Aim

Ventricular tachycardia (VT) and atrial fibrillation (AF) are the single most frequent arrhythmias (ARRHY) in our ICU. The present study investigated whether there is a circadian variation in the onset of these ARRHY in critically ill patients in a medical cardiologic ICU which also admits cardiac surgery patients.

Results

Between 11/96 and 7/99 there were 98 consecutive patients with VT (43 pts) or AF (55 pts). There were a total of 218 ARRHY episodes (AF, n = 83; VT, n = 135). The time of onset of these ARRHY was not evenly distributed across the 24 hours day. Both, VT and AF showed a nadir during the night. The circadian variation in the occurrence of VT, but not AF, could well be modeled by a sine wave function. For VT, but not AF, there was a significant correlation between the observed frequency distribution and a sine wave function (VTr = 0.71, P < 0.001; AFr = 0.29, P > 0.05). The circadian variation with/without analgosedation was not significantly different for VT episodes (n = 86 and n = 49; χ2 = 20.3, P = 0.56). For the distribution of VT episodes, there was a significant correlation to a sine wave function irrespective of the presence of anal-gosedation (no analgosedation, r = 0.59, P < 0.05; analgosedation, r = 0.9, P < 0.001; Fig.). VT occurrence showed a peak in the early afternoon between 1 and 2 PM. As for VT, the distribution of AF episodes was not different during periods with (n = 47) or without analgosedation (n = 36; χ2 = 19.6, P = 0.6).

figure 1

Figure

Conclusion

The distribution of VT and AF episodes across the day in critically ill patients is nonuniform. The distribution of VT episodes follows a sine wave function showing a peak in the early afternoon between 1 and 2 pm. The circadian variation and its representation by a sine wave function is less clear for the onset of AF episodes. Most striking, the circadian variation is present even during periods of analgosedation.