@whidbey I had 123 known HCM genes tested after my septal myectomy, all were normal. The gene I have that causes HCM in me has not been discovered as yet - hopefully it will be by the next time I am tested (was told to check in about 5 years). You said "whether or not this is a pre-existing condition," and it is. Not everyone shows symptoms, but the gene is there. I never heard of HCM till I was in my 60's and had a heart murmur, testing - echocardiogram - showed the thickening near the mitral valve. The thickening grew worse over time (everyone is different with this), and it became obstructive. I realized my dad had it, I remember the symptoms. Hopefully, our specific genes will be found, meanwhile, family members are monitored with echoes.