Diet, exercise, etc. The best way to prevent this is Preventive Medicine. This involves going to the Dr. and getting some tests done (labwork- an EKG if needed- Family history, which is hard for some folks, I realize)......Here are a few sites that may help you out with your question.
Good luck and take care! STAY HEALTHY!!
PS- Some people take an aspirin
a day to prevent their blood from getting too thick, hence causing a heart attack