First off, as long as your heart is healthy and you have reasonable exercise tolerance, an elevated heart rate is unlikely to cause you to go into IPE. It might, however, be a SYMPTOM of it, but would usually be associated with shortness of breath, as well.
Second, this sounds to some extent like a syndrome I see in the ER. I not infrequently see an older person who has a BP monitor at home, who has taken his or her blood pressure and found it high. So they wait around for 15 minutes (worrying like crazy) and check it again -- and to no one's surprise, it's higher yet. So they get even more worried, and wait a few minutes, and do a third check -- and it's gone UP! Then they come to the ER, where the long wait for someone to see them generally makes the BP go back down to normal. Anxiety feeds on itself, and anticipation of anxiety can be a self-fulfilling prophecy.
On the other hand, you might have had a poorly performing reg (did you bring your own gear?) that caused increased work of breathing, which causes anxiety. You could have been narced, which can manifest as anxiety. Or perhaps you are hyperthyroid?
It's really hard to diagnose over the internet. I would hope you had a really thorough physical evaluation at the time of your IPE, including thyroid studies. But it might be reasonable to check with your physician again, since things have changed.
