I Woke Up In The Middle Of The Night, Because

I woke up in the middle of the night, because I felt like I needed to go to the bathroom. My chest was heavy, I felt faint. On the way back from the bathroom I was having trouble walking, then I lost my balance, fell and blacked out for a few seconds. When I awoke my speech was incoherent and then I was fine. I had a stress test a few months ago and I was fine. Any ideas as to my problem?