• Study reports abnormally high VTE and high bleed risk in critically ill COVID-19 patients and calls for more effective prevention strategies.
  • Clinicians at NHS hospitals are supporting the care of COVID-19 patients with the use of geko™ devices to reduce the risk of blood clots in the most at risk patients.
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Life threatening blood clots form in leg arteries of COVID-19 patients

4th December 2020

New study reports that COVID-19 patients with symptoms of inadequate blood supply to the lower extremities tend to form larger clots and have a significantly higher rate of amputation and death than uninfected people with the same condition1.

COVID-19’s association with blood clots in the pulmonary arteries is well-established2. Less known is the virus’ connection to lower extremity arterial thrombosis, a condition characterized by blood clots in the arteries that impede the flow of oxygenated blood.


The study, published in Radiology (and shared here), reports that during the peak of the COVID-19 pandemic in New York City, radiologists at the city’s Montefiore Medical Centre observed an increase in patients testing positive for lower extremity arterial thrombosis on CT angiography exams. The patients had arrived at hospitals with coldness, pain or discoloration of their legs. Frequently these symptoms of leg ischemia, a condition in which blood flow to the lower extremities is restricted, were accompanied by respiratory distress, cough, fever and altered mental status.

The alarming trend prompted the researchers to look more closely at a possible connection between COVID-19 and lower extremity arterial thrombosis and whether people with the virus had a worse prognosis.

They identified 16 C-19-positive patients, average age 70, who underwent CT angiography of the lower extremities for symptoms of leg ischemia. These patients were retrospectively compared with 32 COVID-19-negative patients, average age 71, who underwent CT angiography with similar symptoms, in previous years, and who were well matched with the C-19 cohort for demographic and clinical characteristics.

All patients with COVID-19 infection undergoing lower extremity CT angiography had at least one clot in the leg, compared with only 69% of controls. The clots in the C-19 patients were significantly larger and affected arteries higher up in the leg with greater frequency than those in controls. Death or limb amputation was more common in the C-19 patients.

“We found that arterial thrombosis associated with COVID-19 infection was characterized by dire outcomes, namely strikingly increased rates of amputation and death, which in our series were 25% and 38%, respectively,” said study lead author Inessa A. Goldman, M.D., a radiologist at Montefiore and assistant professor at Albert Einstein College of Medicine in New York City. “For comparison, the rate of both amputation and death was only 3% among controls. It is unclear whether the patients’ concurrent C-19-related pneumonia, the virulence of the C-19-related clotting disorder or delayed initial arrival to the hospital contributed to these outcomes.”

“COVID-19 patients presenting with symptoms of leg ischemia only, were more likely to avoid amputation or death than patients who had symptoms of ischemia plus other systemic symptoms including cough, respiratory distress or failure, hypoxia, fever, or altered mental status.” she said.

“In our cohort none of the five patients presenting with complaints pertaining to leg symptoms only, such as pain or discoloration, without systemic symptoms sustained amputation or died,” Dr. Goldman said.

Dr. Goldman noted that with infection rates rising in many parts of the country, it is important that physicians be mindful of the connection between COVID-19 and lower extremity arterial thrombosis.

The paper concludes that recognition of lower extremity ischemia and arterial thrombosis as a symptom or complication of COVID-19 disease may allow for prompt diagnosis and treatment of this condition.

With regards to VTE prophylaxis, global guidance recognises that critically-ill C-19 patients breach two out of three criteria of Virchow’s triad.  Reduced venous flow due to immobility and inflammation of the endothelium in blood vessels results in pro-thrombotic changes and increased risk of VTE. Patients with severe C-19 are immobile, have an acute inflammatory state leading to a hypercoagulable state (ref: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7305763/) and there is the possibility of endothelial cell damage due to binding of the virus to ACE2 receptor3.

The optimal thromboprophylaxis in COVID patients is still unknown. Drug-to-drug interactions between antiviral treatments and direct oral anticoagulants, and the difficulty in maintaining stable INRs (international normalized ratio – is a calculation) in patients taking vitamin K antagonists while unwell, mean that patients on these drugs are typically switched to low molecular weight heparins (LMWHs – blood thinners) or unfractionated heparins (UFH) with or without mechanical prophylaxis 3.

Whilst low dose blood thinners are considered low risk, giving larger doses can cause excessive bleeding with poor clinical outcomes4. C-19 coagulation guidance therefore advocates stepping-up preventative dosing but reinforces the need for individual patient bleed risk assessment4. This unpredictable, high bleed risk is why guidance also supports use of mechanical prophylactic devices in combination with drugs or when drugs and other mechanical compression devices are deemed impractical or contraindicated.

Sky Medical Technology’s clinically proven mechanical therapy, used to prevent VTE in immobile acute stroke patients, is the innovative geko™ device5. Recommended by NICE6 and cleared by the FDA7 for VTE prevention, geko™ is a small, battery powered, disposable, neuromuscular electro-stimulation 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 calf8, at rate equal to 60%9 of walking without the patient having to move.

Highly portable, the geko™ device is:

  • Disposable – no need to sterilise after single patient use.
  • No decontamination required – not the case with other mechanical devices.
  • Easy-to-fit – minimal training.
  • Less nurse-to-patient contact time – reduced exposure to C-19 viral load.
  • No tripping hazard – no leads or hoses.

The geko™ device is also clinically proven to improve endothelial function10,12 , through its  systemic blood flow increase, exerting laminar (steady) shear stress on endothelial cells, releasing protective substances, such as nitric oxide and prostacyclin and the production of anti-thrombotic, pro-fibrinolytic and vasodilation agents to help combat C-19 micro- clotting. Link to blog: https://www.gekodevices.com/news-events/covid-19-potentially-an-endothelial-disease/

About DVT

DVT occurs when a blood clot forms in a large vein, usually in the calf. Swelling, pain and serious complications, such as PE (a sudden blockage in the lung) can occur and makes DVT a potentially fatal condition. Rapid treatment is imperative. DVT formation is attributed to the three major risk factors of Virchow’s triad: venous stasis, vessel injury and hypercoagulability11.

Geko™ device evidence – VTE prevention

A real-world in service evaluation conducted in the UK National Health Service shows the geko™ device is clinically proven to prevent VTE5. 1,000 immobile, hyper-acute stroke patients had their contraindication and/or intolerance to IPC reviewed and quantified. The audit showed that 68.8% of patients were in need of IPC (intermittent pneumatic compression) but 29.5% of these patients were either contraindicated or were unable to tolerate IPC, revealing a significant unmet need for an alternative anti-stasis (blood clot prevention) intervention. The geko™ device was fitted to patients who had no other means of DVT prophylaxis.

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 a greater tolerance of the device compared to IPC. Furthermore, the geko™ device provided an anti-stasis intervention where previously patients would have had no other intervention available to them, ensuring that there were no immobile stroke patients with a high risk if VTE without a mechanical VTE prophylactic intervention.

(Note – anticoagulant drugs are not recommended for use by NICE to treat patients post-acute stroke in the UK).


  1. Inessa A, et al. Lower extremity arterial thrombosis associated with COVID-19 is characterized by greater thrombus burden and increased rate of amputation and death. Radiology, 2020; 202348 DOI: 1148/radiol.2020202348.
  2. Bompard F, et al. Pulmonary embolism in patients with COVID-19 pneumonia. Eur Respir j. 2020 Jul: 56(1): 2001365. Published on-line 2020 Jul. doi: 10.1183/13993003.01365-2020.
  3. Prof Beverley Hunt OBE, Dr Andrew Retter, Dr Claire McClintock. Practical guidance for the prevention of thrombosis and management of coagulopathy and disseminated intravascular coagulation of patients infected with COVID-19. March 2020.
  4. Xu et al. Risk assessment of venous thromboembolism and bleeding in COVID-19 patients. Pre-clinical.
  5. 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.
  6. NICE medical technologies guidance [MTG19] Published date June 20 2014.
  7. FDA clearance: https://www.fdanews.com/articles/193424-sky-medicals-geco-device-cleared-for-marketing.
  8. Nicolaides, M Griffin, Measurement of blood flow in the deep veins of the lower limb using the geko™ neuromuscular electro-stimulation device. Journal of International Angiology August 2016-04.
  9. Tucker A, et al. Augmentation of venous, arterial and microvascular blood supply in the leg by isometric neuromuscular stimulation via the peroneal nerve. The International journal of angiology: official publication of the International College of Angiology, Inc. 2010 Spring;19(1): e31-7.
  10. Lavi S et al. The Impact of Peripheral Nerve Stimulation on Coronary Blood Flow and Endothelial Function. Cardiovasc Drugs Ther (2015) 29:527–533 DOI 10.1007/s10557-015-6628-z.
  11. Virchow’s Triad. Virchow triad is a basis for understanding the factors that contribute to thrombosis, including: From: Radiology Secrets Plus (Third Edition), 2011.
  12. Barnes R, et al. Fibrinolytic effects of peroneal nerve stimulation in patients with lower limb vascular disease. Blood Coagulation & Fibrinolysis: April 2016 – Volume 27 – Issue 3 – p 275-280 doi: 10.1097/MBC.0000000000000409.

Sue Davenport-VP Marketing Communications
4th December 2020