Platelet Function at the Intersection of the COVID-19 “Cytokine Storm” and Mechanical Circulatory Support

ABSTRACT

Purpose: Release and circulation of pro-inflammatory cytokines or “cytokine storm,” a pathophysiologic component of severe COVID-19, is associated with thrombosis and clot embolization. Compromised patients often require extracorporeal oxygenation and mechanical circulatory support (MCS), imparting blood flow disturbances and exogenous shear stress, further amplifying thrombotic potential. Central in these processes is the platelet. The dynamic interaction of MCS flow/shear and inflammatory cytokines and their propensity for altering platelet function remains unknown. We hypothesized that platelet function is modified in an MCS + pro-inflammatory cytokine environment. We examined platelet aggregation as a function of time, exposing platelets to COVID-19-associated cytokines under MCS flow in vitro. Methods: An Impella5.5® was affixed in a closed loop and positioned with outflow cannula in a 1-inch tube region, maintained at differential 60mmHg pressure. Alternatively, a CentriMag® was affixed in series with a similar closed loop. Porcine PRP, obtained via centrifugation of fresh, ACD-A anticoagulated whole blood was used as circulating fluid. A cytokine “COVID cocktail” of porcine IL-6 (4.5 ng/mL), IL-1β (0.5 ng/mL), IL-8 (2.7 ng/mL), and TNFα (1 ng/mL) was added to PRP and circulated at 5 L/ min. After 5, 60 and 240min of circulation, platelet samples were taken and measured for aggregation with ADP (20uM), and expression of activation markers (CD62P, AnnV) via flow cytometry. Samples were measured in duplicate from N ≥ 2 pigs per experiment. Results: The addition of COVID Cocktail cytokines led to an increase in overall aggregability of platelets over time. In contrast, the addition of shear via MCS devices led to a decrease in platelet aggregability despite Cytokine addition (Fig 1). Notably, platelet aggregability was more greatly reduced with CentriMag (85% reduction) than with Impella (65% reduction). There was no significant difference in platelet activation (AnnV binding, CD62P exposure) between CentriMag and Impella 5.5 in the cytokine environment. (Figure Presented).