Background: Cardiac Magnetic Resonance (CMR) has a key role in subjects presenting with acute myocarditis, independent from left ventricular ejection fraction; it is widely used as a non-invasive imaging test for both diagnostic and prognostic purposes. However, poor data is available about the CMR-derived prognostic parameters of acute myocarditis with preserved ejection fraction (AMpEF). The aim of this study was to investigate the role of CMR in predicting outcomes in patients followed up for AMpEF, using a composite endpoint of all-cause mortality and hospitalization for heart failure (HF). Methods: We retrospectively enrolled 61 patients with diagnosed AMpEF. All patients underwent biohumoral, echocardiographic and CMR evaluation in the acute phase. Myocarditis was confirmed by Lake-Louis criteria assessed on CMR images. Mean follow-up was 4.8 ± 0.6 years during which a composite endpoint of all-cause mortality and hospitalization for HF was investigated. Results: The population was fairly homogeneous regarding baseline clinical features. In particular, no significant differences in age and main cardiovascular risk factors were found between patients with and without events at follow-up. Seven patients met the endpoint. They had significantly higher levels of circulating neutrophils in the acute phase (76 ± 7% vs. 61 ± 11%, p = 0.014) and a higher amount of left ventricular mass with delayed enhancement (DE-LVM, 18 (14-29.5) vs. 12 (8-16) g, p = 0.028). At Cox univariate analysis, DE-LVM was the only significant predictor of endpoint, regardless of the site of inflammation. Conclusions: DE-LVM can predict the composite endpoint of all-cause mortality and hospitalization for HF in a population of patients with AMpEF, representing a new added tool for prognostic stratification.
Keywords: acute myocarditis; cardiac magnetic resonance; late gadolinium enhancement; myocarditis with preserved ejection fraction.