Atrial Tachycardia but no diagnosis

My doctor diagnosed me with atrial tachycardia, but he does not know why i am having these heart palpitations. I have had a EKG,Echocardiagram,and a 24hr holter monitor. All of these tests came back normal, and my holter moniter test said that my symptoms don't correlate with what i wrote in my diary. What is left for me to do? These palpitations are not going away and they last all day everyday some times.

[sissy28]

I also feel tired,headaches,light-headed, sometimes i will breathe faster with my palpitations, and sometimes i might sweat a little.

[GravesLady]

Have you been test for thyroid and/or MVP - Mitral Valve Prolaps? which is tested by an echocardiogram.

[sissy28]

thanks for the info