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Cardiac parameters suggestive of myocarditis were no more common at 6 months after mild or asymptomatic COVID-19 than among people who never had the infection, a prospective case-control study found.

Compared with seronegative healthcare workers, those who had generally mild SARS-CoV-2 had no differences in cardiac structure, function, MRI markers of myocarditis, or cardiac injury biomarkers 6 months later, James Moon, MD, of St. Bartholomew's Hospital in London, and colleagues reported in .

The maximum prevalence of myocarditis in the type of healthcare worker population they studied may be less than 4% at 6 months, the analysis suggested.

"Thus, screening in asymptomatic patients following nonhospitalized COVID-19 is currently not indicated," the group concluded, pointing to it as yet more evidence counteracting an early but alarming finding that 78% of COVID survivors had lingering myocardial inflammation and other cardiac MRI abnormalities.

Colin Berry, PhD, and Kenneth Mangion, PhD, both of the University of Glasgow, agreed in an , calling the findings welcome reassurance for healthy individuals.

The analysis included a subset of the 731 healthcare workers at three London hospitals who had been monitored weekly in the for COVID-19 symptoms, PCR testing, and serology assessment during a 4-month period in the first wave of the pandemic there before May 2020.

Of that cohort, 74 seropositive individuals (half of those available in COVIDsortium) were followed up at 6 months with a full panel of cardiovascular biomarkers and cardiovascular MR (CMR) imaging along with 75 seronegative controls from the same cohort who were matched for age, sex, and ethnicity. Only one of this seropositive group had been hospitalized for COVID-19 (for 2 days), while 11 (15%) had asymptomatic infections.

The study population was fairly young (median age 37) and skewed toward white females (42% men, 32% non-white ethnicity).

"This is a reasonably reassuring result drawn from a healthy population," the editorialists wrote, "however, the sample size limits the precision of this estimate, and the prevalence of cardiovascular abnormalities (e.g., myocardial scar) would be expectedly higher in an unbiased community population including individuals from less-advantaged socioeconomic circumstances (e.g., unemployed) and with pre-existing health problems.

"Nonetheless, healthcare workers represent an important subgroup of the infected population, and dedicated research in this workforce is welcome," Berry and Mangion added.

No statistically significant differences turned up between the seropositive and seronegative groups in the pre-specified primary endpoints: left ventricular ejection fraction, indexed end-diastolic volume, late gadolinium enhancement on CMR indicative of cardiac scar, and septal T1 and T2 indicating inflammation. The same was true for the pre-specified secondary endpoints: left ventricular mass, left atrial area area, global longitudinal shortening, septal extracellular volume, and aortic distensibility.

Troponin and N-terminal pro–B-type natriuretic peptide likewise were similar between groups.

Using the seronegative group to define normal for these parameters, myocarditis-like scar was seen in 4% of both the seropositive and seronegative groups without any significant difference. While 13 had late gadolinium enhancement (median 1%, maximum 5% of myocardium), these were split between groups.

However, the researchers cautioned that their study "does not prove that apparently mild SARS-CoV-2 never causes chronic myocarditis. The study design would not distinguish between individuals who had sustained completely healed myocarditis and pericarditis and those in whom the heart had never been affected."

Study imitations, the team said, included lack of pre-COVID and early post-infection scans and biomarkers for comparison, and not having assessed CMR "abnormalities" by .

Importantly, the editorial pointed out: "Healthcare workers are not representative of the wider, unselected, at-risk, community population. Cardiovascular risk factors and concomitant health problems may be more prevalent in an unselected community population than in healthcare workers, and prior studies have highlighted the clinical implications (interaction) for disease pathogenesis in COVID-19."

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