Physical activity, height, and left atrial size are independent risk factors for lone atrial fibrillation in middle-aged healthy individuals

Left Atrium Size in Elite Athletes

OBJECTIVES

The goal of this study was to perform a meta-analysis of the published literature to investigate the relationship of high levels of exercise training to left atrial (LA) size.

BACKGROUND

The "athlete's heart" is a series of cardiac adaptations to systematic exercise training and may include LA enlargement.

METHODS

We conducted a systematic review of English-language studies in MEDLINE and Scopus from inception through April 29, 2014, that reported LA size in elite athletes.

RESULTS

A total of 54 studies comprising 7,189 elite athletes and 1,375 controls were included. Forty-eight of the 54 studies reported absolute LA diameter in 7,018 athletes and 1,044 controls. Nine of the 54 studies (including 992 athletes and 426 controls) presented LA volume corrected for body surface area. The adjusted weighted mean LA diameter was 4.1 mm greater in athletes overall compared with sedentary controls (p < 0.0001), and LA volume index was 7.0 ml/m(2) greater in athletes than controls (p < 0.01). Compared with controls, LA diameter was 4.6 mm greater in endurance-trained athletes (p < 0.0001), 2.9 mm greater in strength-trained athletes (p < 0.03), 3.5 mm greater in combined strength- and endurance-trained athletes (p < 0.0001), and 4.2 mm greater in athletes with unspecified training (p < 0.02).

CONCLUSIONS

To our knowledge, this is the largest compilation of studies documenting that elite athletes have larger LA dimensions compared with controls when evaluated by either LA diameter or LA volume corrected for body surface area. The largest average LA diameters were reported in endurance athletes. Physicians evaluating athletes should be aware that the LA is increased in both strength- and endurance-trained elite athletes.

Physical activity measured by accelerometry and its associations with cardiac structure and vascular function in young and middle-aged adults

BACKGROUND

Physical activity is associated with several health benefits, including lower cardiovascular disease risk. The independent influence of physical activity on cardiac and vascular function in the community, however, has been sparsely investigated.

MEASURES AND RESULTS

We related objective measures of moderate- to vigorous-intensity physical activity (MVPA, assessed by accelerometry) to cardiac and vascular indices in 2376 participants of the Framingham Heart Study third generation cohort (54% women, mean age 47 years). Using multivariable regression models, we related MVPA to the following echocardiographic and vascular measures: left ventricular mass, left atrial and aortic root sizes, carotid-femoral pulse wave velocity, augmentation index, and forward pressure wave. Men and women engaged in MVPA 29.9±21.4 and 25.5±19.4 min/day, respectively. Higher values of MVPA (per 10-minute increment) were associated with lower carotid-femoral pulse wave velocity (estimate -0.53 ms/m; P=0.006) and lower forward pressure wave (estimate -0.23 mm Hg; P=0.03) but were not associated with augmentation index (estimate 0.13%; P=0.25). MVPA was associated positively with log(e) left ventricular mass (estimate 0.006 log(e) [g/m(2)]; P=0.0003), left ventricular wall thickness (estimate 0.07 mm; P=0.0001), and left atrial dimension (estimate 0.10 mm; P=0.01). MVPA also tended to be positively associated with aortic root dimension (estimate 0.05 mm; P=0.052). Associations of MVPA with cardiovascular measures were similar, in general, for bouts lasting <10 versus ≥10 minutes.

CONCLUSIONS

In our community-based sample, greater physical activity was associated with lower vascular stiffness but with higher echocardiographic left ventricular mass and left atrial size. These findings suggest complex relations of usual levels of physical activity and cardiovascular remodeling.

Increased atrial arrhythmia susceptibility induced by intense endurance exercise in mice requires TNFα

Atrial fibrillation (AF) is the most common supraventricular arrhythmia that, for unknown reasons, is linked to intense endurance exercise. Our studies reveal that 6 weeks of swimming or treadmill exercise improves heart pump function and reduces heart-rates. Exercise also increases vulnerability to AF in association with inflammation, fibrosis, increased vagal tone, slowed conduction velocity, prolonged cardiomyocyte action potentials and RyR2 phosphorylation (CamKII-dependent S2814) in the atria, without corresponding alterations in the ventricles. Microarray results suggest the involvement of the inflammatory cytokine, TNFα, in exercised-induced atrial remodelling. Accordingly, exercise induces TNFα-dependent activation of both NFκB and p38MAPK, while TNFα inhibition (with etanercept), TNFα gene ablation, or p38 inhibition, prevents atrial structural remodelling and AF vulnerability in response to exercise, without affecting the beneficial physiological changes. Our results identify TNFα as a key factor in the pathology of intense exercise-induced AF.

The association between job strain and atrial fibrillation in Swedish men

Objectives

The purpose of this study was to investigate whether psychosocial stress defined as high strain based on the job demand–control model increases risk for atrial fibrillation.

Methods

The present study comprised 6035 men born between 1915 and 1925 and free from previous coronary heart disease, atrial fibrillation and stroke at baseline (1974–1977). Work-related psychosocial stress was measured using a job-exposure matrix for the job demand–control model based on occupation at baseline. The participants were followed from baseline examination until death, hospital discharge or 75 years of age, using the Swedish national register on cause of death and the Swedish hospital discharge register for any registration for atrial fibrillation, resulting in the identification of 436 cases. Data were analysed with Cox regression models with atrial fibrillation as the outcome using high strain as the explanatory variable adjusted for age, smoking, body mass index, hypertension, diabetes and socioeconomic status.

Results

There was an increased risk for atrial fibrillation in relation to high strain (HR 1.32, 95% CI 1.003 to 1.75). When the four categories of the job-strain model were included and low strain was used as reference, the risk for high strain decreased (HR 1.23, 95% CI 0.84 to 1.82).

Conclusions

Exposure to occupational psychosocial stress defined as high strain may be associated with increased risk for atrial fibrillation. The observed increase in risk is small and residual confounding may also be present.

Obesity, physical activity, and their interaction in incident atrial fibrillation in postmenopausal women

Background

Atrial fibrillation (AF) is the most common cardiac arrhythmia and is associated with increased risk of stroke and death. Obesity is an independent risk factor for AF, but modifiers of this risk are not well known. We studied the roles of obesity, physical activity, and their interaction in conferring risk of incident AF.

Methods and Results

The Women's Health Initiative (WHI) Observational Study was a prospective observational study of 93 676 postmenopausal women followed for an average of 11.5 years. Incident AF was identified using WHI‐ascertained hospitalization records and diagnostic codes from Medicare claims. A multivariate Cox's hazard regression model adjusted for demographic and clinical risk factors was used to evaluate the interaction between obesity and physical activity and its association with incident AF. After exclusion of women with prevalent AF, incomplete data, or underweight body mass index (BMI), 9792 of the remaining 81 317 women developed AF. Women were, on average, 63.4 years old, 7.8% were African American, and 3.6% were Hispanic. Increased BMI (hazard ratio [HR], 1.12 per 5‐kg/m² increase; 95% confidence interval [CI], 1.10 to 1.14) and reduced physical activity (>9 vs. 0 metabolic equivalent task hours per week; HR, 0.90; 95% CI, 0.85 to 0.96) were independently associated with higher rates of AF after multivariate adjustment. Higher levels of physical activity reduced the AF risk conferred by obesity (interaction P=0.033).

Conclusions

Greater physical activity is associated with lower rates of incident AF and modifies the association between obesity and incident AF.

Increased risk of atrial fibrillation among elderly Norwegian men with a history of long-term endurance sport practice

Atrial fibrillation (AF) is the most common cardiac arrhythmia. The prevalence increases with increasing age. In middle-aged men, endurance sport practice is associated with increased risk of AF but there are few studies among elderly people. The aim of this study was to investigate the role of long-term endurance sport practice as a risk factor for AF in elderly men. A cross-sectional study compared 509 men aged 65-90 years who participated in a long-distance cross-country ski race with 1768 men aged 65-87 years from the general population. Long-term endurance sport practice was the main exposure. Self-reported AF and covariates were assessed by questionnaires. Risk differences (RDs) for AF were estimated by using a linear regression model. After multivariable adjustment, a history of endurance sport practice gave an added risk for AF of 6.0 percent points (pp) (95% confidence interval 0.8-11.1). Light and moderate leisure-time physical activity during the last 12 months reduced the risk with 3.7 and 4.3 pp, respectively, but the RDs were not statistically significant. This study suggests that elderly men with a history of long-term endurance sport practice have an increased risk of AF compared with elderly men in the general population.

Genetic variants related to height and risk of atrial fibrillation: the cardiovascular health study

Increased height is a known independent risk factor for atrial fibrillation (AF). However, whether genetic determinants of height influence risk is uncertain. In this candidate gene study, we examined the association of 209 height-associated single-nucleotide polymorphisms (SNPs) with incident AF in 3,309 persons of European descent from the Cardiovascular Health Study, a prospective cohort study of older adults (aged ≥ 65 years) enrolled in 1989-1990. After a median follow-up period of 13.2 years, 879 participants developed incident AF. The height-associated SNPs together explained approximately 10% of the variation in height (P = 6.0 × 10(-8)). Using an unweighted genetic height score, we found a nonsignificant association with risk of AF (per allele, hazard ratio = 1.01, 95% confidence interval: 1.00, 1.02; P = 0.06). In weighted analyses, we found that genetically predicted height was strongly associated with AF risk (per 10 cm, hazard ratio = 1.30, 95% confidence interval: 1.03, 1.64; P = 0.03). Importantly, for all models, the inclusion of actual height completely attenuated the genetic height effect. Finally, we identified 1 nonsynonymous SNP (rs1046934) that was independently associated with AF and may warrant future study. In conclusion, we found that genetic determinants of height appear to increase the risk of AF, primarily via height itself. This approach of examining SNPs associated with an intermediate phenotype should be considered as a method for identifying novel genetic targets.

Endurance Sport Activity and Risk of Atrial Fibrillation - Epidemiology, Proposed Mechanisms and Management

There is evidence for a higher prevalence of atrial fibrillation (AF) in athletes engaged in long-term endurance sports training compared with the general population. Although atrial anatomic adaptations, alterations in autonomic nervous system, chronic systemic inflammation and fibrosis have been proposed as potential mechanisms, they remain speculative. Medical therapy with long-term antiarrhythmic agents or 'pill in the pocket' medications is hampered by limitations, such as sports eligibility and interference with exercise tolerance. AF ablation represents a valid therapeutic option with results similar to these achieved in other patients. Nevertheless, further clinical trials are needed to confirm whether endurance sport practice affects the maintenance of sinus rhythm following catheter ablation of AF.

Atrial fibrillation is associated with different levels of physical activity levels at different ages in men

OBJECTIVE

This study examines the influence of physical activity at different ages and of different types, on the risk of developing atrial fibrillation (AF) in a large cohort of Swedish men.

METHODS

Information about physical activity was obtained from 44 410 AF-free men, aged 45-79 years (mean age=60), who had completed a self-administered questionnaire at baseline in 1997. Participants reported retrospectively their time spent on leisure-time exercise and on walking or bicycling throughout their lifetime (at 15, 30 and 50 years of age, and at baseline (mean age=60)). Participants were followed-up in the Swedish National Inpatient Register for ascertainment of AF. Cox proportional hazards regression models were used to estimate relative risks (RR) with 95% CIs, adjusted for potential confounders.

RESULTS

During a median follow-up of 12 years, 4568 cases of AF were diagnosed. We observed a RR of 1.19 (95% CI 1.05 to 1.36) of developing AF in men who at the age of 30 years had exercised for >5 h/week compared with <1 h/week. The risk was even higher (RR 1.49, 95% CI 1.14 to 1.95) among the men who exercised >5 h/week at age 30 and quit exercising later in life (<1 h/week at baseline). Walking/bicycling at baseline was inversely associated with risk of AF (RR 0.87, 95% CI 0.77 to 0.97 for >1 h/day vs almost never) and the association was similar after excluding men with previous coronary heart disease or heart failure at baseline (corresponding RR 0.88, 95% CI 0.77 to 0.998).

CONCLUSIONS

Leisure-time exercise at younger age is associated with an increased risk of AF, whereas walking/bicycling at older age is associated with a decreased risk.

Comparison of the frequency of atrial fibrillation in young obese versus young nonobese men undergoing examination for fitness for military service

The association between body mass index (BMI) in young adulthood and long-term risk of atrial fibrillation (AF) has not yet been examined for men. We conducted a population-based 36-year cohort study to examine the BMI-associated risk of AF in 12,850 young men who had BMI measured at their examination of fitness for military service. AF was identified from the Danish National Registry of Patients, covering all Danish hospitals since 1977. We began follow-up on the twenty-second birthday of each subject and continued until the occurrence of AF, emigration, death, or December 31, 2012. We used Cox regression to compute hazard ratios (HRs) with 95% confidence intervals (CIs), adjusting for education and height. The cohort contributed a total of 375,888 person-years of follow-up and the median follow-up time was 26 years (mean 29 years). The incidence of AF per 100,000 person-years was 53 for men of normal weight (BMI: 18.5 to 24.9 kg/m(2)), 54 for underweight men (BMI <18.5 kg/m(2)), 106 for overweight men (BMI: 25.0 to 24.9 kg/m(2)), and 144 for obese men (BMI ≥30 kg/m(2)). With normal weight as the reference group, the adjusted HR for AF was 0.99 (95% CI 0.52 to 1.87) for underweight men, 2.08 (95% CI 1.48 to 2.92) for overweight men, and 2.87 (95% CI 1.46 to 5.62) for obese men. The adjusted HR associating 1 unit increase in BMI with AF was 1.12 (95% CI 1.07 to 1.16). In conclusion, overweight and obese young men had more than twice the risk of AF compared with young men of normal weight.

Recent developments in understanding epidemiology and risk determinants of atrial fibrillation as a cause of stroke

The prevalence of atrial fibrillation (AF) is increasing because of the aging population and advances in the treatment of acute cardiac conditions. It is now approaching epidemic proportions and is associated with significant clinical and public health consequences. Risk factors for the development of AF are numerous and varied and highlight potential treatment measures that could help prevent the occurrence of AF. The emergence of novel risk factors might allow us to increase our understanding of the pathophysiology of the condition and develop novel therapeutic targets. Stroke is the most devastating consequence of AF, and can be prevented with effective oral anticoagulation in patients at increased stroke risk. Our understanding of stroke risk has advanced; we know that the risk is not homogenous and also that only the very lowest risk patients do not benefit from anticoagulation. Clinicians should target their efforts on identifying this "truly low-risk" patient cohort and consider offering formal anticoagulation to all other AF patients. The purpose of this review is to consider the traditional and emerging risk factors for the development of AF itself, and the risk factors for stroke in AF patients and how knowledge of these risk factors can affect clinical practice.

Physical activity ameliorates cardiovascular health in elderly subjects: the functional role of the β adrenergic system

Aging is a complex process characterized by a gradual decline in organ functional reserves, which eventually reduces the ability to maintain homeostasis. An exquisite feature of elderly subjects, which constitute a growing proportion of the world population, is the high prevalence of cardiovascular disorders, which negatively affect both the quality of life and the life expectancy. It is widely acknowledged that physical activity represents one of the foremost interventions capable in reducing the health burden of cardiovascular disease. Interestingly, the benefits of moderate-intensity physical activity have been established both in young and elderly subjects. Herein we provide a systematic and updated appraisal of the literature exploring the pathophysiological mechanisms evoked by physical activity in the elderly, focusing on the functional role of the β adrenergic system.

Risk factors between patients with lone and non-lone atrial fibrillation

Clinical factors such as tall stature, lean body mass, obstructive sleep apnea, alcohol or caffeine, smoking, endurance sports, and genetic factors are proposed as risk factors for lone atrial fibrillation (LAF). The KORAF (KORean Atrial Fibrillation) study is a retrospective multicenter registry that enrolled 3,570 consecutive atrial fibrillation (AF) patients. Data on risk factors were available for 2,133 patients, of whom 398 (18.7%) were identified as having LAF. In univariate analysis, patients with LAF were more likely to be men (82.4% vs 59.8%, P < 0.001) and current smokers (25.9% vs 15.6%, P < 0.01), alcohol drinkers (55.3% vs 31.2%, P < 0.01) and frequent consumers of caffeinated beverages (> 2 cups/day) (31.7% vs 19.3%, P < 0.01), and have a family history of AF (9.0% vs 2.6%, P < 0.001) than the non-LAF patients. Multivariate analysis showed that male gender (OR, 2.30; 95% CI, 1.61-3.27, P < 0.01), family history of AF (OR, 3.12; 95% CI, 1.91-5.12, P < 0.01), current alcohol use (OR, 2.01; 95% CI, 1.46-2.76, P < 0.01), and frequent caffeinated beverage consumption (OR, 1.66; 95% CI, 1.20-2.29, P < 0.01) were independently associated with LAF. In Korean patients, LAF is more closely associated with male gender, family history of AF, current alcohol and frequent caffeinated beverage consumption than non-LAF.

Long-term follow-up of atrial function after cardioversion of atrial fibrillation in horses

Atrial fibrillation (AF) causes atrial electrical and contractile remodelling in horses. The aim of this study was to quantify left atrial (LA) contractile function and its time course of recovery after cardioversion of naturally-occurring AF in horses. The study population included 42 AF horses which were successfully treated using transvenous electrical cardioversion TVEC (n=39) or quinidine sulfate (n=3), with trivial or mild mitral regurgitation present in 25 horses. Thirty-seven healthy horses were used as controls. AF duration was estimated based on the history and previous examinations. Echocardiography was performed during general anaesthesia after TVEC (day 0) and on days 1, 2, 6 and then 7 weeks after cardioversion. The two-dimensional (2D) echocardiographic measurements included LA diameter, area and ejection phase indices such as fractional shortening. Atrial TDI measurements included peak myocardial velocity during atrial contraction (A), time to onset A, time to peak A and duration of A. During follow-up after cardioversion, atrial contractile function measured by 2D echocardiography and TDI gradually improved. At 7 weeks following cardioversion, TDI-based myocardial velocities returned to reference values. However, AF horses still showed significantly larger atrial dimensions, lower 2D ejection phase indices and prolonged TDI-based conduction time compared to the control group. In conclusion, AF-induced atrial contractile dysfunction gradually improves in the weeks following cardioversion, but at 7 weeks post-cardioversion, significant differences remain compared to healthy controls.

Reduced incidence of cardiac arrhythmias in walkers and runners

Purpose

Walking is purported to reduce the risk of atrial fibrillation by 48%, whereas jogging is purported to increase its risk by 53%, suggesting a strong anti-arrhythmic benefit of walking over running. The purpose of these analyses is to compare incident self-reported physician-diagnosed cardiac arrhythmia to baseline energy expenditure (metabolic equivalent hours per day, METhr/d) from walking, running and other exercise.

Methods

Proportional hazards analysis of 14,734 walkers and 32,073 runners.

Results

There were 1,060 incident cardiac arrhythmias (412 walkers, 648 runners) during 6.2 years of follow-up. The risk for incident cardiac arrhythmias declined 4.4% per baseline METhr/d walked by the walkers, or running in the runners (P = 0.0001). Specifically, the risk declined 14.2% (hazard ratio: 0.858) for 1.8 to 3.6 METhr/d, 26.5% for 3.6 to 5.4 METhr/d, and 31.7% for ≥5.4 METhr/d, relative to <1.8 METhr/d. The risk reduction per METhr/d was significantly greater for walking than running (P<0.01), but only because walkers were at 34% greater risk than runners who fell below contemporary physical activity guideline recommendations; otherwise the walkers and runners had similar risks for cardiac arrhythmias. Cardiac arrhythmias were unrelated to walking and running intensity, and unrelated to marathon participation and performance.

Conclusions

The risk for cardiac arrhythmias was similar in walkers and runners who expended comparable METhr/d during structured exercise. We found no significant risk increase for self-reported cardiac arrhythmias associated with running distance, exercise intensity, or marathon participation. Rhythm abnormalities were based on self-report, precluding definitive categorization of the nature of the rhythm disturbance. However, even if the runners’ arrhythmias include sinus bradycardia due to running itself, there was no increase in arrhythmias with greater running distance.

Atrial fibrillation in the 21st century: a current understanding of risk factors and primary prevention strategies

Atrial fibrillation (AF) is the most common arrhythmia worldwide, and it has a significant effect on morbidity and mortality. It is a significant risk factor for stroke and peripheral embolization, and it has an effect on cardiac function. Despite widespread interest and extensive research on this topic, our understanding of the etiology and pathogenesis of this disease process is still incomplete. As a result, there are no set primary preventive strategies in place apart from general cardiology risk factor prevention goals. It seems intuitive that a better understanding of the risk factors for AF would better prepare medical professionals to initially prevent or subsequently treat these patients. In this article, we discuss widely established risk factors for AF and explore newer risk factors currently being investigated that may have implications in the primary prevention of AF. For this review, we conducted a search of PubMed and used the following search terms (or a combination of terms): atrial fibrillation, metabolic syndrome, obesity, dyslipidemia, hypertension, type 2 diabetes mellitus, omega-3 fatty acids, vitamin D, exercise toxicity, alcohol abuse, and treatment. We also used additional articles that were identified from the bibliographies of the retrieved articles to examine the published evidence for the risk factors of AF.

Arrhythmias in athletes: evidence-based strategies and challenges for diagnosis, management, and sports eligibility

Assessment and management of cardiac rhythm disorders in athletes is particularly challenging. An accurate diagnosis and optimal risk-stratification are often limited because of substantial phenotypic overlap between pathological entities and adaptive cardiovascular responses that normally occur in athletes. An accurate diagnosis, however, is particularly important in this population, as 2 competing risks need to be cautiously balanced: the risk of under-diagnosis of an arrhythmogenic substrate that may trigger life-threatening events versus the risk of over-diagnosis that may result in an athlete's improper disqualification. Accordingly, the management of arrhythmias in athletes may pose therapeutic dilemmas, and often differs substantially compared with the general population. In this review, we present the most frequently observed arrhythmias in athletes and briefly discuss their pathophysiologic substrate. We further propose diagnostic and therapeutic strategies based upon current guidelines, official recommendations, and emerging evidence from relevant clinical investigations. We focus particularly on disparities in current guidelines regarding the management of certain rhythm disorders, as these areas of uncertainty may reflect the challenging nature of these disorders and may indicate the need for individualized approaches in every-day clinical practice. A better understanding of the normal electrophysiological responses to chronic exercise, and of the pathophysiological basis and the true clinical significance of arrhythmias in athletes, may enhance decision-making, and may allow for management strategies which more prudently weigh the risk-to-benefit ratio of each approach.

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.

Early life predictors of atrial fibrillation-related mortality: evidence from the health and retirement study

Prior research found that Americans born in 6 southeastern states (the AF-risk zone) had elevated risk of AF-related mortality, but no mechanisms were identified. We hypothesized the association between AF-related mortality and AF-risk zone birth is explained by indicators of childhood social disadvantage or adult risk factors. In 24,323 participants in the US Health and Retirement Study, we found that birth in the AF-risk zone was significantly associated with hazard of AF-related mortality. Among whites, the relationship was specific to place of birth, rather than place of adult residence. Neither paternal education nor subjectively assessed childhood SES predicted AF-related mortality. Conventional childhood and adult cardiovascular risk factors did not explain the association between place of birth and AF-related mortality.

Losartan prevents heart fibrosis induced by long-term intensive exercise in an animal model

Rationale

Recently it has been shown that long-term intensive exercise practice is able to induce myocardial fibrosis in an animal model. Angiotensin II is a profibrotic hormone that could be involved in the cardiac remodeling resulting from endurance exercise.

Objective

This study examined the antifibrotic effect of losartan, an angiotensin II type 1 receptor antagonist, in an animal model of heart fibrosis induced by long-term intense exercise.

Methods and Results

Male Wistar rats were randomly distributed into 4 experimental groups: Exercise, Exercise plus losartan, Sedentary and Sedentary plus losartan. Exercise groups were conditioned to run vigorously for 16 weeks. Losartan was orally administered daily before each training session (50 mg/kg/day). Time-matched sedentary rats served as controls. After euthanasia, heart hypertrophy was evaluated by histological studies; 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. Daily intensive exercise caused hypertrophy in the left ventricular heart wall and originated collagen deposition in the right ventricle. Additionally long-term intensive exercise induced a significant increase in messenger RNA expression and protein synthesis of the major fibrotic markers in both atria and in the right ventricle. Losartan treatment was able to reduce all increases in messenger RNA expression and protein levels caused by exercise, although it could not completely reverse the heart hypertrophy.

Conclusions

Losartan treatment prevents the heart fibrosis induced by endurance exercise in training animals.

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.

Comparison of Atrial Fibrillation in the Young versus That in the Elderly: A Review

The incidence and prevalence of atrial fibrillation (AF) are projected to increase significantly worldwide, imposing a significant burden on healthcare resources. The disease itself is extremely heterogeneous in its epidemiology, pathophysiology, and treatment options based on individual patient characteristics. Whilst ageing is well recognised to be an independent risk factor for the development of AF, this condition also affects the young in whom the condition is frequently symptomatic and troublesome. Traditional thinking suggests that the causal factors and pathogenesis of the condition in the young with structurally normal atria but electrophysiological "triggers" in the form of pulmonary vein ectopics leading to lone AF are in stark contrast to that in the elderly who have AF primarily due to an abnormal substrate consisting of fibrosed and dilated atria acting in concert with the pulmonary vein triggers. However, there can be exceptions to this rule as there is increasing evidence of structural and electrophysiological abnormalities in the atrial substrate in young patients with "lone AF," as well as elderly patients who present with idiopathic AF. These reports seem to be blurring the distinction in the pathophysiology of so-called idiopathic lone AF in the young versus that in the elderly. Moreover with availability of improved and modern investigational and diagnostic techniques, novel causes of AF are being reported thereby seemingly consigning the diagnosis of "lone AF" to a rather mythical existence. We shall also elucidate in this paper the differences seen in the epidemiology, causes, pathogenesis, and clinical features of AF in the young versus that seen in the elderly, thereby requiring clearly defined management strategies to tackle this arrhythmia and its associated consequences.

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.

Atrial fibrillation, physical activity and endurance training

INTRODUCTION

Clinical practice and the results of some studies may indicate that physical exercise in the form of endurance training may influence the development of atrial fibrillation (AF). The aim of this paper is to evaluate the scientific background for the hypothesis that there is a connection between physical activity and AF.

MATERIAL AND METHOD

This paper is a review article based on searches in PubMed on specific topics, limited to the period 1995 through March 2011. We found 17 original articles and three relatively recent reviews. Each was read by at least two of the authors and then discussed. Seven of the original articles were excluded for methodological reasons, and we therefore discuss the other ten.

RESULTS

We found support for the hypothesis that systematic high intensity endurance training such as running can increase the risk of AF, whereas the studies provide no evidence that less intensive physical exercise such as walking increases the risk. Several of the studies have methodological weaknesses.

INTERPRETATION

Important questions remain unanswered. There is a need for more studies that can shed light on the connection between training intensity, total volume of intensive endurance training, age-related changes and AF. Studies that include women are also needed.

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.

The impact of height on the risk of atrial fibrillation: the Cardiovascular Health Study

AIMS

Atrial fibrillation (AF) is the most common sustained arrhythmia. Increased body size has been associated with AF, but the relationship is not well understood. In this study, we examined the effect of increased height on the risk of AF and explore potential mediators and implications for clinical practice.

METHODS AND RESULTS

We examined data from 5860 individuals taking part in the Cardiovascular Health Study, a cohort study of older US adults followed for a median of 13.6 (women) and 10.3 years (men). Multivariate linear models and age-stratified Cox proportional hazards and risk models were used, with focus on the effect of height on both prevalent and incident AF. Among 684 (22.6%) and 568 (27.1%) incident cases in women and men, respectively, greater height was significantly associated with AF risk [hazard ratio (HR)(women) per 10 cm 1.32, confidence interval (CI) 1.16-1.50, P < 0.0001; HR(men) per 10 cm 1.26, CI 1.11-1.44, P < 0.0001]. The association was such that the incremental risk from sex was completely attenuated by the inclusion of height (for men, HR 1.48, CI 1.32-1.65, without height, and HR 0.94, CI 0.85-1.20, with height included). Inclusion of height in the Framingham model for incident AF improved discrimination. In sequential models, however, we found minimal attenuation of the risk estimates for AF with adjustment for left ventricular (LV) mass and left atrial (LA) dimension. The associations of LA and LV size measurements with AF risk were weakened when indexed to height.

CONCLUSION

Independent from sex, increased height is significantly associated with the risk of AF.

Prediction of new onset atrial fibrillation after cardiac revascularization surgery

The aim of this study was to create a simple risk index to predict new-onset atrial fibrillation (AF) after coronary artery bypass grafting in patients with histories of AF. AF after coronary artery bypass grafting (referred to here as AF) is associated with increased morbidity and mortality. Identifying patients at high risk for developing AF may help identify a group of patients who might benefit from strategies to prevent postoperative AF. A cohort of 18,517 patients enrolled from January 1, 1996, to December 31, 2009, was used to derive a risk index for AF prediction. A multivariate logistic regression model determined the independent predictive impact of clinical and demographic characteristics on the occurrence of AF. A subset of these variables was used to construct a risk index to predict AF. This risk index was validated in a sequential cohort of 1,378 consecutive patients who underwent coronary artery bypass grafting from January 1, 2010, to June 30, 2011. AF occurred in 3,486 patients in the calibration cohort (18.83%) and in 269 patients in the validation cohort (19.52%). After considering patients' demographics, co-morbid conditions, and severity of illness, advanced age appeared as the most powerful predictor of AF (odds ratio 1.059/year, 95% confidence interval 1.055 to 1.063). Age, height, weight, and the presence of peripheral vascular disease contributed most to the prediction model. An AF risk index including these variables had adequate discriminatory power, with a concordance index of 0.68. In conclusion, using a large cohort of patients, a simple risk index relying only on preoperative clinical variables was developed, which will help predict AF. This risk index can be used clinically to identify patients at high risk for the development of AF.

2012 HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation: recommendations for patient selection, procedural techniques, patient management and follow-up, definitions, endpoints, and research trial design

This is a report of the Heart Rhythm Society (HRS) Task Force on Catheter and Surgical Ablation of Atrial Fibrillation, developed in partnership with the European Heart Rhythm Association (EHRA), a registered branch of the European Society of Cardiology and the European Cardiac Arrhythmia Society (ECAS), and in collaboration with the American College of Cardiology (ACC), American Heart Association (AHA), the Asia Pacific Heart Rhythm Society (APHRS), and the Society of Thoracic Surgeons (STS). This is endorsed by the governing bodies of the ACC Foundation, the AHA, the ECAS, the EHRA, the STS, the APHRS, and the HRS.

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.