Slow and pounding heart after standing up

[eciftcioglu91]

After sitting or lying for too long when I stand up my heart rate slows, it pounds and then races for a few seconds. It feels weird around my chest and my hands get cold. I DO NOT get dizzy or feel like I am about to black out. Somedays it doesn't happen at all and somedays it happens every time I change positions. I use to have it during my teenager years but it didn't happen this often, now its nearly everyday. It doesn't seem to matter how long I have been sitting or lying down. I do suffer from General Anxiety Disorder, Mitral Valve Prolapse, mild Mitral Valve Regurgitation and occasional PVC's but the doctors keep telling me nothing serious is going on with my heart. I am not on any medications. I am 27 years old. I have had anxiety related problems since I was 17 but during college never had a single symptom or any anxiety and now they have come back worst than ever and is making me miserable. Is there anyone else having similar symptoms because I am having trouble anything remotely close to what is happening to me.