Modified alternating current defibrillation: a new defibrillation technique

Abstract

Defibrillation is the only clinically effective treatment for ventricular fibrillation (VF). Early defibrillation improves the outcome and increases the chance of survival with full recovery. Immediate availability of a home-based defibrillator using mains-derived alternating current (AC) current will drastically improve the outcome. The aim was to develop a defibrillator based on the modulated AC, resembling biphasic configuration, and compare its efficacy, in a pig model, with a standard direct current (DC) defibrillator. A computer controlled, modulated AC defibrillation system was developed using a high-voltage switch and a high-voltage transformer. The efficacy and safety was evaluated in five pigs (30-40 kg), under general anaesthesia with ketamine and isoflouran. A single quadripolar-pacing catheter was inserted percutaneously. Ventricular fibrillation was induced with rapid ventricular burst pacing, and stable VF was defibrillated after 15 s. Defibrillation threshold (DFT) was determined in each animal with AC and standard DC shock using the step-down protocol. A biphasic-like shock was used with a short isoelectric stage between the phases. The DFT with AC was 70.83 +/- 24.81 J and with DC was 65.83 +/- 12.41 J (P = 0.49). No macroscopic damage was observed after AC or DC defibrillation. Modulated AC defibrillation is safe and effective as the commercially available DC defibrillation. The defibrillator is built from an inexpensive high-voltage transformer, without the need for capacitor, batteries, or routine maintenance, delivers repeated shock without any delay, and provides pacing as well. It may be an ideal platform for automatic home defibrillator.