By Robert Preidt
Previously reported rates of myocarditis in COVID-19 patients ranged from 14% among recovered athletes to 60% in middle-aged and older recovered patients.
"Although it is clear that COVID-19 impacts the heart and blood vessels, to date, it has been difficult to know how reproducible any changes are due to the relatively small sample size of most autopsy series," said study author Dr. Richard Vander Heide. He's professor of medicine at Louisiana State University (LSU) Health Sciences Center, in New Orleans.
To get a clearer picture, the investigators analyzed autopsies of 277 people who died of COVID-19 in nine countries.
The rate of myocarditis in these patients was between 1.4% and 7.2%, the researchers found.
The findings suggest that myocarditis caused by COVID-19 may be relatively rare, according to Vander Heide and co-author Dr. Marc Halushka. He's professor of pathology at Johns Hopkins University School of Medicine, in Baltimore.
"What we have learned is that myocarditis is not nearly as frequent in COVID-19 as has been thought. This finding should be useful for our clinical colleagues to reconsider how to interpret blood tests and heart radiology studies," Halushka said.
Vander Heide said the large number of cases studied gave the researchers a better idea about what health changes to expect.
"Even a low myocarditis rate of 1.4% would predict hundreds of thousands of worldwide cases of myocarditis in severe COVID-19 due to the enormous numbers of infected individuals. Low rates of myocarditis do not indicate that individuals infected with SARS-CoV-2 are not having cardiovascular problems, but rather those complications are likely due to other stressors such as endothelial cell activation, cytokine storms or electrolyte imbalances," Vander Heide said in a LSU news release.
The researchers created a checklist for pathologists to use during autopsies of COVID-19 patients so there's consistency in investigating and reporting findings.
The report was published online recently in the journal Cardiovascular Pathology.
"This study demonstrates the importance of the autopsy in helping us determine what is occurring in the hearts of individuals passing away due to COVID-19," Halushka added.
For more on myocarditis, go to the U.S. National Library of Medicine.
SOURCE: Louisiana State University Health Sciences Center, news release, Oct. 30, 2020