There is a strong link between COVID-19 and blood clots and now nearly 2 years on we know a lot more about managing and preventing this common complication. On World Thrombosis Day, let's try and understand this connect.
What is DVT, PE and VTE?
1 in 4 people worldwide die of conditions caused by blockage of their blood vessels by clotting, or thrombosis. Thrombosis is the formation of potentially deadly blood clots in an artery (arterial thrombosis) or vein (venous thrombosis). Once formed, a clot can slow or block normal blood flow, and even break loose and travel to an organ. A clot that forms and moves in the circulation is called an embolism. Thrombosis is the often-preventable underlying pathology of heart attack, thromboembolic stroke, and venous thromboembolism (VTE), the top three cardiovascular killers. Most of the clots in COVID-19 are in the veins though arterial thrombosis also occurs.
Venous thromboembolism (VTE) is a condition in which blood clots form in the veins, most often in the deep veins of the leg known as deep vein thrombosis, DVT and can travel and lodge in the lungs which lead to pulmonary embolism, PE. VTE is a leading cause of death and disability worldwide.
Common risk factors for VTE include hospitalization for any illness or surgery, cancer, prolonged immobility, family history of VTE, obesity, estrogen-containing medications (birth control pills or hormone replacement therapy) and pregnancy. The symptoms associated with DVT are pain or tenderness in the calf or thigh, swelling of the leg, redness or noticeable discolouration. With PE we look for shortness of breath, chest pain, light headedness or passing out and coughing up blood. Immediate medical intervention is recommended once an individual detects these signs.
What's the relationship between COVID-19 and thrombosis?
Early in the pandemic, we realized that blood clots are very common in COVID-19. The SARS-CoV-2 virus can cause severe inflammation, which can trigger the body’s clotting system and cause blood clots. People affected severely with COVID-19 and those who require hospitalization are particularly susceptible. Patients with comorbidities such as heart disorders, diabetes, obesity, cancer and family history of blood clots are also prone to thrombosis. About one in 20 COVID-19 patients admitted to hospital and up to one in five of those on critical care might develop PE so it is important to be aware of this complication and prevent it if possible.
Even before COVID-19, VTE relating to hospitalisation was recognised as a major public health problem. Half of all VTE cases are hospital-associated and VTE is the leading cause of preventable hospital death. The three main causes of VTE are sluggish blood flow, blood vessel damage and sticky blood and often in the hospitalised person we find a combination of these factors. Hospital-associated clots are also called Hospital-Associated Thrombosis or HAT. HAT can occur during hospital stay but more commonly occurs after going home, the risk of HAT extending to 3 months after discharge.
How do we prevent hospital-associated thrombosis?
Most cases of HAT are preventable by the use of blood thinners. In hospital this usually takes the form of low molecular weight heparin injections. Sometimes, particularly after cancer surgery, these
injections are also given outside of hospital. Blood thinning tablets are also available, mainly for VTE prevention after orthopaedic surgery. In patients with a high risk of bleeding, mechanical methods including the use of special stockings as well as ‘intermittent pneumatic compression’ devices can help prevent clots. Simple measures such as paying more attention to hydration as well as early mobilisation after surgery are also helpful. In COVID-19 disease all patients who are ill enough to be admitted to hospital are likely to need blood thinning injections unless they are at a high risk of bleeding.
How do we raise public awareness about thrombosis?
A World Thrombosis Day survey of nine countries found that public awareness of thrombosis and venous thromboembolism, VTE was very low compared to other health conditions such as heart diseases, high blood pressure, breast cancer, prostate cancer, and AIDS. VTE causes more deaths each year in the U.S. and Europe than breast cancer, HIV disease, and motor vehicle crashes — combined. World Thrombosis Day, (WTD) is a year-long campaign that takes place on 13 October to focus attention on attention on the often overlooked and misunderstood condition of thrombosis. Approximately 10 million cases of hospital-associated VTE occur annually across the world, yet the condition can often be preventable with early detection and preventative blood thinners. The World Thrombosis Day campaign calls upon healthcare professionals to provide mandated VTE risk assessments to all hospitalized patients. It seeks to increase global awareness of thrombosis, its causes, risk factors, symptoms and treatment protocols to prevent deaths.
(Dr Roopen Arya is the India Spokesperson for World Thrombosis Day. He is a professor of Thrombosis and Haemostasis at King’s College Hospital, London)
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