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Coronavirus stroke warning: Covid-19 may cause increased blood clotting and raise the risk of blood vessel blockages in the brain, study shows

Coronavirus may cause an increased risk of blood clots and blockages in the brain and could lead to a stroke, according to a new study by University College London.
The small study focused on six patients with confirmed COVID-19 who had suffered a stroke caused by the sudden loss of blood circulation to the brain.
The team, that included neurologists from the National Hospital for Neurology and Neurosurgery, saw an increase in D-dimer - a blood protein linked to clotting.     
The authors say the exaggerated inflammatory immune response known to occur in COVID-19 patients stimulates abnormal blood clotting in the brain. 
The article, published in the Journal of Neurology, Neurosurgery, and Psychiatry, couldn't confirm a direct link between coronavirus and stroke as it was a small study.
'It is also possible that the effects of social distancing measures and anxiety about attending hospital might have influenced the spectrum of ischaemic stroke mechanisms in patients seen at our hospital,' the authors wrote.
However, they say there was evidence of raised D-dimer in the blood - that is a production of antibodies created from an abnormal immune system response. 
Corresponding author, Professor David Werring and colleagues looked at six patients with acute ischaemic stroke due to blockage of a large brain artery.
Acute ischaemic stroke is caused by the sudden loss of blood circulation to an area of the brain, resulting in loss of neurological function. 
The findings suggest early testing for D-dimer in COVID-19 patients, could enable clinicians to prescribe specific treatments at a much earlier stage.
They say this might reduce the number of people subsequently having further strokes or blood clots elsewhere in the body.
Professor Robert Storey, Professor of Cardiology, Department of Infection, Immunity & Cardiovascular Disease, University of Sheffield, said finding a link between COVID-19 and stroke isn't surprising as the infection can cause inflammation in the body.
He said inflammation is linked to increased risk of blood clots forming in blood vessels which is the most common cause of heart attack and stroke. 
'Inflammation can also accelerate the build-up of fatty deposits in blood vessels supplying the heart and brain, which can eventually lead to blood clot forming and blocking the blood vessels.' 
All six patients (aged between 53 and 85) had a large arterial blockage, with markedly elevated blood levels of D-Dimer and confirmed COVID-19.
Researchers say this indicates the presence of abnormally high 'fibrin degradation products' - components in the blood produced when clots break down. 
Five of the six ischaemic strokes occurred 8-24 days after COVID-19 symptom onset, and in one patient during the pre-symptomatic phase.
The researchers say this suggests that COVID-19 associated stroke is usually delayed, but can occur both early and later in the course of the disease.
Professor Tim Chico, Professor of Cardiovascular Medicine and Honorary Consultant Cardiologist, University of Sheffield, said the findings of this study were consistent with other evidence linking COVID-19 to the risk of blood clots.
'Because otherwise healthy people, or people sick with diseases other than COVID-19 often suffer blood clots, it is impossible to say in any individual person that their blood clot was 'caused' by COVID-19,' he said.
'However, the growing numbers of publications, and the experience of doctors treating COVID-19 patients including myself and my colleagues, strongly suggest COVID-19 substantially increases the risk of blood clots in hospitalised patients.  
Discussing the findings, Professor Werring, said we already know that COVID-19 is not just a disease of the lungs - this proves a link to stroke in some patients.
'Our findings suggest that blockages of large brain arteries in COVID-19 patients are associated with highly abnormal blood clotting,' he said.
'Early use of anticoagulant drugs might be helpful, but this needs to be balanced against their brain bleeding risk, especially soon after a stroke.'
He said clinical studies are needed to find out the best treatment to reduce the disability caused by ischaemic stroke in people with COVID-19. 
'Our findings emphasise that even during the lockdown people with suspected stroke must attend hospital immediately to ensure they get the best treatment.' 
As well as clinical trials on vaccines and anti-viral drug studies, there are a number of clinical trials examining what level of blood thinning treatment should be used in people hospitalised with COVID-19.  
'This study cannot tell us what proportion of patients with COVID-19 suffer blood clots, or whether the risk of this is related to the severity of the disease or can occur even in people with mild or no symptoms,' said Professor Chico.
This requires a comprehensive study including thousands of patients, he said.
There has been a 'worrying reduction in non-COVID-19 admissions of stroke and heart attack', said Chico, adding this could be hiding a bigger problem.  
'People who already take blood thinning medication such as aspirin should continue to take these if they develop COVID-19 like symptoms unless otherwise advised by their medical team,' said Chico. 
The research 'Characteristics of ischaemic stroke associated with COVID-19' was published in the Journal of Neurology, Neurosurgery, and Psychiatry.


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