If you are doing an operation on the heart, would you have to break the patients sternum and/or ribs in order to preform the operation successfully?

Depends: Depends on problem being operated on and the surgeon performing the operation. Many heart ailments can today be done via less invasive methods, either through smaller incisions between ribs or via robotic techniques. Special expertise in such approaches make it important to seek out those surgeons trained to perform these less orthodox methods. Some operations still require splitting breastbone

Basically, yes: The chest cavity is opened with an instrument called a sternal saw because...well, it cuts through the sternum allowing access.