Prevalence and Clinical Significance of Left Atrial Remodeling in Competitive Athletes

The Relationship Between Physical Activity and Risk of Atrial Fibrillation-A Systematic Review and Meta-Analysis

Aim: The aim of this systematic literature review and meta-analyses was to explore the relationship between physical activity and risk of new-onset atrial fibrillation (AF) or flutter (AFlu). Results: The search revealed 10 published studies that were eligible for three different meta-analyses. A meta-analysis of six case-control studies showed that risk of AF increased more than 5-fold in athletes compared to non-athletic controls, OR=5.3 [(3.6, 7.9; 95% confidence interval (CI)], p<0.0001. A second meta-analysis of three case-control studies showed a significantly higher prevalence of athletes among AF populations compared to their healthy controls, OR=4.7 (3.1-6.9; 95% CI), p<0.0001. A third meta-analysis of three prospective large-scale long-term studies showed that moderate/high habitual physical activity was associated with significantly reduced risk of AF compared with none or very low intensity physical activity OR=0.89(0.83, 0.96; 95% CI), p=002 Conclusions: Long-term vigorous physical training or lack of physical activity both are associated with increased risk of AF, while habitual moderate physical activity may be associated with reduced risk. Further large-scale prospective randomized controlled studies particularly in athletes are needed to further confirm these findings.

Atrial fibrillation in endurance athletes

There is a growing population of veteran endurance athletes, regularly participating in training and competition. Although the graded benefit of exercise on cardiovascular health and mortality is well established, recent studies have raised concern that prolonged and strenuous endurance exercise may predispose to atrial and ventricular arrhythmias. Atrial fibrillation (AF) and atrial flutter are facilitated by atrial remodelling, atrial ectopy, and an imbalance of the autonomic nervous system. Endurance sports practice has an impact on all of these factors and may therefore act as a promoter of these arrhythmias. In an animal model, long-term intensive exercise training induced fibrosis in both atria and increased susceptibility to AF. While the prevalence of AF is low in young competitive athletes, it increases substantially in the aging athlete, which is possibly associated with an accumulation of lifetime training hours and participation in competitions. A recent meta-analysis revealed a 5-fold increased risk of AF in middle-aged endurance athletes with a striking male predominance. Beside physical activity, height and absolute left atrial size are independent risk factors for lone AF and the stature of men per se may explain part of their higher risk of AF. Furthermore, for a comparable amount of training volume and performance, male non-elite athletes exhibit a higher blood pressure at rest and peak exercise, a more concentric type of left ventricular remodelling, and an altered diastolic function, possibly contributing to a more pronounced atrial remodelling. The sports cardiologist should be aware of the distinctive features of AF in athletes. Therapeutic recommendations should be given in close cooperation with an electrophysiologist. Reduction of training volume is often not desired and drug therapy not well tolerated. An early ablation strategy may be appropriate for some athletes with an impaired physical performance, especially when continuation of competitive activity is intended. This review focuses on the prevalence, risk factors, and mechanisms of AF in endurance athletes, and possible therapeutic options.

Arrhythmias in the athlete

Regular exercise provides substantial health benefits, mostly by reducing cardiovascular risk factors. However, it may also trigger acute cardiac events and cause sudden cardiac death in individuals with a pre-existing condition. In an otherwise healthy population, intense regular exercise may lead to morphological and electrical cardiac adaptations commonly referred as "athlete's heart." Recent data suggest that this may itself produce structural changes of atrial and ventricular myocardium with enlargement and fibrosis, creating the substrate for development of arrhythmias in apparently healthy athletes. The state of the art in this controversial issue is reviewed.

[ECG diagnostics in competitive athletes. Current implications for preparticipation screening]

In young competitive athletes sudden cardiac death frequently occurs as a tragic first manifestation of clinically inapparent underlying structural or electrical cardiac disorders. An increased risk may be reflected by typical electrocardiogram (ECG) alterations preceding symptoms but a correct interpretation is often challenging due to a high prevalence of training-related ECG alterations in competitive athletes mimicking such disorders. Misinterpretation may thus result in either unnecessary disqualification from competitive sports or continuation despite an increased risk or extensive diagnostic work-ups yielding additional equivocal findings. However, as observed in large athlete cohorts in recent years a variety of ECG alterations, such as isolated increased QRS voltage, early repolarization, sinus bradycardia, first degree AV block or incomplete right bundle branch block, represent common variants of ECGs of athletes reflecting physiological and training-related cardiac adaptations. These alterations do not usually require further diagnostic evaluation. In contrast, alterations such as repolarization abnormalities, complete bundle branch block, prolonged QT intervals or pathological Q waves, are strongly suggestive of underlying disorders and require further evaluation even in asymptomatic athletes. Thus, the ECG plays a pivotal role in the prevention of sudden cardiac death in competitive athletes. The present article summarizes current recommendations for the interpretation of athlete ECGs regarding the differentiation between physiological or pathological cardiac adaptation.

Competitive sports and the heart: benefit or risk?

BACKGROUND

Controversy surrounds the cardiac effects of competitive sports and the athlete's heart. In this review, we present and discuss the main cardiological findings in competitive athletes.

METHOD

Selective review of pertinent literature retrieved by a search with the keywords "athlete's heart," "ECG," "echocardiography," "endurance exercise," "longevity," and others.

RESULTS

Regular exercise leads to functional and structural adaptations that improve cardiac function. Athlete's heart, which develops rarely, is a typical finding in endurance athletes. This condition is characterized by physiological, harmonically eccentric hypertrophy of all cardiac chambers. The athlete's ECG can be used to distinguish physiological, training-related changes from pathological training-unrelated changes. The athlete's heart function is normal at rest and increases appropriately during exercise. The cardiac markers troponin and B-type natriuretic peptide are within the normal range in healthy athletes at rest, but can temporarily be mildly elevated after exhausting endurance-exercise, without evidence of myocardial damage. The epidemiological data suggest that participation in competitive sports increases life expectancy.

CONCLUSION

Competitive exercise does not induce cardiac damage in individuals with healthy hearts, but does induce physiological functional and structural cardiac adaptations which have positive effects on life expectancy.

Role of Left Ventricular Diastolic Dysfunction in Predicting Atrial Fibrillation Recurrence after Successful Electrical Cardioversion

The role of left ventricular (LV) diastolic dysfunction in predicting atrial fibrillation (AF) recurrence after successful electrical cardioversion is largely unknown. Studies suggest that there may be a link between abnormal LV compliance and the initial development, and recurrence of AF after electrical cardioversion. Although direct-current cardioversion (DCCV) is a well-established and highly effective method to convert AF to sinus rhythm, it offers little else beyond immediate rate control because it does not address the underlying cause of AF. Preservation of sinus rhythm after successful cardioversion still remains a challenge for clinicians. Despite the use of antiarrhythmic drugs and serial cardioversions, the rate of AF recurrence remains high in the first year. Current evidence suggests that diastolic dysfunction, which is associated with atrial volume and pressure overload, may be a mechanism underlying the perpetuating cycle of AF recurrence following successful electrical cardioversion. Diastolic dysfunction is considered to be a defect in the ability of the myofibrils, which have shortened against a load in systole to eject blood into the high-pressure aorta, to rapidly or completely return to their resting length. Consequently, LV filling is impaired and the non-compliant left ventricle is unable to fill at low pressures. As a result, left atrial and pulmonary vein pressure rises, and electrical and structural remodeling of the atrial myocardium ensues, creating a vulnerable substrate for AF. In this article, we review the current evidence highlighting the association of LV diastolic dysfunction with AF recurrence after successful electrical cardioversion and provide an approach to the management of LV diastolic dysfunction to prevent AF recurrence.

Do big athletes have big hearts? Impact of extreme anthropometry upon cardiac hypertrophy in professional male athletes

AIM

Differentiating physiological cardiac hypertrophy from pathology is challenging when the athlete presents with extreme anthropometry. While upper normal limits exist for maximal left ventricular (LV) wall thickness (14 mm) and LV internal diameter in diastole (LVIDd, 65 mm), it is unknown if these limits are applicable to athletes with a body surface area (BSA) >2.3 m(2).

PURPOSE

To investigate cardiac structure in professional male athletes with a BSA>2.3 m(2), and to assess the validity of established upper normal limits for physiological cardiac hypertrophy.

METHODS

836 asymptomatic athletes without a family history of sudden death underwent ECG and echocardiographic screening. Athletes were grouped according to BSA (Group 1, BSA>2.3 m(2), n=100; Group 2, 2-2.29 m(2), n=244; Group 3, <1.99 m(2), n=492).

RESULTS

There was strong linear relationship between BSA and LV dimensions; yet no athlete with a normal ECG presented a maximal wall thickness and LVIDd greater than 13 and 65 mm, respectively. In Group 3 athletes, Black African ethnicity was associated with larger cardiac dimensions than either Caucasian or West Asian ethnicity. Three athletes were diagnosed with a cardiomyopathy (0.4% prevalence); with two athletes presenting a maximal wall thickness >13 mm, but in combination with an abnormal ECG suspicious of an inherited cardiac disease.

CONCLUSION

Regardless of extreme anthropometry, established upper limits for physiological cardiac hypertrophy of 14 mm for maximal wall thickness and 65 mm for LVIDd are clinically appropriate for all athletes. However, the abnormal ECG is key to diagnosis and guides follow-up, particularly when cardiac dimensions are within accepted limits.

Does long-lasting sports practice increase the risk of atrial fibrillation in healthy middle-aged men? Weak suggestions, no objective evidence

BACKGROUND

Some authors have suggested that sports activity can increase the risk of atrial fibrillation in healthy middle-aged men. Therefore, sport activity, although it prevents coronary artery disease, might be the cause of a potentially dangerous arrhythmia.

METHODS

To verify this assumption, we critically analyzed the current literature including original articles, reviews and meta-analyses.

RESULTS AND CONCLUSIONS

All published articles showed several limitations. The data provided by published studies support the following conclusions: the incidence of atrial fibrillation in sporting middle-aged men is rare (<0.5% per year); a possible facilitating effect on atrial fibrillation is limited to vigorous endurance exercise, not to less vigorous sports; there are no convincing data to demonstrate that sport itself may be the cause of atrial fibrillation in healthy middle-aged men; and a facilitating effect of long-lasting sport cannot be excluded in middle-aged individuals with cardiovascular disorders. Nevertheless, the beneficial effects of exercise should offset this supposed risk, which, albeit increased, remains low.

Cardiovascular health, part 2: sports participation in athletes with cardiovascular conditions

Context:

An athlete’s health may be endangered if he or she continues to compete after diagnosis of certain cardiovascular conditions. The most worrisome risk is sudden cardiac death; the annual rate in US athletes is 1 in 50 000 to 200 000.

Evidence Acquisition:

Part 2 of this review highlights the current guidelines and controversies surrounding compatibility of participation with a variety of cardiac conditions in competitive and recreational athletics. Data sources were limited to peer-reviewed publications from 1984 to the April 2009.

Results:

The guidelines published by the American College of Cardiology and the European Society of Cardiology provide a framework for safe competitive and recreational sports participation in athletes with a broad spectrum of inherited and acquired cardiovascular disorders. These guidelines are necessarily conservative because it is not currently possible to individualize risk prediction. Few data are available in many areas, particularly in the noncompetitive arena or in older athletes.

Conclusions:

Published national guidelines are currently the foundation governing return-to-play decisions in athletes with cardiovascular conditions. Further studies are needed to refine risk stratification algorithms to allow athletes with cardiovascular conditions to reap the health benefits of regular exercise and sports participation without undue risk.

Long-term cardiac remodeling and arrhythmias in nonelite marathon runners

Long-term endurance sports are associated with atrial remodeling and atrial arrhythmias. More importantly, high-level endurance training may promote right ventricular (RV) dysfunction and complex ventricular arrhythmias. We investigated the long-term consequences of marathon running on cardiac remodeling as a potential substrate for arrhythmias with a focus on the right heart. We invited runners of the 2010 Grand Prix of Bern, a 10-mile race. Of 873 marathon and nonmarathon runners who applied, 122 (61 women) entered the final analysis. Subjects were stratified according to former marathon participations: control group (nonmarathon runners, n = 34), group 1 (1 marathon to 5 marathons, mean 2.7, n = 46), and group 2 (≥6 marathons, mean 12.8, n = 42). Mean age was 42 ± 7 years. Results were adjusted for gender, age, and lifetime training hours. Right and left atrial sizes increased with marathon participations. In group 2, right and left atrial enlargements were present in 60% and 74% of athletes, respectively. RV and left ventricular (LV) dimensions showed no differences among groups, and RV or LV dilatation was present in only 2.4% or 4.3% of marathon runners, respectively. In multiple linear regression analysis, marathon participation was an independent predictor of right and left atrial sizes but had no effect on RV and LV dimensions and function. Atrial and ventricular ectopic complexes during 24-hour Holter monitoring were low and equally distributed among groups. In conclusion, in nonelite athletes, marathon running was not associated with RV enlargement, dysfunction, or ventricular ectopy. Marathon running promoted biatrial remodeling.

Potential adverse cardiovascular effects from excessive endurance exercise

A routine of regular exercise is highly effective for prevention and treatment of many common chronic diseases and improves cardiovascular (CV) health and longevity. However, long-term excessive endurance exercise may induce pathologic structural remodeling of the heart and large arteries. Emerging data suggest that chronic training for and competing in extreme endurance events such as marathons, ultramarathons, ironman distance triathlons, and very long distance bicycle races, can cause transient acute volume overload of the atria and right ventricle, with transient reductions in right ventricular ejection fraction and elevations of cardiac biomarkers, all of which return to normal within 1 week. Over months to years of repetitive injury, this process, in some individuals, may lead to patchy myocardial fibrosis, particularly in the atria, interventricular septum, and right ventricle, creating a substrate for atrial and ventricular arrhythmias. Additionally, long-term excessive sustained exercise may be associated with coronary artery calcification, diastolic dysfunction, and large-artery wall stiffening. However, this concept is still hypothetical and there is some inconsistency in the reported findings. Furthermore, lifelong vigorous exercisers generally have low mortality rates and excellent functional capacity. Notwithstanding, the hypothesis that long-term excessive endurance exercise may induce adverse CV remodeling warrants further investigation to identify at-risk individuals and formulate physical fitness regimens for conferring optimal CV health and longevity.

Atrial fibrillation in two adolescents

Idiopathic atrial fibrillation (AF) in adolescents is extremely rare and has usually been associated with structural heart disease. We present two cases of symptomatic AF in adolescents without any identifiable etiology. No definitive guidelines are available for management of such patients.

The athlete's heart in adolescent Africans: an electrocardiographic and echocardiographic study

OBJECTIVES

The goal of this study was to define electrocardiographic (ECG) and echocardiographic characteristics of adolescent African athletes.

BACKGROUND

Recent observations in African athletes reported large prevalence of left ventricular (LV) hypertrophy and ECG abnormalities. No data, so far, exist for adolescent Africans, which comprise a growing proportion of competitive/professional athletes.

METHODS

The study included 154 soccer players participating at the 8th African Under-17 Championship of 2009, representing Algeria, Burkina Faso, Cameroon, Gambia, Guinea, Malawi, Nigeria, and Zimbabwe. For comparison, 62 Italian players with similar ages, sport achievements, and training schedules were included.

RESULTS

African athletes showed higher R5/S1-wave voltages than Caucasian athletes (48.6 ± 12.1 mm vs. 34.1 ± 8.9 mm; p < 0.01), larger prevalence of ECG LV hypertrophy (89% vs. 42%; p < 0.001), ST-segment elevation (91% vs. 56%; p < 0.001), and deeply inverted, or diffusely flat/biphasic, T waves (14% vs. 3% [p < 0.05] and 25% vs. 8% [p < 0.008], respectively). LV wall thicknesses were increased in Africans by 5% compared with Caucasians, and exceeded normal limits (≥13 mm) in 4 Africans but in no Caucasians. No athlete showed evidence of cardiomyopathies (i.e., hypertrophic cardiomyopathy, arrhythmogenic right ventricular cardiomyopathy). On individual analysis, Algerians showed lower R/S-wave voltages compared with other African athletes. Increased wall thickness (≥13 mm) was observed only in sub-Saharian athletes (from Burkina Faso, Cameroon, and Niger).

CONCLUSIONS

African athletes displayed large proportion of ECG abnormalities, including a striking increase in R/S-wave voltage, ST-segment elevation, and deeply inverted or diffusely flat T waves by adolescence. LV remodeling in African athletes was characterized by a disproportionate wall thickening than in Caucasians but similar cavity size. Finally, distinctive peculiarities existed in African athletes according to the country (and ethnic) origin.

Assessment of left ventricular hypertrophy in a trained athlete: differential diagnosis of physiologic athlete's heart from pathologic hypertrophy

Physiologic LV remodeling in young trained athletes as a consequence of chronic training can occasionally mimic certain pathologic conditions associated with sudden death, such as HCM. A small but important subset of elite male athletes may show a borderline increased LV wall thickness of 13 to 15 mm, which defines a gray zone of overlap between the extreme expressions of athlete's heart and a mild HCM phenotype. Such diagnostic ambiguity can be resolved by using the paradigm of noninvasive parameters including testing with echocardiography (and, more recently, with CMR): left atrial and LV chamber dimensions and shape, brief periods of deconditioning to alter LV mass, measurement of oxygen consumption and diastolic filling, and recognition of familial occurrence of HCM or a pathogenic HCM-causing sarcomere mutation. Such distinctions between physiologic/benign athlete's heart and HCM, the most common cause of sudden death in the young in the United States, can be crucial. The recognition of HCM leads to disqualification from intense competitive sports to reduce sudden death risk and, when appropriate, permits initiation of therapeutic interventions.

Aortic root dilatation in athletic population

Remodeling of the aortic root may be expected to occur in athletes as a consequence of hemodynamic overload associated with exercise training; however, there are few data reporting its presence or extent. This review reports the current knowledge regarding the prevalence, upper limits, and clinical significance of aortic remodeling induced by athletic training. Several determinants impact aortic dimension in healthy, nonathletic individuals, including height, body size, age, sex, and blood pressure. Of these factors, anthropometric variables have the greatest impact. In athletes, the effect of exercise training appears to have only a modest additional influence on aortic dimension, although previous studies have produced some conflicting results. Specifically, data derived from the largest available athletic cohort suggest that the most hemodynamically intense endurance disciplines (eg, cycling and swimming) are associated with a significant but mild increase in aortic dimensions. Power disciplines, instead, (eg, weight lifting, throwing events) have only trivial, if any, impact. In contrast, selected data from a different athlete population suggest a more significant dimensional aortic remodeling in strength-trained individuals. In our experience, the 99th percentile value of aortic root diameter corresponds to 40 mm in males and 34 mm in females, which can reasonably be considered the upper limits of physiologic aortic root remodeling. However, a small proportion of apparently healthy male athletes (approximately 1%) show aortic enlargement above the upper limits, in the absence of systemic disease (ie, Marfan syndrome). Athletes presenting with aortic enlargement may demonstrate a further dimensional increase in midlife leading to clinically relevant aortic dilatation. Occasionally, dilation may be severe enough to warrant consideration for surgical treatment. Therefore, serial clinical and echocardiographic evaluations are recommended in athletes when aortic root exceeds the sex-specific thresholds.

Evaluation and management of arrhythmia in the athletic patient

Athletes may present with palpitations, syncope, or arrest resulting in the diagnosis of arrhythmia, or screening may result in diagnosis of conditions with predisposition to arrhythmia. This chapter focuses on 3 common arrhythmic conditions in athletes-atrial fibrillation, premature ventricular contractions (PVCs), and the athlete with an implanted device. (1) Atrial fibrillation: most studies show that atrial fibrillation is more common in competitive athletes, particularly those participating in long-term endurance sports. Postulated mechanisms include morphologic changes such as atrial dilatation, autonomic changes such as increased vagal tone, or inflammatory changes due to sports participation. Treatment options include long-term antiarrhythmic agents, "pill in the pocket" medications, or radiofrequency ablation, a highly successful procedure in athletes. (2) Premature ventricular contractions: data conflict on whether the incidence of PVCs is increased in highly trained individuals. Very frequent PVCs in athletes, however, can be a manifestation of underlying heart disease, and athletes presenting with PVCs should undergo evaluation. In the absence of underlying heart disease, PVCs do not carry a poor prognosis, and US guidelines do not recommend restriction from sports. (3) Implanted devices: the safety of sports for the athlete with an implanted device is unknown, and current guidelines recommend against participation in vigorous competitive sports, based on postulated risks including failure to defibrillate and risk of injury. Many athletes with defibrillators and pacemakers do participate in sports. Ongoing research will better delineate the risks of sports for the athlete with an implanted device.

Exercise-induced cardiac remodeling

Early investigations in the late 1890s and early 1900s documented cardiac enlargement in athletes with above-normal exercise capacity and no evidence of cardiovascular disease. Such findings have been reported for more than a century and continue to intrigue scientists and clinicians. It is well recognized that repetitive participation in vigorous physical exercise results in significant changes in myocardial structure and function. This process, termed exercise-induced cardiac remodeling (EICR), is characterized by structural cardiac changes including left ventricular hypertrophy with sport-specific geometry (eccentric vs concentric). Associated alterations in both systolic and diastolic functions are emerging as recognized components of EICR. The increasing popularity of recreational exercise and competitive athletics has led to a growing number of individuals exhibiting these findings in routine clinical practice. This review will provide an overview of EICR in athletes.

Comparison of pro-atrial natriuretic peptide and atrial remodeling in marathon versus non-marathon runners

Long-term endurance sports are associated with atrial remodeling and an increased risk for atrial fibrillation (AF) and atrial flutter. Pro-atrial natriuretic peptide (pro-ANP) is a marker of atrial wall tension and elevated in patients with AF. The aim of this study was to test the hypothesis that atrial remodeling would be perpetuated by repetitive episodes of atrial stretching during strenuous competitions, reflected by elevated levels of pro-ANP. A cross-sectional study was performed on nonelite runners scheduled to participate in the 2010 Grand Prix of Bern, a 10-mile race. Four hundred ninety-two marathon and nonmarathon runners applied for participation, 70 were randomly selected, and 56 entered the final analysis. Subjects were stratified according to former marathon participations: a control group (nonmarathon runners, n = 22), group 1 (1 to 4 marathons, n = 16), and group 2 (≥5 marathons, n = 18). Results were adjusted for age, training years, and average weekly endurance training hours. The mean age was 42 ± 7 years. Compared to the control group, marathon runners in groups 1 and 2 had larger left atria (25 ± 6 vs 30 ± 6 vs 34 ± 7 ml/m(2), p = 0.002) and larger right atria (27 ± 7 vs 31 ± 8 vs 35 ± 5 ml/m(2), p = 0.024). Pro-ANP levels at baseline were higher in marathon runners (1.04 ± 0.38 vs 1.42 ± 0.74 vs 1.67 ± 0.69 nmol/L, p = 0.006). Pro-ANP increased significantly in all groups after the race. In multiple linear regression analysis, marathon participation was an independent predictor of left atrial (β = 0.427, p <0.001) and right atrial (β = 0.395, p = 0.006) remodeling. In conclusion, marathon running was associated with progressive left and right atrial remodeling, possibly induced by repetitive episodes of atrial stretching. The altered left and right atrial substrate may facilitate atrial arrhythmias.

The feasibility, diagnostic yield, and learning curve of portable echocardiography for out-of-hospital cardiovascular disease screening

BACKGROUND

The reduction in the size of full-capability echocardiographic machines facilitates "out-of-hospital" transthoracic echocardiography (TTE). Data documenting the feasibility, yield, and logistical considerations of out-of-hospital TTE for preparticipation evaluation of athletes are sparse.

METHODS

A multiyear study was conducted to examine the role of 12-lead electrocardiography for athlete screening in which TTE was used to document or exclude underlying structural heart disease. Using a commercially available portable transthoracic echocardiographic system, the rate of technically adequate imaging, diagnostic yield, and the time required for the completion of TTE (including setup, performance, and interpretation) were examined. TTE was performed in university medical offices and at "out-of-office" athletic facilities. Measurements were recorded during each year of the study to determine the impact of targeted attempts to improve efficiency.

RESULTS

Four hundred sixty-seven of 510 participants had transthoracic echocardiographic images that were technically adequate for complete interpretation (imaging success rate, 92%). Echocardiographic evidence of physiologic, exercise-induced cardiac remodeling was observed in 110 of 510 (22%). Cardiac abnormalities with relevance to sports participation risk were detected in 11 of 508 participants (2.2%). Over 3 years, the average time for the completion of TTE (including setup, imaging, and interpretation) decreased (year 1, 17.4 ± 3 min; year 2, 14.0 ± 2.1 min; year 3, 11.0 ± 1.8 min; P < .001). This was driven by a significant decrease in the time required for TTE at out-of-office athletic facilities.

CONCLUSIONS

Community-based TTE in athletes is feasible and is associated with a high rate of technically adequate imaging. Importantly, there appears to be a significant learning curve associated with out-of-hospital TTE.

Atrial fibrillation in athletes

Atrial fibrillation (AF) is the most common arrhythmia in the athletic community and is more frequently observed in middle-aged than in young athletes. Recent studies have shown that the prevalence of AF is higher in individuals who are involved in intense short-term training and long-term sports participation compared to general population of the same age although clear evidence about the causal relation between these conditions is lacking. Anatomic adaptation, chronic systemic inflammation, and alterations in the autonomic system are all possible explanations for the increased prevalence of AF in athletes. AF associated with sports is usually paroxysmal with occasional crisis. Treatment of AF in this population can be challenging because of a lack of randomized trials and clear guidelines. Antiarrhythmic agents are usually the preferred choice of drugs. Several reports of catheter ablation have demonstrated encouraging results. Further studies are needed to understand the mechanism of autonomic hyperactivation and its interaction with the atrial substrate to develop new ablation strategies in this group of patients. Also, studies on the intensity and duration of exercise that would negate the proarrhythmic cardiac effects are also warranted.

[Physical activity and myocardial remodeling]

Myocardial remodeling comprises changes in cardiac shape, mass, diameter, and function in response to changes in hemodynamic load, cardiac damage, or neurohumoral stimulation. Adaptive remodeling is a consequence of physiological stimuli such as physical activity. Maladaptive remodeling results from pathologic conditions such as myocardial ischemia and cardiac valve disease. Since regular vigorous endurance exercise can result in cardiac remodeling cardiologic screening is recommended for athletes to identify individuals with cardiomyopathies. Moderate physical activity is cornerstone of primary and secondary prevention of cardiovascular diseases. In secondary prevention, individual training recommendations need to be adapted to the underlying myocardial disease and individual risk factors. Experimental and clinical studies show that specific training interventions exert cardioprotective effects and reverse remodeling. However, clinical and basic science studies are needed to understand the mechanisms of adaptive and maladaptive remodeling and to better utilize this powerful therapeutic tool in the treatment of myocardial diseases.

[The "athlete's heart": structure, function and differential diagnosis]

Long-term, intense sport activity induces morphologic and functional adaptations on cardiovascular system. The magnitude of these changes is determined by various factors, creating a specific condition: the "Athlete's Heart" (AH). It is important to distinguish this entity from other cardiomyopathies, taking into account that the differential diagnosis can be challenging. There has been an increase in the number of people practicing sports, which goes in parallel with the increase in the prevalence of AH. However, the proportion of asymptomatic subjects affected by cardiovascular diseases taking part on competitive sports, is also growing. We revise the main characteristics of AH, as well as the key points to distinguish AH from pathologic conditions. A delicate characterization as AH or cardiomyopathy would help to settle appropriate measures to lower the risk of sports-related sudden cardiac death.

Assessment of resting electrocardiogram, P wave dispersion and duration in different genders applying for registration to the School of Physical Education and Sports - results of a single centre Turkish Trial with 2093 healthy subjects

BACKGROUND

The 12-lead electrocardiogram shows a broad range of abnormal patterns in trained athletes. The primary end point of this study was to investigate P wave dispersion, and P wave durations and related factors in different genders applying for registration to the School of Physical Education and Sports.

METHODS AND RESULTS

From 2006 to 2009, a total of 2093 students - 1674 boys with a mean age of 19.8 plus or minus 1.9 years and 419 girls with a mean age of 19.1 plus or minus 1.8 years - were included in the study. All 12 leads of the resting electrocardiogram were evaluated for P wave dispersion and electrocardiogram abnormalities. Baseline parameters such as age, body weight, body height, and body mass index, as well as electrocardiogram findings such as P wave maximal duration and P wave dispersion, were significantly higher in boys than in girls. Of all the parameters tested with correlation analysis, only gender (p = 0.03) (r = 0.04), body weight (p < 0.001) (r = 0.07), body height (p = 0.004) (r = 0.06), and body mass index (p = 0.01) (p = 0.05) were correlated with P wave dispersion.

CONCLUSION

The frequencies of all electrocardiogram abnormalities, P wave dispersion, and P wave maximal duration were higher in boys as compared with girls in an unselected student population applying for registration to the School of Physical Education and Sports; in addition, P wave dispersion was correlated with gender, body weight, body height, and body mass index.

Atrial remodeling, autonomic tone, and lifetime training hours in nonelite athletes

Endurance athletes have an increased risk of developing atrial fibrillation (AF) at 40 to 50 years of age. Signal-averaged P-wave analysis has been used for identifying patients at risk for AF. We evaluated the impact of lifetime training hours on signal-averaged P-wave duration and modifying factors. Nonelite men athletes scheduled to participate in the 2010 Grand Prix of Bern, a 10-mile race, were invited. Four hundred ninety-two marathon and nonmarathon runners applied for participation, 70 were randomly selected, and 60 entered the final analysis. Subjects were stratified according to their lifetime training hours (average endurance and strength training hours per week × 52 × training years) in low (<1,500 hours), medium (1,500 to 4,500 hours), and high (>4,500 hours) training groups. Mean age was 42 ± 7 years. From low to high training groups signal-averaged P-wave duration increased from 131 ± 6 to 142 ± 13 ms (p = 0.026), and left atrial volume increased from 24.8 ± 4.6 to 33.1 ± 6.2 ml/m(2) (p = 0.001). Parasympathetic tone expressed as root of the mean squared differences of successive normal-to-normal intervals increased from 34 ± 13 to 47 ± 16 ms (p = 0.002), and premature atrial contractions increased from 6.1 ± 7.4 to 10.8 ± 7.7 per 24 hours (p = 0.026). Left ventricular mass increased from 100.7 ± 9.0 to 117.1 ± 18.2 g/m(2) (p = 0.002). Left ventricular systolic and diastolic function and blood pressure at rest were normal in all athletes and showed no differences among training groups. Four athletes (6.7%) had a history of paroxysmal AF, as did 1 athlete in the medium training group and 3 athletes in the high training group (p = 0.252). In conclusion, in nonelite men athletes lifetime training hours are associated with prolongation of signal-averaged P-wave duration and an increase in left atrial volume. The altered left atrial substrate may facilitate occurrence of AF. Increased vagal tone and atrial ectopy may serve as modifying and triggering factors.

Prevalence of electrocardiographic abnormalities in West-Asian and African male athletes

Objectives

To evaluate the electrocardiographic (ECG) characteristics of West-Asian, black and Caucasian male athletes competing in Qatar using the 2010 recommendations for 12-lead ECG interpretation by the European Society of Cardiology (ESC).

Design

Cardiovascular screening with resting 12-lead ECG analysis of 1220 national level athletes (800 West-Asian, 300 black and 120 Caucasian) and 135 West-Asian controls was performed.

Results

Ten per cent of athletes presented with ‘uncommon’ ECG findings. Black African descent was an independent predictor of ‘uncommon’ ECG changes when compared with West-Asian and Caucasian athletes (p<0.001). Black athletes also demonstrated a significantly greater prevalence of lateral T-wave inversions than both West-Asian and Caucasian athletes (6.1% vs 1.6% and 0%, p<0.05). The rate of ‘uncommon’ ECG changes between West-Asian and Caucasian athletes was comparable (7.9% vs 5.8%, p>0.05). Seven athletes (0.6%) were identified with a disease associated with sudden death; this prevalence was two times higher in black athletes than in West-Asian athletes (1% vs 0.5%), and no cases were reported in Caucasian athletes and West-Asian controls. Eighteen West-Asian and black athletes were identified with repolarisation abnormalities suggestive of a cardiomyopathy, but ultimately, none were diagnosed with a cardiac disease.

Conclusion

West-Asian and Caucasian athletes demonstrate comparable rates of ECG findings. Black African ethnicity is positively associated with increased frequencies of ‘uncommon’ ECG traits. Future work should examine the genetic mechanisms behind ECG and myocardial adaptations in athletes of diverse ethnicity, aiding in the clinical differentiation between physiological remodelling and potential cardiomyopathy or ion channel disorders.

Cardiac Arrhythmogenic Remodeling in a Rat Model of Long-Term Intensive Exercise Training

Background—

Recent clinical studies suggest that endurance sports may promote cardiac arrhythmias. The aim of this study was to use an animal model to evaluate whether sustained intensive exercise training induces potentially adverse myocardial remodeling and thus creates a potential substrate for arrhythmias.

Methods and Results—

Male Wistar rats were conditioned to run vigorously for 4, 8, and 16 weeks; time-matched sedentary rats served as controls. Serial echocardiograms and in vivo electrophysiological studies at 16 weeks were obtained in both groups. After euthanasia, ventricular collagen deposition was quantified by histological and biochemical studies, and messenger RNA and protein expression of transforming growth factor-β1, fibronectin-1, matrix metalloproteinase-2, tissue inhibitor of metalloproteinase-1, procollagen-I, and procollagen-III was evaluated in all 4 cardiac chambers. At 16 weeks, exercise rats developed eccentric hypertrophy and diastolic dysfunction, together with atrial dilation. In addition, collagen deposition in the right ventricle and messenger RNA and protein expression of fibrosis markers in both atria and right ventricle were significantly greater in exercise than in sedentary rats at 16 weeks. Ventricular tachycardia could be induced in 5 of 12 exercise rats (42%) and only 1 of 16 sedentary rats (6%; P =0.05). The fibrotic changes caused by 16 weeks of intensive exercise were reversed after an 8-week exercise cessation.

Conclusions—

In this animal model, we documented cardiac fibrosis after long-term intensive exercise training, together with changes in ventricular function and increased arrhythmia inducibility. If our findings are confirmed in humans, the results would support the notion that long-term vigorous endurance exercise training may in some cases promote adverse remodeling and produce a substrate for cardiac arrhythmias.

Pathological and physiological left ventricular hypertrophy: echocardiography for differentiation

Distinguishing physiological left ventricular hypertrophy of an athlete's heart from that of pathological left ventricular (hypertrophic cardiomyopathy) can be difficult despite the advent of new imaging techniques. Nevertheless, the final diagnosis is of utmost importance as it will have a profound impact on an individual's life. A diagnosis of hypertrophic cardiomyopathy essentially excludes an individual from sport and strenuous exertion and necessitates the need for further tests and treatment, as well as the screening of family members. Hypertrophic cardiomyopathy remains the most common cause of a pathologically hypertrophied heart in young athletes, with a prevalence of one in 500. The issue of sudden death in athletes due to pathological left ventricular hypertrophy and hypertrophic cardiomyopathy has recently gained recognition owing to the death of several word class athletes during sporting participation. What compounds this further is the fact that a proportion of athletes fall into the 'grey zone' (ventricular wall thickness of 13-16 mm) where the increase in cardiac size overlaps with the phenotypic variation of hypertrophic cardiomyopathy - making echocardiographic differentiation of the two entities challenging. This review discusses the echocardiographic differentiation of the athlete's heart, including physiological left ventricular hypertrophy from pathological left ventricular hypertrophy. Although several of the cardiomyopathies cause pathological left ventricular hypertrophy, focus will be given to hypertrophic cardiomyopathy, for reasons mentioned above. Discussion will also focus on the newer and emerging echocardiographic techniques for this purpose. The term 'hypertrophic cardiomyopathy' is used to describe the nonobstuctive form of hypertrophic cardiomyopathy as this review article focuses on distinguishing the 'mild' form of hypertrophic cardiomyopathy from an athlete's heart. When the more severe obstructive form is being described, the term 'hypertrophic obstructive cardiomyopathy' is used.

Prevalence and Clinical Significance of Aortic Root Dilation in Highly Trained Competitive Athletes

Background— Few data are available that address the impact of athletic training on aortic root size. We investigated the distribution, determinants, and clinical significance of aortic root dimension in a large population of highly trained athletes.

Methods and Results— Transverse aortic dimensions were assessed in 2317 athletes (56% male), free of cardiovascular disease, aged 24.8±6.1 (range, 9 to 59) years, engaged in 28 sports disciplines (28% participated in Olympic Games). In males, aortic root was 32.2±2.7 mm (range, 23 to 44; 99th percentile=40 mm); in females, aortic root was 27.5±2.6 mm (range, 20 to 36; 99th percentile=34 mm). Aortic root was enlarged ≥40 mm in 17 male (1.3%) and ≥34 mm in 10 female (0.9%) subjects. Over an 8-year follow-up period, aortic dimension increased in these male athletes (40.9±1.3 to 42.9±3.6 mm; P <0.01) and dilated substantially (to 50, 50, and 48 mm) in 3, after 15 to 17 years of follow-up, in the absence of systemic disease. Aortic root did not increase significantly (34.9±0.9 to 35.4±2.1 mm; P =0.11) in female athletes. Multiple regression and covariance analysis showed that aortic dimension was largely explained by weight, height, left ventricular mass, and age ( R 2 =0.63; P <0.001), with type of sports training having a significant but lower impact ( P <0.003).

Conclusions— An aortic root dimension >40 mm in highly conditioned male athletes (and >34 mm in female athletes) is uncommon, is unlikely to represent the physiological consequence of exercise training, and is most likely an expression of a pathological condition, mandating close clinical surveillance.

Early repolarization, left ventricular diastolic function, and left atrial size in professional soccer players

Recent data have suggested a relation among long-term endurance sport practice, left atrial remodeling, and atrial fibrillation. We investigated the influence of an increased vagal tone, represented by the early repolarization (ER) pattern, on diastolic function and left atrial size in professional soccer players. Fifty-four consecutive athletes underwent electrocardiography, echocardiography, and exercise testing as part of their preparticipation screening. Athletes were divided into 2 groups according to presence or absence of an ER pattern, defined as a ST-segment elevation at the J-point (STE) > or =0.1 mm in 2 leads. For linear comparisons average STE was calculated. Mean age was 24 +/- 4 years. Twenty-five athletes (46%) showed an ER pattern. Athletes with an ER pattern had a significant lower heart rate (54 +/- 9 vs 62 +/- 11 beats/min, p = 0.024), an increased E/e' ratio (6.1 +/- 1.2 vs 5.1 +/- 1.0, p = 0.002), and larger volumes of the left atrium (25.6 +/- 7.3 vs 21.8 +/- 5.0 ml/m(2), p = 0.031) compared to athletes without an ER pattern. There were no significant differences concerning maximum workload, left ventricular dimensions, and systolic function. Univariate regression analysis revealed significant correlations among age, STE, and left atrial volume. In a stepwise multivariate regression analysis age, STE and e' contributed independently to left atrial size (r = 0.659, p <0.001). In conclusion, athletes with an ER pattern had an increased E/e' ratio, reflecting a higher left atrial filling pressure, contributing to left atrial remodeling over time.

Long-term clinical consequences of intense, uninterrupted endurance training in olympic athletes

OBJECTIVES

The aim of this study was to assess incidence of cardiac events and/or left ventricular (LV) dysfunction in athletes exposed to strenuous and uninterrupted training for extended periods of time.

BACKGROUND

Whether highly intensive and uninterrupted athletic conditioning over a long period of time might be responsible for cardiac events and/or LV dysfunction is unresolved.

METHODS

We assessed clinical profile and cardiac dimensions and function in 114 Olympic athletes (78% male; mean age 22 +/- 4 years), free of cardiovascular disease, participating in endurance disciplines, who experienced particularly intensive and uninterrupted training for 2 to 5 consecutive Olympic Games (total, 344 Olympic events), over a 4- to 17-year-period (mean 8.6 +/- 3 years).

RESULTS

Over the extended period of training and competition, no cardiac events or new diagnoses of cardiomyopathies occurred in the 114 Olympic athletes. Global LV systolic function was unchanged (ejection fraction: 62 +/- 5% to 63 +/- 5%; p = NS), and wall motion abnormalities were absent. In addition, LV volumes (142 +/- 26 ml to 144 +/- 25 ml; p = 0.52) and LV mass index (109 +/- 21 g/m(2) to 110 +/- 22 g/m(2); p = 0.74) were unchanged, and LV filling patterns remained within normal limits, although left atrial dimension showed a mild increase (37.8 +/- 3.7 mm to 38.9 +/- 3.2 mm; p < 0.001).

CONCLUSIONS

In young Olympic athletes, extreme and uninterrupted endurance training over long periods of time (up to 17 years) was not associated with deterioration in LV function, significant changes in LV morphology, or occurrence of cardiovascular symptoms or events.

Left atrial volume index in highly trained athletes

BACKGROUND

Increase of left atrial (LA) diameter in trained athletes has been regarded as another component of the "athlete's heart".

AIMS

To evaluate the possible impact of competitive training on LA volume and to define reference values of LA volume index in athletes.

METHODS AND RESULTS

Six hundred fifteen consecutive elite athletes (370 endurance- [ATE] vs 245 strength-trained athletes [ATS]; 385 men; 28.4 +/- 10.2 years, range 18-40 years) underwent a comprehensive transthoracic echocardiography exam. LA maximal volume was measured at the point of mitral valve opening using the biplane area-length method, and corrected for body surface area. LA mild dilatation was defined as a LA volume index between 29 and 33 mL/m(2), while a moderate dilatation was identified by a LA volume index > or =34 mL/m(2). Left ventricular (LV) mass index and ejection fraction did not significantly differ between the 2 groups. Conversely, ATS showed increased body surface area, sum of wall thickness (septum + LV posterior wall), LV circumferential end-systolic stress (ESSc) and relative wall thickness, whereas LA volume index, LV stroke volume and LV end-diastolic volume were greater in ATE. The range of LA volume index was 26 to 36 mL/m(2) (mean 28.2 +/- 9.2) in men and 22 to 33 mL/m(2) (mean 26.5 +/- 7.2) in women (P < .01). LA volume index was mildly enlarged in 150 athletes (24.3%) and moderately enlarged only in 20, all males (3.2%). Mild mitral regurgitation was observed in 64 athletes (10.3%). LA volume index was significantly greater in ATE (P < .01). By multivariate analysis, the overall population type (P < .01) and duration (P < .01) of training and LV end-diastolic volume (P < .001) were the only independent predictors of LA volume index.

CONCLUSIONS

In a large population of highly trained athletes, a mild enlargement of LA volume index was relatively common and may be regarded as a physiologic adaptation to exercise conditioning.

Lone AF - Etiologic Factors and Genetic Insights into Pathophysiolgy

Ever since atrial fibrillation (AF) was first recognized in young people (so called "lone" AF) over 4 decades ago, there has been increasing focus on determining the underlying pathophysiology of the condition. Although lone AF is presumed to be a highly heterogeneous disease, recent studies have identified novel risk factors such as inflammation, oxidative stress, endurance sports and genetics, for the arrhythmia. This monograph aims to highlight some of the recent advances in our understanding of the molecular pathophysiology of lone AF especially insight provided by contemporary genetic studies. These insights may provide novel therapeutic targets for treatment of this challenging arrhythmia in young patients.

High prevalence of atrial fibrillation in long-term endurance cross-country skiers: echocardiographic findings and possible predictors--a 28-30 years follow-up study

BACKGROUND

Lone atrial fibrillation (LAF) seems to be more common in endurance-trained male athletes than in men in the general population. The reason for this has not been found.

AIM

To determine the prevalence of LAF in long-term endurance cross-country skiers and to examine possible predictors.

METHODS

Of 149 healthy, long-term trained cross-country skiers from three different age groups who were invited, 122 and 117 participated in the studies in 1976 and 1981, respectively. At follow-up in 2004-2006, 78 men participated, with 33 in age group I (54-62 years), 37 in group II (72-80 years) and eight in group III (87-92 years), whereas 37 individuals had died and seven could not be tracked. The examination programme applied in 1976, 1981 and 2004-2006 consisted of an electrocardiographic monitoring during rest and exercise and a maximal exercise test. Echocardiography was performed in 2004-2006.

RESULTS

A high prevalence (12.8%) of LAF was found. The only predictor from both 1976 and 1981 associated with LAF was a long PQ time (r=0.38, P=0.001 and r=0.27, P=0.02, respectively), whereas bradycardia was another predictor from 1981 (r=0.29, P=0.012). At follow-up, left atrial enlargement was a marker associated with LAF (P<0.001).

CONCLUSION

Long PQ time, bradycardia and left atrial enlargement seem to be important risk factors for LAF among long-term endurance cross-country skiers.

Efficacy of circumferential pulmonary vein ablation of atrial fibrillation in endurance athletes

Aims

Long-term endurance sport practice has been increasingly recognized as a risk factor for lone atrial fibrillation (AF). However, data on the outcome of circumferential pulmonary vein ablation (CPVA) in endurance athletes are scarce. The aim of the study was to evaluate the efficacy of CPVA in AF secondary to endurance sport practice.

Methods and results

Patients submitted to CPVA answered a questionnaire about lifetime history of endurance sport practice. Endurance athletes were defined as those who engaged in >3 h per week of high-intensity exercise for at least the 10 years immediately preceding their AF diagnosis. A series of 182 consecutive patients was included (51 ± 11 years, 65% with paroxysmal AF, 81% men, 42 ± 6 mm mean left atrial diameter); 107 (59%) patients had lone AF, and 42 of them (23% of the study population) were classified as endurance athletes (lone AF sport group). Freedom from arrhythmia after a single CPVA was similar in the lone AF sport group compared with the remaining patients (P = 0.446). Left atrial size and long-standing AF were the only independent predictors for arrhythmia recurrence after ablation.

Conclusion

Circumferential pulmonary vein ablation was as effective in AF secondary to endurance sport practice as in other aetiologies of AF.