Abstract 17852: A Right Atrial Mass(querader) Causing Complete Heart Block in an Otherwise Healthy Female

Introduction: Right atrial masses are ominous and have a broad differential including thrombus, primary cardiac tumors such as myxoma vs sarcoma, metastatic processes like lymphoma, and, rarely, autoimmune etiologies. In this case, an apple watch notification of bradycardia was a simple start to a complicated course of rapidly progressive conduction disease arising from an unusual presentation of cardiac sarcoidosis. Case Presentation: A 45-year-old previously healthy female originally presented to clinic with a one-month history of exertional dyspnea and palpitations with bradycardia noted on her Apple Watch and an ongoing event monitor revealing transient type II second-degree atrioventricular block. In the office, she was normotensive but bradycardic at 33 beats per minute with electrocardiogram revealing complete heart block with junctional escape. She was admitted for additional work-up with transesophageal echocardiogram (TEE) which was unrevealing. Cardiac magnetic resonance imaging (cMRI) identified two 2 x 2 cm right atrial masses that appeared hypermetabolic on cardiac fluorodeoxyglucose positron emission tomography (FDG cPET) in addition to bilateral hilar lymph nodes. A temporary-permanent pacemaker equipped with a lead capable of floating atrial bipolar sensing was placed while biopsy plans were arranged. Transbronchial ultrasound guided biopsy of the hilar lymph node returned benign. She then underwent two different attempts at transcatheter biopsy of the right atrial masses - one TEE guided, another intracardiac echo (ICE) guided - with most samples unrevealing except one with an inconclusive amount of spindle cells raising concerns for sarcoma. The decision was made to pursue cardiothoracic surgical resection of the right atrial masses with pathology returning with granulomatous lesions consistent with sarcoidosis. Discussion: Cardiac involvement is present in 25% of cases of sarcoidosis and most commonly manifests as conduction abnormalities, ventricular arrhythmia, and/or heart failure. Only a few cases of atrial masses are reported in the literature and its presence in this woman with heart block confounded the picture before a diagnostic biopsy of this treatable condition could be obtained.