What does it mean when a 72 year old man with a history of heart diease has a major cardiac event and has to be revived 3 times in less than an hour?

Arrhythmia : The 72 yo men likely had a cardiac event due to abnormal heart rhythm and when they got the rhythm to normal it probably deteriorated requiring them to bring the rhythm back to normal. The pts cardiologist would likely give you a more complete answer.

Cardiac arrest: It sounds as though he has had an event such as a myocardial infarction which can cause recurrent cardiac arrhythmias which are associated with loss of consciousness and are usually treated with defibrillation and intravenous drugs. This situation is best handled by a team which includes a cardiac electrophysiologist.

Code: 3 times his heart could not pump enough blood to meet his body demand ( this may be the result of a very fast or a very slow heart rates).