UK study Shows That Blood Clots Caused By SARS-CoV-2 Infections Poses A Threat For Fatal Vascular Events For Up To 49 Weeks After Diagnosis!

A British new study by researchers from the University of Bristol,  University of Cambridge, Swansea University, National Health Service Digital- Leeds, University College London, King’s College London, Glasgow Caledonian University, University of Leicester, University of Edinburgh and the British Heart Foundation Data Science Centre has found that blood clots caused by SARS-CoV-2 infections poses a threat for fatal vascular events for up to 49 weeks after diagnosis!


 
The study did not however cover what effects would reinfections and also the various vaccines have on the generation of these blood clots or their durability or any enhanced potency to cause lethal vascular events.
 
To date, it is already known that SARS-CoV-2 infections induces a prothrombotic state, but the long-term effects of COVID-19 on incidence of vascular diseases are still unclear.
 
The research team studied vascular diseases after COVID-19 diagnosis in population-wide anonymized linked English and Welsh electronic health records from January 1 to December 7, 2020.
 
They estimated adjusted hazard ratios comparing the incidence of arterial thromboses and venous thromboembolic events (VTEs) after diagnosis of COVID-19 with the incidence in individuals without a COVID-19 diagnosis. They also conducted subgroup analyses by COVID-19 severity, demographic characteristics, and previous history.
 
It was found that among 48 million adults, 125 985 were hospitalized and 1 319 789 were not hospitalized within 28 days of COVID-19 diagnosis.
 
Interestingly, in England, there were 260 279 first arterial thromboses and 59 421 first VTEs during 41.6 million person-years of follow-up!
 
Adjusted hazard ratios for first arterial thrombosis after COVID-19 diagnosis compared with no COVID-19 diagnosis declined from 21.7 (95% CI, 21.0–22.4) in week 1 after COVID-19 diagnosis to 1.34 (95% CI, 1.21–1.48) during weeks 27 to 49. Adjusted hazard ratios for first VTE after COVID-19 diagnosis declined from 33.2 (95% CI, 31.3–35.2) in week 1 to 1.80 (95% CI, 1.50–2.17) during weeks 27 to 49. Adjusted hazard ratios were higher, for longer after diagnosis, after hospitalized versus non-hospitalized COVID-19, among Black or Asian versus White people, and among people without versus with a previous event.
 
Importantly, the estimated whole-population increases in risk of arterial thromboses and VTEs 49 weeks after COVID-19 diagnosis were 0.5% and 0.25%, respectively, corresponding to 7200 and 3500 additional events, respectively, after 1.4 million COVID-19 diagnoses.
 
The study findings showed that high relative incidence of vascular events soon after COVID-19 diagnosis declines more rapidly for arterial thromboses than VTEs.
 
Worrying however, incidence of vascular events remains elevated up to 49 weeks after COVID-19 diagnosis.
 
The study findings also indicated that frequent health checks after COVID-19 diagnoses and post-‘recovery’ are needed along with risk factor control, and use of secondary preventive agents in high-risk patients.
 
The study findings were published in the peer reviewed journal: Circulation (A Journal of the American Heart Association or AHA).
< ;a href="https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.122.060785">https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.122.060785
 
It should be noted that the study findings were based on the health records of more than 48 million unvaccinated adults from the first wave of the pandemic.
 
How the vaccinations and boosters along with the new SARS-CoV-2 variants affects the generation, durability and ‘potency’ of these blood clots are unknown and could be actually more worrisome!
 
The study findings already suggest that the early part of the COVID-19 pandemic may have led to an additional 10,500 cases of heart attacks, strokes and other blood clot complications such as deep vein thrombosis in England and Wales in 2020 alone, although the excess risk to individuals remains small and reduces over time!
 
The study also showed that not just hospitalized patients with disease severity were affected but also individuals with only mild or moderate disease.
 
The study team suggests that preventive strategies, such as giving high-risk patients medication to lower blood pressure, could help reduce cases of serious clots.
 
The research team studied de-identified electronic health records across the whole population of England and Wales from January to December 2020 to compare the risk of blood clots after COVID-19 with the risk at other times. Data were accessed securely and safely via the NHS Digital Trusted Research Environment for England, and the SAIL Databank for Wales.
 
Interestingly, it was found that in the first week after a COVID-19 diagnosis, individuals were 21 times more likely to have a heart attack or stroke, conditions which are mainly caused by blood clots blocking arteries!
 
This however dropped to 3.9 times more likely after 4 weeks which still as worrisome.
 
The medical researchers also studied conditions caused by blood clots in the veins: these include deep vein thrombosis and pulmonary embolism ie a clot in the lungs that can be fatal.
 
Shockingly, the risk of blood clots in the veins was 33 times greater in the first week after a COVID-19 diagnosis!
 
The study findings showed that this dropped to eight times higher risk after four weeks.
 
Importantly, the higher risk of blood clots after COVID-19 remained for the study duration, although by 26 to 49 weeks it had dropped to 1.3 times more likely for clots in the arteries and 1.8 times more likely for clots in the veins.
 
It should be noted that most past studies only focused on the impact of COVID-19 on blood clotting in individuals hospitalized with COVID-19.
 
This new study however shows that there was also an effect on individuals whose COVID-19 did not lead to hospitalization, although their excess risk was not as great as for those who had severe disease and were hospitalized.
 
The study team told Thailand Medical News that in individuals at the highest risk ie men over the age of 80 …an extra 2 men in 100 infected may have a stroke or heart attack after COVID-19 infection!”
 
All the study data analyzed was collected in 2020, before the mass vaccination rollout in the UK, and before more recent COVID-19 variants such as Delta and Omicron were widespread.
 
The study team are now studying data beyond 2020 to understand the effect of vaccination and the impact of newer variants.
 
However, preliminary data emerging from that new study is showing an even worrisome trend according to the study team.
 
Dr Jonathan Sterne, Professor of Medical Statistics and Epidemiology at the University of Bristol, Director of the NIHR Bristol Biomedical Research Centre and Director of Health Data Research UK South West, who co-led the study told Thailand Medical News, "We are reassured that the risk drops quite quickly, particularly for heart attacks and strokes but the finding that it remains elevated for some time highlights the longer-term effects of COVID-19 that we are only beginning to understand."
 
Study co-lead, Dr Angela Wood, Professor of Biostatistics at the University of Cambridge, Associate Director of the British Heart Foundation Data Science Centre added, “Our study findings have shown that even individuals who were not hospitalized faced a higher risk of blood clots in the first wave. While the risk to individuals remains small, the effect on the public's health could be substantial and strategies to prevent vascular events will be important as we continue through the pandemic."
 
Another study co-lead, Dr William Whiteley, Clinical Epidemiologist and Neurologist at the University of Edinburgh further added, "The effect that the SARS-CoV-2 infection has on the risk of conditions linked to blood clots is poorly studied, and evidence-based ways to prevent these conditions after infection will be key to reducing the pandemic's effects on patients."
 
Blood thinners and drugs that reduce clots are very important for post-COVID individuals pending a thorough assessment by their physicians.
 
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