Right Atrial Mass Discovered During Routine Follow-Up After Cardiac Procedures: Diagnostic Challenges and Management.

Cardiac masses pose significant diagnostic and therapeutic challenges in clinical practice. A 73-year-old male with a history of atrial fibrillation and percutaneous atrial septal defect (ASD) closure presented with an asymptomatic right atrial mass detected during routine transthoracic echocardiography follow-up. The mass measured 17 mm, with highly echoic peripheral areas and a heterogenous, low-echoic interior. The patient was asymptomatic and had no fever, embolic, or neurological symptoms. Multimodal imaging, including contrast-enhanced computed tomography, magnetic resonance imaging, and transesophageal echocardiography, revealed a mobile nodular mass in the right atrium (RA); however, the results of each modality were not consistently suggestive of a specific disease. The presumptive diagnosis of thrombus was made based on the change and variability of echocardiographic findings over time and the response to antithrombotic medications. Anticoagulant therapy with edoxaban led to the complete resolution of the mass, confirming the diagnosis of a thrombus. This case highlights the importance of multimodal imaging and temporal changes in findings in the diagnosis and management of RA masses and underscores the need for careful thrombotic risk assessment in patients with a history of atrial fibrillation, ASD, and cardiac procedures.