Cardiac potential and potential gradient fields generated by single, combined, and sequential shocks during...

Area of Science:

• Cardiovascular physiology
• Biomedical engineering
• Electrophysiology

Background:

• Determining potential gradient fields is crucial for understanding defibrillation shock effects.
• Established requirements for defibrillation using varied electrode configurations are lacking.

Purpose of the Study:

• To evaluate potential gradient field requirements for defibrillation.
• To assess the impact of different electrode configurations on defibrillation efficacy.

Main Methods:

• Recorded potential fields using 74 epicardial electrodes in 12 open-chest dogs during defibrillation shocks.
• Tested four electrode configurations: R:V, L:V, (R+L):V, and sequential R:V----L:V shocks.
• Measured defibrillation threshold (DFT) current and minimum potential gradients.

Main Results:

• The sequential R:V----L:V configuration had a significantly lower DFT current.
• Minimum potential gradients at DFT were similar across configurations (approx. 6-7 V/cm).
• Potential gradient fields were uneven (15-27-fold change), with weak fields in certain areas, correlating with activation sites after unsuccessful shocks.

Conclusions:

• Defibrillation fields from small epicardial electrodes are highly uneven.
• A minimum potential gradient across both ventricles is essential for defibrillation.
• Variations in shock strength needed to achieve this gradient explain DFT differences among configurations.
• High gradient areas can induce ectopic activation post-shock.