With heart issues, it would be helpful to have a vet cardiologist on your team monitoring the dog and the treatment plan. One supplement to ask your vet team about is VetriScience's CardioStrength, which combines several heart-supportive ingredients:
Our rescue's vet suggested it for a few dogs we had with severely damaged hearts from Heartworms. It's available OTC, though sometimes vet clinics sell it. Her feeling was that it could only help these particular dogs. She also uses it with boxers with congenital heart issues too. DO NOT USE without checking with your vet to see if there's any potential interaction with meds your dog is on!
Regular glucosamine pills from the supermarket or drug store are likely to be a waste of money. I've linked the long-term, excellent studies on them and arthritis many times. You can find those threads easily with a search -- one was as recent as a couple of weeks ago. The good, long-term studies have had very disappointing results. You'll find a lot of info linked here:
There's ONE patented
form of glucosamine/condroitin that's proprietary to NuMax (Cosequin, Dasuquin) that has had good study results in Europe. Their results were so different from the GAIT study results here that it makes on go "hmmm..." Either the form they're using is absorbed differently, or something is hinky with the study. At least they've got pretty good data that it works though. If you're not going to use that, I wouldn't bother with a commercial supplement -- just feed food rich in gluc/chon (like beef tracheas). Add in Natural Eggshell Membrane, and maybe Collagen Type-II.
The real game changer is Adequan (RX-only, series of injection), which can give lame dogs back some quality of life or keep early arthritis from getting worse by lubricating the joint and sometimes rebuilding cartilage. We've had lots of threads on this too. I just posted about it last night in another thread, but there are probably 50 great threads about it in the archives -- it's frequently discussed here.