What happens if you get a blood clot in the leg (vein), can it cause a stroke (artery)?

Maybe: If you have thrombophlebitis, a clot could go directly to the lung causing a life threatening pulmonary embolism. But if there is a congenital hole within the heart, such as patent foramen ovale, the embolism can be paroxysmal and go to brain, causing a stroke. Anti-coagulation can be protective in these circumstances.

Rare: In rare cases, there is a communication between the right and left side of the heart allowing a clot from a vein to enter into the arterial circulation called a paradoxical embolism.