– The prospective study shows no evidence of myocarditis.
By Crystal Phend
Cardiac parameters suggestive of myocarditis were no more common 6 months after mild or asymptomatic COVID-19 than among people who had never had the infection, a prospective case-control study found.
Compared with seronegative healthcare workers, those with generally mild SARS-CoV-2 had no differences in cardiac structure, function, magnetic resonance myocarditis markers, or biomarkers of cardiac injury 6 months later, James Moon, MD, of St. Bartholomew's Hospital in London, and colleagues reported in JACC: Cardiovascular Imaging .
The analysis suggested that the peak prevalence of myocarditis in the type of healthcare worker population they studied may be less than 4% at 6 months.
"Therefore, screening in asymptomatic patients after COVID-19 who are not currently hospitalized is not indicated," the group concluded, noting that this is further evidence to counter an early but alarming finding that 78% of COVID survivors had persistent myocardial inflammation and other cardiac abnormalities on MRI.
Colin Berry, PhD, and Kenneth Mangion, PhD, both from the University of Glasgow, concurred in an accompanying editorial, calling the findings a welcome welcome for healthy people.
The analysis included a subset of the 731 healthcare workers in three London hospitals who had been monitored weekly in the study. COVIDsortium to detect COVID-19 symptoms, PCR tests and serological evaluation over a 4-month period during the first wave of the pandemic there before May 2020.
Of that cohort, 74 seropositive individuals (half of those available in COVIDsortium) were followed at 6 months with a full panel of cardiovascular biomarkers and cardiovascular MRI (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 leaned towards white women (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 scarring) would be higher in an unbiased study of the community population, including people from less favored socioeconomic circumstances (e.g., the unemployed) and with pre-existing health problems."
"However, 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 were found between the seropositive and seronegative groups in the prespecified primary endpoints: left ventricular ejection fraction, indexed end-diastolic volume, late gadolinium enhancement on cardiac MRI indicative of cardiac scarring, and septal T1 and T2 indicating inflammation. The same was true for the prespecified secondary endpoints: left ventricular mass, left atrial area, global longitudinal shortening, septal extracellular volume, and aortic distensibility.
Troponin and pro-B N-terminal natriuretic peptide were also similar between the groups.
Using the seronegative group to define normal for these parameters, myocarditis-like scarring was observed in 4% of both the seropositive and seronegative groups, with no significant difference. While 13 patients had late gadolinium enhancement (median 1%, maximum 5% of the myocardium), these were divided between the 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 people who had suffered fully healed myocarditis and pericarditis and those in whom the heart had never been affected."
The study's shortcomings, the team said, included the lack of pre- and post-COVID scans and biomarkers for comparison, and the failure to assess CMR "abnormalities" according to the modified Lake-Louise criteria.
It is important to note that the editorial pointed out: “Health 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 health workers, and previous studies have highlighted the clinical implications (interaction) for disease pathogenesis in COVID-19.”