A Red Blood Cell Model to Estimate the Hemolysis Fingerprint of Cardiovascular Devices

One of the most relevant and open issues within cardiovascular prosthetic hemodynamic performance is a realistic quantification of the damage sustained by red blood cells (RBCs). Specifically, the optimal design of bileaflet mechanical heart valves (BMHVs) requires both low shear stresses along the leaflets and short particle resident times. This study approaches RBC damage estimation by developing a numerical model of RBCs and computing the damage sustained by a set of passive RBCs immersed within in vitro flows. The RBC is modeled as an ellipsoidal shell with size dependent on age. Mechanically, a viscous hyper-elastic model was adopted to compute the stress-deformation transmitted by the experimental flow field to the RBC layer. The rupture parameters were calibrated using experimental results on real RBCs submitted to Couette flow. Moreover, the integrated hemolysis index (HI) through a BMHV was computed for a set of RBCs injected in a flow field derived from an in vitro study and for multiple RBC passages. The main results are (1) a good capability of the RBC model to replicate in vitro experiments performed with real RBCs, finding realistic rupture parameters; (2) the spatial distribution for the HI, maximal along the leaflet boundary layer and for long resident times; (3) 90% of HI is produced by the less damaging trajectories, which are favored by local flow dynamics; (4) cumulated HI in 8 days is about 0.01% smaller than the clinical warning threshold, the latter being obtained only after a period of time comparable with the RBC lifetime.