mentioned reinforcements or no reinforcement for controls. Histologic evaluations were carried out 1 month and 3 months after surgery. The biomechanical strength of the anastomosis was assessed along the longitudinal axis of the aortic segments using a tensile tester. Local compliance at the anastomotic site was also evaluated in the circumferential direction.ResultsThe media was significantly thinner in the PTFE group than in the control group (65.8% ± 5.1% vs 95.0% ± 9.3% of normal thickness; P < .05). Relative to the control group, the adventitial layer was significantly thinner in the PTFE group (42.3% ± 8.2% of control; P < .05) but significantly thicker in the PGA and the PGA + bFGF groups (117.2% ± 11.3% and 134.1% ± 14.2% of control, respectively; P < .05). There were more vessels in the adventitial layer in the PGA + bFGF group than in the control, PTFE, and PGA groups (29.2 ± 2.1/mm2 vs 13.8 ± 0.8, 5.4 ± 0.7, 17.0 ± 1.3/mm2, respectively; P < .01). There were no significant differences between the four groups in the failure force at anastomotic sites. Local compliance at the anastomotic site was higher in the PGA group than that in the PTFE group (11.6 ± 1.6 10−6 m2/N vs 5.6 ± 1.9 10−6 m2/N; P < .05).ConclusionReinforcement of the experimental aortic wall with PTFE felt resulted in thinning of the media and adventitia and fewer vessels at the anastomotic site. These histologic changes were not observed when biodegradable felt was used. The bFGF failed to augment the modification of the aortic wall with the exception of increased adventitial vessel number. Biomechanical strength of the anastomosis along the longitudinal axis was comparable in all four groups; however, local vascular compliance was better in the biodegradable PGA felt group.

Clinical RelevanceThis investigation was conducted to extend our previous investigation on a biodegradable felt strip into more practical form before we proceed in a clinical application of the new material. We hypothesized that sustaining compression of the aorta by the nonbiodegradable felt strip may cause structural derangement and local ischemia on the aortic wall, which may lead to occurrence of late postoperative false aneurysm after aortic surgery. We attempted to find a clue for preventing adverse effects of reinforcement with a conventional felt strip. We have found that biodegradable felt prevented thinning of both the media and adventitia and increased adventitial vessels with increased vascular compliance at the aortic anastomotic sites.