Multidimensional Flow Cytometry for Testing Blood-Handling Medical Devices

Blood handling devices such as left ventricular assist devices and total artificial hearts offer life-saving treatments for patients suffering from severe heart failure. Current devices have clinically proven that heart assist pumps are a safe and effective therapy, and indeed in many cases they are the only available method of treatment. However, current devices cause side effects including stroke, bleeding, infection, and thrombosis, preventing the technology from reaching its full potential. If the side effects could be reduced, then more patients could benefit from these devices. The complications are related to damage to blood cells and proteins as a result of contact with foreign materials and mechanical stress. There is a need for better devices with minimal blood impact to enable more patients to be safely treated; better tools, especially flow cytometry, could support the device development life cycle. In this chapter we review the clinical, in vivo, and in vitro flow cytometry data available for ventricular assist devices, conduct a gap analysis, and identify areas of future possibilities for device developers to establish new flow cytometry-based methodologies

Leukocyte deformation in cardiac assist devices

Ventricular Assist Devices (VADs) are pumps which support failing hearts. While considered by some surgeons as gold standard treatment, current VADs have many complications related to the imposed stress on the blood. In particular, damage to the leukocytes may contribute to infections, currently the biggest post-surgical problem. Our aim was to create a numerical model of a leukocytewhich can be used to investigate leukocyte deformation in VADs. The leukocyte was modelled as a compound liquid droplet and solved in OpenFOAM using the multiphaseInterfoam solver. Initial results are presented for different shear rates, extensional versus planar shear, and for different nucleus sizes

The Inflammatory Response to Ventricular Assist Devices

The therapeutic use of ventricular assist devices (VADs) for end-stage heart failure (HF) patients who are ineligible for transplant has increased steadily in the last decade. In parallel, improvements in VAD design have reduced device size, cost, and device-related complications. These complications include infection and thrombosis which share underpinning contribution from the inflammatory response and remain common risks from VAD implantation. An added and underappreciated difficulty in designing a VAD that supports heart function and aids the repair of damaged myocardium is that different types of HF are accompanied by different inflammatory profiles that can affect the response to the implanted device. Circulating inflammatory markers and changes in leukocyte phenotypes receive much attention as biomarkers for mortality and disease progression. However, they are seldom used to monitor progress during and outcomes from VAD therapy or during the design phase for new devices. Even the partial reversal of heart damage associated with heart failure is a desirable outcome from VAD use. Therefore, improved understanding of the interplay between VADs and the recipient’s inflammatory response would potentially increase their uptake, improve patient lives, and fuel research related to other blood-contacting medical devices. Here we provide a review of what is currently known about inflammation in heart failure and how this inflammatory profile is altered in heart failure patients receiving VAD therapy

Ovine leukocyte microparticles generated by the CentriMag ventricular assist device in vitro

Ventricular assist devices (VADs) are a life-saving form of mechanical circulatory support in heart failure patients. However, VADs have not yet reached their full potential due to the associated side effects (thrombosis, bleeding, infection) related to the activation and damage of blood cells and proteins caused by mechanical stress and foreign materials. Studies of the effects of VADs on leukocytes are limited, yet leukocyte activation and damage including microparticle generation can influence both thrombosis and infection rates. Therefore, the aim was to develop a multicolour flow cytometry assessment of leukocyte microparticles (LMPs) using ovine blood and the CentriMag VAD as a model for shear stress. Ovine blood was pumped for 6 hours in the CentriMag and regular samples analysed for haemolysis, complete blood counts and leukocyte microparticles by flow cytometry during three different pump operating conditions (low flow, standard, high speed). The high speed condition caused significant increases in plasma-free haemoglobin; decreases in total leukocytes, granulocytes, monocytes and platelets; increases in CD45+ LMPs as well as two novel LMP populations: CD11bbright/HLA-DR- and CD11bdull/HLA-DR+, both of which were CD14-/CD21-. CD11bbright/HLA-DR- LMPs appeared to respond to an increase in shear magnitude whereas the CD11bdull/HLA-DR+ LMPs significantly increased in all pumping conditions. We propose that these two populations are released from granulocytes and T cells, respectively, but further research is needed to better characterise these two populations

The CentriMag Centrifugal Blood Pump as a Benchmark for In Vitro Testing of Hemocompatibility in Implantable Ventricular Assist Devices

Abstract: Implantable ventricular assist devices (VADs) have proven efficient in advanced heart failure patients as a bridge-to-transplant or destination therapy. However, VAD usage often leads to infection, bleeding, and throm-bosis, side effects attributable to the damage to blood cells and plasma proteins. Measuring hemolysis alone does not provide sufficient information to understand total blood damage, and research exploring the impact of cur-rently available pumps on a wider range of blood cell types and plasma proteins such as von Willebrand factor (vWF) is required to further our understanding of safer pump design. The extracorporeal CentriMag (Thoratec Corporation, Pleasanton, CA, USA) has a hemolysis profile within published standards of normalized index of hemolysis levels of less than 0.01 g/100 L at 100 mm Hg bu

Multidimensional Flow Cytometry for Testing Blood-Handling Medical Devices

In this paper, a statistical analysis had been carried out on the measured joint angles of the human hand’s fingers while performing some common tasks. By exploiting the correlation existing on some couples of joints, we can reduce the number of myoelectric sensors necessary to drive a (virtual or real) hand prosthesis, while still maintaining an acceptable hand’s Degree of Freedom (DoF). In order to do such kind of analysis we measured the common hand tasks by means of our HITEG data glove we developed. The results of this analysis shows that the number of sensors can be halved, extrapolating the value of remaining sensors by means of linear regression, with an error which for most applications can result acceptable. This method will allow the subject, who has to drive an hand prosthesis, to perform all common hand actions and gestures with only few, not severe, limitations

Virtual implantations to transition from porcine to bovine animal models for a total artificial heart

Realheart total artificial heart (TAH) is a novel, pulsatile, four-chamber total artificial heart which had been successfully tested acutely in a porcine animal model. However, the bovine model is better suited for long-term testing and thus an evaluation of how the design would fit the bovine anatomy was required. Virtual implantation is a method that enables a computer simulated implantation based on anatomical 3D-models created from computer tomography images. This method is used clinically, but not yet adopted for animal studies. Herein, we evaluated its suitability in the redesign of the outer dimensions and vessel connections of Realheart TAH to transition from the porcine to the bovine animal model. Virtual implantations in combination with bovine cadaver studies enabled a series of successful acute bovine implantations. Virtual implantations are a useful tool to replace the use of animals in early device development and refine subsequent necessary in vivo experiments. The next steps are to carry out human virtual implantations and cadaver studies to ensure the design is optimized for all stages of testing as well as the final recipient.status: publishe

Altered Th17/Treg Ratio in Recurrent Miscarriage after Treatment with Paternal Lymphocytes and Vitamin D3: a Double- Blind Placebo-Controlled Study

ABSTRACT Background: Recurrent miscarriage (RM) affects 2-5% of pregnant women. Paternal lymphocyte immunotherapy is a common treatment for RM patients but the outcome has not been consistent. Therefore, combined therapy with other immunosuppressive drugs such as 1a, 25-dihydroxy-vitamin-D3 (vitamin D3) may improve the outcome. Objectives: To investigate the effect of vitamin D3 on the balance of two essential T cells subsets, T helper (Th) 17 and T regulatory (Treg) cells, which contribute to the immune tolerance during pregnancy. Methods: The expression levels of CD4 and forkhead box protein 3 (FOXP3) in Treg cells, and the expression levels of CD4 and IL-17 in Th17 cells, were evaluated pre-and 3 months post-immunotherapy in RM patients treated with a combination of paternal lymphocytes and vitamin D3 compared with RM patients receiving lymphocyte immunotherapy alone. Results: Vitamin D3 therapy decreased the frequency of Th17 cells in addition to reducing the Th17/Treg ratio in peripheral blood of RM patients compared with the control group (p<0.05). Conclusion: Considering that RM patients have a higher Th17/Treg ratio in peripheral blood, vitamin D3 may be a candidate therapeutic approach in this disease. Rafiee M, et al. Iran J Immunol. 2015; 12(4):252-262