Prognostic Value of Myocardial Parametric Mapping in Patients with Acute Myocarditis: A Retrospective Study

Purpose To investigate the prognostic value of T1 mapping, extracellular volume fraction (ECV), and T2 mapping in a large cohort of patients with acute myocarditis. Materials and Methods This retrospective study included patients with acute myocarditis who underwent cardiac MRI (3.0 T) between March 2016 and October 2022. Diagnosis was confirmed by diagnostic cardiac MRI criteria or endomyocardial biopsy. The primary end point was major adverse cardiovascular events (MACEs), defined as the composite of cardiac death, heart failure hospitalization, heart transplantation, sustained ventricular arrhythmia, and recurrent myocarditis. Univariable and multivariable Cox regression analyses were performed to assess the association of clinical and cardiac MRI variables with the primary end point. The prognostic value of each model was assessed using the Harrell C index. Results A total of 235 patients (mean age, 32 years ± 13 [SD]; 150 [63.8%] men) were included. During a mean follow-up of 1637 days (IQR: 1441-1833 days), MACEs occurred in 45 (19%) patients. Patients with MACEs had higher global native T1, ECV, and T2 values (1342 msec ± 64 vs 1263 msec ± 48; <i>P</i> < .001; 39.1% ± 8.7 vs 32.7% ± 5.7; <i>P</i> < .001; 61.1 msec ± 10.0 vs 55.3 msec ± 9.4; <i>P</i> = .03, respectively). In a series of multivariable Cox regression models, native T1 (per 10-msec increase: hazard ratio, 1.61; 95% CI: 1.31, 1.98; <i>P</i> < .001) and ECV (per 5% increase: hazard ratio, 1.70; 95% CI: 1.38, 2.08; <i>P</i> < .001) independently predicted MACE occurrence, and the addition of native T1 (Harrell C index = 0.76) or ECV (Harrell C index = 0.79) to the model including only clinical variables, left ventricular ejection fraction, and septal late gadolinium enhancement (Harrell C index = 0.72) improved discrimination for the primary end point. Conclusion Cardiac MRI-derived native T1 and ECV were independent predictors of MACEs in patients with acute myocarditis and provided incremental prognostic value when combined with conventional parameters. <b>Keywords:</b> MRI, Cardiac, Heart, Inflammation <i>Supplemental material is available for this article.</i> © RSNA, 2025.