COVID-19 and thrombotic microangiopathy

As shown by numerous studies conducted during the pandemic, the severe course of COVID-19 is accompanied by multiple organ failure. Cytokine storm, hypercoagulation, complement hyperactivation and other arms comprise the overall picture of the pathogenesis of the severe disease course. The frequent diagnosis of multiple microvascular thrombosis in lung, heart, and kidneys, as well as the presence of platelet-fibrin thrombi there and signs of terminal organ damage, suggest a possible involvement of thrombotic microangiopathy (TMA) in the development of multiple organ failure. In this regard, it is especially important to timely diagnose TMA and start pathogenetic therapy. These measures can significantly reduce mortality due to the novel disease. Heparins and direct oral anticoagulants are the mainstay for prevention and treatment of venous thromboembolism in patients with COVID-19, but their effectiveness in the presence of TMA is questionable. It has been proven that anticoagulants use in critically ill patients with COVID-19 for prevention of large vessel thrombosis is effective, but their role in the prevention of microthrombosis is not clear. Here we review the currently available information on thrombotic microangiopathy, as well as a review of literature data describing TMA-like conditions in COVID-19, discuss potential pathophysiology of the condition development and proposed therapeutic approaches. © Obstetrics, Gynecology and Reproduction 2021.

Vaccine-induced immune thrombotic thrombocytopenia: Definition, risks with different vaccines, and the regulators’ responses

After the vaccination campaign initiation in Europe and the UK, reports of rare cases of atypical thrombosis, including sinus vein thrombosis and splanchnic venous thrombosis, began to appear in association with the use of AstraZeneca (ChAdOx1) and J&J/Janssen adenovirus vector vaccines. The syndrome called VITT (vaccine-induced immune thrombotic thrombocytopenia) is manifested as thrombosis simultaneously with decreased platelet count, significantly increased D-dimer levels and detected anti-factor 4 platelet (PF4) antibodies. We present a detailed review on the epidemiology, pathogenesis, clinical picture, diagnostics and treatment of VITT, which by its nature is an immune complication similar to the processes occurring in heparin-induced thrombocytopenia (HIT). All international and national organizations and regulatory authorities, including experts in the field of thrombosis and hemostasis and the VITT expert council recommend continuing the prompt mass vaccination against COVID-19 as the only method able to reduce the incidence of severe cases, stop the spread of COVID-19 infection and emergence of new dangerous mutations in the viral genome. Failure to vaccinate poses an incomparably greater risk of fatal thrombotic and inflammatory complications associated with infections, compared with the risks of extremely rare adverse events that can occur after vaccination. It should be noted that information on VITT, described as a sporadic phenomenon of abnormal immune response to some variants of vaccines against COVID-19, cannot be translated to other vaccines (including those registered in the Russian Federation) and, moreover, cannot be a reason to refuse their administration. © 2021 Obstetrics, Gynecology and Reproduction. All rights reserved.

Macrophage activation syndrome in COVID-19

The novel coronavirus epidemic is characterized by high rates of morbidity and relatively high mortality. Laboratory test results in patients include leukopenia, an increase in liver function tests and ferritin levels reaching hundreds, and sometimes thousands of units. These data remind us about the macrophage activation syndrome (MAC). Secondary hemophagocytic lymphohistiocytosis syndrome, MAC, which pathogenesis is based on a defect in the mechanisms of T-cell cytotoxicity and decreased level of natural killer cells associated with the defect in the perforin-encoding gene as well as hyperproduction of a number of cytokines - interleukin (IL)-1β, tumor necrosis factor-α, etc. by T-lymphocytes and histiocytes, indirectly leading to the activation of macrophages and production of proinflammatory cytokines, in particular IL-6 hyperproduction. MAC is one of "hyperferritinemic syndromes". These disorders have similar clinical and laboratory manifestations, and they also respond to similar treatments, suggesting that hyperferritinemia may be involved in the overall pathogenesis and is characterized by elevated ferritin level and cytokine storm. Despite the fact that data on the immune and inflammatory status in patients with COVID-19 have only started to appear, it is already clear that hyperinflammation and coagulopathy affect the disease severity and increase the risk of death in patients infected with SARS-CoV-2. Hence, understanding the pathogenesis of the novel coronavirus infection can help in its early diagnostics and treatment.

Neutrophil extracellular traps: A role in inflammation and dysregulated hemostasis as well as in patients with COVID-19 and severe obstetric pathology

Numerous studies have proven a close relationship between inflammatory diseases and the state of hypercoagulability. In fact, thromboembolic complications represent one of the main causes of disability and mortality in acute and chronic inflammatory diseases, cancer and obstetric complications. Despite this, the processes of hemostasis and immune responses have long been considered separately;currently, work is underway to identify the molecular basis for a relationship between such systems. It has been identified that various pro-inflammatory stimuli are capable of triggering a coagulation cascade, which in turn modulates inflammatory responses. Neutrophil extracellular traps (NETs) are the networks of histones of extracellular DNA generated by neutrophils in response to inflammatory stimuli. The hemostasis is activated against infection in order to minimize the spread of infection and, if possible, inactivate the infectious agent. Another molecular network is based on fibrin. Over the last 10 years, there has been accumulated a whole body of evidence that NETs and fibrin are able to form a united network within a thrombus, stabilizing each other. Similarities and molecular cross-reactions are also present in the processes of fibrinolysis and lysis of NETs. Both NETs and von Willebrand factor (vWF) are involved in thrombosis as well as inflammation. During the development of these conditions, a series of events occurs in the microvascular network, including endothelial activation, NETs formation, vWF secretion, adhesion, aggregation, and activation of blood cells. The activity of vWF multimers is regulated by the specific metalloproteinase ADAMTS-13 (a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13). Studies have shown that interactions between NETs and vWF can lead to arterial and venous thrombosis and inflammation. In addition, the contents released from activated neutrophils or NETs result in decreased ADAMTS-13 activity, which can occur in both thrombotic microangiopathies and acute ischemic stroke. Recently, NETs have been envisioned as a cause of endothelial damage and immunothrombosis in COVID-19. In addition, vWF and ADAMTS-13 levels predict COVID-19 mortality. In this review, we summarize the biological characteristics and interactions of NETs, vWF, and ADAMTS-13, the effect of NETs on hemostasis regulation and discuss their role in thrombotic conditions, sepsis, COVID-19, and obstetric complications.

Anticoagulant, anti-inflammatory, antiviral and antitumor properties of heparins

Our knowledge regarding chemical structure and properties of heparin and its derivatives, including biological properties in blood plasma, on the cell surface and while interacting with receptors, has been progressively growing. New insights are followed by the expansion of therapeutic opportunities and indications for the use of heparins. There are prerequisites for the creation of new generation drugs with modified properties that reduce a bleeding risk while applied for a non-anticoagulant goal. The non-anticoagulant heparin properties allow to consider it as a candidate for pathogenetic treatment of patients with COVID-19. This review focuses on the anticoagulant and non-anticoagulant heparin properties as well as the underlying molecular mechanisms.

Coronavirus disease (COVID-19) and disseminated intravascular coagulation

COVID-19 is an infectious disease caused by the beta-coronavirus SARS-CoV-2 that in 2020 has spread worldwide. In most severe patients, the clinical picture begins with respiratory failure further deteriorating up to multiple organ failure. Development of coagulopathy is the most adverse prognostic. Analyzing currently available clinical data revealed that 71.4 % and 0.6 % of survivors and fatal cases, respectively, demonstrated signs of overt disseminated intravascular coagulation (DIC). Monitoring D-dimer level, prothrombin time, platelet count and fibrinogen content is important for determining indications for treatment and hospitalization in COVID-19 patients. In case such parameters deteriorate, a more pro-active “aggressive” intensive care should be applied. Low molecular weight heparin (LMWH) should be administered to all patients with diagnosed COVID-19 infection (including non-critical patients) requiring hospitalization, but having no contraindications to LMWH.