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Circadian variation in defibrillation energy requirements
F J Venditti1, R M John, M Hull
1Section of Cardiovascular Medicine, Lahey-Hitchcock Medical Center, Burlington, Mass 01805, USA.
Circulation
|October 1, 1996
Summary
Defibrillation energy needs for implantable cardioverter-defibrillators (ICDs) are higher in the morning. This morning peak in defibrillation threshold (DFT) and shock failure aligns with increased cardiac events, impacting ICD efficacy.
Area of Science:
- Cardiology
- Circadian Biology
- Biomedical Engineering
Background:
- Circadian variations are documented for myocardial infarction, ventricular arrhythmias, and sudden cardiac death.
- The study investigated whether defibrillation energy requirements exhibit similar daily fluctuations.
Purpose of the Study:
- To determine if defibrillation threshold (DFT) in patients with implantable cardioverter-defibrillators (ICDs) varies with time of day.
- To assess if energy requirements for terminating ventricular tachyarrhythmias change throughout the day.
Main Methods:
- Retrospective analysis of 345 DFT measurements from 134 patients with ICDs at various time points.
- Evaluation of 1238 ventricular tachyarrhythmia episodes treated with shock therapy in 930 patients, analyzing first shock failure rates hourly.
Main Results:
- Morning DFT (8 AM-12 noon) was significantly higher (15.1 J) compared to midafternoon (13.1 J) and late afternoon (13.0 J).
- A significant peak in failed first shocks was observed in the morning hours.
Conclusions:
- A morning peak in DFT and failed shock frequency exists, mirroring patterns seen in sudden cardiac death.
- These findings highlight potential implications for ICD programming and patient management, especially for those with marginal DFTs.