I can relate to your story. I am a 72 year old female, was also diagnosed with HOCM in my mid 60's and was told that nothing would ever come of it. Hypertension seemed to be the root cause of my HOCM. And I also have a very good friend who had the same thing happen about the same age but she did not have hypertension. We will never know how or why this happened to us but it did and we just have to deal with it. After many years of medication, I had a septal myectomy in Feb. 2020. My friend also had a septal myectomy this past spring after medications did not help her situation. Both our surgeries were successful. We will never really know why this "happened to us". It is important to work with a qualified medical team to guide you through this process. There are many good options for treatment. We were both treated at Cleveland Clinic since it was closer to us than Mayo. They are both excellent choices for treatment of HOCM.
Even though this is a touch road, we are very fortunate that there are are good options available to treat HOCM with good outcomes. Good luck on your journey. You are not alone.