Effect of altered hydration on the internal shear properties of porcine aortic valve cusps

Background. Dehydration of tissue due to glutaraldehyde fixation has been r eported and was examined in this study of porcine aortic valve cusps. The e ffect of altered hydration on cusp internal shear properties was also exami ned. Methods. Hydration level was assessed by wet mass measurement of cusps stor ed in solutions for times up to 1000 minutes. Solutions used in this study included Hanks solution, porcine blood, 0.5% glutaraldehyde, and several de xtran solutions. Shear testing was performed on physiologically hydrated, s uperhydrated, and dehydrated cusps. Results. There was very little difference between the physiologic and super hydrated leaflets; however, dehydration caused significant stiffening with increased hysteresis and stress relaxation. Conclusions. Glutaraldehyde has been shown to increase shear stiffness of v alve cusps. Tissue dehydration also increased shear stiffness but increased stress relaxation and hysteresis, which was contrary to observations repor ted after glutaraldehyde fixation. The significant effect of dehydration on cusp mechanical properties does not account for the effects observed after glutaraldehyde fixation, but it demonstrates that hydration level is an im portant factor that affects internal shear properties of valve cusps. (C) 2 001 by The Society of Thoracic Surgeons.