I am so sorry about the recent loss of your Merle. I am new to this group but understand having to make a painful decision such as this in the past. Part of grief can certainly involve second guessing these decisions and a frustration about what could have been done. Please let yourself go through all these feelings and know they are valid. It sounds as if Merle was a very sick kitty and you made the best decision you could about his care. One that was based on love of him and sense of responsibility about his well being. Yes, there may be different treatments for HCM and its various stages but that does not always mean they may have been the best choice for Merle. I wish you all the best and please take good care of yourself.