Circadian variation of symptomatic paroxysmal atrial fibrillation : Data from almost 10 000 episodes

To determine the circadian rhythm of paroxysmal atrial fibrillation in a very large outpatient population. We reviewed all emergency telephone calls received in Shahal (a medical service covering 44 000 subscribers), from 1987 to 1997. Patients were included if new-onset atrial fibrillation was recorded. During this study period, 9989 episodes of paroxysmal atrial fibrillation were recorded. The time of onset was not uniformly distributed throughout the 24 h period. Instead, the distribution of arrhythmic episodes showed a double peak, with a significant increase in the number of episodes in the morning and a second rise in the evening (P