title: Factors affecting diurnal variability of ventricular tachyarrhythmias detected by multiprogrammable implantable cardioverter-defibrillators.
abstract: Many cardiovascular events, including ventricular arrhythmias, display diurnal variability with a morning peak, and a less pronounced afternoon peak. Since the advent of multiprogrammable implantable cardioverter-defibrillators (ICDs), it has been possible to analyse ventricular tachyarrhythmic events. This study aims to evaluate the circadian pattern of ventricular tachycardias in patients treated with ICDs and examines whether antiarrhythmic medications affect this pattern. Data recorded from 83 patients' ICDs were manually analysed and events other than ventricular arrhythmias were excluded. There was a morning peak of ventricular arrhythmias at around 9.00 a.m. This peak was maintained in patients with ejection fractions of less than 40% and those whose arrhythmias had cycle lengths of less than 230ms. Beta blockers appeared to have no effect on this morning peak but the peak appeared later with amiodarone.
authors.affiliation: Department of Cardiology, Westmead Hospital, Westmead, New South Wales 2145, Australia.
authors.forename: Astin K Y
authors.initials: AK
authors.lastname: Lee
authors.forename: Mahidi
authors.initials: M
authors.lastname: Mardini
authors.forename: David L
authors.initials: DL
authors.lastname: Ross
authors.forename: Robert
authors.initials: R
authors.lastname: Denniss