@retirement75 I hope the antibiotics will do the trick if there is an infection. Have you consulted your cardiologist about these recent developments? Whatever the outcome of your tests, the heart doctor should be informed and may help with your decision. Perhaps another opinion might be a good idea. Did they tell you how they can confirm an infection on imaging or blood tests or do they need to take a biopsy?
That's a lot to think about. They should be able to explain if the hardware is possibly causing an artifact on imaging. That can be a cause of something looking unusual on an MRI. Let's hope that is it. You can ask them if the hardware causes artifacts or shadows and what that should look like as compared to an infection. I hope you'll share what you learn. I'll keep my fingers crossed for you!