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COVID-19 Makes It More Important Than Ever to Know the Risk Factors and Warning Signs of Blood Clots

TORONTO–()–On World Thrombosis Day, Thrombosis Canada is warning Canadians that it is more critical now than ever before to learn the signs and symptoms of thrombosis, or blood clots. With new COVID-19 cases growing, there is an increased risk of some patients developing blood clots in the veins that cause leg clots (called deep vein thrombosis, or DVT) and lung clots (called pulmonary embolism, or PE).

“COVID-19 is the ‘perfect storm for thrombosis’, so it is critical that all Canadians have the knowledge to recognize signs and are empowered to seek immediate medical attention,” said Dr. James Douketis, President, Thrombosis Canada, and Director of Vascular Medicine, Staff Physician in Vascular Medicine and General Internal Medicine at St. Joseph’s Healthcare Hamilton. “Although evidence is growing that patients with severe cases of COVID-19 are at greater risk of thrombosis, the underlying mechanisms remain unclear. Ongoing research will improve patient management.”

Several Thrombosis Canada members are on the forefront of research to investigate ways to prevent and treat thrombosis in patients with COVID-19. For example, a major international study called Antithrombotic Therapy to Ameliorate Complications of COVID-19 ( ATTACC ), includes co-principal investigator Dr. Ryan Zarychanski from the University of Manitoba, and other members: Dr. Marc Carrier (Ottawa), Dr. Peter Gross (Hamilton), Dr. Jean-Phillippe Galanaud (Toronto), Dr. Susan Kahn (Montreal) and Dr. Vicky Tagalakis (Montreal).

In Canada, both Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE) – collectively known as venous thromboembolism (VTE) – are serious medical conditions and are potentially life threatening. Thrombosis is a major public health problem, affecting about 100,000 Canadians and causing 10,000 deaths each year. Blood clots are the underlying cause of the top three cardiovascular killers in Canada, including heart attack, stroke and VTE. Annually, VTE causes more deaths in Canada than breast cancer, HIV and motor vehicle accidents combined.

Blood Clots: Know the Warning Signs

In an effort to improve public awareness about blood clots to save lives, Thrombosis Canada encourages Canadians to review its educational materials for consumers, healthcare professionals and medical facilities. One resource, based on the ‘C-L-O-T-S’ mnemonic, contains the most common warning signs of blood clots: Chest pain, Light headedness, Out of breath, leg Tenderness and leg Swelling.

“If someone has some of these critical signs, then it is important to see a doctor or go to the emergency department,” said Dr. Deborah Siegal, Associate Professor, University of Ottawa. “We hope that ‘C-L-O-T-S’ will help people recognize that they could be experiencing a blood clot so that they will seek medical attention.”

To recognize World Thrombosis Day, a number of Canadian landmarks and buildings will be illuminated in red and blue, including: Niagara Falls (October 12); Vancouver Sails of Light, Calgary Tower, City of Hamilton Sign, City of London buildings, London Sifton Properties building; London Canada Life building (all on October 13); and the CN Tower (October 14).

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Thrombosis Canada comprises a membership that includes the most eminent and internationally recognized thrombosis experts globally. Members have made many significant contributions to the body of knowledge in vascular medicine and disseminated that knowledge through hundreds of peer-reviewed publications, as well leading the development of international clinical practice guidelines.


Launched in 2014 and held annually on October 13, World Thrombosis Day (WTD) aims to increase awareness of thrombosis among the public, healthcare professionals and health care systems, and ultimately, to reduce deaths and disabilities from thromboembolic disease through a greater awareness of its causes, risk factors, signs and symptoms, and evidence-based prevention and treatment. WTD’s mission supports the World Health Assembly’s global target of reducing premature deaths by non-communicable disease by 25 per cent by 2025, as well as the WHO global action plan for the prevention and control of non-communicable diseases in the 2013-2020 timeframe.

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