Pulmonary Embolism Support Group
By far the most common form of pulmonary embolism is a thromboembolism, which occurs when a blood clot, generally a venous thrombus, becomes dislodged from its site of formation and embolizes to the arterial blood supply of one of the lungs. Symptoms may include difficulty breathing, pain during breathing, and more rarely circulatory instability and death.
http://www.fvleiden.org/recently-diagnosed/what_test.html
As most of us will tell you, the first rule of PE Club is that all your doctors will probably tell you something a little different. That's always fun to sort through when you're trying to process this whole thing.