In-Vitro Hemocompatibility Evaluation of the HeartMate 3 Under Realistic Operating Conditions

Operating conditions significantly influence hemolysis generation in rotodynamic blood pumps (RBPs). Previous experiments conducted under constant operating conditions have demonstrated that lower flow rates are associated with a higher normalized index of hemolysis (NIH). However, in clinical scenarios, the pump flow rate fluctuates in response to the residual cardiac function. This study aims to investigate the effects of various pulsatile operating conditions on hemolysis generation and von Willebrand Factor (vWF) degradation of RBP.

To investigate these conditions, pulsatile flow experiments were conducted for 12 hours using HeartMate 3 (HM3, Abbott Inc, USA) in a hybrid mock circulatory loop with citrated human blood from hemochromatosis patients. Three operating conditions (high, low, and no residual cardiac function) were examined under two pump speed settings: normal (5400 rpm, 4.3 L/min) and low (4800 rpm, 2.5 L/min). Hemolysis was assessed by measuring delta free hemoglobin every 30 minutes (dfHb_{30 min}) and calculating NIH. High molecular weight (HMW) vWF multimer degradation was assessed using immunoblotting.

There was no significant difference in dfHb_{30 min} (p>0.388), NIH (p > 0.382), and HMW vWF multimers degradation (p > 0.364) between the three operating conditions, but differences in these parameters were observed between the normal and low speed settings. Meanwhile, a consistent trend in the hemolysis outcomes was observed with slightly elevated hemolysis in no and high pulsatility conditions of both speed settings.

Hemocompatibility of the HM3 is not significantly affected by periodic high/low flow or backflows through the pump in in-vitro evaluation but rather by the pump operating condition: flow rate and pump speed.