Discussion
The main finding of this study is the higher propensity of athletes population of remaining free from AF recurrences after a single AF ablation procedure compared with Non-athletes population, especially when CTI ablation was associated with PVI. Furthermore, the majority of our athletes population quickly resumed competitive sport activity.
Data from the literature suggest that freedom from AF is between 50-80% in patients with either persistent or paroxysmal AF5-10. However, there are few and conflicting long-term data available in athletes and no difference in long-term freedom from AF has been observed between athletes and NA.
In 2008 Furlanello et al. reported in a small population of 20 athletes (mean age 44.4±13 years) 90% freedom from AF at 36.1±12.7 months after PVI11. Another study including 182 subjects undergoing PVI reported similar arrhythmia-free survival at one year in the lone AF sport group versus controls (59% vs 48%, p=0.44), and similar rates of procedure related complications (7.1% vs. 4.3%; p=0.45). The frequency of redo PVI procedures was similar between the lone AF sport group and controls (40.5% vs 37.3%, p=0.5)12. Koopman et al. studied 94 endurance athletes and reported similar AF recurrence after first PVI procedure13: both groups showed similar arrhythmia free survival at 3 years (87 vs. 85%, p=0.88).
More recently, the case-control study by Decroocq et al.14 showed the same AF recurrences rates at 1-year follow-up after CA between 73 athletes and 73 matched sedentary patients. After 5-year follow-up, AF recurrences rates did not differ statistically between 38 (52%) athletes and 35 (47.9%) NA who recurred. Finally, Mandsager et al.15 reported no difference in arrhythmia recurrence between athletes and a matched cohort of NA who underwent PVI. Single-procedure freedom from arrhythmia was 75%, 68%, and 33% at 1 year for paroxysmal, persistent, and long-standing persistent AF, respectively. Multiple-procedure freedom from arrhythmia off antiarrhythmic drugs was 86%, 76% and 56% in respective group at the end of follow-up (mean 1.4 ± 0.7 ablation per athletes).
In our study, after a median follow-up of 787 days, 62.5% of athletes were free from recurrences after one CA procedure and mostly without antiarrhythmic drugs (87%), while after a redo procedure the overall freedom from recurrences was 84%. However, in contrast with previous data, our study showed a higher propensity of athletes of remaining free from AF recurrences after a single AF ablation procedure compared with NA population. After the first year of follow-up, athletes had, in fact, a 48% reduced risk of recurrences than NA, especially in an age-related analysis. Young athletes had a risk of AF recurrences 4 times lower than young NA, while elderly athletes had a 46% reduced risk of AF recurrences than elderly NA. These differences were not statistically significant due to low sample size, but showed a positive trend in athletes.
Different reasons may explain a better outcome of CA in athletes compared to NA. First of all, athletes were slimmer than NA and the correlation between BMI and AF is clearly demonstrated16-18. Moreover, in NA LA volume was significantly higher and persistent AF significantly more prevalent, suggesting the presence of atrial remodelling and more advanced electric LA disease. It has been demonstrated, in fact, that even small difference in LA volume is an independent predictor of increased odds of AF recurrence19. The negative trend showed in endurance athletes may be correlated with atrial remodelling described in this subpopulation of athletes20. Endurance training leads to a harmonic enlargement of all four cardiac chambers as an adaptation to exercise conditioning; however, the atrial walls are significantly thinner than the ventricular walls and the higher stress during episodes of training-related volume overload may contribute to progressive LA enlargement and remodelling. Repetitive episodes of atrial stretching and chronic inflammation secondary to excessive endurance training may be contributing factors for atrial fibrosis and AF, especially in aging athletes21,22.
Furthermore, in our study concomitant CTI ablation in athletes seemed to be associated with an additional positive trend in terms of freedom from recurrences, regardless previous documentation of typical AFL. AFL often precedes or coexists with AF in athletes as a consequence of exercise-induced enlargement of the atria23 and it may also be life-threatening during exertion due to 1-to-1 conduction to the ventricles under high sympathetic tone. Our results are in contrast with available data from literature in NA population showing that prophylactic CTI ablation irrespective of the previous documentation of typical AFL is not associated with improvement in recurrence of atrial arrhythmia compared with PVI alone. After the small randomized controlled trial by Pontoppidan et al. in 200924, more recently Mesquita et al.25 compared the outcomes of patients without any previous documentation of typical AFL who underwent PVI alone vs. PVI + prophylactic CTI ablation using a registry dataset of more than 1900 consecutive patients who underwent a first AF CA. CTI ablation remained unassociated with AF-free survival. The same results were obtained by Lee et al. in 2019 in their retrospective study of 139 patients26 and they were confirmed also by the meta-analysis by Romero et al. in 202027. Ongoing randomized control trials in general population may give further evidence to support or refuse prophylactic CTI ablation. Increased vagal tone and structural atrial changes (i.e. fibrosis) associated with high intensity sport practice may have a causative role in the development of typical AFL in athletes and it may explain our results. However, further data are requested. Recent recommendations for participation in leisure-time physical activity and competitive sports suggest that in an athlete presenting with AFL, there should be a very low threshold to ablate the CTI, given the efficacy and safety of the procedure versus the risk for recurrences during sports. European recommendations even advice that CTI should be ablated prophylactically in athletes with AF who want to engage in intensive exercise, especially when drug treatment is considered or concomitantly with PVI28.
Lastly, the high success rate of AF CA obtained in our study confirmed the possibility to permanently abolish AF in athletes, offering a unique option for resume competitive sport. Most of our athletes were, in fact, declared eligible to competitive sport activity after at least 3 months from the CA as per Italian sport protocol.