Advances in the diagnosis of myocarditis in idiopathic inflammatory myopathies: an overview of diagnostic tests

Abstract

Cardiac involvement in idiopathic inflammatory myopathies (IIM) purports to worse clinical outcomes and therefore early identification is important. Research has focused on blood biomarkers and basic investigations such as electrocardiography and echocardiography, which have the advantage of wide availability and low cost but are limited in their sensitivity. Imaging the myocardium to directly look for inflammation and scarring has therefore been explored, with a number of new methods for doing this gaining wider research and clinical availability. Cardiovascular magnetic resonance (CMR) with contemporary multiparametric mapping techniques and late gadolinium enhancement imaging, is an extremely valuable and increasingly used non-invasive imaging modality for the diagnosis of myocarditis. The recently updated CMR based Lake Louise Criteria for the diagnosis of myocarditis incorporate the newer T1 and T2 mapping techniques which have greatly improved the diagnostic accuracy of IIM myocarditis.18F-FDG-PET/CT is a well-utilised imaging modality in the diagnosis of malignancies in IIM which also has a role for the diagnosis of myocarditis in multiple systemic inflammatory diseases. Endomyocardial biopsy however remains the gold standard technique for the diagnosis of myocarditis and is necessary for the diagnosis of specific cases of myocarditis. This article provides an overview of the important tests and imaging modalities which clinicians should consider when faced with an IIM patient with potential myocarditis.