I heard in my ACLS (Advance Cardiac Life Support) course of studies done in Las Vegas with MI's and the AEDs (Defibrillators). They could watch the times because of so many security cameras. And the time needed was more like three minutes. No way an ambulance could get there in that time, so they trained the security guards to use the civilian friendly automatic defib. machines. All very cool and scary, and I would love to hear about this from other sources.