I'm sorry to hear that about your Amos.
I've never heard of a dog named that. It's a cute name.
We had a Dachshund who lived to be 16 years old but about a year before we had to put her to sleep, she developed kidney failure. At lst she would just leak urine and as it got worse she was peeing and pooping in the house and God Love her, I don't think she even knew she was doing it.
I don't know anything about the heart condition you mentioned, sorry. But just wanted to tell you my experience with an older dog and bladder control.
Is Amos going blind?
I only ask cause right around the time the vet diagnosed our Dauxie with the kidney failure, the vet also said she could tell GiGi was going blind. Near the end, we use to come home to see where she had even stepped in her poop and didn't even know she did that.
I really should have put doggie diapers on her but I just know she would have tried to chew them off.
Good Luck with your precious Amos and please keep us informed. It is so very hard when our furbabies get old.