Effects of COVID-19 Infection on Endothelial Vascular Function

Most studies analyzing data from patients who experienced at least one episode of acute COVID-19 infection have attributed the cascade of immediate and late complications to disruption of the inflammatory system and neutrophil activity in particular. Among the various functions of neutrophils is the release of pro-inflammatory mediators, including interleukin-6 (IL-6). Oxidative stress induced by pro-inflammatory mediators secreted by neutrophils leads to vascular endothelial dysfunction. Neutrophil counts and the neutrophil-to-lymphocyte ratio (NLR) are directly associated with COVID-19 patient survival, with higher values correlating with increased mortality. To assess endothelial dysfunction secondary to COVID-19 infection, we conducted a retrospective study involving two patient cohorts, each comprising 99 participants: one group with a history of COVID-19 infection and another without. The study aimed to demonstrate the presence of endothelial dysfunction in patients with moderate COVID-19 infection using flow-mediated dilatation (FMD) of the brachial artery and to evaluate its correlation with key inflammatory markers (erythrocyte sedimentation rate-ESR, fibrinogen, NLR, IL-6). FMD values were significantly reduced (<i>p</i> < 0.0001) in post-COVID-19 patients compared to those without prior infection. ESR (<i>p</i> < 0.0001), fibrinogen (<i>p</i> < 0.0001), C-reactive protein (CRP) (<i>p</i> < 0.0001), leukocyte count (<i>p</i> < 0.0001), and granulocyte count (<i>p</i> < 0.0001) were inversely correlated with FMD values. Among post-COVID-19 patients, all analyzed parameters demonstrated a statistically significant impact on FMD, with ESR showing the strongest effect, accounting for nearly 63% of the dependency. ANOVA testing confirmed an inverse association between NLR quartiles and FMD, as well as between IL-6 levels and FMD. In conclusion, this study highlights the presence of endothelial dysfunction in post-COVID-19 patients, as assessed by FMD, and demonstrates statistically significant inverse correlations between FMD values, IL-6 levels, and the neutrophil-to-lymphocyte ratio.