Contemporary Epidemiology, Management, and In-Hospital Outcomes of Acute Myocarditis: The Prospective Multicenter MyocarditIRM Study

Abstract

Background: Despite a frequently favorable evolution during the initial phase, acute myocarditis (AM) remains associated with heart failure and ventricular arrhythmia. There are no large prospective databases to provide robust results.

Objectives: The aim of this study was to describe baseline characteristics, real-life management, in-hospital outcomes, and determinants of prognosis in a large cohort of patients with AM admitted to cardiology, with a comparison of patients with and without initial severity criteria.

Methods: MyocarditIRM (French National Observatory Tracking Viral Myocarditis: Mortality, Cardiovascular Events, Sequels on [Magnetic Resonance Imaging] MRI) is a multicenter prospective observational study of patients with AM confirmed by cardiac magnetic resonance. Patients initially admitted to the intensive care unit or those who died before cardiac magnetic resonance-confirmed diagnosis were not included.

Results: In total, 803 consecutive hospitalized patients were enrolled at 49 participating centers between May 2016 and February 2019. The median age was 31 years (Q1-Q3: 23-41 years), and 82% were men. Chest pain was the most frequent symptom (93%), and 112 patients (14%) had severity criteria upon admission (left ventricular ejection fraction <50%, severe ventricular arrythmia, high-degree atrioventricular block, or cardiogenic shock). ST-segment elevation was observed in 49% of patients. Overall, 64 patients (8%) experienced in-hospital complications, defined as a composite of death; left ventricular ejection fraction ≤40%; sustained ventricular or supraventricular arrythmia; cardiogenic shock; and need for mechanical circulatory support, inotropic drugs, temporary cardiac pacing, pacemaker, or cardiac defibrillator implantation. Patients with severity criteria at admission were 10 times more likely to experience in-hospital complications.

Conclusions: This prospective cohort represents the largest AM database worldwide. Although the recruitment process likely led to a selection of patients with lower risk AM, 8% experienced in-hospital complications, the major prognosis factor being severity criteria upon admission. (French National Observatory Tracking Viral Myocarditis: Mortality, Cardiovascular Events, Sequels on (Magnetic Resonance Imaging) MRI; NCT02717143).

Keywords: CMR; acute myocarditis; management; prognosis.