Doug,
I had exactly the same problem that you did, although my AME was much nicer about it. I went in one time, and he said that I had a heart murmer-I guess that it comes and goes, cause sometimes they can hear it and sometimes they can't. So he had me see my regular doctor, who determined that my was innocent(not a problem) The AME can hold the paperwork for 10 working days while the cardio eval is done, but after 10 days he has to send it off the the FAA. Trust me, you don't want the paperwork to go to the FAA unfinalized if you can help it, as it will take a while for them to approve your medical.
I also have white coat syndrome. As long as your B.P. is 155/95 or less, it's passing regardless of your age or class of physical, as long as you don't have any heart problems. If any AME tells you different, he obviously doesn't know what he is talking about.
Anyway, best wishes and I am sure that you'll get you medical.