EPIDEMIOLOGICAL FRAMEWORK OF MYOCARDITIS DURING SARS–COV–2 PANDEMIC AND VACCINATION CAMPAIGN

Abstract

Abstract Rationale Myocarditis is an inflammatory condition of cardiomyocytes whose clinical course can be heterogeneous. Etiologies include infections (mostly viral), drugs or toxic exposures or auto–immunity, while few cases have been reported in association with vaccines (following, mainly, attenuated smallpox vaccine). Estimated prevalence is 2–22 cases/100000 people/year, with greater frequency in males aged 30–40. Since SARS–CoV–2 outbreak and vaccination campaigns there is growing interest in their association with myo–pericardial inflammatory conditions, with incidence reports of 1–5/100.000 and 1–5/1.000.000 respectively among vaccinated and unvaccinated subjects (as part of COVID–19) and relatively higher incidence in males after second (mRNA) vaccine administration. Study Design and Objective We designed this observational registry and included patients with CMR–confirmed myocarditis diagnosis admitted to Maggiore Hospital in Bologna from March 2017 to April 2023. Primary goal was to conduct an epidemiological analysis on myocarditis incidence in the era of SARS–CoV–2 and respective vaccination. Results We enrolled 48 patients, among which 37 were diagnosed during SARS–CoV–2 pandemic. 86% were male, and mean age at diagnosis was 31 years old; the vast majority did not show major modifiable CV risk factors (apart from cigarette smoking: 42%) or previous/comorbid CV conditions. Median LVEF (by CMR) at diagnosis was 56%, with 3 patients (6%) with LVEF < 47%. Median hsTnI and CRP peaks were respectively 7317 ng/L and 4,5 mg/dl. We reported 6 (12.5%) arrhythmic events during index hospitalization (1 patient had sustained VT and 5 had non–sustained VT). 8 out of 37 patients with myocarditis during SARS–CoV–2 outbreak reported previous COVID–19, with a median time of 130 days from infection, but only 1 had myocarditis as part of its clinical course. 16 patients had already received at least one SARS–CoV–2 vaccine dose (median: 2 doses) at diagnosis, with a median time of 117 days from dose administration (only two patients were diagnosed < 30 days from last administration). Conclusions Myocarditis epidemiology of our cohort seems to reflect available incidence data; furthermore, myocarditis as part of COVID–19 course or occurring shortly after vaccination appears to be an uncommon event. Our cohort consisted only of low or intermediate risk presentations. Data about diagnosis in the “COVID era” suggest a relative “underdiagnosis” in the previous period.