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Inspiration induced by phrenic nerve stimulation increases internal defibrillation energy requirements
D E Euler1, T A Whitman, M J Kallok
1Angeion Corporation, Minneapolis, Minnesota, USA. dave.euler@medtronic.com
Journal of Cardiovascular Electrophysiology
|October 9, 1999
Summary
Active inspiration, induced by phrenic nerve stimulation, significantly increases the energy required for successful defibrillation (E50). This finding suggests inspiration may reduce defibrillation efficacy by altering electrical field distribution.
Area of Science:
- Cardiology
- Biomedical Engineering
- Physiology
Background:
- Defibrillation success is critical for treating cardiac arrhythmias.
- Understanding factors influencing defibrillation energy requirements is essential for optimizing device performance.
Purpose of the Study:
- To systematically evaluate the impact of active inspiration, induced by phrenic nerve stimulation, on the energy needed for 50% successful defibrillation (E50).
Main Methods:
- Anesthetized pigs underwent defibrillation attempts using a biphasic waveform.
- Energy required for 50% successful defibrillation (E50) was determined using an up/down method.
- Shocks were delivered during passive expiration or active inspiration induced by phrenic nerve stimulation.
Main Results:
- Active inspiration increased the E50 by 31% compared to expiration (13.0 J vs 9.8 J, P=0.001).
- Leading-edge voltage and current at E50 also increased significantly during inspiration.
- No significant change in thoracic impedance was observed between inspiration and expiration.
Conclusions:
- Inspiration induced by phrenic nerve stimulation decreases defibrillation efficacy.
- This reduction in efficacy occurs without changes in impedance, suggesting altered electrical field distribution.
- Active inspiration is a critical factor to consider in defibrillation energy optimization.