Thanks everyone. I appreciate your replies.
I have a congenital heart defect. My Mayo surgeon (now retired), pioneered the technique to "repair" my defective heart valve. The local surgeon to whom I was initially referred, and who worked at the Nationally Recognized Best Hospital in St. Louis, told me that he had only previously performed this operation 2 times (versus the 450 times my surgeon had).
I put "repair" in quotes because with congenital heart defect surgery, there's no such thing as a cure. I return to the Mayo Clinic every other year for a checkup because I know that I will eventually need a re-operation.
I *could* forgo the Mayo Clinic and receive care locally, but I'd be putting myself in inexperienced hands, especially surgically. As a friend told me once, you never want your doctor to look at your condition and say "that's interesting, I've never seen that before". You want a doctor who has seen patients like you a thousand times.
I investigated plans outside of the ACA and found that all of them come with pre-existing conditions clauses, which is a no-go for me.
Previously, I had only considered moving to Illinois because I could maintain relationships with family and friends. I hadn't considered it seriously because, with ACA plans changing every year, moving to get coverage might be for naught the following year. For example, in Missouri, in 2018, Anthem Blue Cross pulled out of the counties in and around St. Louis and Kansas City - where the best hospitals and most expensive doctors are located. In order to get Anthem Blue Cross (and it looks like they only offer an HMO), you have to live outside of the two biggest cities in the state.
Currently, it looks like BCBS of MN has a plan that includes the Mayo Clinic in network. Now that I think about it, I'd be surprised if the ACA plans in the Rochester area *don't* cover the Mayo Clinic. Since my eventual reoperation will be an elective procedure (versus an emergency), I suppose I could move to Rochester just before needing it. Recovery would be difficult without family nearby, but I imagine that problem could be solved. I hadn't thought of this option before talking to you all, so thank you. This conversation has helped me see some things I hadn't considered before.