Thanks for the information. I have been on a beta blocker for 15 years and this is the first time I had a problem. I am hoping that perhaps the nortriptyline may still be in my system. Well one way or another should know more after the stress test on Friday. I had my potassium checked last week and it was normal but good point about a magnesium test. I take omeprazole for reflux and I believe this could impact the magnesium also. Will request test when I speak to the Dr. Blood pressure is getting better staying over 100/70 but so is the elevated heart rate. All I can say is just when you think you have seen it all with neuropathy there is a new surprise.