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Local electrogram changes in response to a high-voltage intracardiac shock in humans
J R Smith1, A H Kadish, S Inbar
1Department of Medicine, Northwestern University Medical School, Chicago, Illinois, USA.
Journal of Cardiovascular Electrophysiology
|May 1, 1996
Summary
Defibrillator shocks can alter intracardiac electrograms, potentially hindering arrhythmia detection. The proximity of the shocking coil to the sensing electrode significantly impacts these electrogram changes.
Area of Science:
- Electrophysiology
- Cardiovascular Devices
Background:
- Transvenous defibrillators may fail to sense ventricular fibrillation after an unsuccessful shock.
- This study investigates electrogram changes post-defibrillator shock that could impair arrhythmia redetection.
Purpose of the Study:
- To characterize changes in intracardiac electrograms after defibrillator shocks.
- To identify factors contributing to the failure of arrhythmia redetection.
Main Methods:
- Recorded unipolar and bipolar electrograms during sinus rhythm before and after monophasic/biphasic shocks in 29 patients.
- Analyzed electrogram amplitude, dV/dt, and activation recovery time.
- Assessed the influence of shock waveform, recording type, and clinical variables.
Main Results:
- Biphasic shocks reduced unipolar electrogram amplitude by 19.6% and bipolar amplitude by 20.8%.
- Mean dV/dt decreased by 30.7% (unipolar) and 33.0% (biphasic).
- Electrogram changes were more pronounced with closer shocking coil proximity to the distal sensing electrode.
Conclusions:
- Defibrillator shocks cause significant changes in intracardiac electrograms.
- These changes, observed even during sinus rhythm, may be linked to shocking coil-electrode proximity.
- Understanding these alterations is crucial for improving defibrillator sensing performance.