COVID-19 vaccine-associated myocarditis (C-VAM) has a mild initial clinical course, but myocardial injury is common, according to a study published online in the October issue of eClinicalMedicine.

Supriya S. Jain, M.D., from New York Medical College-Maria Fareri Children’s Hospital at Westchester Medical Center in Valhalla, and colleagues examined the clinical characteristics, myocardial injury, and longitudinal outcomes of C-VAM.

A total of 333 patients aged 30 years or younger with C-VAM were compared to 100 patients with multisystem inflammatory syndrome in children (MIS-C). The presence of myocardial injury as evidenced by late gadolinium enhancement (LGE) on cardiac magnetic resonance (CMR) imaging was the primary outcome.

Patients with C-VAM were mainly White (67%), adolescent (age, 15.7 ±2.8 years) males (91%). The researchers found that compared with MIS-C, the initial clinical course of C-VAM was significantly more likely to be mild (80 versus 23%) and cardiac dysfunction was less common (17 versus 68%). LGE on CMR was significantly more prevalent in C-VAM than MIS-C (82 versus 16%).

The probability of LGE was significantly higher in male and older patients and when C-VAM occurred after the first or second versus the third mRNA vaccine dose. At a median follow-up of 178 days, midterm clinical outcomes of C-VAM were reassuring. In 60% of patients, LGE persisted at follow-up.

“While midterm clinical sequelae are rare and LGE severity decreases over time, the persistence of LGE at follow-up in most patients warrants continued clinical surveillance, additional research, and longer-term studies in this subset of patients,” the authors write.

Several authors disclosed ties to relevant organizations.

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