Hi, so a couple years ago I was diagnosed with a heart murmur and irregular heartbeats. Since then, I ve been having spells where my heart would beat super fast, and depending how bad it was, it s hard to breathe. My first question is, should I get my heart checked out again? And then, for maybe a week or two now, if I stand up too fast I get dizzy and have a pressure on the side of my head, today I got up too quick but instead of feeling dizzy my vision blacked out for a couple seconds but got better when I say down. What could this be a sign of?