Myocarditis and pericarditis during COVID-19 pandemic: a study of the Italian Society of Cardiology.

Aims: Some studies about myocarditis and pericarditis following COVID-19 vaccination raised concerns worldwide. However, the heterogeneous diagnostic criteria for postvaccination inflammatory heart diseases may result in overestimating incidence rates. The aim of this multicentre Italian registry is to evaluate the impact of COVID-19 vaccines on the incidence of myocarditis and pericarditis in the Italian population.

Methods: Consecutive patients admitted to Italian hospitals for endomyocardial and/or cardiac magnetic resonance proven acute myocarditis and/or pericarditis in the same period (1 June-31 October) of 2019 and 2021 were enrolled, irrespective of the potential association with the COVID-19 vaccines. Acute pericarditis and/or myocarditis were defined as 'vaccine-related' if clinical presentation occurred within 15 days after COVID-19 vaccination, independently of the dose.

Results: There was a comparable incidence rate ratio (IRR) for inflammatory heart diseases in 2019 and 2021 (2019: IRR 0.67 versus 2021: IRR 0.74, P = 0.45). In particular, the IRR did not differ in myocardial involvement (2019: IRR 0.33 versus 2021: IRR 0.33, P = 1) and pericarditis (2019: IRR 0.37 versus 2021: IRR 0.49, P = 0.09) in both periods. Among 125 cases registered in 2021, 32 (25.6%) were 'vaccine-related'. Among those who experienced 'vaccine-related' myocarditis and/or pericarditis, men with age under 40 years were over-represented (53.12%, P = 0.021).

Conclusion: In a nationwide Italian survey comparing pandemic with prepandemic periods, the overall data do not indicate significant concerns about an increased incidence of pericarditis and myocarditis, suggesting that the vaccine is generally well tolerated for these specific conditions.