Effect of lifetime endurance training on left atrial mechanical function and on the risk of atrial fibrillation

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Abstract

Background

Left atrium (LA) dilation and P-wave duration are linked to the amount of endurance training and are risk factors for atrial fibrillation (AF). The aim of this study was to evaluate the impact of LA anatomical and electrical remodeling on its conduit and pump function measured by two-dimensional speckle tracking echocardiography (STE).

Method

Amateur male runners > 30 years were recruited. Study participants (n = 95) were stratified in 3 groups according to lifetime training hours: low (< 1500 h, n = 33), intermediate (1500 to 4500 h, n = 32) and high training group (> 4500 h, n = 30).

Results

No differences were found, between the groups, in terms of age, blood pressure, and diastolic function. LA maximal volume (30 ± 5, 33 ± 5 vs. 37 ± 6 ml/m2, p < 0.001), and conduit volume index (9 ± 3, 11 ± 3 vs. 12 ± 3 ml/m2, p < 0.001) increased significantly from the low to the high training group, unlike the STE parameters: pump strain − 15.0 ± 2.8, − 14.7 ± 2.7 vs. − 14.9 ± 2.6%, p = 0.927; conduit strain 23.3 ± 3.9, 22.1 ± 5.3 vs. 23.7 ± 5.7%, p = 0.455. Independent predictors of LA strain conduit function were age, maximal early diastolic velocity of the mitral annulus, heart rate and peak early diastolic filling velocity. The signal-averaged P-wave (135 ± 11, 139 ± 10 vs. 148 ± 14 ms, p < 0.001) increased from the low to the high training group. Four episodes of non-sustained AF were recorded in one runner of the high training group.

Conclusion

The LA anatomical and electrical remodeling does not have a negative impact on atrial mechanical function. Hence, a possible link between these risk factors for AF and its actual, rare occurrence in this athlete population, could not be uncovered in the present study.

Introduction

The structural and functional adaptation of the left ventricle (LV) to endurance and strength training has been described previously [1], [2]. More recently, the focus of interest has shifted to the left atrium (LA) and the right ventricle (RV) [3], because they are subjected to the same amount of volume overload during exercise training, but are less able to adapt, because of their thin-walled structure. LA dilation and ECG P-wave duration are linked to the amount and intensity of training as shown in several studies [4], [5], [6], [7], [8]. There is growing evidence that this atrial anatomical and electrical remodeling could be the link to the increased risk of developing atrial fibrillation (AF) observed in retrospective cohort studies of athletes [9], [10], [11]. Endurance exercise training has been associated with an 8.8-fold risk of incident AF, and athletes with over 1500 h of sports practice were particularly at risk [12]. Little is known about the impact of this remodeling on the mechanical function of the LA and about a link between LA functional adaptation and AF. The conflicting results in the different studies published up to now [13], [14], [15] regarding the impact of training on atrial function, have been due to the heterogeneity of the techniques used to assess atrial mechanics and to varying populations studied.

Two-dimensional speckle tracking echocardiography (STE) is a promising technique permitting to calculate mechanical deformation as strain and strain rate (SR). It has already been used to measure LA function in different cohorts of normal subjects and patients [16], [17], [18].

The aim of this study was to evaluate the impact of LA anatomical and electrical remodeling, in the context of lifetime exercise endurance training, on its passive (conduit) and active (pump) function measured by STE, and to find a link between LA functional adaptation and AF.

Section snippets

Methods

Amateur male runners older than 30 years were recruited among the participants of the 2011 edition of the Grand Prix of Bern which is one of the most popular 10-mile race in Switzerland with > 25,000 participants. The study was approved by the ethics committee of the Kanton of Bern, Switzerland and all study subjects gave written informed consent to participate in the study.

Subjects with known cardiovascular disease or risk factors were excluded from the study. The following parameters were

Results

One hundred eight men were recruited for the study, whereby 12 subjects had to be excluded because of systemic arterial hypertension, and one because of treated hypercholesterolemia. Ninety-five runners were included in the final analyses. No significant differences were found between the groups in terms of age, BSA, daytime systolic and diastolic BP, and strength training during 3 months preceding the study beginning. Mean and minimal HR during 24 h significantly declined from the low and the

Discussion

The novelty of our study is the absence of a measurable “dose–response” effect of lifetime endurance training on LA mechanical function. However we confirmed the association between long-term endurance exercise training and risk factors for AF [8]. No link between LA mechanical myocardial deformation and arrhythmic risk could be provided.

Conclusion

The known left atrial anatomical and electrical remodeling due to long-term endurance exercise does not have a negative impact on atrial mechanical function at rest. Hence, a possible link between these risk factors for atrial fibrillation and its actual, rare occurrence in this athlete population, could not be uncovered in the present study.

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