Difference between heart attack & cardiac arrest explained here: http://www.aedhelp.com/sca/sca_same.cfm
Also, heart attacks leave artefacts; cardiac arrest does not, IIRC.
Thanks for the link.
Like a lot of people I never knew the difference between the two.
That link says you've only got ten minutes to get help if your heart just suddenly stops beating.
That's not much time.