Cardiac MRI Findings in COVID‐19 Vaccine‐Related Myocarditis: A Pooled Analysis of 468 Patients

Understanding the pattern and severity of myocarditis caused by the coronavirus disease 2019 (COVID‐19) vaccine is imperative for improving the care of the patients, and cardiac evaluation by MRI plays a key role in this regard. Our systematic review and meta‐analysis aimed to summarize cardiac MRI findings in COVID‐19 vaccine‐related myocarditis. We performed a comprehensive systematic review of literature in PubMed, Scopus, and Google Scholar databases using key terms covering COVID‐19 vaccine, myocarditis, and cardiac MRI. Individual‐level patient data (IPD) and aggregated‐level data (AD) studies were pooled through a two‐stage analysis method. For this purpose, all IPD were first gathered into a single data set and reduced to AD, and then this AD (from IPD studies) was pooled with existing AD (from the AD studies) using fixed/random effect models. I 2 was used to assess the degree of heterogeneity, and the prespecified level of statistical significance ( P value for heterogeneity) was <0.1. Based on meta‐analysis of 102 studies ( n = 468 patients), 79% (95% confidence interval [CI]: 54%–97%) of patients fulfilled Lake Louise criteria (LLC) for diagnosis of myocarditis. Cardiac MRI abnormalities included elevated T2 in 72% (95% CI: 50%–90%), myocardial late gadolinium enhancement (LGE) in 93% (95% CI: 83%–99%; nearly all with a subepicardial and/or midwall pattern), impaired left ventricular ejection fraction (LVEF) (<50%) in 4% (95% CI: 1.0%–9.0%). Moreover, elevated T1 and extracellular volume fraction (ECV) (>30), reported only by some IPD studies, were detected in 74.5% (76/102) and 32% (16/50) of patients, respectively. In conclusion, our findings may suggest that over two‐thirds of patients with clinically suspected myocarditis following COVID‐19 vaccination meet the LLC. COVID‐19 vaccine‐associated myocarditis may show a similar pattern compared to other acute myocarditis entities. Notably, preserved LVEF is probably a common finding in these patients.