Silk fibroin (SF) is well known to be biocompatible, degradable, and nontoxic. In this study, SF was impregnated into a porous polyester graft (InterVascular external velour, InterVascular, Inc., La Ciotat, France), 8 mm in diameter. The SF-impregnated graft was investigated in vitro and in vivo to evaluate its potential for use as a new vascular graft impervious to blood, while retaining high porosity for tissue ingrowth and biological healing. For in vitro investigation, the water permeability, coating weight, morphology, and mechanical properties of the SF-impregnated grafts were compared with collagen-coated grafts (InterGard grafts, InterVascular, Inc.). The water permeability of the controls (1388 +/- 30.5 mL/cm(2)/min at 120 mm Hg) was reduced >99% by SF impregnation, rendering the graft impervious to blood. The coating weight of the collagen was 117 +/- 22 mg/g of graft, producing a slightly lower value than the InterGard prosthesis (302 +/- 23 mg/g). For the in vivo experiment, six SF-sealed vascular grafts were implanted in the abdominal aorta of dogs for scheduled periods ranging from 4 h to 6 months. Commercial collagen-impregnated grafts (InterGard) and untreated external velour grafts (InterVascular) were also implanted for scheduled periods ranging from 1 to 6 months for comparison. Gross observation of the explanted grafts and histological examination of the representative sections were conducted for two types of grafts using a light microscope after hematoxylin-eosin staining. These SF-impregnated grafts showed less foreign body and inflammation reactions, and the SF layer was almost completely absorbed. The average of the values in each period for the SF grafts was 48% neointima at 1 month, 85% at 3 months, and 97% at 6 months, whereas those of the InterGard prostheses was 34, 46, and 90%, respectively. This study demonstrated that the use of a biodegradable SF as biological sealant can be a feasible approach to prepare impervious textile arterial prostheses. The SF-impregnated graft showed less thrombogenesis and induced host cell migration along the matrix without foreign body or inflammatory reactions. Moreover, it appears to facilitate the development of endothelial-like cells.

The risk factors for in-hospital mortality and mid-term survival in patients undergoing composite graft replacement of the aortic root with reimplant or coronary arteries by a modified button technique were evaluated with special emphasis on the underlying aortic pathology. Between 1985 and 1993 74 patients underwent replacement of the ascending aorta and the aortic valve following a modified button technique. The patients were divided into three groups according to aortic pathology: annuloaortic ectasia (43.58%), type A dissection (18.24%), and miscellaneous (13.18%). In-hospital mortality rates were 4.7%, 33.3% and 23.1%, respectively (P = 0.011). Univariate analysis showed that aortic pathology, NYHA class, emergency operation, redo operation, acute aortic dissection, preoperative cardiogenic shock, preoperative cardiac tamponade, longer cardiopulmonary bypass (CPB) and aortic cross-clamp times, and the need of femoral vein or femoral artery cannulation at intervention had univariate influence on in-hospital mortality. Multivariable stepwise logistic regression analysis identified CPB time odds ratio (OR) = 1.021/min, P = 0.007), the need of femoral vein cannulation at intervention (OR= 4.85, P = 0.008) and preoperative cardiac tamponade (OR = 3.11, P = 0.07) as independent predictors of in-hospital death. Follow-up ranged from 1 to 98 months (mean 39 +/- 30 months) with an actuarial survival rate of 75 +/- 9%, 52 +/- 13% and 67 +/- 14% at 5 years in annuloaortic ectasia, type A dissection, and miscellaneous patients, respectively (P = 0.18); when survival was evaluated in hospital survivors only, Kaplan-Meier survival rates were 77 +/- 9%, 79 +/- 14% and 89 +/- 10% at 5 years (P = 0.87). Comparing survival of annuloaortic ectasia patients (5-year survival 75 +/- 9%) versus survival of all other patients pooled together (5-year survival 55 +/- 11%), there was a statistically significant difference (P < 0.05); such a difference was no longer significant when comparing hospital survivors alone (5-year survival rate 77 +/- 9% annuloaortic ectasia patients vs 79 +/- 12% all other patients P = 0.61). Although aortic root replacement carries higher in-hospital mortality in some high-risk subgroups of patients, mid-term survival seems to be less affected by aortic pathology; high-risk patients are expected to have an out-hospital outcome comparable to the low-risk ones.