Cardiac magnetic resonance (CMR) is widely used to confirm the diagnosis of acute myocarditis (AM). And, it is often repeated after 6 months to assess the evolution of myocardial involvement.

This study sought to investigate the value of a control CMR within six months of an episode of AM.

This monocentric, observational study included patients with AM who were hospitalised between January 2009 and December 2019 in Toulouse University Hospital; 230 patients were included retrospectively in this study, among 137 had a control CMR (CMR+ group) and 93 without (CMR− group). The primary clinical endpoint was the occurrence of at least one of the cardiac events defined by: cardiology hospitalisation, heart failure, recurrence of myocarditis, death, and heart transplantation.

The two groups were equivalent with a mean age of 30±11, (P=0.374), 191 were male (83%; P=0.06) with a low cardiovascular risk. However, the MRI+ group had a larger left ventricular volume (P=0.03) as well as predominantly inferior enhancement (P=0.02) and lateral (P=0.001).

Regarding the primary endpoint, the two groups did not present any significant difference: 17 events in the CMR+ group (12%), and 13 events in the CMR− group (14%) (P=0.61). Kaplan–Meier analysis curve indicated that there was no significant difference between the two groups (P=0.614). There was no significant difference concerning the follow-up with a cardiologist (P=0.664) and the median duration of treatment (6 months, P=0.49 for beta-blockers, P=0.25 for angiotensinogen-converting enzyme inhibitors). Regarding the Cox model analysis to predict the occurrence of the primary endpoint in the control, if performed, the control CMR did not provide any prognostic information.

With regard to the results of our study, performing a control CMR after an episode of AM does not improve the prognosis of the patients.