A previously healthy 65-year-old woman is brought to the emergency department because of acute stroke. Examination shows acute bilateral lower extremity deep vein thrombosis. Injection of agitated saline contrast during echocardiogram shows the presence of bubbles crossing into the left atrium. 

The presence of which of the following is most likely to explain her symptoms?
Biscupid aortic valve
Patent foramen ovale
Tetra logy of Fallot
Transposition of the great vessels