A large, new study published by the American Heart Association reveals the threat of blood clots leading to life-threatening strokes, heart attacks and pulmonary embolism can linger for nearly a year after contracting COVID-19.
Researchers examined the electronic health records of 48 million unvaccinated adults from the first wave of the pandemic in England and Wales. They discovered the coronavirus may have led to an additional 10,500 cases of heart attacks, strokes and other blood clot complications such as deep vein thrombosis in 2020 alone.
The study shows risks wane over time. In the first week after a COVID-19 diagnosis, people were 21 times more likely to have a heart attack or stroke, conditions mainly caused by blood clots blocking arteries. This dropped to 3.9 times more likely after four weeks. By 26 to 49 weeks, blood clots were 1.3 times more likely in the arteries and 1.8 times more likely in the veins.
People at the highest risk for blood clots were men over the age of 80, who were 2% more likely to suffer a stroke or heart attack after COVID-19 infection.
How does COVID-19 cause blood clots?
Once considered to primarily be an upper respiratory illness, COVID-19 can cause severe inflammation, which can trigger the body’s clotting system. Unlike when a person falls and skins a knee, a widespread and inflammatory infection like COVID can create a tendency to clot that can become dangerous.
As COVID-19 patients follow stay-at-home or quarantine orders, they become immobile, another increased risk factor for blood clots.
The combination of inflammation and immobility creates a near perfect environment for blood clots to form in patients’ legs and lungs. Patients are especially susceptible to blood clots if they have a severe case of COVID-19 or have other health risk factors such as cancer, obesity and a history of blood clots.
Prevention strategies needed
The study results support strategies to prevent vascular events after severe COVID-19 leading to hospitalization and should include an early review in primary care and risk factor management. Researchers also determined that after severe COVID-19, individuals at high risk of vascular events should be prescribed preventive therapies and counseled about the importance of adherence to them. There also is a need for new, simple treatment strategies to reduce infection-associated venous thromboembolism and arterial thromboses.
“These results support continued policies to prevent severe COVID-19 with effective COVID-19 vaccines, early review and management of vascular risks in patients with COVID-19, and use of secondary preventive agents in patients at high risk of vascular diseases,” the study concluded. “New simple treatment strategies to reduce infection-associated VTE and arterial thromboses are needed.” The researchers are now studying data beyond 2020 to understand the effect of vaccination and the impact of newer variants.