Suspected Myocarditis After COVID-19 Vaccination

Quick Takes

  • Among 140 episodes of myocarditis temporally related to vaccination for COVID-19, nearly all patients presented with chest pain, and all had elevated troponin.
  • Myocarditis tended to be mild, with 18.7% of patients having LVEF <55%. There was no mortality and no requirement for mechanical circulatory support. All patients with follow-up had normalization of LV function.
  • Abnormal cMRIs were common, with the most frequent findings being late gadolinium enhancement (76.3%) and myocardial edema (55.7%).

Study Questions:

What are the clinical course and short-term outcomes of suspected myocarditis following coronavirus disease 2019 (COVID-19) vaccination in patients <21 years of age?


A case series at multiple centers in the United States and Canada was performed. Patients presented prior to July 4, 2021 and had suspected myocarditis within 30 days of vaccination. Myocarditis cases were classified as confirmed or probable based on the Centers for Disease Control and Prevention definitions.


A total of 139 patients with 140 episodes of suspected myocarditis (49 confirmed, 91 probable) were enrolled at 26 centers. Most patients were male (90.6%) and White (66.1%), while 20.9% were Hispanic. The median age was 15.8 years (range 12.1-20.3 years). Symptoms started a median of 2 days after vaccination, with 91.4% of myocarditis cases occurring after the second dose. The most common symptom was chest pain, which occurred in 99.3% of patients. Troponin was elevated in all patients, and 68.9% of patients had abnormal electrocardiograms and/or arrhythmias. Median hospital stay was 2 (range 0-10) days. There were no deaths, and no patients required mechanical circulatory support, although two were treated with inotropic/vasoactive support. Left ventricular ejection fraction (LVEF) was <55% in 18.7% of patients. Among these 26 patients, all with follow-up (n = 25) had normalized function. Of the cohort, 97 patients underwent cardiac magnetic resonance imaging (cMRI) at a median of 5 days from symptom onset. cMRI was abnormal in 77.3% of patients, with 76.3% demonstrating late gadolinium enhancement, and 55.7 % with myocardial edema. Fifty-five percent met Lake Louise Criteria for myocarditis on cMRI.


The authors concluded that most cases of suspected COVID-19 vaccine myocarditis in patients <21 years of age have a mild clinical course with rapid resolution of symptoms. Abnormal findings on cMRI are common in the acute phase of illness.


Myocarditis has been found to occur following vaccination for COVID-19, specifically with the mRNA vaccines. Myocarditis appears to occur most commonly in young males after the second dose of the mRNA vaccines. A recent study from a large health care organization in Israel showed an overall incidence of 2.13 per 100,000 persons, with the highest risk in males between the ages of 16 and 29 years, with an incidence of 10.69 per 100,000 persons. The current study provides a closer look at the natural history of vaccinate-associated myocarditis, and this is overall reassuring. Symptoms are generally mild, and a large majority of patients show normal LV systolic function on echocardiogram. All patients with decreased LV systolic function on echocardiogram had normalization of function on follow-up. Given the large number of patients with abnormal cMRI findings, further follow-up is required to understand the long-term outcomes and issues for myocarditis temporally related to COVID-19 vaccination.

Clinical Topics: Arrhythmias and Clinical EP, Congenital Heart Disease and Pediatric Cardiology, COVID-19 Hub, Heart Failure and Cardiomyopathies, Noninvasive Imaging, Prevention, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias, CHD and Pediatrics and Arrhythmias, CHD and Pediatrics and Imaging, CHD and Pediatrics and Prevention, Echocardiography/Ultrasound, Magnetic Resonance Imaging

Keywords: Adolescent, Arrhythmias, Cardiac, Chest Pain, COVID-19, COVID-19 Vaccines, Diagnostic Imaging, Echocardiography, Edema, Electrocardiography, Gadolinium, Length of Stay, Magnetic Resonance Imaging, Myocarditis, Pediatrics, RNA, Messenger, Secondary Prevention, Stroke Volume, Troponin, Vaccination, Ventricular Function, Left

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