Myocarditis Following Covid-19 Vaccination In Adolescents And Adults In 2021

BACKGROUND: Clinical course and outcomes of myocarditis after COVID-19 vaccination remain variable. METHODS: We retrospectively collected data on patients >12 years old from 01/01/2021 to 12/30/2021 who received COVID-19 vaccination and were diagnosed with myocarditis within 60 days of vaccination. Myocarditis cases were based on case definitions by authors. RESULTS: We report on 238 patients of whom most were male (n=208; 87.1%). The mean age was 27.4 +/- 16 (Range 12-80) years. Females presented at older ages (41.3 +/- 21.5 years) than men 25.7 +/- 14 years (p=0.001). In patients >20 years of age, the mean duration from vaccination to symptoms was 4.8 days +/-5.5 days but in <20, it was 3.0 +/- 3.3 days (p=0.04). Myocarditis occurred most commonly after the Pfizer-BioNTech vaccine; (n=183; 76.45) and after the second dose (n=182; 80%). Symptoms started 3.95 +/-4.5 days after vaccination. The commonest symptom was chest pain (n=221; 93%). Patients were treated with non-steroidal anti-inflammatory drugs (n=105; 58.3%), colchicine (n=38; 21.1%), or glucocorticoids (n=23; 12.7%). About 30% of the patients had left ventricular ejection fraction but more than half recovered on repeat imaging. Abnormal cardiac MRI was common; 168 patients (96% of 175 patients that had MRI) had late gadolinium enhancement, while 120 patients (68.5%) had myocardial edema. Heart failure guideline-directed medical therapy use was common (n=27; 15%). Eleven patients had a cardiogenic shock, and 4 patients required mechanical circulatory support. Five patients (1.7%) died, of these, 3 patients had endomyocardial biopsy/autopsy-confirmed myocarditis. CONCLUSIONS: Most cases of COVID-19 vaccine myocarditis are mild. Females presented at older ages than men and the duration from vaccination to symptoms was longer in patients >20 years. Cardiogenic shock requiring mechanical circulatory support was seen and mortality was low. Future studies are needed to better evaluate risk factors and long-term outcomes of COVID-19 vaccine myocarditis.