The Role of T1 and T2 Mapping in the Diagnosis of Different Types of Myocarditis

Background. Myocarditis is a heterogeneous inflammatory disease of the myocardium with a wide etiologic spectrum and highly variable clinical course, ranging from subclinical forms to severe heart failure and sudden cardiac death. Its diagnosis is particularly challenging in subacute, chronic and post-COVID presentations.Aim. To evaluate the diagnostic and clinical value of T1 and T2 mapping and extracellular volume quantification in patients with acute, healed, post-COVID and chronic myocarditis, as well as in the recovery phase, in comparison with established reference values.Materials and methods. Between January 2023 and October 2025, 166 patients (42 children, 124 adults) with suspected myocarditis underwent CMR at 1.5 T using a standardised protocol including native T1 and T2 mapping, post-contrast T1 mapping for extracellular volume calculation.Results. Acute myocarditis was confirmed in 31 patients, who showed markedly reduced left ventricular ejection fraction (40.4±12.8 %) and significantly increased native T1 mapping (1131±82 ms), T2 (54.7±5.6 ms) and extracellular volume (33.1±5.8 %; all p<0.0001). In 116 patients with healed myocarditis, including 67 (57.8 %) with prior COVID-19, left ventricular ejection fraction was moderately reduced (49.3±13.8 %), T2 mapping values were near-normal, whereas T1 mapping (1035.8±100.7 ms) and extracellular volume (28.6±4.2 %) remained elevated. No significant differences in T1, T2 mapping or extracellular volume were found between post-COVID and non-COVID subgroups. In seven patients in the recovery phase, T2 nearly normalized while T1 mapping and extracellular volume remained mildly increased, whereas six patients with chronic myocarditis exhibited the lowest left ventricular ejection fraction (27.2±3.9 %) and the highest T1 mapping and extracellular volume values, consistent with advanced fibrotic remodelling. Serial CMR in six patients confirmed a pronounced decrease in T2 with relatively stable or slightly elevated extracellular volume over time.Conclusions. These findings underscore the pivotal role of T1, T2 mapping and extracellular volume as quantitative biomarkers for phase differentiation, detection of post-COVID myocardial involvement and longitudinal monitoring in myocarditis.