Microthrombus burden

Microthrombus burden refers to the quantitative or qualitative extent of microscopic blood clots (microthrombi) within the microvasculature, including capillaries, arterioles, and venules [3, 11]. These microclots are primarily composed of a fibrin matrix and activated platelets, typically forming as a result of systemic inflammation, endothelial dysfunction, or dysregulated coagulation [3, 10]. In clinical states such as sepsis, disseminated intravascular coagulation (DIC), and thrombotic microangiopathy (TMA), an elevated microthrombus burden leads to widespread microvascular occlusion, resulting in tissue hypoxia and potential multi-organ failure [11]. Recently, the concept has gained significant attention in the study of COVID-19 and Post-Acute Sequelae of COVID-19 (Long COVID), where persistent 'fibrinaloid' microclots are hypothesized to drive ongoing symptoms like fatigue and cognitive impairment [1, 6]. Therapeutic management focuses on reducing this burden through the use of anticoagulants to inhibit the coagulation cascade, antiplatelet agents to prevent aggregation, or fibrinolytic therapy to dissolve existing obstructions [2, 4, 13]. Monitoring the microthrombus burden is essential for assessing disease severity and the efficacy of antithrombotic interventions in both acute and chronic inflammatory conditions [5, 15].

Other names

Microvascular thrombus burdenMicroclot burdenMicrovascular thrombosisFibrinaloid microclotsMicrovascular clot density

Reduction of microthrombus burden is achieved by inhibiting the coagulation cascade (e.g., via Factor Xa or Thrombin inhibition), preventing platelet activation and aggregation (e.g., via P2Y12 or GPIIb/IIIa antagonism), or promoting the enzymatic degradation of existing fibrin clots (fibrinolysis).