Clinical Presentation and Outcome in a Contemporary Cohort of Patients with Acute Myocarditis: The Multicenter Lombardy Registry

Background
-There is controversy regarding outcome of patients with acute myocarditis (AM), and lack of data on how patients admitted with suspected AM are managed. We report characteristics, in-hospital management and long-term outcome of patients with AM based on a retrospective multi-center registry from 19 Italian hospitals.
Methods
-A total of 684 patients with suspected AM and recent onset of symptoms (<30 days) were screened between May 2001 and February 2017. Patients >70 years and those older than 50 years without coronary angiography were excluded. The final study population comprised 443 patients (median age 34 years, 19.4% female) with AM diagnosed either by endomyocardial biopsy (EMB) or increased troponin plus edema and late gadolinium enhancement at cardiac magnetic resonance (CMR).
Results
-At presentation, 118 patients (26.6%) had either left ventricular (LV) ejection fraction (EF) <50%, sustained ventricular arrhythmias (VA) or a low cardiac output syndrome (LCOS) whilst 325 (73.4%) had no such complications. EMB was performed in 56/443 (12.6%), and a baseline CMR was performed in 415/443 (93.7%) of patients. Cardiac mortality plus heart transplant (HTx) at 1 and 5 years were 3.0% and 4.1%. Cardiac mortality plus HTx were 11.3% and 14.7% in patients with complicated presentation and 0% in uncomplicated cases (Log-rank p<0.0001). Major AM-related cardiac events after the acute phase (post-discharge death and HTx, sustained VA treated with electrical shock or ablation, symptomatic heart failure needing device implantation) occurred in 2.8% at 5-year follow up, with a higher incidence in patients with complicated forms (10.8% vs. 0% in uncomplicated AM, Log-rank p<0.0001). Beta adrenoceptor blockers were the most frequently employed medications both in complicated (61.9%) and in uncomplicated forms (53.8%, p=0.18). After a median time of 196 days, 200 patients had follow-up CMR and 8/55 (14.5%) with complications at presentation had LVEF<50% compared with 1/145 (0.7%) of those with uncomplicated presentation.
Conclusions
-In this contemporary study, overall serious adverse events after AM were lower than previously reported. However, patients with LVEF<50%, VA or LCOS at presentation were at higher risk compared with uncomplicated cases that had a benign prognosis and low risk of subsequent LV systolic dysfunction.