Necrotic ear margins can be a sign of a heart condition. See "signs to watch for" and a link to an article with more info.
Heart problems can be caused by lots of different things. It would be a good idea to ask your vet questions about heart conditions in guinea pigs, what types of tests can be done, types of medications and treatment plans available and what kind of supportive care you can provide for her at home.
Just a few of my own thoughts you could think about and consult with your vet about and maybe research on your own as well - If a guinea pig does have a heart issue, sometimes they are a bit less active. If they are less active, they may spend less time eating hay. If this happens, their teeth can grow longer than they should and eventually cause problems with eating. Not eating enough hay is also not good for their digestive health, which could leave her more prone to tummy issues which are a big deal for piggies. If she has easy access to hay and water and a warm cozy spot right beside it, that would be ideal. I have a senior piggy and I visit him and gently encourage him to eat hay by adding fresh little handfuls, keeping the area really clean and hand feeding him a few pieces to get the ball rolling. Also, depending on what your vet advises, I would think it's a good idea for her to have a chance to explore and exercise a little bit if she doesn't already. If she's out on the floor, you'd want to make sure to feel the floor with my hands and make sure there are no drafts down at her level. I always have a warm hiding spot, hay and water available during 'floor time'.
Sorry lots of little details there and don't mean to get off topic, maybe lots of things I mentioned are things you already think about. I have just noticed how little issues with piggies can all be connected or have a domino effect at times, so I wanted to talk about the big picture a little bit. Wish you and the little one all the best!
Heart Problems in Guinea Pigs
Signs to watch for include:
- Labored breathing, wheezing, a “hooting” sound that may go away and later return
- Reduced activity/deep sleeping
- Pale or blueish gums
- Necrotic ear margins (looks black on pink ears and white on black ears)
The Truth About Heart Problems in Guinea Pigs | Small Pet Select