Quantitative analysis of circadian variation in atrial fibrillation frequency

Circadian variation in atrial fibrillation (AF) frequency is explored in this paper by employing recent advances in signal processing. Once the AF frequency has been estimated and tracked by a hidden Markov model approach, the resulting trend is analyzed for the purpose of detecting and characterizing the presence of circadian variation. With cosinor analysis, the results show that the short-term variations in AF frequency exceeds the variation that may be attributed to circadian. Using the autocorrelation method, circadian variation was detected in 13 of 18 ambulatory ECG recordings (Holter) acquired from patients with long standing persistent AF. Using the ensemble correlation method, the highest AF frequency usually occurred during the afternoon, whereas the lowest usually occurred during late night. It is concluded that circadian variation is present in most patients with long standing persistent AF but the short-term variation in AF frequency is considerable.