Complete heart block as the first manifestation of systemic sarcoidosis: a case report highlighting the diagnostic utility of multimodality imaging.

Background: Sarcoidosis is a systemic inflammatory disease of unknown aetiology characterized by the formation of non-caseating granulomas. Cardiac involvement occurs in up to 30% of cases but only manifests clinically in 5%. In young patients presenting with high-grade atrioventricular block, infiltrative processes such as sarcoidosis should be considered in the differential diagnosis.

Case summary: We present the case of a 35-year-old male who presented to hospital with symptomatic complete heart block as the first manifestation of multi-system sarcoidosis with cardiac involvement. Initial blood testing, chest x-ray and transthoracic echocardiography were unremarkable, leaving a broad differential to be considered. Cardiac magnetic resonance imaging revealed late gadolinium enhancement in a highly variable and non-coronary distribution, with simultaneous involvement of subepicardial, subendocardial, and midwall tissue. High-resolution computed tomography of the thorax revealed significant intrathoracic lymphadenopathy. Endobronchial ultrasound-guided lymph node sampling and analysis revealed the presence of non-caseating granulomas, providing histological confirmation of the disease. The patient's clinical course was complicated by the development of ventricular standstill, thus insertion of an implantable cardioverter-defibrillator was carried out. Immunosuppressive therapy with oral prednisolone was commenced prior to discharge.

Discussion: Cardiac sarcoidosis can produce life-threatening complications if left untreated. Our case serves to highlight the need for consideration of sarcoidosis as a cause for cardiac conduction disease in young patients, and the utility of multimodality imaging in its diagnosis. Cardiac magnetic resonance imaging serves as a useful tool when faced with this clinical picture.