Circadian occurence patterns of atrial fibrillation after cardiac surgery during 2.5 years of continuous rhythm monitoring
Authors: Kawczynski M , Gilbers M D , Zeemering S , Isaacs A , Maessen J G , Verheule S , Bidar E , Schotten U 
Published: May 2024

Abstract

Background
Atrial fibrillation (AF) is a common complication after cardiac surgery, and current theories suggest that the autonomic nervous system plays a major role in the development of early postoperative AF (early-POAF).(1) However, its role in late recurrences is still unknown. Previous studies in non-surgical patients have revealed distinct preferential patterns of AF occurrence, such as adrenergic/daytime AF or nocturnal AF.(2, 3) Nevertheless, circadian onset patterns for POAF have never been studied before.

Purpose
To establish the circadian occurrence patterns of POAF after cardiac surgery during 2.5 years of continuous rhythm monitoring.

Methods
Patients with and without a history of AF undergoing cardiac surgery were included. Continuous rhythm monitoring was performed over a period of 2.5 years. POAF was defined as an AF episode lasting 2 minutes or longer, detected by the ILR algorithm, and all episodes were manually checked by the investigators. Circadian distribution of AF episode onset was presented in circadian plots for the early postoperative phase (first 90 days) and late postoperative phase (after the first 90 days). Additionally, comparisons for circadian occurrence patterns were made between early and late POAF, after dividing the daytime period into four equal time intervals (night = 12 a.m. to 5.59 a.m., morning = 6 a.m. to 11.59 a.m., afternoon = 12 p.m. to 5.59 p.m., evening = 6 p.m. to 11.59 p.m.), both in patients with and without a preoperative AF history.

Results
The study population consisted of 98 patients (71 without a preoperative AF history and 27 with a preoperative AF history), of which 53 developed POAF (29 without a preoperative AF history and 24 with a preoperative AF history), resulting in a total of 3607 confirmed AF episodes (Figure 1). Early-POAF occurred in 46 patients, while late-POAF occurred in 36 patients. In both patients with and without AF history, the majority of early-POAF episodes occurred between 12 a.m. and 12 p.m. (59.2% and 55.9%, respectively) (Figure 2). In patients without AF history, late-POAF occurred predominantly in the evening (26.7%), particularly episodes lasting between 10 and 360 minutes, and in the afternoon (32.3%), with a greater number of episodes lasting &lt;10 minutes (Figure 2). Patients with AF history experienced most late-POAF episodes at night (26.4%) and during the morning (33.1%), with a peak of short episodes (&lt;10 minutes) in the morning (Figure 2). The circadian distribution was significantly different between early- and late-POAF for both patients with and without AF history (p&lt;0.001 and p&lt;0.001, respectively).

Conclusion
In patients without a preoperative AF history, early-POAF showed a more heterogeneous circadian occurrence pattern compared to late-POAF, which occurred mostly in the evening and afternoon. In patients with a preoperative AF history, POAF initiated mostly during the night and in the morning.Figure 1Figure 2