Ten seconds is nothing!
Speaking from a CPR Certified Firefighter (not an Emergency First Responder yet) standpoint, and quoting info I just read from the Red Cross First-Aid: The Vital Link book:
0-4 minutes after going into cardiac arrest- clinical death
4-6 minutes-brain damage possible
6-10 minutes-brain damage likely
10+minutes - biological death.
If we roll onto a scene and the patient has been in cardiac arrest for more than ten minutes, there's not much we can do.
De-fibs are great things though. Just as an interesting side-note, when a person goes into cardiac arrest (their heart stops), they probably still have some electrical activity going on in their heart, only it's so messed up that the heart isn't pumping blood anymore. If a trained person can hook the patient up to a defibrilator quickly enough, the de-fib can detect those odd electrical charges and will advise the operator to admister a shock. Hopefully, the shock will 'shock' the heart into resuming a normal rythmn.
If you want the re-starting of the heart to be dramatic, you better plan on the cardiac arrest lasting for AT LEAST two or three minutes. Honestly, if I was the reader, I'd like to see the MC biologically dead, then brought back to life, but that's just my opinion.
Oh, if you go into respiratory arrest (not breathing), such as when you're choking, you have 45 seconds before you'll pass out and at least a minute or two before you heart will stop (sorry, I forget those numbers).
JrFF