Electrical requirements for ventricular defibrillation.

Most deaths from ischaemic heart disease are sudden, occur outside hospital, and result from ventricular fibrillation. But defibrillators have only limited availability because of their size and weight. A miniature defibrillator has been developed. A singe low-energy shock succeeded in removing ventricular fibrillation in 73 out of 82 episodes, and a further shock was successful in seven more episodes. Primary ventricular fibrillation probably always responds to low-energy electrical shocks, which challenges the conventional view that correction of ventricular fibrillation requires high-energy direct-current shock. Thus even smaller and lighter defibrillators are possible. Furthermore low-energy shocks cause less myocardial damage.