Systematic Review and Meta-Analysis of Myocarditis Prevalence and Diagnostics in COVID-19:Acute, Post-COVID, and MIS-C (2020-2025).

Background: Myocarditis is a recognized complication of COVID-19, but prevalence estimates vary by disease phase and diagnostic method. Methods: We conducted a systematic review and meta-analysis of 54 studies including 32,500 patients, stratified by acute COVID-19, post-COVID, and MIS-C phases. Results: The pooled prevalence of myocarditis was 1.2% (95% CI: 0.8-1.6) in acute COVID-19, 7.4% (95% CI: 5.1-9.8) in post-COVID, and 39.8% (95% CI: 32.4-47.2) in MIS-C. CMR-based diagnosis yielded higher prevalence than clinical criteria (8.1% vs. 0.9%). Major cardiac outcomes included reduced LVEF in 22% and ventricular arrhythmias in 15% of cases. Heterogeneity across studies remained high (I2 = 98%). Conclusions: Myocarditis prevalence in COVID-19 varies widely across phases and diagnostic methods. Findings suggest a need for cautious screening approaches, particularly in MIS-C and selected post-COVID or athlete populations, while emphasizing the importance of standardized reporting and long-term follow-up data.