Arrhythmia episodes and clinical events during exercise in endurance athletes with paroxysmal atrial fibrillation

Background Atrial fibrillation (AF) is the most common cardiac arrhythmia in athletes. However, knowledge regarding the temporal relationship between exercise and recurrent AF episodes and other clinical events in endurance athletes with AF is limited. Purpose To study AF recurrence, ventricular arrhythmias and other clinical events in relation to exercise sessions of different intensities in endurance athletes with paroxysmal AF continuously monitored with insertable cardiac monitor (ICM). Methods We included endurance athletes with symptomatic paroxysmal AF monitored with ICM participating in an ongoing randomised controlled trial on effects of exercise intensity on AF burden. ICM-detected AF episodes were validated by a cardiologist. Sports watches and chest-straps were used to monitor exercise sessions. Exercise with heart rate (HR) ≤75% of the individual maximum HR (HRmax) was classified as low- to moderate intensity, high-intensity as 76-84% of HRmax, and very high-intensity as ≥85% of HRmax. Recurrent AF episodes were assessed in relation to exercise sessions. Results Forty-seven athletes (3 female) were included, Table 1 shows selected baseline characteristics. Athletes were monitored with ICM for a total of 55,944 hours (median 1,008, IQR 840-1,344]) and performed a total of 1,722 hours of exercise, of which 592 hours at high- or very high intensity. We observed a total of 1,445 (median 3, IQR 3-33]) AF episodes among 31 (66%) of the athletes. Among athletes with at least one AF episode, the mean number of episodes was 47±86 (median 17, IQR 3-33). A total of 152 episodes had a duration of >60 minutes, with a median duration of 3 minutes (IQR 1.2-13.0). Thirteen athletes (28%) had recurrent AF during exercise, of whom 11 (85%) also had AF unrelated to exercise. Median AF duration during exercise was 2.4 minutes (IQR 1.2-8.2). Only two athletes had an AF episode during a high-intensity exercise session, none of these episodes were high-rate AF. The rate of recurrent AF episodes was not higher during or within first 3 hour after exercise, compared to unrelated to exercise (Figure 1). Of the 28 (60%) athletes who reported exercise as a common AF trigger, 11 (39%) also reported prevalent AF recurrence during sleep. We did not observe any exercise-related ventricular tachycardias or serious adverse events during monitoring. Conclusions One out of four athletes experienced AF episodes during exercise sessions, but the rate of AF episodes was not higher during and within first three hours after exercise compared to unrelated to exercise. During >1,700 hour of exercise, including 592 hours of high-and very high intensity, we observed no ventricular tachycardia or serious clinical adverse events.