Transthoracic ventricular defibrillation in adults.

A prospective study of the energy required for transthoracic ventricular defibrillation in adults showed that in 42 (81%) out of 52 episodes of ventricular fibrillation shocks of 100 watt-seconds (Ws) of stored energy were successful. Out of 233 episodes, 222 (95%) were converted by 200 W s shocks. Among patients in whom primary ventricular fibrillation occurred within one hour of the onset of acute myocardial infarction, 200 W s shocks were successful in 40 (98%) out of 41 episodes. When low-energy shocks failed, a stored energy of 400 W s invariably succeeded. The need for large and expensive defibrillators that store more than 400 W s and are less readily available is therefore questioned.