A higher percentage of patients with COVID 19-related myocarditis presented with the two main cardiac MR imaging findings for myocarditis based on the Revised Lake Louis Criteria, qualified by late gadolinium enhancement and myocardial edema. These two are markers for myocardial injury, with the presence of both giving strong evidence of myocardial inflammation.
However, this study also shows that these patients exhibit significantly better cardiac functions as compared to myocarditis from other causes. Patients with COVID 19-related myocarditis exhibit higher ejection fractions and lower end diastolic volumes for both right and left ventricles.
This may suggest that despite strong evidence of myocardial inflammation, there are less functional derangements and as such, better outcomes for COVID-19 related myocarditis as compared to other causes. Other studies have also postulated that like certain forms of myocarditis, COVID 19-related myocardial tissue changes may precede functional derangements4. This may indicate that patients with COVID 19-related myocarditis are still in the earlier stages of cardiac involvement and that follow-up imaging examinations are needed to better characterize the functional derangements of the disease.
Apart from these findings, this study also found that the most common cardiac segments which exhibited LGE in COVID 19-related myocarditis were the basal inferior, mid anterior, mid inferior, basal anterior septal, and basal inferolateral segments.
Limitations and Recommendations:
This single-center study was limited by the current capacity, availability of cases, and documented clinical data in the supporting institution. Cases included in the study were one-point CMR exams which aimed to diagnose myocarditis. Longitudinal follow-up studies are also suggested to better prognosticate and assess the progression of the disease. This study described the distribution of LGE in terms of cardiac segments, however, further studies may be done to include the pattern of enhancement, whether transmural, subepicardial, subendocardial, epicardial, midwall, or patchy. Myocardial edema was classified in this study as present or absent, however, it might also be interesting to note if there is a significant difference in the distribution of edema between these cases. COVID-19 vaccine-related myocarditis were not differentiated from post-illness COVID 19-related myocarditis. Separate studies which specifically focus on COVID 19-vaccine related myocarditis may also be undertaken.