Your grandfather's heart was probably restarted or shocked back into a correct rhythm with a defibrillator, which does not injure the ribs or sternum. If a person requires extensive manual CPR in order to restart the heart or keep it beating until medical help arrives, there WILL be broken/cracked ribs. Otherwise the CPR is not being done correctly and will not work.
Your grandfather's heart was probably restarted or shocked back into a correct rhythm with a defibrillator, which does not injure the ribs or sternum. If a person requires extensive manual CPR in order to restart the heart or keep it beating until medical help arrives, there WILL be broken/cracked ribs. Otherwise the CPR is not being done correctly and will not work.