Graft detachment, a cause of incompetence in stent-mounted aortic valve allografts

The detachment of allograft tissue from supporting stent posts has been a common mode of failure of stent-mounted aortic allografts. In an effort to reduce the localized stress loading on the tissue at the top of the stent posts, two changes were introduced to the previous fabrication protocol followed by Green Lane Hospital. Specifically, they were the use of a flexible acetyl-copolymer stent and covering of the peripheral attachment sutures with a bias strip of Dacron cloth. This study showed that these changes did not reduce the incidence of allograft failure caused by graft detachment. Unexpectedly, covering antibiotic-treated allograft tissue with a bias strip actually increased the likelihood of failure of the valve, by accelerating the biological degradation of the underlying graft aortic wall. The weakened aortic wall tissue was consequently less able to resist the high stress loadings at the top of the stent posts where detachment first occurred.