Abstract and Introduction

Although the benefits of regular exercise in controlling cardiovascular risk factors have been extensively proven, little is known about the long-term cardiovascular effects of regular and extreme endurance sport practice, such as jogging, cycling, rowing, swimming, etc. Recent data from a small series suggest a relationship between regular, long-term endurance sport practice and atrial fibrillation (AF) and flutter. Reported case control studies included less than 300 athletes, with mean age between 40 and 50. Most series recruited only male patients, or more than 70% males, who had been involved in intense training for many years. Endurance sport practice increases between 2 and 10 times the probability of suffering AF, after adjusting for other risk factors. The possible mechanisms explaining the association remain speculative. Atrial ectopic beats, inflammatory changes, and atrial size have been suggested. Some of the published studies found that atrial size was larger in athletes than in controls, and this was a predictor for AF. It has also been shown that the left atrium may be enlarged in as many as 20% of competitive athletes. Other proposed mechanisms are increased vagal tone and bradycardia, affecting the atrial refractory period; however, this may facilitate rather than cause the arrhythmia. In summary, recent data suggest an association between endurance sport practice and atrial fibrillation and flutter. The underlying mechanism explaining this association is unclear, although structural atrial changes (dilatation and fibrosis) are probably present. Larger longitudinal studies and mechanistic studies are needed to further characterize the association to clarify whether a threshold limit for the intensity and duration of physical activity may prevent AF, without limiting the cardiovascular benefits of exercise.

Regular and extreme endurance sport practice (jogging, cycling, swimming, etc.) has become very popular even among adults in their forties. The benefits of regular exercise in controlling cardiovascular risk factors have been extensively proved,[1,2,3,4] and therefore cardiologists widely recommend regular exercise to improve cardiovascular health. However, recent data have documented a relationship between long-term endurance sport practice or rigorous occupational physical activity and atrial fibrillation (AF) and atrial flutter.[5,6,7,8,9,10] The association is being increasingly recognized and has raised the need for larger epidemiological studies.[11,12,13] On the other hand, moderate physical activity may indeed decrease the risk for AF in older adults.[14]

Atrial fibrillation is the most common arrhythmia and has a great impact in morbidity and mortality.[15,16] The current increase in incidence is not fully explained by the aging population or higher prevalence of newly described risk factors such as obesity.[17,18] Therefore, non-identified factors apart from family history[19] may be present. Atrial fibrillation is associated with a number of cardiac and extracardiac diseases, such as hypertension, structural heart disease, and hyperthyroidism. However, in a significant proportion of patients, its aetiology remains unknown.[20] This condition, called lone AF (LAF), is defined as AF in patients younger than age 60 and without any identifiable aetiologic factor. The prevalence of LAF ranges from 2-10% in the general population to 30% in studies performed in patients with paroxysmal AF who seek medical attention.[21,22] Lone atrial fibrillation is commonly associated with atrial flutter, as described by Coumel;[23] therefore, they seem to be two expressions of the same underlying condition.

The aim of this review is to analyse the evidence of the association between LAF and endurance sport practice or occupational physical activity, the pathophysiological mechanisms underlying this association, the clinical characteristics of this arrhythmia, and the available therapeutic options.