I'm not sure if you are asking about symptoms or what happens during an attack. Here are some links:
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001246/
and
http://health.nytimes.com/health/gui.../overview.html
Be aware that symptoms for women are not always the same as those for men.
My husband just had a triple bypass this week, so this is serious. Don't know if you are checking for yourself or someone else, but do seek help immediately if you have any questions!