Cardiac sarcoidosis: state-of-the-art review

Abstract

© Author(s) (or their employer(s)) 2021. No commercial reuse. See rights and permissions. Published by BMJ. INTRODUCTION Sarcoidosis is a systemic inflammatory disease characterised histologically by the formation of noncaseating granuloma in multiple organs. 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 longterm 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 nonspecific 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 longterm 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. Clinically overt CS has been reported in 5%–10% of cases with systemic sarcoidosis. However, the true prevalence is likely to be higher based on postmortem analyses and registries using advanced imaging modalities. 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. 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. Therefore, the true burden of CS remains unknown with a significant number of patients being undiagnosed who may experience adverse cardiac adverse events in the future. Even when a confident diagnosis of CS is made, the treatment options are often based on individual patient characteristics rather than uniform clinical guidelines. This is in view of the paucity of randomised controlled studies due to the disease being relatively rare. A multidisciplinary team approach provides a more robust model for diagnosing the condition and providing a treatment plan for patients (table 1). Patients with CS may require implantation of a cardiac defibrillator (ICD) as a primary or secondary preventative strategy or catheter ablation for the management of arrhythmias. In the presence of active myocardial inflammation, immunosuppression may be required to prevent the development of irreversible changes in cardiac structure and function. This review summarises our current knowledge of the epidemiology and clinical manifestations of CS, highlights the importance of noninvasive cardiac imaging in the diagnosis of the condition and describes the basic principles of management from the respiratory and cardiac perspective.