Ageing, comorbidities, and the complex determinants of atrial fibrillation in athletes

Previous Exercise Levels and Outcome in Patients with New Atrial Fibrillation: "Past Achievements Do Not Predict the Future"

INTRODUCTION

Long-term endurance exercise is suspect to elevate the risk of atrial fibrillation (AF), but little is known about cardiovascular outcome and disease progression in this subgroup of AF patients. We investigated whether previous exercise level determines cardiovascular outcome.

METHODS

In this post hoc analysis of the RACE 4 randomized trial, we analyzed all patients with a completed questionnaire on sports participation. Three subgroups were made based on lifetime sports hours up to randomization and previous compliance to the international physical activity guidelines. High lifetime hours of high dynamic activity patients were defined as more than 150 min·wk -1 of high-intensity physical exercise. The primary endpoint was a composite of cardiovascular death and hospital admissions.

RESULTS

A total of 879 patients were analyzed, divided in 203 high lifetime hours of high dynamic activity, 192 high lifetime hours of activity, and 484 low lifetime hours of activity patients. Over a mean follow-up of 36 months (±14), the primary endpoint occurred in 61 out of 203 (30%) high lifetime hours of high dynamic activity, 53 out of 192 (27%) high lifetime hours of activity, and 135 out of 484 (28%) low lifetime hours of activity patients ( P = 0.74). During follow-up, 42 high lifetime hours of high dynamic activity (35%), 43 high lifetime hours of activity (32%), and 104 low lifetime hours of activity patients (34%) with paroxysmal AF received electrical or chemical cardioversion or atrial ablation ( P = 0.90).

CONCLUSIONS

In patients included in the RACE 4, there seems to be no relation between previous activity levels and cardiovascular outcome and the need for electrical or chemical cardioversion or atrial ablation. Cardiovascular outcome was driven by AF-related arrhythmic events.

High-Intensity Exercise Promotes Deleterious Cardiovascular Remodeling in a High-Cardiovascular-Risk Model: A Role for Oxidative Stress

Although the benefits of moderate exercise in patients at high cardiovascular risk are well established, the effects of strenuous exercise remain unknown. We aimed to study the impact of strenuous exercise in a very high cardiovascular risk model. Nephrectomized aged Zucker obese rats were trained at a moderate (MOD) or high (INT) intensity or were kept sedentary (SED) for 10 weeks. Subsequently, echocardiography and ex vivo vascular reactivity assays were performed, and blood, aortas, perivascular adipose tissue (PVAT), and left ventricles (LVs) were harvested. An improved risk profile consisting of decreased body weight and improved response to a glucose tolerance test was noted in the trained groups. Vascular reactivity experiments in the descending thoracic aorta demonstrated increased endothelial NO release in the MOD group but not in the INT group, compared with SED; the free radical scavenger TEMPOL improved endothelial function in INT rats to a similar level as MOD. An imbalance in the expression of oxidative stress-related genes toward a pro-oxidant environment was observed in the PVAT of INT rats. In the heart, INT training promoted eccentric hypertrophy and a mild reduction in ejection fraction. Obesity was associated with LV fibrosis and a transition toward β-myosin heavy chain and the N2Ba titin isoform. Exercise reverted the myosin imbalance, but only MOD reduced the predominance of the N2Ba titin isoform. In conclusion, moderate exercise yields the most intense cardiovascular benefits in a high-cardiovascular-risk animal model, while intense training partially reverts them.

Right heart structure and function in lifelong recreational endurance athletes with and without paroxysmal atrial fibrillation

BACKGROUND

Healthy young athletes adapt to the increased demands of endurance exercise with symmetric cardiac remodeling. Male veteran endurance athletes have an increased risk of atrial fibrillation (AF), and some athletes seem susceptible to changes mimicking arrhythmogenic cardiomyopathy. Intense exercise puts a disproportionate hemodynamic load on the right-sided heart chambers. Despite this, data describing right heart structure and function in older veteran athletes are scarce. We aimed to investigate structural and functional characteristics of the right heart in veteran athletes with and without AF to contribute to the understanding of exercise-induced cardiac remodeling in this group.

METHODS

Three hundred and two male participants, of whom 151 were veteran skiers (62 with paroxysmal AF) and 151 were controls from the general population (62 with paroxysmal AF) underwent an echocardiographic examination in sinus rhythm to evaluate right atrial (RA) and right ventricular (RV) structure and function. While 87 of the participants had never exercised regularly, 50, 43, and 122 men had practiced regular endurance exercise for 1-20, 20-40, and >40 years, respectively.

RESULTS

RA volume and RV size increased with cumulative years of exercise (p<0.001), with a disproportionate increase in RV size compared with left ventricular (LV) size, regardless of AF status (p<0.001). RA and RV function assessed by strain remained similar despite lifelong exposure to endurance exercise. AF was associated with reduced RA strain irrespective of exposure to exercise (p<0.001).

CONCLUSION

RA and RV size and RV/LV ratio showed a dose-response relationship with cumulative years of endurance exercise, whereas RA and RV function did not. Indicating that increasing RV/LV ratio may represent a physiological adaptation to prolonged endurance exercise. AF was associated with reduced RA function, regardless of exposure to exercise, suggesting RA functional parameters are more closely linked to AF than RA size in veteran athletes.

Atrial fibrillation and sport: need for monitoring

Historically, regular exercise contributed to reduce the arrhythmic burden and improve cardiovascular outcomes in the general population. However, a heightened risk of Atrial Fibrillation (AF) seems to occur mainly amongst endurance athletes. The exact mechanisms are not fully elucidated, but dynamic interactions between electroanatomical changes induced by exercise, the autonomic system, variable triggers, along individual genetic predisposition are the main contributors to AF development in athletes. The type and training load of sports are also crucial in determining the arrhythmogenic milieu predisposing to AF insurgence and perpetuation. Moreover, a sex difference seems to influence an increased risk of AF only in men undergoing strenuous exercise, whereas women appear protected even during more vigorous training. In the absence of solid evidence, the advent of modern technologies could help to monitor and deep investigate the peculiar aspects of AF in these athletes. This review aims to describe the pathophysiology, diagnosis, and management of AF in athletes, shedding light on possible future strategies to face AF in this population.