Defibrillation threshold and electrode configurations: an experimental study testing three configurations in twelve...

Area of Science:

• Cardiology
• Biomedical Engineering

Background:

• Implantable automatic defibrillators (IADs) typically use a transvenous endocardial configuration.
• Additional patches are sometimes necessary when the defibrillation threshold (DFT) remains high.
• The choice between epicardial and subcutaneous patches is often based on team preference.

Purpose of the Study:

• To evaluate the impact of additional epicardial versus subcutaneous patches on DFT.
• To compare the effectiveness of subcutaneous array and epicardial patches in reducing DFT.

Main Methods:

• Three configurations were tested in 12 pigs: Endovenous lead alone (Endo), Endovenous lead + subcutaneous patch (Endo + SQ), and Endovenous lead + epicardial patch (Endo + Epi).
• Defibrillation thresholds (DFTs) were determined using the up/down procedure after inducing ventricular fibrillation.
• Paired t-tests and analysis of variance were used for statistical comparison.

Main Results:

• The Endo configuration had a DFT of 14.6 +/- 11.0 J.
• Adding a subcutaneous patch (Endo + SQ) reduced DFT to 9.4 +/- 7.2 J (p < 0.01).
• Adding an epicardial patch (Endo + Epi) reduced DFT to 8.9 +/- 6.5 J (p < 0.01), with no significant difference between SQ and Epi configurations.

Conclusions:

• Additional patches significantly decrease DFT, by approximately 35-39%.
• Subcutaneous patches are recommended over epicardial patches for patients requiring an additional patch to lower DFT.
• Utilizing subcutaneous patches may also contribute to generator battery savings.