Hi Jackie
I’m sorry to hear about Jasper. I have never had to deal with HCM so could not answer this correctly for you. I have had a look on the web for you and found a few sites but the link under seems to explain it quite well. It explains what HCM is and what syptoms to watch for. The web link is
I hope this helps you but if not please let me know and I will get the vet we get our information from to try and explain it for you.
I also hope Jasper is around for a long time to come and you get to cuddle Jasper and love him as much as possible