Cardiac sarcoidosis: state-of-the-art review

### Learning objectives Sarcoidosis is a systemic inflammatory disease characterised histologically by the formation of non-caseating granuloma in multiple organs.1 The cause of the disease remains unknown. It is hypothesised that exposure to an antigen in patients with a genetic predisposition results in an exaggerated immune response leading to granuloma formation. Clinicians face several challenges including achieving a confident diagnosis and providing patients with a long-term management plan. These challenges largely relate to the heterogeneity of the original presentation, disease evolution and outcome. Sarcoidosis may be diagnosed incidentally in patients who have no symptoms, those with non-specific respiratory symptoms such as a persistent cough or those with prominent systemic features (fever, weight loss and fatigue). Moreover, in many patients, the condition will remit spontaneously, whereas in others long-term immunomodulation is required to prevent disease progression. While the lungs and intrathoracic lymph nodes are involved in 90%–95% of cases, the exact prevalence of cardiac sarcoidosis (CS) remains largely unknown.2 Clinically overt CS has been reported in 5%–10% of cases with systemic sarcoidosis.2 However, the true prevalence is likely to be higher based on postmortem analyses and registries using advanced imaging modalities.3–12 Patients with CS may present with arrhythmias (such as advanced atrioventricular block or ventricular tachycardia) and/or unexplained new onset heart failure without a history of systemic sarcoidosis.13 14 The initial investigation of such cases should focus on identifying extracardiac disease to improve the certainty of the diagnosis. Histologically confirmed isolated CS has also been reported.7 Therefore, the true burden of CS …