Circadian variation of sudden cardiac death reflects age-related variability in ventricular fibrillation.

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Abstract
BACKGROUNDPrevious studies report a morning peak in the occurrence of out-of-hospital sudden cardiac death but lack detailed information on underlying arrhythmias. We used the documentation system of the semiautomated defibrillators used by emergency medical technicians to investigate the circadian pattern of defined arrhythmias and the influence of demographic patient characteristics on this pattern.METHODS AND RESULTSFrom December 1988 to December 1990, 703 consecutive patients (63% men; age, 67 +/- 17 years) with sudden cardiac death were registered in the Klinikum Steglitz area of the Berlin emergency care system. Determination of time of day of the event was based on the arrival time of the rescue squad. A marked circadian variation (P < .0001) in the occurrence of sudden cardiac death was observed with a primary morning peak (6 AM to noon) and a secondary afternoon peak (3 to 7 PM). The subgroup of 294 patients with ventricular fibrillation as initially documented arrhythmia showed a similar circadi...