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covid-19 and myocarditis: was it a false alarm?
early in the covid-19 pandemic, an alarming number of patients hospitalized with the virus were also found to have inflammation in their hearts, but now researchers aren't so sure.
mar 31 2023
4 minute read
as much as 30 per cent of patients hospitalized with covid-19 also had evidence of damage to the heart.
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research is beginning to cast doubt on the explosion of myocarditis findings during the start of the covid-19 pandemic.
myocarditis refers to inflammation of the heart muscles, reducing the heart’s ability to pump blood and potentially causing damage to the heart cells. while there are a few causes for the condition, the primary culprit is a viral infection — like a coronavirus — triggering inflammatory immune cells to flock to the heart muscles. the first case of myocarditis from a covid-19 illness was reported in a 63-year-old male in early 2020. afterwards, autopsy studies and case report began to note the presence of inflammation in the heart at an alarming rate.
however, thorough investigation of data collected at the start of the pandemic is beginning to tell another story, one that speaks to the multisystem impact of the sars-cov-2 virus that causes covid-19.
“yes, there is some myocarditis, but it’s much, much lower [than previously thought],” explains john greenwood, mb chb, professor of cardiology at the university of leeds. “it seems to be much less important than the clotting effects that covid-19 causes, so that blood clots either in the heart arteries or the tiny [blood vessels].”
hypervigilance for myocarditis
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while other coronaviruses have been implicated in myocarditis, its connection to covid-19 was high. so high, in fact, that many practitioners began to recommend that anyone at risk who had covid-19 and were complaining of symptoms like chest pain should be screened for the condition. and the more we looked for myocarditis, the more we found.
“initially there was widespread recommendations to screen and do some cardiology-specific tests to look for myocarditis in all athletes from asymptomatic covid-19 to severely sick with covid,” explains meagan wasfy, m.d., sports cardiologist at mass. general brigham. “every single one of them would get a series of tests.”
however, tests like electrocardiograms and mris are highly sensitive — for obvious reasons, they are designed to pick up even the slightest abnormality. these results are meant to be integrated with other tests, signs, and symptoms to come to a conclusion, but often any indication of inflammation of the heart in covid-19 patients was reported and attributed to the virus.
“when you know a patient’s got a disease — particularly a new disease that you’ve never seen before — and you do a scan of the body, then anything that you see abnormal you automatically attribute to the disease,” explains greenwood.
myocarditis is actually rare
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wasfy explains that many of the symptoms — shortness of breath, dizziness or fainting — is often more accurately explained by other factors caused by the virus. factors like blood clots (which wasfy didn’t see in her team’s study), lingering effects of pneumonia that could have occurred during a bout of covid-19, or inflammation in the lungs that interfered with getting enough oxygen.
“i think covid-19 myocarditis does exist, but it’s pretty rare,” says wasfy. “and it doesn’t explain the vast majority of symptoms that occur post-covid in athlete patients.”
the team looked specifically at student athletes who had been experiencing a cardiovascular symptom — like chest pain, heart palpitations or fainting — at least a month after coming down with the virus. in total, 21 patients underwent a cardiac ultrasound and blood tests, and many received heart mri scans. none of the participants were diagnosed with myocarditis.
once athletes were determined safe to exercise, the team then measured the athletes’ vo2 max and heart activity during intense bouts of exercise, finding that 42 per cent had an abnormal spirometry (a measure of how well the lungs are functioning). thirteen of the participants returned three to six months later for follow up tests, once they were feeling better. these patients generally had a reduction in cardiopulmonary symptoms, better oxygen metabolism and a lower heart rate than in their initial studies.
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now, the clinic is seeing fewer and fewer covid-19 patients with concerns about their heart, which wasfy attributes to a better understanding of how to prevent complications from the virus — like using inhalers for inflammation in the lungs and medications to prevent blood clots. vaccinations also helped reduce the amount of severe illness, limiting the amount of damage the virus could do.
less myocarditis, more blood clots and microinfarctions
outside of the athletic population, signs of heart damage were also connected to severe bouts of covid-19 illness. however, some research points to the effects of blood clots rather than inflammation as the cause.
during the first wave of the pandemic, greenwood and his team collected blood samples and mri scans from more than 300 hospitalized patients who had high levels of a protein called troponin in their blood — an indication that heart damage had occurred. these mri scans were added to a pool of patient scans who didn’t have covid-19, or who previously had covid-19 and didn’t have high troponin levels. the key, explains greenwood, was that the doctors analyzing the scans weren’t aware of who had covid-19 or not, or who had high blood levels of troponin.
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unsurprisingly, the really sick covid patients with troponin elevation had about twice the amount of heart abnormalities then the other groups. however, while there were some cases of myocarditis in the patient groups, it turned out the majority of the heart injuries they saw weren’t so much related to inflammation in the heart as they were related to heart attacks or tiny areas of tissues death (called microinfarctions). these injuries, greenwood explains, were likely related to the coagulation, or clotting effects of the virus.
greenwood is now investigating if these cases heal over time, and what the long-term effects of such damage are.
emma jones is a multimedia editor with healthing. you can reach her at emjones@postmedia.com or on instagram and twitter @jonesyjourn .
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