Favourable outcome of acute myocarditis diagnosed by cardiac magnetic resonance imaging.

Aim: Acute myocarditis (AM) is increasingly diagnosed in the era of more sensitive imaging techniques. The natural history of AM diagnosed on cardiac magnetic resonance imaging (cMRI) may be different to historic cohorts due to the detection of milder disease. This study aims to measure the outcome of patients with AM detected by cMRI.

Methods: We retrospectively reviewed all cMRI studies performed over a 10-year period between 2012 and 2022. Patients with a diagnosis of AM based on cMRI criteria and clinical assessment were selected for inclusion.

Results: One hundred and ninety-six patients were included. The mean age was 42 years and 79% were male. Chest pain, fever or viral prodrome and dyspnoea were the most common presenting symptoms, and one patient presented with cardiac arrest. On cMRI, nine patients had left ventricular ejection fraction <40% and 174 patients had evidence of late gadolinium enhancement, most commonly affecting the basal inferolateral and inferior segments in a subepicardial and mid-wall distribution. Five patients required admission to intensive care unit (ICU). Important outcomes included the occurrence of ventricular arrhythmias in 17, recurrent or chronic myocarditis in 15 and implantable cardioverter defibrillator insertion in five patients, respectively. After a median follow-up of 4.6 years, there were no cardiac-related deaths, and three patients died from malignancy-related causes.

Conclusion: Patients with AM diagnosed by cMRI have a favourable medium-term outcome. Severe left ventricular dysfunction and ICU admission are rare. cMRI should be considered early in patients with suspected AM.