Oh hell, brings back bad memories Dan. Went through stress test-OK, then a heart cat-great, couple weeks later I passed out twice at home. Off to the Horspital, lots of scans/mri, blood tests. Bottom line...pulmonary embolism (blood clot).
Scared the heck out of me. Now I am fine (this all happened eight years back), but keep checking and looking since this is a killer.