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.