For MRIs, I just close my eyes and try to send myself to a different dimension as the music plays. It's tough.
My wife has had some arrythmia as well. They discovered it when she got a "thunderclap" headache. One moment she was fine, and the next her head hurt so badly we went to ER thinking she might have had a stroke. It locked her up, and she could not move a millimeter. A blood vessel in her head had constricted, giving her the instant, massive headache. With eight weeks of medication they reversed the constriction, and her heart has settled down as well. Scary.
For you guys with blood pressure issues, I had a coworker who said he got up in the night to pee, and the last thing he remembers is standing in front of the toilet starting to go. He woke up on the floor with a concussion and broken nose. He had passed out and pitched forward, hitting his face on the back of the toilet. The doc said his standing and peeing too fast caused a rapid drop in blood pressure and dropped him like a rock. He was only about 40. He says he now sits down.
Getting old: it's not for pussies. (as X4 would say!)