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. (J Am Coll Cardiol 2019;74:2439-48) (c) 2019 by the American College of Cardiology Foundation.