I did have a septal myectomy in 2017. It didn't help much. They couldn't reduce the thickness of my lower heart. I didn't have any of those side effects from surgery. Still had to be on a betta blocker. Just recently went on Mavacamten...Not for me. After 6 months, it triggered unusual side effects for me. Everyone is different. Now going on a clinical trial. Hopefully to be approved soon.
To answer your question, yes it did keep my pressure low. Since I am off, the pressure is still good, but not as low. Mavacamten did show good effects on echo...but I just felt that I couldn't handle it anymore. I needed to see if the side effects would subside. so far, no luck.
Good luck to you.