Q: Are endurance athletes really at higher risk for atrial fibrillationAtrial fibrillation, often shortened to AFib, is a fast and irregular heartbeat that starts in the upper chambers of the heart.?

A: Yes. Atrial fibrillation (AF) is common in the general population, with a lifetime risk of roughly 1 in 4 adults.¹ While moderate exercise protects cardiovascular health, long-term, high-volume endurance training is associated with significantly higher AF rates. Meta-analyses show endurance athletes have about 2.5–3.6× higher odds of AF than non-athletes.² Among older Masters athletes, AF prevalence often reaches 5–10%, depending on the sport and cumulative years of training.³⁴

Q: What structural changes increase AF risk in highly trained athletes?

A: Years of intense endurance training can produce remodeling often called “athlete’s heart.” These changes include:

• Left atrial enlargementStructural expansion of the left atrium of the heart, associated with chronic alcohol consumption; the enlarged and remodeled atrium develops low-voltage zones (fibrotic areas) that act as substrates sustaining persistent atrial fibrillation.
• Atrial wall stretch from increased cardiac output
• Patchy fibrosis (microscopic scarring)
• Increased vagal toneThe level of activity of the parasympathetic (vagus nerve) branch of the autonomic nervous system acting on the heart; high vagal tone slows the resting heart rate and is generally cardioprotective, but in extreme endurance athletes it has been proposed to contribute to atrial fibrillation risk., promoting electrical instability

Together, these changes create an arrhythmogenic substrate, making AF more likely both to develop and to recur.⁵ Structural studies also show that larger left atrial size from long-term endurance training is linked with a higher risk of incident AF.⁶

Q: After catheter ablationA procedure in which a cardiologist threads a thin flexible tube (catheter) into the heart and uses energy — typically radiofrequency heat or cryotherapy — to destroy small areas of tissue responsible for triggering abnormal electrical signals; the main interventional treatment for AF., what are the success and recurrence rates in endurance athletes?

A: Catheter ablation can substantially reduce AF burdenA measure of how much of the time a person is in atrial fibrillation, expressed as a percentage or total duration over a monitoring period; catheter ablation aims to reduce AF burden even when it does not eliminate AF entirely., but recurrence is not rare.

• In endurance athletes, about 60% remain arrhythmia-free after a single ablation.⁷
• With multiple procedures, long-term success rises to around 77%.⁷

That means roughly 23–40% of endurance athletes experience recurrent AF despite modern ablation techniques.⁷

In the broader AF population, long-term studies report about 50–70% freedom from AF at five years, depending on whether patients have one or multiple procedures and on AF type.⁸⁹

Comparative work suggests that endurance athletes are less likely to remain arrhythmia-free two to three years after ablation than non-athletes treated with similar strategies.¹⁰

Q: Does continuing hard endurance training after ablation increase the chance of AF coming back?

A: The evidence strongly suggests yes, although current research cannot provide a precise percentage.

What we know:

• Long-term endurance athletes often have persistent atrial enlargement and fibrosis that do not fully reverse after ablation.⁵⁶
• Continued high-volume training maintains elevated atrial pressures, stretch, and wall stress, the same forces that contributed to AF in the first place.⁵⁶
• Atrial enlargement and fibrosis are well-established predictors of AF recurrenceThe return of atrial fibrillation after a period of successful rhythm control, whether achieved by ablation or medication; in endurance athletes, recurrence rates after a single ablation are approximately 40%, and persistent atrial enlargement and fibrosis are the main predictors. after ablation.⁵
• Ablation outcome studies show substantial recurrence rates in endurance athletes and generally less durable rhythm controlA treatment strategy aimed at restoring and maintaining normal sinus rhythm, as opposed to rate control, which simply slows the heart rate during AF; catheter ablation is the most invasive rhythm-control approach. compared with non-athletes.⁷¹⁰

What is not yet known: no published long-term prospective study has directly compared post-ablation athletes who continue high-intensity endurance training versus those who reduce it. As a result, we cannot state an exact “X% increase” in relapse risk — but mechanistically and clinically, ongoing hard training almost certainly raises the probability of AF coming back.

Q: Why don’t we have exact numbers on relapse risk from continued high-intensity training?

A: To get exact numbers, researchers would need to follow two groups of post-ablation endurance athletes over many years: one group continuing high-intensity training, the other reducing it, with careful tracking of AF recurrence. Such a trial has been proposed, but results are not yet available. Until then, recommendations are based on physiology, imaging data, and observed ablation outcomes in athletes.²⁵⁶⁷

Q: What do electrophysiologistsA cardiologist subspecialist who focuses on the electrical system of the heart, diagnosing and treating arrhythmias; responsible for performing catheter ablation and managing AF in athletes. generally recommend for athletes after ablation?

Most experts advise reducing training intensity and/or volume, at least temporarily, especially for athletes who:

• Have left atrial enlargement
• Show atrial fibrosisMicroscopic scarring of atrial muscle tissue, often resulting from chronic mechanical stretch or inflammation; fibrosis disrupts normal electrical conduction and is a well-established predictor of AF recurrence after ablation. on imaging
• Have recurrent or persistent AF
• Are older Masters athletesCompetitive or highly trained endurance athletes typically defined as individuals over the age of 35 who have engaged in years of high-intensity or high-volume training; they are the primary population studied in the athlete paradox research because their long exercise histories can paradoxically be associated with elevated coronary calcium scores.
• Train year-round at high volume or intensity

This does not mean stopping exercise altogether. Rather, it usually means shifting toward moderate, sustainable training zones and avoiding chronic extreme endurance loads while rhythm stability and atrial size are monitored.⁵⁶

Q: Can an endurance athlete return to high-level training after ablation?

A: Some can, particularly those with paroxysmal AFA form of atrial fibrillation in which episodes start and stop on their own, typically within 48 hours but by definition within 7 days; generally associated with better ablation outcomes than persistent or long-standing persistent AF., relatively small atria, and minimal fibrosis. Many athletes feel dramatically better after ablation.

However, several realities remain:

• The arrhythmogenic substrate (enlarged and sometimes fibrotic atria) often persists.⁵⁶
• Even with good treatment, 23–40% of endurance athletes will have AF recur over time.⁷
• Continued extreme endurance training likely increases the probability of recurrence, even though we cannot yet quantify by how much.⁷¹⁰

A sports cardiologistA cardiologist with specialized training in the cardiovascular effects of exercise and athletic performance, able to distinguish normal athletic adaptations (athlete's heart) from pathological conditions and guide return-to-sport decisions. or electrophysiologist familiar with athletes is best positioned to help balance performance goals with long-term heart health.

Q: What’s the bottom line?

• Endurance athletes have a higher baseline AF risk than non-athletes.²³⁴
• Catheter ablation reduces symptoms and AF burden but is not guaranteed to be curative.⁷⁸⁹
• Continued high-intensity endurance training likely raises AF recurrence risk by maintaining atrial stretch and structural remodeling.⁵⁶⁷¹⁰
• Moderating training load and aggressively managing other risk factorsA risk factor is something that raises your chance of developing a disease — high cholesterol particles, high blood pressure, smoking, diabetes, family history. (blood pressureBlood pressure is the force of blood pushing against your artery walls. It is written as two numbers, like 120/80. The top number is the pressure when your heart squeezes, the bottom is when it relaxes., weight, sleep apneaSleep apnea is repeated pausing of breathing during sleep, usually because the airway collapses., alcoholAlcohol is the ingredient in beer, wine, and spirits that makes them intoxicating., etc.) may help improve long-term rhythm stability.⁵⁶
• Individualized care from a knowledgeable electrophysiologist is essential for any athlete navigating AF and ablation.

References

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8. Ngo L, Lee XW, Elwashahy M, et al. Freedom from atrial arrhythmia and other clinical outcomes at 5 years and beyond after catheter ablation of atrial fibrillation: a systematic review and meta-analysis. Eur Heart J Qual Care Clin Outcomes. 2023;9(5):447-458. doi:10.1093/ehjqcco/qcad037
9. Ichijo S, Miyazaki S, Kusa S, et al. Impact of catheter ablation of atrial fibrillation on long-term clinical outcomes in patients with heart failure. J Cardiol. 2018;72(3):240-246. doi:10.1016/j.jjcc.2018.02.012
10.  Carbone A, Monda E, Ferrara F, et al. Aortic Dimension in Elite Athletes: Updated Systematic Review and Meta-Analysis. Eur J Prev Cardiol. Published online November 26, 2024. doi:10.1093/eurjpc/zwae385