Background: Acute myocarditis frequently mimics an acute myocardial infarction, and its diagnosis is a clinical challenge.
Aim: To describe the characteristics of cardiac magnetic resonance imaging in patients with acute myocarditis hospitalized with a diagnosis of ST-segment elevation myocardial infarction.
Patients and methods: Twenty-four patients aged 33 ± 11 years (21 men) with a definitive diagnosis of acute myocarditis hospitalized with a presumptive diagnosis of ST-segment elevation myocardial infarction, in whom a coronary angiogram excluded significant atherosclerotic coronary lesions, were included. Cardiac magnetic resonance imaging with cine-resonance images was performed to assess global and regional ventricular function, and to study myocardial tissue characteristics. T2-STIR sequences were used for the assessment of oedema and late gadolinium enhancement for necrosis/fibrosis.
Results: Patients had high levels of total CK, CK-MB, troponin I, brain natriuretic peptide and C-reactive protein. Cardiac magnetic resonance imaging revealed myocardial edema and late gadolinium enhancement was identified in all patients. The edema was transmural in 86% and subepicardial in 14%. Enhancement was subepicardial in 74% of patients and intramural in 26%. It was located in the inferior and lateral walls of the left ventricle in 93%, without affecting the endocardium. In all patients, two of three Lake Louise criteria were met, and an acute myocarditis was diagnosed.
Conclusions: Cardiac magnetic resonance imaging is the diagnostic method of choice for diagnosing acute myocarditis when it mimics an acute myocardial infarction.