Right Atrial and Endocardial Lead Mass Secondary to Anterior Mediastinal Mass Encasing Left Subclavian Vein.

INTRODUCTION: Multimodality cardiac imaging is a valuable tool for the noninvasive evaluation of right atrial masses (tumor, vegetation, or thrombus). CASE PRESENTATION: We report a case of right atrial mass that was discovered on a transthoracic echocardiogram ordered for pacemaker-pocket erythema in a 101-year-old man with heart failure/reduced left-ventricular ejection fraction and a dual-chamber pacemaker. Transthoracic and transesophageal echocardiogram showed a large hypoechoic mobile RA mass extending from the superior vena cava, with pacemaker device lead attachment. Infective endocarditis was excluded (no symptoms of systemic infection; negative blood cultures). CT angiography of the chest revealed an anterior mediastinal mass, highly suspicious for malignancy, encasing the left subclavian vein. The patient chose not to pursue invasive assessment of the mediastinal mass. Role of anticoagulation is unclear. CONCLUSION: Computed tomography complemented echocardiographic assessment and management of a right atrial mobile echo density due to a large anterior mediastinal mass.