Hemolysis associated with Impella heart pump positioning: In vitro hemolysis testing and computational fluid dynamics modeling

Introduction: Short-term mechanical circulatory support devices provide temporary hemodynamic support in heart failure and are increasingly used to enable recovery or as a bridge to decision. Blood damage with mechanical circulatory support devices is influenced by many factors, including the magnitude and duration of shear stress and obstruction to blood flow. This study aimed to evaluate the effects of the Impella CP (R) heart pump positioning on hemolysis using in vitro hemolysis testing and computational fluid dynamics modeling. Methods: The in vitro hemolysis testing was conducted per the recommended Food and Drug Administration and American Society for Testing and Materials guidelines. The bench hemolysis testing and computational fluid dynamics simulation analysis were performed for both normal operating (outlet unobstructed) and outlet-obstructed condition of Impella CP (mimicking outlet on the aortic valve due to improper positioning). Results: The modified index of hemolysis was 2.78 +/- 0.69 at normal operating conditions compared to 18.7 +/- 7.8 when the Impella CP outlet was obstructed (p = 0.002). Computational fluid dynamics modeling showed about three times increase in exposure time to regions of high shear stress when the Impella CP outlet was obstructed compared to unobstructed condition, thus supporting the experimental observations. Conclusion: Based on these results, it is recommended to ensure proper placement of Impella CP via regular monitoring using echocardiographic guidance or other methods to minimize the risk of hemolysis associated with an obstructed outflow.