Without direct access to patient unfortunately, it is very difficult to give a definitive opinion. In generic terms, fever may come because of the heart attack it self and may last for a few days and then go a way spontaneously. Some times fever may be reactionary to the drugs and extraneous material used during stenting and lastly unrelated causes like infection, malaria or any other such cause may be responsible for fever. I therefore feel, your treating doctor would be the best person to answer this query as to the cause of the fever.
I hope, we have answered your questions to your satisfaction, but if you have any doubts, please feel free to contact us and it shall be our pleasure to answer them.