A circadian pattern of occurrence of ventricular tachycardia and atrial fibrillation is present during periods of analgosedation

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

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.