Considering that the intensity of systemic microvascular changes in patients in the acute phase of COVID-19 could be related to disease progression and prognosis, the present cross-sectional and observational study aims to investigate the presence of endothelial dysfunction in these patients, also looking for to evaluate associations between the presence of endothelial dysfunction and demographic, clinical and laboratory variables.

An association between the presence of previous cardiovascular disease and adverse prognosis has been demonstrated in patients with COVID-19 (coronavirus disease-19), presenting increases of up to 5-10 times in mortality.

As an initial process, the SARS-CoV-2 virus, anchored in the transmembrane angiotensin-converting enzyme 2 (ECA2), penetrates host cells, including endothelial cells, pericytes and macrophages, in addition to type II pneumocytes.

Cellular invasion results in massive release of several pro-inflammatory cytokines ("cytokine storm"), such as IL-1β, IFN-1 and IL-6, by the cells of the immune system. In turn, cytokines increase the process of vascular inflammation and the expression of leukocyte-vascular endothelium adhesion proteins, which results in endothelial activation accompanied by a pro-coagulant and pro-adhesive phenotype - between leukocytes, platelets, red blood cells and vascular endothelium - characteristic of the dysfunctional endothelium in the microcirculation, which results in severe changes in the microvascular flow and, as a result, in tissue perfusion.

It is also worth noting that the patients most vulnerable to the development of complications are those with pre-existing endothelial dysfunction, associated with several risk factors such as male gender and smoking, and comorbidities such as hypertension, diabetes and obesity, all of which are associated with poor prognosis in COVID -19.

Considering that the intensity of systemic microvascular changes in patients in the acute phase of COVID-19 could be related to disease progression and prognosis, the present cross-sectional and observational study aims to investigate the presence of endothelial dysfunction in these patients, also evaluating associations between the presence of endothelial dysfunction and demographic, clinical and laboratory variables.

• Age> 18 years admitted to the hospital
• SARS-CoV-2 positive real-time PCR molecular test

Exclusion Criteria:

• Presence of non-COVID infection with systemic and microbiologically documented repercussions.

- We will include adult patients will with SARS-CoV-2 positive RT-PCR, admitted to the hospital in a ward or intensive care unit.