The Dura Mater Valve: In Vitro Characteristics and Pathological Changes After Implantation in Calves

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Abstract
Human dura mater valves of various sizes with rigid and flexible stents were tested in an in vitro pulsatile mock circulatory system. A 22 mm flexible stent valve incorporating a new fabrication technique showed almost the same pressure gradient as a 28 mm rigid stent valve. The backflow/stroke volume ratio was about 4% at a net flow of 10 l/min. Rigid stent-mounted dura mater valves (105) were used in 51 pump implantations for up to 316 days. Collagen fiber degeneration began 3 mo. after implantation. Microscopic and macroscopic calcification of the valve tissue was seen in 8 of 105 valves, giving an overall incidence of 7.6%. The calcified degeneration was dystrophic in nature, not accompanied by cellular reactions and was seen in the areas of the valve under stress. The degenerative changes were more severe in the left side than in the right side of the total artifical heart. Mechanical damage to the tissue may be important in the pathogenesis of calcification.