Distribution of sudden death in 3690 patients with a witnessed cardiac arrest. Top panel: There is a diurnal pattern with a first arrest, with a peak occurrence during the morning hours. Bottom panel: There is also a diurnal pattern of sudden death in the 597 patients with a second cardiac arrest although, for the individual patient, there was no association between the time for the first and second event.
Data from Peckova, M, Fahrenbruch, CE, Cobb, CE, et al, Circulation 1998; 98:31.