Evaluation of in vitro hemolysis and platelet activation of a newly developed maglev LVAD and two clinically used LVADs with human blood

Abstract

In vitro hemolysis testing remains one of the most important performance measures to judge the hemocompatibility of a left ventricular assist device (LVAD). Clinically relevant operating conditions and appropriate testing blood are essential to infer in vitro data for potential clinical use. This in vitro study was carried out to evaluate and compare the hemolytic performance of a newly developed magnetically levitated (maglev) LVAD (CH-VAD) with two clinically used LVADs (HVAD and HeartMate II (HMII)) using fresh human blood. A small volume (~300 mL) in vitro circulating flow loop was constructed with a LVAD generated flow of 4.5 L/min at the nominal or reported clinical operating speed for each LVAD. The blood was circulated in the loop for 4 hours with samples drawn at baseline and hourly. Plasma-free hemoglobin (PFH) concentrations in the hourly blood samples were determined with spectrophotometry. Normalized index of hemolysis (NIH) was calculated to compare the hemolytic performance of the CH-VAD and the two reference LVADs. Platelet activation was measured with flow cytometry. The experimental test for each device was repeated at least 7 times. The data from this study showed that all the three LVADs generated very low hemolysis (NIH <0.01 g/100 L). The CH-VAD was found to have a significantly lower NIH value (0.00135 ± 0.00032 g/100 L) compared to the HVAD (0.00525 ± 0.00183 g/100 L) and the HMII (0.00583 ± 0.00182 g/100 L). No statistically significant difference in device-generated hemolysis was found between the HVAD and the HMII. The level of platelet activation induced by the CH-VAD is significantly lower than those by the HVAD and the HMII. The data suggest that the shear-induced hemolysis and platelet activation of the CH-VAD are acceptable relative to the two LVADs currently in clinical use.

Keywords: hemocompatibility; hemolysis; left ventricular assist device; magnetically levitated blood pump.

Figure 1

The inner structures of the CHVAD (A), the HVAD (B) and the HeartMate II (C).

Figure 2

Photograph of the pumps of the CHVAD, the HVAD and the HeartMate II.

Figure 3

The H-Q curves of CH-VAD. The water-glycerin mixture with a viscosity of 0.0035 Pa.s was used in H-Q curve measurement.

Figure 4

Photograph of the small volume circulating flow loop with a test LVAD.

Figure 5

The comparison of hematocrit (A), platelet (B) and white blood cell (C) count of the blood samples from the circulating flow loops over 4 hours for the three study LVADs.

Figure 6

The comparison of mean PFH concentration in the baseline blood sample and the hourly collected samples (A) and the NIH values for the three study LVADs (B).

Figure 7

Representative dot plots of the flow cytometry compensation data using beads labeled with V450 CD41a (A) and FITC-PAC-1 (B) antibodies, respectively, the gating strategy for platelet identification (C), and the comparison of platelet activation in the baseline blood sample and hourly collected samples for the three study LVADs. The platelet activation is indicated by the activation of platelet surface receptor GPIIb/IIIa (PAC-1) (D).

Figure 7

Representative dot plots of the flow cytometry compensation data using beads labeled with V450 CD41a (A) and FITC-PAC-1 (B) antibodies, respectively, the gating strategy for platelet identification (C), and the comparison of platelet activation in the baseline blood sample and hourly collected samples for the three study LVADs. The platelet activation is indicated by the activation of platelet surface receptor GPIIb/IIIa (PAC-1) (D).