My post was from a year ago and I’m off all meds except for albuterol and sodium nebs, I’m sorry you have so much going on. I’m not sure what kind of pacer you have but I was given a Biotronic pacer in Toledo by my POTS specialist for my first replacement. It was a game changer as far as preventing me from passing out. It senses the b/p drop and kicks the heart rate up. I haven’t heard of MSA but hope Mayo can help you.