Blood clot risk higher for six months after having Covid

Blood clot risk higher for six months after having Covid

The BBC has reported results from a recent study that show people with severe Covid-19, and those infected during the first wave, had an increased risk of developing a serious blood clot for up to six months following a positive test. According to the study, conducted in Sweden, people with Covid-19 who required hospital treatment were more likely to develop serious blood clots.

Researchers tracked the health of more than one million people in Sweden who had Covid-19 between February 2020 and May 2021 with four million people of the same ages and sex who had not tested positive.

After Covid infection, they found an increased risk of:

– blood clots in the leg, or deep vein thrombosis (DVT), for up to three months
– blood clots in the lungs, or pulmonary embolism (PE), for up to six months
– internal bleeding, such as a stroke, for up to two months

The study reported that blood clots in the lung, in seriously ill Covid-19 patients, was 290 times greater than normal, and seven times higher than normal after mild Covid, but with no raised risk of internal bleeding in mild cases.

The researchers can’t prove that Covid caused the blood clots but they have several theories on why it happens and point to the direct effect of the virus on the layer of endothelial cells which line blood vessels, an exaggerated inflammatory response to the virus, or the body making blood clots at inappropriate times.

The study, published in the BMJ, discusses that the raised risk, higher in the first wave than later waves, was probably due to treatments improvement during the pandemic and older patients who were starting to be vaccinated by the second wave.

Immobility a prevalent risk factor – and the benefit of lower limb VTE prophylaxis

Immobility is an important and highly prevalent risk factor for venous thromboembolism (VTE)—both deep vein thrombosis (DVT) and pulmonary embolism (PE).1,2 A sustained period of immobility can lead to vascular stasis (clotting), one of the cornerstones of Virchow’s triad in the pathology of thrombosis3,4  – which has particular relevance to blood clots that form in the legs, in both Covid and non-Covid-19 patients.

Whilst the optimal duration of VTE prophylaxis (prevention therapies) was less clear during the first Covid-19 wave, guidance at that time and since recommends that acutely ill medical patients, who are immobile and at high risk of clotting, should receive VTE prophylaxis5. Current standard of care (SoC), both then and now, includes drug prophylaxis (blood thinners), intermittent pneumatic compression (IPC) – a plastic sleeve that wraps around the leg inflating and deflating to increase blood flow – or compression stockings. Not all patients, however, are able to tolerate SoC and therefore receive no VTE prophylaxis – a problem that is particularly significant to acute-stroke, where 30% of patients are reported as contraindicated or unable to be tolerate IPC6.

The geko™ device – clinically proven to prevent VTE in immobile acute stroke patients – an immobility burden Covid-19 patients share 

A real-world study conducted in the UK NHS shows the geko™ device is clinically proven to prevent post-stroke VTE7.

1,000 immobile, hyper-acute stroke patients had their contraindication and/or intolerance to IPC reviewed and quantified. The study reported that 68.8% of patients were in need of IPC (intermittent pneumatic compression) but 29.5% were either contraindicated or unable to tolerate IPC, revealing a significant unmet need for an alternative anti-stasis (blood clot prevention) intervention. It is to this cohort the geko™ device was fitted to address unmet need.

The study measured VTE events at 90 days post-stroke. The data shows that the patients treated with IPC alone, as the standard of care, 2.4% suffered a VTE event, compared to a 0% incidence of VTE in patients prescribed the geko™ device alone. Patients prescribed the geko™ device also showed no adverse events and reported greater tolerance of geko™ compared to IPC. Furthermore, the geko™ device provided an anti-stasis intervention where previously patients would have had no other intervention available to them (drugs following acute stroke are not recommended by NICE in the UK). The data has subsequently driven wider NHS adoption and international, ensuring immobile acute-stroke patients, with a high risk if VTE, are no longer without a mechanical VTE prophylactic intervention.

About the geko™ device – approved by NICE Guidance (MTG19)8

The size of a small wrist-watch, geko™ is a battery powered, disposable, neuromuscular electro-stimulation medical device that is applied non-invasively to the skin over the common peroneal nerve at the side of the knee. It gently stimulates the nerve, once every second, activating the calf and foot muscle pumps resulting in increased blood flow in the deep veins of the calf9, at rate equal to 60%10 of walking without the patient having to move.

Geko™ device use during Covid-19:


    1. Geerts WH et al. American College of Chest Physicians. Prevention of venous thromboembolism: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines, 8th Ed). Chest. 2008;133(6 suppl):381S-453S.
    2. Piazza G, et al. Venous thromboembolism in heart failure: 274 Clinical and Applied Thrombosis/Hemostasis 19(3) preventable deaths during and after hospitalization. Am J Med. 2011;124(3):252-259.
    3. Lowe GD. Virchow’s triad revisited: abnormal flow. Pathophysiol Haemost Thromb. 2003/2004;33(5-6):455-457.
    4. Virchow R. Gesammalte abhandlungen zur wissenschaftlichen. Frankfurt, Germany: Medinger Sohn and Son; 1856:219-732.
    5. NICE guideline [NG89]Published: 21 March 2018 Last updated: 13 August 2019. Venous thromboembolism in over 16s: reducing the risk of hospital-acquired deep vein thrombosis or pulmonary embolism.
    6. Dennis M. et al. The Clots in Legs Or sTockings after Stroke (CLOTS) 3 trial: a randomised controlled trial to determine whether or not intermittent pneumatic compression reduces the risk of post-stroke deep vein thrombosis and to estimate its cost-effectiveness. 2015 Sep;19(76):1-90. DOI: 10.3310/hta19760.
    7. Williams J et al. The use of the geko™ device and the activation of the foot and calf pumps for prevention of venous thromboembolism in patients with acute stroke. Data on file Firstkind Ltd 2019.
    8. NICE medical technologies guidance [MTG19] Published date June 20 2014.
    9. A Nicolaides, M Griffin. Measurement of blood flow in the deep veins of the lower limb using the geko™ device neuromuscular electro-stimulation device, Journal of International Angiology, August 2016-04.
    10. Tucker AT et al. Int J Angiol.2010 Spring; 19(1):e31-e37.



No Comments

Post A Comment