Freeze-Drying Effect on the Hydrodynamic Performance of Bovine Pericardium Biological Valves

Freeze-drying is a process that allows biological tissues and tissue based devices such as biological valves to be stored dry, making their storage more convenient. The purpose of the present work is to evaluate the alterations in hydrodynamic performance of biological prosthetic valves after freeze-drying. Bovine pericardium biological heart valves with 25 mm obtained from two manufacturers were tested on a pulse duplicator (5.0 L/min) before and after freeze-drying. The instantaneous signals of pressures and flows were recorded simultaneously with images of opening and closing of the valves. The results show that freeze-drying did not caused significant modifications in transvalvular pressure gradients (12 ± 3 and 11 ± 2 mmHg), effective orifice areas (1.4 ± 0.2 and 1.5 ± 0.1 cm2) and regurgitation fractions (5 ± 2 and 6 ± 3%), respectively, considering devices produced by the same manufacturer. Our findings show that the lyophilization process did not significantly modify the performance of the prostheses tested, suggesting the process can be applied to bovine pericardium. Further investigation is necessary to evaluate the influence of lyophilization in fatigue and the long term performance of prosthetic heart valves.