Abstract: A method and apparatus for delivering a truncated damped sinusoidal external defibrillation waveform which, when applied through a plurality of electrodes positioned on a patient's torso will produce a desired response in the patient's cardiac cell membranes is provided. The external defibrillator is utilized for applying a damped sinusoidal waveform having a first waveform phase and a second waveform phase to a pair of electrodes. The external defibrillator has a first capacitive component, a first inductive component, a first truncating switch, and waveform control circuitry. The waveform control circuitry of the defibrillator controls the first and second truncating switches such that the duration of the second phase waveform delivered by the second charge storage component is greater than the duration of the first phase waveform delivered by the first charge storage component.

Abstract: A system and method for predicting the defibrillation threshold energy of a defibrillation lead arrangement by determining the upper limit of vulnerability of the heart by shocking the heart at varying times during the T-wave at decreasing test shock energy levels until fibrillation is induced in the heart. The lowest energy level which fails to induce fibrillation is determined to be the upper limit of vulnerability and the defibrillation threshold is predicted to be an energy level incrementally higher in the range of about 5 Joules.