A heart attack is different to a cardiac arrest, the later of which implies that circulation has stopped. There are many causes of arrest and it would be unusual for a woman of child bearing age to have an arrest as a result of a heart attack.

The training for emergency room doctors is for us to have the c section kit ready to go on arrival of the woman and be prepared to open the abdomen after the first cycle or compressions/resus - otherwise we have left it too long and the fetus is suffering. My point in illustrating this was only to show that It is interesting to consider how quickly you need to make an enormous decision.