Results:
Of 520 invited individuals, 394 (76%) met for examination. After exclusions, 57 athletes with paroxysmal AF, 87 athletes without AF, 88 non-athletes without AF, and 61 non-athletes with paroxysmal AF were included (Figure 1).
Baseline characteristics: All participants were men, with a mean age of 70.7 ± 6.7 years. Athletes with and without AF reported a median of 40-50 years of performing regular endurance exercise and a median of 16 completed annual Birkebeiner XC-races. Eighty-six participants had never practiced regular endurance exercise, whereas 49 participants had practiced regular endurance exercise for 1 to 20 years, 43 participants for 20 to 40 years, and 115 participants for >40 years. Almost 80% of the athletes still participated in regular endurance exercise at the time of examination. Athletes had a very low comorbidity burden, a lower BMI and a lower resting heart rate than non-athletes. Blood pressure was similar between all four groups. Individuals with AF were taller than those without AF. The AF burden was low in both AF groups, with more than three out of four individuals experiencing paroxysms of AF less than once a month. While a higher proportion of athletes had performed AF ablation, the use of antiarrhythmic drugs was higher among non-athletes (Table 1).
Echocardiographic parameters: LA echocardiographic parameters are presented in Table 2, and LV echocardiographic values are presented as supplemental material (Table S1). There was no significant interaction between athletic status and AF status regarding atrial parameters. LA size was associated both with athletic status and AF status. SD-TPS stated in ms was associated with AF status but not athletic status. When correcting SD-TPS by the R-R interval, we found SD-TPS (%) to be associated with both athletic and AF status. LASr, LAScd, and LASct were lower in the AF groups regardless of athletic status. As opposed to LAVImax, we could not identify any significant trend between years of performing endurance exercise and SD-TPS in individuals without a history of AF (p=0.893) (Figure 3).
SD-TPS remained significantly associated with AF after adjusting for height, weight, CHA2DS2-VASc score, LAVImax, GLS, and QRS width in all participants and the athletic group alone (Table S2 and S3). However, SD-TPS did not remain significantly associated with AF in athletes when LASr was included in the model (p=0.06) (Table S4). Hence, in a hierarchical logistic regression model, SD-TPS did not add independent incremental value in identifying individuals with AF on top of clinical characteristics, CHA2DS2-VASc score, QRS width, standard echocardiographic values, and LASr (Figure 4).
Athletes had larger left ventricles and slightly lower GLS and E/e‘ than non-athletes. There were no significant interactions between AF and athletic status regarding LV values except for LV mass index. GLS was not significantly affected by AF status.