[Improving outcome of COVID-19-associated thrombosis: the need for evaluation of fibrinolytic activation].

Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 and is known to have thrombotic complications. Various-sized thrombosis occurs in the arteries and veins, especially in lung tissue. The prevention and treatment of thrombosis is an important issue that is directly linked to its prognosis. Additionally, the drastic fibrinolytic enhancement and lethal bleeding in some severe COVID-19 are important issues. The efficacy of antiplatelet for COVID-19 is controversial. Thus, warfarin or tranexamic acid alone should be avoided. Heparin is effective for mild to moderate COVID-19 but is ineffective in severe cases since the anticoagulant activity of heparin is insufficient or heparin increases major bleeding. In severe COVID-19 cases with drastic fibrinolytic enhancement, heparin and nafamostat combination therapy may avoid lethal bleeding. In COVID-19 clinical practice, not only the coagulation activation was evaluated but also the fibrinolytic activation to consider treatment strategies.