Is it possible for you to get a heart attack or stroke from blocked veins?

Yes, can happen: The venous sinuses within the brain circulation can be the issue in some strokes, and heart problems could be caused by venous obstruction with secondary emboli. This is complex with many varying mechanisms. The mayo clinic, and johns hopkins websites provide more detail.

No: Heart attacks caused by arterial disease, blocked veins can throw off clots causing problems - see pcpc about blocked veins.