Myocarditis: An Important Presentation of Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)

Background Arrhythmogenic right ventricular cardiomyopathy (ARVC) traditionally presents with ventricular arrhythmias or, less commonly, heart failure. Myocardial inflammation has been implicated in the pathogenesis of ARVC, but clinical myocarditis in ARVC is not well described. We describe myocarditis as a presenting phenotype of ARVC, and hypothesized that patients with this presentation have distinct clinical characteristics. Methods Using the Johns Hopkins ARVC Registry, we examined patients diagnosed with myocarditis at index presentation based on European Society of Cardiology criteria, who were subsequently diagnosed with ARVC by Task Force Criteria (TFC). Results Of the 12 patients (all female, median age 20) initially diagnosed with myocarditis, the majority presented with chest pain (n=7, 58%) or ventricular arrhythmia (n=3, 25%). All patients had troponin elevations and left ventricular function was reduced in 5 (42%). Cardiac magnetic resonance imaging demonstrated LV delayed gadolinium enhancement and/or pericardial enhancement in 10 (83%), however only 3 (25%) patients had RV abnormalities. Treatment of suspected myocarditis during index presentation consisted of steroids (n=3/12, 25%) and/or non-steroidal anti-inflammatory drugs (NSAIDs) (n=4/12, 33%). Pathogenic genetic variants were identified in 11 (92%) patients: 10 desmoplakin (DSP) and 1 desmoglein-2 (DSG2). The clinical course timeline for each patient is shown in Figure 1. Patients were diagnosed with ARVC 1.8 years (IQR 2.7 years) after myocarditis presentation. After diagnosis, an additional 5 (42%) patients were recommended for implantable cardiac defibrillator and screening led to 17 family member diagnoses of ARVC. Conclusions Myocarditis may be the initial presentation of ARVC in some patients. These patients may have distinct characteristics such as female predominance, LV involvement and DSP gene variants. Genetic testing is key to ARVC diagnosis, especially in left ventricle dominant forms, and should be considered in appropriately selected patients presenting with myocarditis.