It goes without saying that the COVID-19 pandemic had profound effects on society and health across the globe. Between April 2020 and February 2022, around 4 million individuals had tested positive for Covid-19. Up to February 2022, an estimated 44 million people had the virus in the UK alone*.
Some people who have recovered from the immediate effects of COVID-19 describe ongoing symptoms including poor exercise tolerance, fatigue, chest pains, inappropriate increases in heart rate when standing and dizziness, common symptoms of ‘Post-COVID-19 Syndrome’ (sometimes termed long COVID-19). These symptoms typically last for more than 12 weeks and can be severely debilitating.
Post-Covid
As of March 2023, an estimated 1.9 million people in the UK self-reported post-COVID-19 syndrome symptoms. At present, the reasons why some people develop the syndrome and others do not is unknown. Understanding the causes of the condition may help in the development of new therapies to aid recovery.
Evidence has suggested that issues with multiple body systems might be driving post-COVID-19 symptoms, including the brain and parts of the nervous system that control heart rate and blood pressure.
A team from the University of Bristol’s School of Physiology, Pharmacology and Neuroscience including Dr Ahmed El-Medany, Dr Emma Hart, Dr Angus Nightingale and Dr Katrina Hope, used funding from a combined Elizabeth Blackwell Institute/Development Alumni Relations Office scheme for COVID-19 research, alongside funding from Bristol and Weston Hospitals Charity, for a pilot study investigating the effects of COVID-19 on bodily systems that control heart rate and breathing.
Carotid body
Nestled within branches of the carotid arteries - key blood vessels in the neck - are the carotid bodies. These tiny organs, around 2mm to 6mm across, monitor blood oxygen as well as CO2 , blood pH and temperature: they can thus influence heart rate, blood pressure and breathing rate. Carotid bodies are also potentially particularly susceptible to infection by the Coronavirus, which might explain some of the symptoms of post-COVID-19 syndrome, such as breathlessness, inappropriate increases in heart rate, and dizziness.
Dr El-Medany explains: “We were aiming to investigate whether the carotid body is involved in the development of post-COVID-19 syndrome in men and women. We recruited patients from two populations: Firstly, a group with Post-COVID-19 Syndrome, with symptoms lasting more than 12 weeks, and secondly a matched control group with COVID-19, whose symptoms lasted no longer than 4 weeks - as per NICE guidelines. We compared the carotid body control of heart rate and breathing at rest and during exercise.”
Elevated sensitivity
Dr El-Medany continued, “We showed for the first time that the carotid body amplifies its sensitivity to chemical changes in non-hospitalised patients with post-COVID-19 syndrome compared to a control group, and that this hypersensitivity is correlated to hyperventilation and poor breathing efficiency during exercise in affected patients. This elevated sensitivity could explain several of the ongoing symptoms experienced by patients living with post-COVID-19 syndrome.”
“These findings suggest that modulating carotid body excitability might be a new treatment option for post-COVID-19 syndrome. Our group has previously demonstrated a mechanism by which targeting receptors in the carotid body might help to reduce its overexcitability in an animal model of hypertension and heart failure, and this could also be a viable strategy in humans with post-COVID-19 syndrome.”
Continuation
As well as several international presentations and a publication resulting from the study, the group has used the pilot data generated in an application to the Medical Research Council Research Grant (Experimental Medicine Panel). Funding of £750K, was recently awarded, enough to initiate a new, 3 year project which will start in September 2024.
*source BBC https://www.bbc.co.uk/news/uk-51768274.