Hi mmert1,
Yes, I can tell you from personal experience that it is possible for stress to cause those symptoms. About 8 months ago I was peaking on my stress level, and my resting heart rate was often about 80, much higher than usual. Standing up and walking around it would spike up to 110 or 120. (I knew this because I had an event monitor on that displayed my heart rate, and like a fool I was checking it about every 30 seconds.)
When the stress went away, so did the fast heart rate.
I assume that by
ECG and
EKG you actually mean
echocardiogram and electrocardiogram (ultrasound and rhythm strips) - if you've had those and your doctor is satisfied that you're OK, then you probably are. See if you can't find a way to de-stress (I usually need a week), and see if the problem doesn't go away for you.
Jeff