Perplexed - heart disease or hypersensitivity?

Under normal conditions, my 76 year old father has what appears to be angina.  When he exerts himself he must rest and his chest pain will subside.

He has been rushed to the hospital in an ambulance 5x over the last 3-4 years because of severe chest pain.  Each time there was no indication of a heart attack and tests did not reveal a cause for the pain, which went away in a few hours.

He has had a stent put in because of a partial blocked artery (possibly because his doctors are unsure what the cause of the pain is and thought that could help).

He has an arterial fibrilation and takes a blood thinner for that.

In his latest visit to the emergency room, it was clear that he was hypersensitive to pain.  The thing wrapped around his arm to take his blood pressure caused an unusual amount of severe pain, so did removing bandaids, inserting needles, resting his arm on the rail next to the bed, etc.

Is it possible that he has angina but that the trips to the ER are more about sporadic hypersensitivity?  What causes sporadic and temporary hypersensitivity and is it correlated with heart disease?

Thank you.

Ben in NYC