Contribution of Cardiac MRI in the Diagnosis of Acute Myocarditis

Objective: To describe the MRI abnormalities observed in acute myocarditis. Materials and Methods: Retrospective cross-sectional study with a descriptive aim, carried out at the North Franche-Comte Hospital, over a period of 12 months, from January 2021 to December 2021. It covered all patients who received an MRI of heart disease and were diagnosed with myocarditis. The diagnosis of myocarditis was retained in all patients on the basis of two arguments: a T2 PSIR hyper signal and a late enhancement at 15 min in T1 PSIR with gadolinium. Results: Myocarditis was diagnosed in 20 patients out of a total of 214 who performed cardiac MRI, i.e. 10.30% of cases. The average age was 33.7 ± 14.3 with extremes of 17 and 69 years. We observed a male predominance with 11 men (55%) for 9 women (45%) or a sex ratio of 1.2. Clinical suspicion of myocarditis and acute coronary syndrome were the main indications for MRI. The lesion sites were subepicardial (95%) and/or intramural (30%), respecting the subendocardium, interesting for the majority, segments 12 (anterolateral) in 50% and/or 11 (inferolateral) in 43% of cases. Global hypokinesia was observed in 30% of patients associated with a decrease in LVEF. There was no cardiac volume abnormality or valvular abnormality. Conclusion: Cardiac MRI is nowadays the most efficient non-invasive imaging in the diagnosis of acute myocarditis. The diagnosis of myocarditis was made on 2 pathognomonic signs, namely a T2 STIR hyper signal and late enhancement at 15 min in T1 PSIR after injection of gadolinium. The morphology and lesion locations were in agreement with those described in previous studies. Global hypokinesia and pericardial effusion were observed in some patients. On the other hand, there was neither valvular anomaly, nor cardiac volume anomaly.