Prognostic Value of Repeating Cardiac Magnetic Resonance in Patients With Acute Myocarditis

Background: Cardiac magnetic resonance (CMR) is widely used to confirm the diagnosis of acute myocarditis (AM) in the acute setting. CMR is often repeated after 6 months to assess the evolution of myocardial involvement. However, the clinical and prognostic role of 6-month CMR is unknown. Objectives: This multicenter study aimed to evaluate the clinical and prognostic role of 6-month repetition of CMR in patients with AM. Methods: In a subgroup of 187 patients from the ITAMY (ITAlian study in MYocarditis) registry, CMR was performed within the first week after symptom onset (CMR-I) and repeated after 6 months (CMR-II). Results: Myocardial edema was detected in all the patients at CMR-I and persisted in 31 (16%) at CMR-II. LGE was detected in 182 (96%) patients at CMR-I and in 164 (86%) at CMR-II. At CMR-II, 20 (11%) patients presented a complete recovery from edema and LGE, 30 (16%) patients had edema with LGE, and 137 (73%) presented LGE without edema. LGE disappeared completely in 18 (10%) patients, the number of LGE segments decreased in 87 (46%), unchanged in 58 (31%), and increased in 26 (14%). During a median clinical follow-up of 7 years (25th to 75th percentile: 6 to 8 years) cardiac events occurred in 22 patients. At Kaplan-Meier curves, patients with LGE and without edema had worse prognosis than others (p < 0.0001). Patients with increased extent of LGE (p = 0.02) had a worse prognosis than those with decreased/unchanged LGE. At multivariate Cox regression analysis, the midwall septal pattern of LGE and the presence of LGE without edema at CMR-II were independent predictors of a cardiac event. Conclusions: In the acute setting, LGE does not mean definite fibrosis, and it may disappear at 6 months. The presence of LGE without edema at 6-month CMR is associated with worse prognosis, particularly when distributed with a midwall septal pattern. LGE without edema could represent definite fibrosis whereas the presence of edema suggests a residual chance of recovery.