In vitro study on the hemocompatibility of plasma electrolytic oxidation coatings on titanium substrates.

Passively levitated ventricular assist devices (VADs) are vulnerable to impeller-housing contact and could benefit from surface coatings that improve wear resistance. Such coatings can be manufactured by plasma electrolytic oxidation (PEO), but their suitability for blood-contact applications needs further investigation. We therefore compared blood-surface interactions of polished titanium grade 5 (Ti Gr 5), as a general VAD reference material, uncoated ground titanium grade 4 (Ti Gr 4) and two commercially available PEO coatings on Ti Gr 4. In n = 4 static platelet adhesion tests, material samples were incubated with platelet-rich plasma (PRP) and consecutively analyzed for adhesive platelets by immunofluorescence microscopy. Additionally, PRP supernatant of incubated material samples was analyzed for changes in antithrombin III and fibrinogen concentrations by turbodimetry and enzyme-linked immunosorbent assay, respectively. We could not find any significant differences between the materials in the analyzed hemocompatibility markers (P > .05). Thus, we conclude that PEO coatings might offer a similar hemocompatibility to that of polished Ti Gr 5 and uncoated Ti Gr 4. Nevertheless, future studies should investigate blood-surface interactions of PEO coatings under realistic VAD-related flow conditions to better evaluate their potential for VAD applications.

In vitro thrombogenicity evaluation of rotary blood pumps by thromboelastometry.

In vitro thrombogenicity tests for rotary blood pumps (RBPs) could benefit from assessing coagulation kinematics, as RBP design improves. In this feasibility study, we investigated if the method of thromboelastometry (TEM) is able to assess coagulation kinematics under the in vitro conditions of RBP tests. We conducted in vitro thrombogenicity tests (n=4) by placing Deltastream® DP3 pumps into test loops that were filled with 150 mL of slightly anti-coagulated porcine blood, adjusted to an activated clotting time (ACT) well below clinically recommended levels. Blood samples were taken at certain time points during the experiment until a continuous decrease in pump flow indicated major thrombus formation. Blood samples were analyzed for ACT, platelet count (PLT), and several TEM parameters. While visible thrombus formation was observed in three pumps, ACT indicated an ongoing activation of coagulation, PLT might have indicated platelet consumption. Unexpectedly, most TEM results gave no clear indications. Nonetheless, TEM clotting time obtained by non-anticoagulated and chemically non-activated whole blood (HEPNATEM-CT) appeared to be more sensitive for the activation of coagulation in vitro than ACT, which might be of interest for future pump tests. However, more research regarding standardization of thrombogenicity pump tests is urgently required.

Miniaturized Test Loop for the Assessment of Blood Damage by Continuous-Flow Left-Ventricular Assist Devices.

Although the hemocompatibility of left-ventricular assist devices (LVADs) has continuously improved, assessment of hemolysis remains mandatory in pre-clinical testing. The ASTM-F1841 has standardized this assessment since 1997. However, the recommended usage of fresh, non-pooled human blood is hardly feasible with the test loop volume specified therein, when testing the device under test versus a predicate device as required by the international standard 10993-4. In this study, we compared ASTM-conforming (ASTM) and downscaled (mini) test loops with a one-third priming volume for the assessment of blood damage at the ASTM operating point. Blood damage was assessed for HeartMate 3 and BPX-80 in 6 experiments with heparinized porcine slaughterhouse blood for 6 h. We analyzed plasma free hemoglobin (pfHb), von Willebrand factor (vWF) concentration and collagen-binding functionality and calculated indices of hemolysis and vWF-ratios. The mini test loops provided significantly higher pfHb increase and consistently stronger vWF-ratio decrease and yielded a significantly better differentiation of the pumps. Interestingly, indices of hemolysis were generally lower in the mini set-up, indicating less adverse effects by the mini loop itself. Thus, we propose our mini test loop as suitable tool for clinically relevant standardized assessment of blood damage by future LVADs with single-donation human blood.