Favourable Outcomes of Patients With Acute Myocarditis Diagnosed by Cardiac Magnetic Resonance Imaging: A Retrospective Study of 196 Patients

Abstract

Acute myocarditis (AM) is increasingly being recognised in the era of sensitive diagnostic techniques, and cardiac magnetic resonance imaging (cMRI) is central to the diagnosis of this condition. This study aimed to measure the outcome of patients with AM detected by cMRI. All cMRI for Auckland City Hospital patients (scanned at the Auckland University Centre for Advanced MRI) between June 2012 and June 2022 were retrospectively reviewed. Patients with a diagnosis of AM based on cMRI criteria and clinical assessment were included. A total of 196 patients were included. The mean age was 42 (SD, 18) years and 155 (79%) were male. Chest pain was the most common symptom (80%), followed by fevers or viral prodrome (48%), and dyspnoea (27%). One patient presented with cardiac arrest. The mean peak C-reactive protein was 58 mg/L and high-sensitivity troponin T 709 ng/L. Electrocardiographic abnormalities included ST-segment elevation (32%) and bundle branch block (9%). Coronary angiography was performed in 54% and none had obstructive coronary disease. In-hospital arrhythmia occurred in 12%. Five patients required admission to the intensive care unit (ICU). Mean cMRI left ventricular ejection fraction (LVEF) was 56% and nine patients (5%) had LVEF <40%. Median follow-up duration was 5.7 years and recurrent AM occurred in 15 patients (8%). Three patients died from malignancy and there were no cases of cardiovascular death. Patients with AM diagnosed by cMRI had favourable short- and medium-term outcomes. Severe left ventricular dysfunction and ICU admission were rare. cMRI should be considered in patients with myocardial infarction with non-obstructive coronary arteries (MINOCA).