@mbi , that is frustrating isn't it?
This was my experience, maybe it is true for you:

I was sent to cardiac rehab six weeks after my open heart surgery.
It was approved by the hospital coordinator and insurance for six weeks.
On my fourth week the nurse told me there was an issue with insurance and I was not approved afterall.
What? Why?
I had a choice, I could pay for the rest out of pocket ($248 per visit, or something like that) or not come anymore.
Because I felt fine I chose not to go anymore.
Then several months later a bigger confusing insurance issue arose, and even though I was told there would be no charge, it was the hospital's mistake...I was sent to collections.
Grrr!
That made me mad.
Long story, longer...I was told because of the diagnosis used, insurance would not pay.
It's a congenital condition in their opinion because it's genetic.
Totally messed up response in my opinion, because open heart surgery is the reason for the rehab. It should not matter why... your chest was cut open!
I was not on Medicare at the time, Blue Cross of Texas.
Never-the-less it was never paid. And I fought the collection agency and won.
Good thing I kept good records about all the misinformation!
Anyway, that's my little rehab fiasco story. It had to do with the ICD-10 codes used and they ultimately did not approve it.

@mbi the administration is making dangerous decisions. Insurance is a racket. That’s just my opinion.
Walking and swimming helped me after bypass.

@mbi I feel ya re insurance issues.

I'm 73, had my septal myectomy in late July. At the time I was still covered by employer health insurance. I switched to Medicare Part B, plus supplemental (aka Medigap), effective September 1.

I discovered that neither employment-related insurance nor Medicare with supplemental covers cardiac rehab after a septal myectomy, but I had a mitral valve repair at the same time as the myectomy, and both insurances cover cardiac rehab after the valve repair. So I am 3 weeks into the 12-week cardiac rehab program and find it very helpful, not least because I'm wearing a heart monitor at the rehab sessions, which I find reassuring as I build up confidence that my newly reconfigured heart can take the stress of exercise.

I personally don't know the medical/insurance justification for treating the two differently, but I see karukgirl Debra sez she was told post-myectomy rehab is not covered because HCM is congenital.

I agree with Debra that that is a distinction without a legitimately justifiable difference, as anyone undergoing open heart surgery could benefit from a structured, guided post-op program as they return to active physical activity.

I'm a member of the HCM Association. Writing this makes me think I'll suggest to that organization that they lobby for coverage of post-op cardiac rehab for all septal myectomy patients (or maybe the HCMA already recognizes this issue; I'll at least look into it with them). In any event, the HCMA is a great resource for a host of reasons. Find them at < 4hcm.org>.

@mbi I cannot understand why insurance companies do not focus on the cheaper and preventative measures for healthcare. I cannot imagine what could/would happen if we all did not get off our duffs and get moving! I have a nonprofit Advantage Plan, a PPO, that focuses on prevention and there was no copay for cardio rehab as long as I needed it. (I fear changes in this company's plans are coming, definitely for the non-Medicare age subscribers and maybe Advantage subscribers due to our present national health care status, we will have to deal with that). I was referred for cardio rehab to two different places; one by my cardiologist (6 week wait) and the other by Mayo (6+ week wait). Imagine! Meanwhile, the owners of my gym used to work at the one the cardiologist called to set me up. Their employee did her internship at the other (a better facility). So, I talked to them and got started under their direction - without a heart monitor - when it was time according to my cardiologist, 2-3 weeks after surgery. I had been walking since the day after surgery and by that time I was up to a slow half mile several times a day. By the time I did go to cardio rehab, I was doing a mile in 20 minutes on the treadmill as well as able to do many other parts of my routine at or close to pre-surgery levels. So, I went 3 times, no heart monitor issues, then cancelled the rest of my appointments to use the gym only.