Objective: Red blood cell (RBC) role is both passive action, oxygen delivery to the tissues as well as carbon dioxide to the lungs and active action involvement in the regulation of vascular tone.

The aim was to investigate pathophysiological and ultrastructural changes of RBC in heart failure (HF) patients with hypertension (HT) and long Covid.

Design and method: In total 12 patients with HF of Coronary Artery Disease origin, HT, and long Covid were examined. Mean age of patients was 62 ± 5.8 years. The control group consisted of 10 apparently healthy people. The functional state and ultrastructure of RBC were studied using electron microscopy.

Results: During ultrastructure examination, structural pathologies of RBC in HF patients with HT and long Covid were revealed. RBC anisocytosis and poikilocytosis as structural damage variations in size and shape were found respectively. Reticulocytes were found much more often in HF patients with HT and long Covid than in the control group. In healthy control group, RBC had a typical discoid shape. In the presence of long Covid, both calcification as a marker of RBC apoptosis and destruction was also detected (Fig.1). Neutrophil extracellular traps (NETs) were found in RBC surrounding (Fig.1).

Conclusions: Altered RBC function has important implications for HF patients with HT and long Covid. RBC has been shown to induce endothelial cell dysfunction and to increase cardiac injury as well as increased inflammatory processes in long Covid. The presence of HF, HT and long Covid leads to RBC calcification and activation of blood cell apoptosis. Prognostic role of RBC calcium distribution in combination with other important prognostic measures, such as biomarkers like Thrombospondin - 1, NT-proBNP and ST2 is subject of interest and requires further research.