The BNT162b2 (Pfizer- BioNTech) and mRNA 1273 (Moderna) vaccines are the first messenger RNA (mRNA)-based vaccines ever approved. In both vaccines, a mRNA sequence determines the structure and assembly of the immunogen, the SARS-CoV-2 spike (S) glycoprotein. Previous studies reported cases of myocarditis and/or pericarditis mainly in males less than 30 years of age following immunization with mRNA COVID-19 vaccines. Symptoms usually occur within the first three days following the second dose of mRNA COVID-19 vaccines. Most reported cases had a clinically mild course, but, some patients required intensive care support or even died of acute heart failure. In this study, the authors from Hong Kong, China, investigated the cardiac outcomes in adolescents diagnosed with COVID-19 vaccine-associated myocarditis up to one year after the diagnosis.
The findings like elevated troponin serum levels, abnormal ST-elevations in the electrocardiogram (ECG), altered ventricle movement in echocardiogram, or late gadolinium enhancement (LGE) in cardiac magnetic resonance imaging (MRI), suggest the development of myocarditis. The short-term clinical trajectory shows a resolution of cardiac symptoms and normalization of the left ventricular ejection fraction in most young patients, however, in a small proportion of symptomatic adolescents myocardial tissue sequelae (myocardial inflammation and edema) have been found approximately two months after the vaccination. https://discovermednews.com/pet-and-mri-visualization-of-myocardial-tissue-sequlae-in-17-patients-with-myocarditis-after-covid-19-vaccination/
About the Study and Results
In this study that evaluated the cardiac outcome of myocarditis associated with COVID-19 vaccination in adolescents up to one year after diagnosis, researchers included 40 patients, representing all cases identified in Hong Kong during the study. The majority, (33 participants) were males. The median age was 15.1 years, ranging from 12.7 to 17.9 years. All participants underwent ECG, echocardiogram, and cardiac MRI at presentation and the latest follow-up, and were followed for 10.0±1.3 months (ranging from 5.6 to 12.3 months).
During the follow-up period, 73% of included patients (29/40) were asymptomatic, 18% (7/40) reported noncardiac chest pain, 8% (3/40) palpitations, and 3% (one patient) a fatigue. There were no patients diagnosed with cardiac arrhythmias, angina pectoris, or heart failure.
At presentation, 78% (31/40) had abnormal ECG results with ST-segment or T-wave abnormalities. At the latest follow-up, ECG was normalized in all patients.
At presentation, the echocardiogram showed normal left ventricular ejection fraction in all patients. However, 15% of patients (6/40) had mildly increased echogenicity of the pericardium or left ventricular lateral wall, whereas 5% of patients (2/40) had minimal (<2 mm) pericardial effusion. At the latest follow-up, 5% of patients (2/40) had borderline left ventricular ejection fraction (51.1% and 53.6%), whereas in 95% of patients (39/40) the left ventricular ejection fraction was normal.
At presentation, cardiac MRI was done in 39 patients, and abnormal findings were found in 26 patients. These findings included features of myocarditis in 56% (22/39), abnormal T1 values in 54% (21(39), abnormal T2 values in 62% (24/39), LGE in 49% (19/39), and reduced left ventricular ejection fraction in 18% of patients (7/39).
At follow-up, cardiac MRI underwent 26 patients with initial abnormal MRI. 42% of patients (11/26) had normal findings, mild residual LGE was found in 58% (15/26), and borderline left ventricular ejection fraction in 8% (2/26). There were no patients with abnormal T1 values or features of myocarditis. The presence of LGE at diagnosis correlated with the presence of LGE on follow-up. Similar echocardiographic parameters were found in patients with (n=16) or without (n=11) LGE on follow-up cardiac MRI.
Conclusion
According to the authors, this study is, to their knowledge, the longest follow-up study of the cardiac outcome of vaccine-associated myocarditis in adolescents. The results showed that the global systolic ventricular function appears to be preserved. However, a comprehensive cardiac evaluation and imaging revealed impaired left and right ventricular myocardial deformation and persistence of residual LGE in a significant number of patients ( 58%) up to one year of follow-up.
The researchers suggested that these results are indicators of subclinical myocardial dysfunction and fibrosis with a potential long-term effect on exercise capacity and cardiac functional reserve during stress.
This article was published in Circulation.
Journal Reference
Kwong-man Yu C et al. Cardiovascular Assessment up to One Year After COVID-19 Vaccine–Associated Myocarditis. Circulation. 2023;148:436–439. Published online 2023 Aug 1 (Open Access) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10373639/
