Abstract Body (Do not enter title and authors here): An 80-year-old male with a history of Parkinson's disease, dementia, and prostate cancer presented to the hospital with new onset right-sided weakness and aphasia. Emergency CT angiogram of the head and neck demonstrated occlusion of the M2 segment of the left middle cerebral artery (LMCA). The patient was out of the window for thrombolytics, and underwent mechanical thrombectomy. Brain MRI revealed acute multifocal infarcts in the LMCA territory and the left anterior cerebral artery (LACA) territory suggesting a thromboembolic etiology. A transthoracic echocardiogram (TTE) with agitated saline injected from the left upper extremity showed opacification of the left atria and ventricle but not the right-sided chambers, suggesting an extracardiac right-to-left shunt. A cardiac CT scan showed a persistent left levoatriocardinal vein(LACV) extending from the left brachiocephalic vein and draining into the left superior pulmonary vein. A left upper extremity venous ultrasound doppler showed a non-occlusive deep venous thrombus (DVT) in the left cephalic vein, which was the possible source of the embolic stroke. The patient was discharged on lifelong anticoagulation with Apixaban. At 3 months follow up, the patient developed no new strokes.