mRNA COVID-19 Vaccination and Development of CMR-confirmed Myopericarditis

Introduction: Several case reports or small series have suggested a possible link between mRNA COVID vaccines and the subsequent development of myocarditis and pericarditis. This study is a prospective collection and review of all cases with a myocarditis/pericarditis diagnosis over a 2-month period at an academic medical center. Methods: Prospective case series from 1st June 2021 until 31st July 2021. Patients were identified by admission and discharge diagnoses which included myocarditis or pericarditis. Inclusion criteria were: in receipt of mRNA vaccine within one month prior to presentation; The CMR protocol included cine imaging, native T1 and T2 mapping, late gadolinium enhancement and post contrast T1 mapping. All CMR studies were read in consensus by two experienced readers. Diagnosis was based on clinical presentation, ECG/echo findings and serial troponins and was confirmed in each case by CMR. Incidence was estimated from total doses of mRNA vaccine administered in the Ottawa region for the matching time-period. This data was obtained from the Public Health Agency of Ottawa. Results: 32 patients were identified over the period of interest. Eighteen patients were diagnosed with myocarditis; 12 with myopericarditis; and 2 with pericarditis alone. The median age was 33 years (18-65 years). The sex ratio was 2 females to 29 male. In 5 cases, symptoms developed after only a single dose of mRNA vaccine. In 27 patients, symptoms developed after their second dose of. Median time between vaccine dose and symptoms was 1.5 days (1-26 days). Chest pain was the commonest symptom, but many others were reported. Non-syncopal non-sustained ventricular tachycardia was seen in only a single case. Median LV ejection fraction (EF) was 57% (44-66%). Nine patients had an LVEF below the normal threshold of 55%. Incidence of myopericarditis overall was approximately 10 cases for every 10,000 innoculations. Summary and Conclusions: This is the largest series in the literature to clearly relate the temporal relationship between mRNA COVID vaccination, symptoms and CMR findings. In most patients, symptom onset began within the first few days after vaccination with corresponding abnormalities in biomarkers and on ECG. Cardiac MRI confirmed acute myocardial and pericardial changes with the presence of edema demonstrated with both tissue mapping and late gadolinium enhancement. Symptoms settled quickly with standard therapy and patients were discharged within a few days. No major adverse cardiac events and no significant arrhythmias were noted during inpatient stay. Further follow up will be required to ascertain the longer-term outcomes of this patient group.