High-Grade Atrioventricular Block and Recurrent Cardiac Arrest in Suspected Isolated Cardiac Sarcoidosis

Cardiac sarcoidosis may cause advanced atrioventricular block, ventricular dysfunction, and sudden cardiac death. Isolated cardiac presentations are diagnostically challenging when histologic confirmation and fluorodeoxyglucose positron emission tomography are unavailable.

An 18-year-old woman with recurrent syncope developed high-grade atrioventricular block and recurrent brady-asystolic cardiac arrest requiring temporary transvenous pacing. Echocardiography showed severe left ventricular dysfunction. Cardiac magnetic resonance demonstrated regional septal thickening, basal to midseptal midmyocardial late gadolinium enhancement and a left ventricular ejection fraction of 38.9%. No extracardiac sarcoid pattern or biopsy target was identified. Giant cell myocarditis and inherited cardiomyopathy remained important alternative diagnoses. She received corticosteroid therapy and subsequently underwent cardiac resynchronization therapy-defibrillator implantation.

Cardiac sarcoidosis should remain a diagnostic consideration in young patients with malignant conduction disease and inflammatory cardiomyopathy, while important mimics must be actively considered.