Extension of durability of jellyfish valve for long-term use in artificial hearts

Background: A chronic animal experiment of over 300 days in which jellyfish valves were incorporated into conventional sac-type blood pumps revealed fracture and calcification on the thin flexible leaflet. The aim of the present study was to make clear the cause of these problems from an engineering point of view, with the goal of facilitating longer durability (a guarantee of approximately 1 year) of the jellyfish valve. Design improvement of jellyfish valve: Finite element analysis of the closed phase of the jellyfish valve indicated that the mechanical strain generated on the leaflet was a prominent cause of fracture and calcification, as found in the animal experiment. Moreover, further analysis suggested that incorporation of an additional concentric ring into the valve seat would be effective in reducing strain concentration. In vitro steady and pulsatile flow tests demonstrated that a modified valve with a 0.5 mm-wide ring located at a radius of 7.0 mm had a comparable hydrodynamic performance to the original jellyfish valve. Durability tests: A commercially available accelerated fatigue tester was employed; tests revealed that the durability of the modified valve had been extended beyond that of the original jellyfish valve by 10 times. Animal experiment: By means of conventional sac-type blood pumps and undulation pump total artificial hearts, 13 animal experiments have been performed. The modified jellyfish valve showed excellent blood compatibility after a minor modification of the configuration of the valve seat at the attachment of the leaflet. Conclusion: The modification of this polymer valve shows great promise for clinical artificial heart application.