Sports and the heart : on structural and electrical remodeling
Authors:   , Miljoen Hielko 
Published: June 2024

Engaging in regular physical activity (more than three hours per week) leads to cardiac adaptation, resulting in remodeling, both structurally (thickening of the heart muscle, expansion of the heart) and electrically (changes in the heart's excitability). Remodeling can proceed healthily (referred to as athlete's heart) but may also become pathological, potentially leading to heart failure, rhythm disorders, and even sudden death. Moreover, there are arguments that even the ‘healthy remodeling’ may statistically increase the risk for arrhythmias. This remodeling was examined in three ways: At the atrial level: manifestation of a rhythm disorder, atrioventricular reentrant tachycardia in athletes as compared to non-athletes. At the (right) ventricular level: exploration of the electrocardiographic expression of a recently described condition, exercise-induced right ventricular dysplasia. Additionally, the mechanism of ventricular rhythm disorders in a group of patients with classic right ventricular dysplasia was analyzed. Recom-mendations on how athletes and physicians can handle implantable cardioverter-defibrillators (ICDs), the only adequate protection against sudden cardiac death in (advanced) right ventricular dysplasia to date, were formulated. By evaluating the effect of contracting a SARS-CoV-2 infection on athletes' hearts. The impact of booster vaccination on maximum oxygen uptake capacity was also investigated. Atrium Previous research demonstrated that atrial fibrillation, an irregular rhythm disorder originating in the atria, is more common in endurance athletes due to exercise-induced remodeling. We explored a different rhythm disorder: atrioventricular reentrant tachycardia, the most common regular rhythm disorder originating in the atria. This disorder is based on a circuit in the atrioventricular node, where the only electrical conduction between the atria and ventricles normally occurs. In non-athletes, this circuit runs forward (from atrium to ventricle) over a slow pathway within this node and back via a fast pathway in 80% of cases. We found that in athletes, this occurs only in 55% of cases. We also observed that in athletes, we needed more additional material to successfully treat the rhythm disorder through ablation (applying a small scar to the critical point of the circuit). In the short term, the success of such procedures was equal in both groups: 96%. After about two months, the rhythm disorder had recurred more frequently in athletes: 10% versus 4%. This likely indicates that the underlying substrate in athletes has changed due to sports efforts, theoretically based on changes in the length of pathways, their conduction characteristics, and/or the regulation of conduction by the autonomic nervous system. Right Ventricle The right ventricle can exhibit maladaptive remodeling due to intense endurance sports, morphologically manifesting (at imaging studies, such as echocardiography and magnetic resonance imaging) as a known (hereditary) condition called arrhythmogenic right ventricular dysplasia. We demonstrated that the exercise-related form also manifests at the (exercise)ECG level like the known form, specifically through negative T-waves beyond V2 and more frequent occurrences of ventricular rhythm disorders. Additionally, we found electrocardiographic evidence of left ventricular involvement, as previously shown morphologically. The classical form of the disease often manifests first as rhythm disorders, specifically ventricular tachycardia (a potentially life-threatening rhythm disorder originating in the ventricle). This can be treated through ablation (burning away the circuit). We confirmed the previously moderate long-term results of such procedures and the importance of epicardial substrates. To prevent sudden death resulting from these rhythm disorders, implantation of an implantable cardioverter-defibrillator is currently the only therapy with sufficient proven effect. We formulated sports-specific considerations regarding the material and implantation technique, but especially concerning the counseling of athletes wearing such a device, emphasizing athlete safety and shared decision-making. SARS-CoV-2 Myocarditis, or inflammation of the heart muscle, is a feared condition among athletes as it can lead to sudden cardiac death. In this context, we investigated the effect of contracting COVID-19 in athletes, finding no individuals with myocarditis. We also observed no increased scarring or rhythm disorders compared to a historical control population. Finally, we evaluated the effect of booster vaccination with the Pfizer vaccine on exercise capacity. We observed a discrete reduction in peak oxygen uptake capacity in recreational athletes over the course of a week. Further research is needed to determine the medium- and long-term effects of this reduction.