Cardiac MRI monitoring in acute myocarditis: predicting outcomes through serial imaging

OBJECTIVES: Myocarditis is a common disease with a risk of chronic progression. The aim of this study is to assess changes in MRI parameters during serial monitoring in patients with acute myocarditis (AM), and to evaluate their prognostic implications for the prediction of major adverse cardiac events (MACE). MATERIALS AND METHODS: In this prospective multicenter study, patients with MRI-confirmed AM between 2016 and 2020 underwent serial MRI: at baseline (6 interquartile range (IQR), 3-10 days after symptom onset), short-term (median 36 IQR, 33-42 days) and long-term (392 IQR, 358-435 days). Cardiac MRI parameters, including mapping, were evaluated. MACE at 5-year follow-up were collected. RESULTS: A total of 105 patients (age 38 IQR, 28-45 years; men 75, 71%) were enrolled. Infarct-like clinical presentation (80, 76%) was the most common, followed by heart failure (18, 17%) and arrhythmia (7, 7%). MACE occurred in 20/105 patients (28.5%). Persistence of active disease using LLc 2018 was found in 91% (87) of patients at short-term and 61.5% (48) of patients at long-term MRI. Lateral LGE pattern was associated with better prognosis (HR 95% CI = 0.19 0.09; 0.38; p-value < 0.0001), while scar burden at long-term MRI was associated with MACE (HR 95% CI = 1.15 1.07; 1.24; p-value < 0.001). Native T1 at short-time MRI (HR 95% CI = 1.021.01; 1.02; p-value < 0.0001) and T2 mapping at long-term MRI (HR 95% CI = 1.271.07; 1.52; p-value = 0.006) resulted independent predictors of events at multivariate analysis. Changes of MRI parameters at different time points were not predictors of MACE. CONCLUSION: Cardiac MRI allows for monitoring of the healing process. Persistence of inflammation after 1 year from onset is associated with unfavorable outcomes. KEY POINTS: Question Serial cardiac MRI with mapping may provide information about myocarditis healing vs chronic progression that can be useful for risk stratification? Findings Cardiac MRI showed persistence of active disease using LLc 2018 in 91% (87/96) of patients at short-term MRI and in 61.5% (48/79) at long-term MRI. At the long term, altered T2 mapping resulted predictors of adverse events together with higher LGE burden, altered troponin and dyspnea. Clinical relevance In acute myocarditis, serial cardiac MRI allows to monitor the healing process and identify the persistence of inflammation, which is associated with chronic evolution and unfavorable outcome.