Session S73.4

In-Vitro Investigation of Very Long Defibrillation Shocks: Design and Testing of a Capacitor-Free Defibrillator

M Triventi, E Mattei, A Delogu, F Censi, G Calcagnini*,
P Bartolini, F Aguel, J Stohlman, V Krauthamer

Italian National Institute of Health
Roma, Italy

Introduction: Research to understand and improve defibrillation waveforms has, so far, suffered from the intrinsic limitation of the capacitor discharge approach. In vitro investigations (explanted perfused hearts from small animals) require energy levels (up to 10J) which may allow the design of defibrillators based on linear power amplifiers. Such a solution allows the investigation of true arbitrary waveforms (morphology and duration). The aim of this paper is to present a new PC controlled defibrillator which allows the delivery of arbitrary waveform shocks, with energy up to 10J and duration up to 100ms. In addition, data on shocks delivered to isolated rabbit’s hearts are presented.
Materials and Methods: The solutions adopted in the design and realization of the defibrillator were: rechargeable battery power; linear AB class power amplifier output in bridge configuration (voltage swing ± 130V); optical isolation of analog and digital lines to and from the PC; measurement of the actual voltage, current and energy delivered to the load.
Results: Laboratory testing of the device on known loads showed that the defibrillator is capable of delivering shocks with a rise time less than 150 us, no tilting also for long waveforms (100ms), peak current up to 10 A. The system was then used on rabbit hearts to define a protocol to investigate the effect of waveform duration on defibrillation threshold. Monophasic Damped Sinusoidal (MDS) waveforms of 20 ms duration were used to defibrillate rabbit hearts with an estimated load impedance of 12 ohms. After inducing ventricular fibrillation using a 60 Hz AC sinusoidal signal (100V pk-pk), a defibrillation threshold of 1.525 J +/- 0.347 (Mean +/- STD, n=7, derived from 2 rabbit hearts) was established using the arbitrary waveform defibrillator. Additional testing using the defibrillator is ongoing, including the acquisition of the defibrillation threshold, conduction velocity and dispersion voltage mapping for MDS waveforms of increasing duration and Biphasic Truncated Exponential waveforms having similar properties.
Discussion and Conclusions: We demonstrate the feasibility of an experimental defibrillator design, based on linear output stages, which overcomes the major limitations of the capacitor discharge approach and allows the generation and delivery of true arbitrary waveforms.

(Abstract Control Number: 100)