What I am picking up for you is a need to relax and as the ekg test and the blood tests are both normal it may be worth considering other course.
I just wanted to check that you are drinking enough water? As being dehydrated may add to the condition?
The other thing that can quite often feel like a heart problem is trapped wind. May be try a couple of cups of peppermint tea may ease this:>)
You are also more than welcome to listen to the energy balancing meditation on the home page of my web site: http://www.healergeorge.com This works from the inside out and balances your energies at very subtle levels.
You may also like to start doing some Yoga stretching in the upper part of your body. There should be a teacher near to where you live.
Please let me know how you get on. I have been sending you distant healing since you posted your request have you felt this and relieved your symptoms?