My Kitten Has HCM, HELP?

While I can't answer for your kitten, I can tell you my experience with one of my foster cats. She had HCM and a very severe murmur, properly diagnosed by a cardiologist. She was eventually put on a drug called Atenolol, which allows the heart to beat with less force, and hopefully allows the thickened heart walls to thin out again. With her - it worked! She was an older cat - 8 or 9, and was still going strong 5 years later. Her cardiologist changed her appointments from every 6 months to a yearly interval. Her adopters love her, and are thankful that her condition has improved. So what I am saying to you is this - it can have a happy ending, and as long as you keep following up with the specialist, your cat will be in good hands. Hang in there, and good luck!