Ventricular assist device with built-in trileaflet polyurethane valves

Summary

A diaphragm-type ventricular assist device (VAD) with one-piece conduit valves made of polyurethane (PU) was developed and its hydrodynamic function, durability, and antithrombogenicity were evaluated.

The mock-loop test indicated that as a result of rapid closure of the leaflet, a pump with the PU valves yielded equivalent output to that of ordinary Björk-Shiley (BS) valves, although a pressure gradient across the PU valves was higher than with BS valves. A durability test, using an accelerated fatigue tester of disk-rotating type, proved that failure occurred in 5% of cases after 2.6 million cycles, corresponding to 1 month’s pumping. Fourteen PU valves with the leaflet thickness of 0.30 mm were used for four animal experiments. The animals were divided into two groups: a high-bypass flow group (3.5–4.51/min) and a low-flow group (1.8–2.5 1/min). When a thrombus was detected, the pump was changed. In the high-flow group, thrombi on the pump inlet side appeared on the 8th, 16th, and 17th pumping days, while there was no thrombus on the pump outlet side over the same period. Conversely, at the low-flow rate, thrombus formation was found almost simultaneously at the pump inlet and outlet in three of four pairs of valves, on the 5th, 13th, and 25th pumping days. In conclusion, a pump with our prototype PU valves has adequate hydrodynamic performance and acceptable durability for 1 month. Although the antithrombogenicity of the present model was not satisfactory, improvement of the design should upgrade the in vivo performance.