Preliminary in vivo testing of a novel pump for short-term extracorporeal life support

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 multicolor 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 h in the CentriMag and regular samples analyzed for hemolysis, complete blood counts and LMP by flow cytometry during three different pump operating conditions (low flow, standard, high speed). The high speed condition caused significant increases in plasma-free hemoglobin; decreases in total leukocytes, granulocytes, monocytes, and platelets; increases in CD45⁺ LMPs as well as two novel LMP populations: CD11b^bright /HLA-DR^- and CD11b^dull /HLA-DR⁺ , both of which were CD14^- /CD21^- . CD11b^bright /HLA-DR^- LMPs appeared to respond to an increase in shear magnitude whereas the CD11b^dull /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 characterize these two populations.

In vivo testing of a novel blood pump for short-term extracorporeal life support

BACKGROUND

Centrifugal pumps are used increasingly for temporary mechanical support for the treatment of cardiogenic shock. However, centrifugal pumps can generate excessive negative pressure and are afterload sensitive. A previously developed modified roller pump mitigates these limitations both in vitro and in preliminary animal experiments. We report the results of intermediate-term testing of our evolving pump technology, known as the BioVAD.

METHODS

The BioVAD was implanted in 6 adult male sheep (62.5±3.9 kg), with drainage from the left atrium and reinfusion into the descending aorta. The sheep were monitored for 5 days. Heparin was given during the initial implantation, but no additional anticoagulants were given. Data collected included hemodynamic status, pump flow and pressures, laboratory values to monitor end-organ function and hemolysis, pathologic specimens to evaluate for thromboembolic events and organ ischemia, and explanted pump evaluation results.

RESULTS

All animals survived the planned experimental duration and there were no pump malfunctions. Mean BioVAD flow was 3.57±0.30 L/min (57.1 mL/kg/min) and mean inlet pressure was -30.51±4.25 mm Hg. Laboratory values, including plasma free hemoglobin, creatinine, lactate, and bilirubin levels, remained normal. Three animals had small renal cortical infarcts, but there were no additional thromboembolic events or other abnormalities seen on pathologic examination. No thrombus was identified in the BioVAD blood flow path.

CONCLUSIONS

The BioVAD performed well for 5 days in this animal model of temporary left ventricular assistance. Its potential advantages over centrifugal pumps may make it applicable for short-term mechanical circulatory support.