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Improved defibrillation thresholds with large contoured epicardial electrodes and biphasic waveforms.
E G Dixon1, A S Tang, P D Wolf
1Department of Pathology and Duke University Medical Center, Durham, NC 27710.
Circulation
|November 1, 1987
Summary
New defibrillation patch electrodes significantly lowered energy requirements for restoring normal heart rhythm in dogs. This research paves the way for smaller, safer implantable cardioverter-defibrillators by reducing shock strength needed for defibrillation.
Area of Science:
- Biomedical Engineering
- Cardiovascular Research
- Medical Devices
Background:
- Reducing defibrillation shock strength is crucial for smaller, safer automatic implantable cardioverter-defibrillators (AICDs).
- Current internal defibrillation electrodes often require high energy levels (5-25 J), potentially causing myocardial damage.
Purpose of the Study:
- To design and evaluate novel, large titanium defibrillation patch electrodes to decrease the energy needed for defibrillation.
- To assess the defibrillation thresholds (DFTs) using these electrodes in a canine model.
Main Methods:
- Two large, contoured titanium patch electrodes (approx. 33 and 39 cm²) were applied to the epicardium or pericardium of anesthetized open-chest dogs.
- Ventricular fibrillation was induced, and truncated exponential monophasic and biphasic shocks were delivered to determine DFTs.
- Shock parameters included varying phase durations for biphasic waveforms.
Main Results:
- Epicardial application yielded DFTs of 3.2 ± 1.9 J for monophasic and 1.3 ± 0.4 J for biphasic shocks (5-5 msec).
- Pericardial application showed similar DFTs: 3.1 ± 1.2 J for monophasic and 1.6 ± 0.5 J for biphasic shocks (5-5 msec).
- Biphasic shocks with longer first-phase durations also achieved low DFTs.
Conclusions:
- Novel large titanium patch electrodes effectively lower defibrillation energy requirements in a canine model.
- These findings support the development of AICDs requiring lower energy, potentially reducing myocardial injury.
- Electrode placement (epicardial vs. pericardial) did not significantly impact defibrillation thresholds with these large patches.