Objective To evaluate whether in a population of patients with ‘lone atrial flutter’, the proportion of those engaged in long-term endurance sports is higher than that observed in the general population.
Design An age and sex-matched retrospective case–control study.
Setting A database with 638 consecutive patients who underwent ablation for atrial flutter at the University of Leuven. Sixty-one patients (55 men, 90%) fitted the inclusion criteria of ‘lone atrial flutter’, ie, aged 65 years or less, without documented atrial fibrillation and without identifiable underlying disease (including hypertension). Sex, age and inclusion criteria-matched controls, two for each flutter patient, were selected in a general practice in the same geographical region.
Methods Sports activity was evaluated by detailed questionnaires, which were available in 58 flutter patients (95%). A transthoracic echocardiogram was performed in all lone flutter patients.
Main outcome measures Types of sports, number of years of participation and average number of hours per week.
Results The proportion of regular sportsmen (≥3 h of sports practice per week) among patients with lone atrial flutter was significantly higher than that observed in the general population (50% vs 17%; p<0.0001). The proportion of sportsmen engaged in long-term endurance sports (participation in cycling, running or swimming for ≥3 h/week) was also significantly higher in lone flutter patients than in controls (31% vs 8%; p=0.0003). Those flutter patients performing endurance sports had a larger left atrium than non-sportsmen (p=0.04, by one-way analysis of variance).
Conclusion A history of endurance sports and subsequent left atrial remodelling may be a risk factor for the development of atrial flutter.
- atrial arrhythmias
- atrial flutter
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Atrial flutter is a common supraventricular tachycardia. Typical atrial flutter is based on a macro-re-entrant circuit in the right atrium, in which the re-entrant wave front travels up the interatrial septum and down the atrial free wall in a counterclockwise direction.1 Most often, atrial flutter occurs in the setting of structural heart disease or comorbidities such as hypertension, diabetes mellitus or chronic obstructive lung disease.2 In the remaining patients, the aetiology remains unknown. Atrial flutter may have a significant impact on morbidity and mortality, even in the absence of atrial fibrillation (AF). During exercise, very rapid ventricular rates could occur because of 1:1 atrioventricular conduction to the ventricles in response to increased sympathetic activity. The sudden rise in ventricular rate may result in syncope or presyncope.3
The beneficial influence of an active lifestyle on general health has been widely accepted. Furthermore, regular physical activity has been recommended by cardiological societies to reduce cardiovascular risk.4–6 At present, dynamic sports (cycling, running, swimming) have become very popular among people of all ages. Even older adults in their 50s or 60s participate in endurance sports competitions such as marathons and triathlons. In contrast to the benefits of regular sports practice, recent observational studies have reported a higher incidence of AF among competitive athletes compared with the general population.7–10 Furthermore, large population studies have indicated that high-intensity exercise is associated with the development of AF.11 12 Lone AF is defined as AF in patients younger than 65 years of age, in the absence of any identifiable aetiological factor, such as hyperthyroidism or structural heart disease. So far, endurance sports activity has only been investigated as a risk factor for lone AF. As described by Coumel,13 high vagal tone in young healthy adults may create a substrate in which lone AF and atrial flutter co-exist. Consistent with this premise, Hoogsteen et al14 reported that 10% of endurance athletes with paroxysmal AF also had paroxysmal atrial flutter. In addition, Baldesberger et al10 found that atrial flutter was even more common than AF in their series of former professional cyclists (6% vs 3%, respectively). In a recent study,8 we reported that a history of endurance sports activity is associated with an increased risk of AF development after succesful flutter ablation. Several pathophysiological mechanisms have been suggested as a possible link between physical activity and arrhythmias in athletes. In addition to autonomic influences, it has been postulated that structural atrial modifications, as well as inflammatory changes due to sports participation, may play a role in the pathogenesis, although the exact mechanism remains poorly understood.
The aim of this study was to evaluate whether in a population of patients with ‘lone atrial flutter’, the proportion of those engaged in long-term endurance sports is higher than that observed in the general population.
The study was an age and sex-matched retrospective case–control study. The study was approved by the local research ethics committee, it complies with the Declaration of Helsinki and all participants provided written informed consent.
The case series was part of a database with 638 consecutive patients who underwent ablation for atrial flutter at the University of Leuven between October 1995 and January 2010. A total of 61 patients (10%) fitted the inclusion criteria of lone atrial flutter and were younger than 65 years (figure 1). In all patients, at least two ECGs with documented atrial flutter were available, ie, the indication for ablation was recurrent symptomatic flutter. All patients had also undergone Holter recording to evaluate the presence of intermittent AF. Lone atrial flutter was defined as atrial flutter in the absence of structural heart disease (coronary artery disease, valvular heart disease, dilated cardiomyopathy or hypertrophic cardiomyopathy) or any other identifiable cause for the arrhythmia such as arterial hypertension (ie, blood pressure on repeated measurements ≥140/90 mm Hg and/or the administration of one or more drugs), hyperthyroidism or chronic obstructive lung disease. Patients with previous documentation of AF, on surface ECG or Holter monitoring, were exluded from the study.
Sports activity was evaluated by detailed questionnaires in which the types of sports, number of years of participation and average number of hours per week were assessed. This information was systematically obtained at the time of ablation as part of a wider assessment of cardiovascular risk factors and medication use. Data were obtained concerning each type of regular sports activity and its intensity. Light leisure-time activities, defined as physical activities with low cardiovascular demand, such as walking or relaxed biking, were excluded. Complete follow-up questionnaires were available for a total of 58 of the 61 patients (95%) and were double-checked by personal interview to ensure accuracy. Patients performing at least 3 h of sports per week, between the age of 9 years and the age at presentation, were considered as performing regular sports activity and analysed against those performing less. Sports practice more than 1 h per week, but less than 3 h per week, was considered sporadic sports practice. Sports activity needed to be moderate to intense, defined by competitive participation or aiming for a training effect (semicompetitive). Endurance sports was defined as (semi-)competitive participation in cycling, running and/or swimming for at least 3 h per week.
A sex and age-matched control population was selected in a general practice in the same geographical region. Consecutive patients were screened during visits for non-cardiological reasons. All subjects younger than 65 years, and matching the inclusion and exclusion criteria of the flutter population, were included. The general practitioner presented the same questionnaires concerning sports practice, and clarified responses by interviews if needed. For each male patient in the flutter group, two age and sex-matched subjects were randomly selected in the control population without information about other variables. We extended the inclusion of female controls beyond a two-for-one match (up to 75) to be able to compare sports practice in women versus men in the control populations.
A transthoracic echocardiogram was performed in all lone flutter patients to exclude any structural heart disease, using a standardised examination.15 Structural heart disease was defined as left ventricular systolic or diastolic dysfunction, more than mild left ventricular hypertrophy and/or valvular heart disease. Patients with mild dilatation or mild hypertrophy of the left ventricle and/or atrium were included in the study, because these changes were considered as secondary to long-term sports practice, ie, athlete's heart.
Summary values are given as mean±SD or median and IQR for not normally distributed values. The Fisher's exact test or the χ2 test were used for categorical variables. The Student's t test or Mann–Whitney test were used for comparison of continuous variables. Differences in echocardiographic findings among male lone flutter patient subgroups were determined using Tukey's test following one-way analysis of variance. A p value of less than 0.05 was considered significant.
Fifty-two of the 58 patients (90%) in the lone flutter group were men, with a mean age of 52±7 years. The control population consisted of 104 male subjects, with a mean age of 52±8 years. The clinical characteristics of all subjects in the lone flutter group and in the control population are shown in table 1. Of the 52 male lone flutter patients, 26 were performing regular sports activity (50%; 95% CI 36.4 to 63.6), compared with 18 patients (17%; 95% CI 10.04 to 24.58) in the control group (p<0.0001; figure 2A). The main sports activity was endurance sport for 16 of the 26 sportsmen in the flutter group (62%) and eight of the 18 sporting controls (44%; p=0.6). In the lone flutter group, the proportion of those engaged in long-term endurance sports was significantly higher than that observed in the control population (31% vs 8%; p=0.0003; figure 2B). Moreover, sports were performed on a competitive basis more often (35% vs 11%; p<0.001). In contrast, there was no difference in the proportion of sporadic sports practice between the two groups (27% vs 28%). The OR for the development of atrial flutter in patients with a history of regular sports practice was 4.78 (95% CI 2.27 to 10.05) and for a history of long-term endurance sports practice 5.33 (95% CI 2.1 to 13.53). Comparison of the lifetime number of hours of sports practice and the number of hours of sports practice per week, between the male lone flutter patients and the controls, is shown in figure 2C,D. Men in the lone flutter group were sporting significantly more hours per week (3.13 (IQR 1.3–6.17) vs 0.84 (IQR 0–2.47); p<0.0001). In addition, there was a clear difference in the lifetime number of hours of sports participation (6213 (IQR 3113–12965) vs 2000 (IQR 0–4938); p<0.0001). Table 2 summarises the echocardiographic findings in the male lone flutter patients. Quantitative data were available in 44 of the male flutter patients (85%). Those flutter patients performing endurance sports had a larger left atrium than non-sportsmen (p=0.04 by one-way analysis of variance; p<0.05 by Tukey's test).
Only six of the 58 lone flutter patients (10%) were women. None of them performed sports on a regular basis (≥3 h/week) in contrast with the men with flutter. Compared with the 75 female subjects in the control population, there were no significant differences in the proportion of regular sports practice and the proportion of endurance sports participation. Comparison of the lifetime number of hours of sports practice and the number of hours of sports practice per week between the male and female subjects in the control group shows that men are sporting significantly more hours per week (0.84 (IQR 0–2.47) vs 0.26 (IQR 0–1.38); p<0.05) and lifelong (2000 (IQR 0–4938) vs 500 (IQR 0–2700); p<0.05) compared with their female counterparts (figure 3A,B).
The main finding of our study is that an important proportion of male lone flutter patients had been engaged in regular and intensive sports practice (mainly endurance) for many years, and that this proportion was significantly greater than that observed in men in the general population. Nearly three out of four flutter patients were sporting at least 1 h per week compared with a much smaller proportion in the control group. These findings suggest that chronic sports practice, in particular endurance sports, may indeed play a role in the pathogenesis of atrial flutter in some patients.
In recent years, the relationship between long-term endurance sports practice and atrial arrhythmias has been extensively documented.7–10 In two large prospective, population-based studies an association was found between high-intensity exercise and the development of AF.11 12 Several possible mechanisms have been suggested to explain the increased vulnerability to AF in athletes, such as changes in autonomic tone, systemic inflammation, and/or structural atrial changes such as dilatation and hypertrophy. The atrial morphological adaptations in athletes may be the consequence of long-standing volume and/or pressure overload due to long-term (endurance) sports practice. Chronic haemodynamic alterations may thus create an atrial substrate for tachyarrhythmias in sportsmen. This would also imply that the underlying mechanism may be analogous to the pathophysiology in other predisposing conditions such as heart failure, hypertension and valvular cardiomyopathies. As mentioned before, previous studies have shown that atrial flutter and AF frequently occur together in athletes.8 10 14 In our series, AF co-existed in 156 of 217 patients (72%) with atrial flutter without any identifiable aetiology. Furthermore, 23 of the 58 lone flutter patients (40%) developed AF during long-term follow-up after flutter ablation. This is in line with other reports on the incidence of atrial flutter in the general population.2 Previous studies also suggest that this clinical association may not be just coincidental, but in fact could reflect linkage of their underlying pathophysiologies.1 Further studies are required to determine the mechanisms leading to lone atrial flutter in some patients or lone AF in others.
The subjects performing endurance activities clearly had echocardiographic signs of athlete's heart. Interestingly, they had larger left atria than flutter patients without a history of sports practice. Whether left atrial dilatation constitutes a particular type of athlete's heart remodelling and a specific risk marker for flutter development requires further study.
We only identified six women in the lone flutter population (10% of all cases). None of them were engaged in endurance sports activities. In our control population we found that women participated in sports in a proportion that was similar to that of men. However, the lifetime number of years of sports participation and the average number of hours of sports practice per week were significantly higher among men than women. This may have permitted more left atrial remodelling. Studies with a higher number of female flutter patients are needed to determine if the observed association between long-term endurance sports practice and the occurrence of atrial flutter is also true for women.
The total number of years of sports participation and the average number of hours per week was obtained retrospectively, which may be biased. However, both cases and controls had the same age, which may preclude recall bias. So far, there are no valid instruments other than detailed questionnaires to measure the lifetime number of hours of exercise. Prospective studies, in which sports activity can be more accurately measured and monitored, are needed to confirm our observations, but will be difficult to perform given the considerable lag time before the development of arrhythmias.
Patients in the lone flutter group were referred because they were symptomatic, and thus we do not know whether the same association between sports and lone flutter also applies to asymptomatic flutter patients. Moreover, we cannot exclude the possibility of previous asymptomatic AF episodes. On the other hand, the concept of asymptomatic episodes is mainly relevant in elderly patients with decreased nodal conduction, but is less so in younger and more active patients with atrial flutter as in our study group, in whom the arrhythmia is often conducted in a 2:1 fashion.
In a recent study from Pelliccia et al,16 none of the highly trained endurance athletes developed atrial arrhythmias over a mean observation period of 8.6±3 years despite increased left atrial size. The results of that study seem to differ from our observations. However, Pelliccia et al16 included younger athletes (mean 22±4 years), whereas our sportsmen with atrial flutter tended to be older (mean 52±8 years) and had been sporting for a longer period of time (mean 35±11 years). It is possible that an excess of atrial arrhythmias only becomes apparent when these athletes reach an age at which arrhythmias are more prevalent in general.
These findings do not mean that sports practice is dangerous or should be discouraged. However, our data suggest that long-term endurance sports practice may predispose to the development of atrial arrhythmias by athlete's heart-related remodelling. These findings do not negate current recommendations for exercise and physical activity. The benefits of an active lifestyle on cardiovascular risk factors and general health are well documented in large prospective studies, and before more definitive data are available, the benefits certainly outweigh the risks. The heart should not be excluded from the sports medicine paradigm that overuse may confer a risk of injury.
Patients with ‘lone atrial flutter’ (ie, in the absence of other identifiable causes) are four times as often engaged in endurance sports activity as the general population. Those flutter patients performing endurance sports have larger left atria. Therefore, endurance sports and subsequent left atrial remodelling may be a risk factor for the development of ‘lone atrial flutter’.
Competing interests None.
Patient consent Obtained.
Ethics approval This study was conducted with the approval of the UZ Leuven Medical Ethics Committee.
Provenance and peer review Not commissioned; externally peer reviewed.
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