The effect of valve type and drive line dP/dt on hemolysis in the pneumatic ventricular assist device.

The objective of this experiment was to investigate the relationship between blood damage and drive line dP/dt and valve type in the pneumatic ventricular assist device. Two mock circulatory loops were assembled using 70-ml Penn State pneumatic ventricular assist devices, one fitted with convexo-concave (CC) valves and one fitted with monostrut (MS) valves. Use of a compliance chamber established three ranges of drive line dP/dt values. Using bovine blood and the methods of generalized estimating equations, it was found that drive line dP/dt was significantly associated with the index of hemolysis (p = 0.00): the lower drive line dP/dt values yielded lower indices of hemolysis. In addition, this association differed between MS and CC valves (p = 0.01); the MS valves consistently yielded a higher index of hemolysis than the CC valves across all drive line dP/dt ranges. However, the relative hemolytic potential of each valve type became much closer at low drive line dP/dt values (2,000-3,000 mm Hg).