Pump-Induced Hemolysis of Speed Modulated Axial-Flow Left Ventricular Assist Devices.

Background: Reduced arterial pulsatility during continuous-flow left ventricular assist device (LVAD) support is associated with certain adverse events. An approach to increase arterial pulsatility is pump speed modulation. Therefore, this in vitro study compares the pump-induced hemolysis of constant speed and modulated speed modes for two different axial-flow LVADs. Furthermore, the hemolytic performance of both LVADs is compared.

Methods: Two Sputnik1 and two HeartMate2 (HM2) axial-flow LVADs were operated simultaneously for 6 h in automated hemolysis test benches (n = 7 for each mode). Rectangular speed patterns with modulation rates of 70 and 140 bpm were investigated. Speed modulation amplitudes provided head pressures between 80 and 120 mmHg. To quantify hemolysis, plasma-free hemoglobin was determined every hour and the modified index of hemolysis (MIH) was calculated.

Results: Speed modulation increased all MIH values of the Sputnik1 LVADs, but decreased most MIH values of the HM2 LVADs compared to the constant speed mode. However, significant differences were only observed for one Sputnik1. Furthermore, the Sputnik1 pumps induced lower MIH levels compared to the HM2 pumps using constant speed mode.

Conclusions: It seems that the HM2 can be operated in speed modulation mode without an increased risk of hemolysis. However, for the Sputnik1, the potential benefits of speed modulation must be balanced against the risk of increased hemolysis. The underlying causes need to be investigated in future studies using computational fluid dynamics. Furthermore, using the clinically established constant speed mode, it appears that the Sputnik1 will cause fewer hemolytic issues than the HM2.