Sternum non fusion and bone infection 18 months after a heart attack and triple bypass. why would be the possible course of mtreatment?

Bone infection: From your description it sounds as if you may have had a bone infection of the sternum. This is called osteomyelitis and can be very difficult to treat ; a minimum of months of anabiotic therapy would be required and in certain situations chronic osteomyelitis can require indefinite therapy. If there is a concern that you still have active osteomyelitis then consideration should be given to see an infectious disease specialist