Circadian variation in ventricular tachycardia and atrial fibrillation in a medical-cardiological ICU

Objective: To assess the diurnal distribution of ventricular tachycardia (VT) and atrial fibrillation (AF) in critically ill patients. Design and setting: Prospective observational study (episode-based design) in an eight-bed medical/cardiological ICU at a university hospital that also admits postoperative patients. Patients: 98 consecutive patients with AF (n=55) or ventricular tachycardia (n=43). Measurements and results: There were a total of 218 arrhythmia episodes (83 AF, 136 VT). The time of arrhythmia onset was not evenly distributed. Circadian variation in VT but not AF onset was well represented by a sine wave function. Both VT and AF fibrillation showed a trough during the night. The distribution of VT and AF episodes did not differ significantly with or without analgosedation. Conclusions: In critically ill patients the onset of VT and AF over 24-h is nominiformly distributed. In VT this circadian pattern of occurrence is well modeled by a sine wave function peaking between noon and 2 p.m. The circadian pattern is less clear for AF. The circadian variation is seen irrespective of the presence of absence of analgosedation for both arrhythmias.