Prognostic role of updated Lake Louise criteria for the diagnosis of acute myocarditis (ITAMY-mapping study)

Aims: To assess the prognostic value of LL criteria in AM. Methods: 257 consecutive hemodynamically stable patients fulfilling updated LL criteria for diagnosis of clinically suspected AM (presenting with chest pain, troponin raise and no obstructive coronary artery) were enrolled. CMR imaging was performed using 1.5-T scanners following Updated LL criteria. Patients were divided into two groups accordingly to the combination of LL criteria: those with AM diagnosis made using the “original” LL Criteria (DOC), who exhibited both myocardial edema on T2-STIR images and non-ischemic late gadolinium enhancement (LGE), and those in whom diagnosis requiring at least one “mapping” Criteria (DMC) group, where the diagnosis was made either solely on the basis of mapping criteria (T2 + T1 and/or ECV) or by combination of only one original plus ≥1 mapping criterion. Cardiac death, resuscitated cardiac arrest, appropriate implantable cardioverter-defibrillator (ICD) shock, heart failure hospitalization and myocarditis recurrence were considered as cardiac events during the follow-up. Results: Final population included 210 patients. During a median follow-up of 57 months, cardiac events were recorded in 31 patients, all of them occurred in the DOC group and none in DMC group. The Kaplan-Meier curves analysis showed that DOC group (p < 0.0001), LGE presence (particularly if midwall-septal/ring-like pattern, p < 0.0001) and a higher number of LL criteria (p = 0.0002) were associated with worse prognosis. At multivariate analysis the number of LL criteria, DOC and midwall septal/ring-like LGE pattern were confirmed to be independent predictors of major cardiac events. Conclusions: In patients with hemodynamically stable AM, conventional LL criteria including edema at T2-STIR and positive LGE provide significant prognostic information, while mapping criteria had a limited role.