Hi JOan, sometimes they equate those feelings of impending doom with adrenal fatigue, The body depletes its adrenal reserves and you get symptoms like fear (ist the flight or fight response) and heart palpitations.
Here is a link on a intersting scorecard where symptoms of adrenal fatigue are listed
http://www.drrind.com/scorecardmatrix.asp
I will go in phases and sometimes when from significant stress I have worn down my adrenals. I do two things. Each morning I have an 8oz glass of water with 1/8 tsp of sea salt. Please don't do this though it you have high blood pressure. You know today they stress low salt diets etc but your body needs salt to move nutirents in and out of cells.
In adrneal fatigue you get salt wasting and you body cannot hang onto water and you get very dehydrated wthout knowing it. Second your adreneals have the highest % of vitamin C in your body. So when I am feeling like this I start to supplement with vitamin C 1000 mg a day.
I'll be honest most docs do not believe in adrenal fatigue unless it is so severe you need to be hospitalized. BUt with us, chronic pain people pain wears out and stresses you body and adreneals. If I do the vit c and sea salt water for a month I feel better and calmer etc and back to more normal.
GIve it a shot it may help.