Endurance sport implicated in lone atrial flutter
LEUVEN, BELGIUM. Several large studies have found a clear association between long-term participation in endurance sports and the development of atrial fibrillation (see Exercise and Afib). Now researchers at the University of Leuven report that endurance sports activity is also associated with a significantly increased risk of developing lone atrial flutter. Lone atrial flutter is defined as right atrial flutter in the absence of structural heart disease where structural heart disease, in turn, is defined as coronary artery disease, left ventricular systolic or diastolic dysfunction, more than mild left ventricular hypertrophy, and/or valvular heart disease.

The Leuven study included 58 patients (90% men) with a mean age of 52 years who had undergone a right atrial flutter ablation. The extent of physical activity among the men in the group was compared to the physical activity level in a group of 104 age-matched men who had not been diagnosed with lone atrial flutter. NOTE: None of the 6 female patients having undergone flutter ablation participated in regular sports activities so a comparison was not possible in this case.

Of the 52 male flutter patients, 26 (56%) had performed regular sports activity defined as at least 3 hours of sports a week. The main sports activity was endurance sport (competitive or semi-competitive participating in cycling, running and/or swimming for at least 3 hours a week) for 16 (62%) of the 26 flutter patients. In contrast, only 18 (17%) of the members of the control group had participated in regular sports activity and, of these, only 8 (44%) had participated in endurance sport. Thus, in the flutter group the proportion of those engaged in long-term endurance sports was significantly higher (31%) than that observed in the control population (8%).

The authors conclude that men participating in regular sports activity more than 3 hours a week have a 4.8 times higher risk of developing lone atrial flutter than do those without such regular participation. For men engaging in long-term endurance exercise, the risk of flutter development was found to increase by a factor of 5.3. The researchers observed that endurance sports participants had a significantly larger left atrium diameter (average of 41.1 mm) than did men just participating in regular sports activity or exercising less than 3 hours a week (average of 36.6 mm). They also noted that 40% of the patients who had undergone a right atrial flutter ablation later developed atrial fibrillation. The authors conclude that their findings should not be interpreted to mean that sports practice is dangerous and should be discouraged. The benefits of an active lifestyle in regard to cardiovascular and general health are well-documented and the benefits of an active lifestyle certainly outweigh the risks.

Claessen, G, Heidbuchel, H, et al. Long-term endurance sport is a risk factor for development of lone atrial flutter. Heart, Vol. 97, 2011, pp. 918-22

Editor's comment: Several mechanisms have been suggested to explain the association between long-term endurance exercise and the development of lone atrial fibrillation. These include changes in autonomic tone (vagal dominance), systemic inflammation, and/or structural atrial changes such as atrium enlargement. It is likely that the mechanism underlying the association between endurance sports and atrial flutter are similar.