Abstract 15497: Novel Methods of Reducing the Energy Required to Cardiovert Atrial Fibrillation in Ovine Models
Introduction: Atrial fibrillation (AF) is a chaotic breakdown of electrical activity in the upper chamber of the heart with consequent deterioration of atrial mechanical function. AF is the most common arrhythmia in clinical practice, accounting for approx. one-third of hospitalizations for cardiac rhythm disturbances. Current AF defibrillation energies are reported to cause pain and discomfort in some patients. The use of defibrillation waveforms that enable lower energy cardioversion, and therefore less pain to the patient, is an area of considerable interest for the treatment of this condition. The aim of this study was to investigate if the energy required to internally defibrillate AF could be reduced by using novel defibrillation waveforms.
Methods: Ethical approval was granted for this ovine study from the NI home office. Defibrillation leads were placed transvenously into the coronary sinus and the right atrial appendage of 14 (70±5kg) ovine models. The leads were connected to a modified defibrillator containing R- wave synchronisation circuitry. Sustained atrial fibrillation (>30 seconds) was induced using rapid atrial pacing (100 Hz, duration 2 ms, 50 V for 5 sec.; Grass S44 stimulator) in 8 (57%) of 14 animals. Cardioversion was attempted via 2 atrial defibrillation leads using a number of different voltages, pulse widths and waveforms.
Results: The two most successful waveforms tested both had defibrillation energies below 0.15 Joules. The chopped biphasic 30V 4ms waveform (0.122±0.028J) and the chopped monophasic 30V 8ms waveform (0.083±0.006J) successfully converted sustained AF with success rates of 100% in some models. Overall success rates were negatively impacted by model variation. Overall cardioversion success rates for the chopped biphasic 30V 4ms waveform was 44.1% (n=68) and was 61.5% for the chopped monophasic 30V 8ms waveform (n=13).
Conclusions: These findings are of interest for transvenous internal cardioversion of chronic persistent AF. Further examination of these waveforms, with minimised model variation and in an improved model of AF, may prove that the waveforms may be clinically relevant and preferable to those higher energy waveforms used in current commercially available ICDs.
- © 2011 by American Heart Association, Inc.