Factors affecting diurnal variability of ventricular tachyarrhythmias detected by multiprogrammable implantable...

Area of Science:

• Cardiology
• Chronobiology
• Medical Devices

Background:

• Many cardiovascular events exhibit diurnal variability, often with a morning peak.
• Implantable cardioverter-defibrillators (ICDs) allow for detailed analysis of ventricular tachyarrhythmic events.

Purpose of the Study:

• To evaluate the circadian pattern of ventricular tachycardias in patients with ICDs.
• To examine the influence of antiarrhythmic medications on this circadian pattern.

Main Methods:

• Manual analysis of data from 83 patients' ICDs.
• Exclusion of non-ventricular arrhythmia events.
• Assessment of event timing and correlation with patient characteristics and medications.

Main Results:

• A significant morning peak for ventricular arrhythmias was observed around 9:00 a.m.
• This morning peak persisted in patients with reduced ejection fractions (<40%) and short arrhythmia cycle lengths (<230ms).
• Beta-blockers did not affect the morning peak, whereas amiodarone appeared to delay its occurrence.

Conclusions:

• Ventricular arrhythmias demonstrate a clear circadian rhythm with a morning predominance.
• Specific patient subgroups (low ejection fraction, short cycle length) maintain this pattern.
• Amiodarone may modify the timing of ventricular tachyarrhythmias, suggesting a potential interaction with circadian mechanisms.