Acute myocarditis (AM) diagnosis is a challenge based on the association of clinical and para-clinical criteria. This pathology is thought to favour the evolution towards dilated cardiomyopathy and the occurrence of severe arrhythmias. Three months after the acute episode, re-evaluation including cardiac MRI could help to identify patients at risk for unfavourable evolution. The use of MRI has rarely been investigated in AM prognosis stratification.

we report a prospective series of 31 consecutive patients hospitalized for AM: 28 men and 3 women, 33 years old on average, without sign of heart failure. All patients presented with troponine I elevation. Echocardiography showed moderate global left ventricular dysfunction in 6 cases and segmental wall motion abnormalities in 18. MRI performed early after admission never showed myocardial first-pass perfusion defect after gadolinium injection but subepicardial delayed-enhancement (DE) areas in 29 cases mainly located in lateral segments. Three months after the acute episode, no patient was symptomatic. Echocardiography, Holter monitoring and biological check-up were normal. MRI showed the persistence of DE in 17 cases without wall motion abnormality in the affected segments. The presence of these latter abnormalities led to effect an annually clinical examination with an ECG. One patient was lost at further follow-up. Among the other 16 patients, none was symptomatic or displayed ECG abnormalities at 3–year mean follow-up.

at the time of admission, the absence of early perfusion defect at cardiac MRI after gadolinium injection and the subepicardial localization of the DE constitute reliable criteria in favour of AM diagnosis, allowing to rule out an acute coronary syndrome. During the follow-up the persistence of a DE does not allow any prognosis stratification. In our series after a mean 3-year follow-up, it is not associated with any clinical and paraclinical disorder.