Copyright © 1995 by the European Society of Cardiology.
© 1995 The European Society of Cardiology
At what time are implantable defibrillator shocks delivered?
Evidence for individual circadian variance in sudden cardiac death
Cardiovascular Research and Teaching Institute Aalst Cardiovascular Center, O.L. V. Hospital Aalst, Belgium
revised 27 September 1994; accepted 28 October 1994.
Correspondence: Pedro Brugada, MD, Professor of Cardiology, Cardiovascular Research and Teaching Institute Aalst, Cardiovascular Center, OLV Hospital, Moorselbaan, 164-9300 Aalst, Belgium.
Abstract
Background: As in myocardial infarction and transient ischaemia, out-of-hospital sudden cardiac death has an increased morning incidence. However, sudden death occurring in hospital is evenly distributed over the 24 h period suggesting that there might be subgroups of patients with atypial circadian patterns of sudden death. Patients who received an implantable defibrillator constitute an ideal group for studies of circadian patterns of sudden death since this generation of devices are able to store the exact time when defibrillation occurred
Methods: The distribution of sudden death aborted by the implantable defibrillator was analysed during the 24 h period for 87 presumed appropriate shocks delivered in a group of 22 patients, 18 men and four women, 58.7 ± 11.9 years old and with a mean left ventricular ejection fraction of 39.4 ± 17.6%.
Results: Each patient received an average of 4.42 ± 3.04 shocks during a mean follow-up of 9.4 ± 5.6 months. Apart from a clear tendency for shocks to occur during the morning hours (42% of total shocks), five of 16 patients who received multiple shocks also showed a trend to repeat the shocks around the same period during the day.
Conclusion: Our results support the accepted view that changes in autonomic tone in the early morning play a role in the circadian variations of sudden death. Sudden death not only occurs more frequently in the morning hours, but it also clusters in certain periods for individual patients.
Key Words: Sudden death • circadian variance • implantable defibrillator
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