You said it comes on suddenly, can it go away rather quickly too? It's only about the third time it's happened in a year or so, but I have experienced a sudden tightening of the chest, feels like I can't breathe though I can and although I know I'm moving air my chest doesn't seem to agree with me, but I also notice that I get really hot when it happens to the point of sweating profusely, and it pretty much lasts until I get myself cooled down, usually throwing an ice pack over my chest and dropping the A/C a few degrees. Once the body decides its cool again, chest loosens up and I can breathe normally again. It might sound bad but I honestly never thought anything about it till seeing this post, I guess I should tell my neuro about that