Thrombotic Complications in acute COVID-19 infected patients

An increasing incidence of blood clot formation and its related complications are being seen in acute COVID-19 infected patients.

These complications can include:

  1. Blood clot in the lung blood vessels (Pulmonary Embolism)
  2. Blood clot in the deep veins of the limbs (Deep Vein Thrombosis)
  3. Blood clot in the arteries of the limbs (Arterial thromboembolism)
  4. Blood clot in the heart chambers (Intracardiac Thrombus)
  5. Blood clot in the small blood vessels/capillary system (Microvascular Thrombi)
  6. Blood clot in the blood vessels of the brain (Stroke)
  7. Blood clot in the tubes and lines outside the body (Thrombosis of extracorporeal circuits): e.g. continuous veno-venous hemofiltration for dialysis; catheter-related thrombosis (e.g. central venous catheters)

Hospitalized Patients with COVID-19

In patients with acute COVID-19 infection, an intense inflammatory response is sometimes seen. This commonly occurs in hospitalized patients with severe or critical COVID-19. This marked inflammatory response can also lead to the formation of widespread small blood clot development in the bloodstream (disseminated intravascular coagulopathy, also known as DIC), in critically ill patients. Coagulopathy tends to be associated with higher mortality in this group of hospitalized patients.

In addition to the excessive inflammation, there can also be platelet activation, blood vessel inner lining dysfunction, and blood stasis which can increase the incidence of blood clot formation.

Hospitalized patients with COVID-19 who are confined to their bed; have pre-existing conditions that increase their risk of blood clot formation (e.g. active cancer), or who require intensive care should receive medication to prophylactically reduce the incidence of Venous Thromboembolism (VTE) in the form of blood thinners (anti-coagulation) unless there are contraindications.

Pre-COVID era patients already receiving blood clot prevention (antithrombotic) therapy

To complicate matters, pre-COVID era patients already receiving antithrombotic therapy for a pre-existing thrombotic disease may develop COVID-19 infection as well, which can have implications for choice, dosing, and laboratory monitoring of antithrombotic therapy.

For these patients, due to the pandemic, resources allocation/ limited resources, as well as social distancing measures in place in hospitals (e.g. minimizing of investigations/ treatment to lower the risk of exposure to healthcare staff; to minimize transport and movement of COVID-19 patients between their isolation rooms and radiological facilities), may adversely affect the care of patients without COVID-19 but who present with thrombotic events.

Patients with the pre-existing thrombotic disease without COVID-19 infection

In the outpatient setting, for patients with the pre-existing thrombotic disease (e.g. recurrent DVT) without COVID-19 infection, they should continue with their medications similar to pre-COVID times. There is currently no evidence that blood thinners (like antiplatelet agents or anticoagulants), increase the risk of contracting COVID-19, or of developing severe COVID-19. The physician managing such patients should educate these patients to empower them for self-monitoring of symptoms, and to avoid unnecessary visits to the emergency department for nuisance bleeding (e.g. self-limiting gum bleeding).

AUTHOR: Dr. Ang Teck Kee, Consultant & Interventional Cardiologist, Livingstone Cardiology

1. Incidence of venous thromboembolism in hospitalized patients with COVID‐19. doi:10.1111/JTH.14888
2. COVID-19 and Thrombotic or Thromboembolic Disease: Implications for Prevention, Antithrombotic Therapy, and Follow-up. Journal of the American College of Cardiology (2020), doi:

*Information is accurate at the time of publication: 20th May 2020