Does my mother have a medical negligence case?

Mom had a pacemaker put in at a hospital. Later it was converted to a defibrillator by adding new leads to it. Afterward she started not feeling well and one day got dizzy and fell, hurting her back which she is still having issues with. she was transported to a different hospital where it was determined she had a staff infection. they transferred her to the hospital that had done the procedure. They performed several test and it was eventually determined the infection was caused by the pacemaker. They did another procedure and removed it and sent it off to be tested, later putting in a other one. She was in ICU at the hospital during that time. She is now being billed for the procedures and testing to correct the issue. This also caused much pain and expense including dads expenses to travel to the hospital and back daily, wear and tear on their car, expenses for having to buy food at the hospital, etc. mom is in her late 79’s and dad is in his mid 80’s. they have been turned down but