Effect of dynamic fixation parameters on the viscoelastic properties of bioprosthetic porcine aortic heart valve tissue

Premature failure of implanted commercial bioprosthetic aortic heart valves has been associated with the reduction in the natural shearing ability of the valve cusp tissue after conventional low pressure static glutaraldehyde fixation. Dynamic fixation in 0.5% glutaraldehyde at variable pulsation rates (1-10 Hz) and pressures (0-40 mmHg) was investigated as a technique that may preserve the natural shearing ability of the tissue by reducing interfibre crosslinking. When tested in our high speed materials testing system, the dynamically-fixed tissue was observed to relax more quickly (mean ±S.D.)(-7.4±0.7% stress remaining per log(second)) (n=5) than the conventionally statically fixed (-3.9±1.7% log(s)^-1 )(n=5) and similar to the fresh material (-6.7%±1.2% log(s) ^-1)(n=7), Denaturation temperatures suggest greater internal crosslinking and thermostability for dynamically fixed valves (89.4±0.5°C)(n=4) compared to the statically fixed (83.5±0.3°C)(n=4) or fresh tissue (65.6±0.8°C)(n=4)(p<0.05). This technique appears promising in that a tissue with micromechanics closer to that of the natural aortic valve is produced