According to the 2010 American Heart Association guidelines:
The precordial thump should not be used for unwitnessed out-of-hospital cardiac arrest (Class III, LOE C). The precordial thump may be considered for patients with witnessed, monitored, unstable ventricular tachycardia including pulseless VT if a defibrillator is not immediately ready for use (Class IIb, LOE C), but it should not delay CPR and shock delivery. There is insufficient evidence to recommend for or against the use of the precordial thump for witnessed onset of asystole.!
Given that the American Heart Association give no direction, is this something you would consider before the arrival of an AED?