Endobronchial Ultrasound Diagnosis of a Malignant Superior Vena Cava Tumor Thrombus Extending Into the Right Atrium: An Unusual Cause of Recurrent Syncope

The superior vena cava (SVC) is mainly responsible for the return of blood flow from the head, upper limbs, and neck into the right atrium. The large vein can be subject to extrinsic tumor compression and invasive intraluminal tumors-metastatic and mediastinal tumors that can lead to complete or partial occlusion. SVC occlusion can also result from chronic inflammation or scarring of the vessel iatrogenically by pacemaker wires or venous access ports used for chemotherapy, long-term antibiotics, or hemodialysis. Patients with SVC occlusion present with a constellation of clinical abnormalities that make up SVC syndrome. SVC syndrome includes varying degrees of facial fullness, neck and upper extremity swelling, dyspnea, and classically dilated collateral veins in the upper chest. Very rarely do patients present with syncope, hoarseness, dysphagia, or acute encephalopathy. The diagnosis of SVC syndrome is best established on imaging such as CT Chest with contrast; however, on rare occasions, it can be discovered by endobronchial ultrasound. We present an unusual presentation of SVC syndrome- primarily presenting as frequent syncopal episodes- diagnosed via endobronchial ultrasound.