Individual Circadian Variation and Sudden Death

Abstract

To the Editor: Because the identification of patients with certain circadian trends may permit individualized prevention of cardiac arrest or sudden death, we read the article by Peckova et al with interest.1 We were, however, puzzled by the investigators’ results emphasizing that the phenomenon of individual circadian variation for sudden cardiac death was not present. We believe there are important caveats to heed when one interprets these results. In 1995, when analyzing the distribution of sudden death due to ventricular fibrillation (VF) aborted by implanted defibrillators (ICDs), we reported a clear tendency for shocks to occur in the morning hours in a group of 22 patients.2 3 Interestingly, 16 patients who received multiple appropriate shocks showed a trend for the repeated shocks to occur around the same period of the day that the initial shock occurred.2 Two patients each experienced 6 shocks that occurred within the same 3-hour period of the day. This trend was noted even …