Observational StudyMYocarditis and/or Pericarditis Following mRNA COVID-19 VACCination National Surveillance Study

Inclusion Criteria:

• Inclusion criteria for vaccine associated myocarditis/pericarditis.

1. COVID-19 vaccination within previous 42 days. AND
2. At least one cardiac symptom of suspected myocarditis/pericarditis (Appendix 5).

OR At least two non-specific symptoms (Appendix 5). OR In infants and young children, at least two non-specific pediatric symptoms (Appendix 5).

OR No symptoms, but abnormal histopathology or a combination of abnormal cardiac biomarkers with abnormal cardiac imaging (echo or MRI).

AND
3. At least one of the following objective findings (Brighton Criteria case definitions, Appendices 1 to 5):

1. Histopathologic examination of myocardial tissue (autopsy or endomyocardial biopsy) showed myocardial inflammation.
2. Elevated myocardial biomarker (Troponin T, Troponin I, or CK-MB).
3. Cardiac MRI abnormality.
4. Echocardiographic abnormality.
5. New or worsening arrhythmia on electrocardiogram, Holter monitor, or telemetry.
6. Elevated inflammation biomarkers: erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), hs-CRP, or D-Dimer.
7. Physical examination pericardial friction rub or pulsus paradoxus.
8. Pericardial fluid or inflammation by imaging (echo, MRI, or CT).
9. Enlarged heart on chest radiograph.

AND
4. No alternative cause of presentation. e.g. infectious or autoimmune myocarditis.

• Inclusion criteria for COVID-19 associated myocarditis/pericarditis

1. COVID-19 infection within the previous 42 days.

AND
2. Myocarditis/pericarditis as per Brighton Criteria for vaccine associated myocarditis/pericarditis.

AND
3. No alternative cause of presentation.

Inclusion criteria alternative etiology myocarditis.

1. Myocarditis/pericarditis as per Brighton Criteria for vaccine associated myocarditis/pericarditis.

AND
2. No alternative cause of presentation.

Exclusion Criteria:

• For prospective invitation and follow-up, inability to provide informed consent. Consent will be sought from patients or their authorised substitute decision maker.
• Patients not fulfilling Brighton Criteria levels 1-3 will be excluded if they are level 4 (insufficient evidence for myocarditis) or Level 5 (not myocarditis) or have an alternative diagnosis such as myocardial infarction.