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Updates in Sports Cardiology
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Any views and opinions expressed are those of the author(s) and/or participants and do not necessarily reflect the views, policy, or position of EP Lab Digest or HMP Global, their employees, and affiliates.
EP LAB DIGEST. 2023;23(5):1,8-12.
The field of sports cardiology continues to rapidly evolve into a subspecialty with a growing body of evidence-based medicine. From professional athletes to active people encompassing all age ranges, the impact of regular exercise on cardiovascular physiology and pathology overwhelmingly leads to beneficial outcomes.1,2 However, the extremes of exercise may be associated with uncommon side effects, such as a potential proarrhythmic effect.3 Furthermore, sport-related sudden cardiac deaths (SCDs) are tragic and highly publicized events that lead to debates regarding preparticipation screening programs and uncertainty of the safety of exercise in those with already pre-existing conditions. In this review, we highlight recent advances in 3 central themes related to sports cardiology and electrophysiology (EP), including atrial fibrillation (AF), SCD, and return to play (RTP) with inherited arrhythmia syndromes.
AF
The association between volume of exercise and development of AF is well-established as a U-shaped relationship, at least in men, in which both low and high volumes of exercise, specifically endurance exercise, increases the risk of AF.4-7 Several hypotheses have been proposed to explain the mechanism underlying AF in athletes, such as adverse cardiac remodeling from pressure and volume overload leading to left atrial enlargement and reduced atrial strain, cytokine-induced myocardial inflammation and fibrosis, and enhanced vagal tone that may shorten and increase the heterogeneity of atrial refractory periods.8-10 In addition to the unclear underlying mechanism of AF in athletes, several other issues are yet to be addressed. First, the impact of detraining on exercise-induced cardiac remodeling remains understudied and difficult to implement in the athletic population,11 although a clinical trial is currently underway to evaluate the impact of detraining to reduce AF burden.12 Second, the association of high levels of endurance exercise and AF has not been confirmed in females as the current literature mostly includes male participants. Third, the risk of stroke in endurance athletes with AF is unknown, as there is not data validating the CHA2DS2-VASc score in adults. Lastly, the increased risk of AF with exercise only applies to a select group of athletes participating in high levels of endurance exercise, such as greater than 10 or more hours per week of high-intensity exercise.13
Therefore, it is important to note that the protective benefits of exercise far outweigh the risks in the general population and can be used as an adjunctive therapy for the management of AF.14 In a recent publication, the ACTIVE-AF trial evaluated the role of exercise in 120 patients with symptomatic nonpermanent AF.15 The exercise arm received a tailored intervention according to baseline exercise capacity, which included supervised exercise training along with home-based programs with the goal of 210 minutes of moderate activity per week. The control group was encouraged to achieve 150 minutes of moderate activity per week, without individualized training plans. At 12 months, freedom from AF off antiarrhythmic drugs and without ablation was achieved in 40% of the exercise group and 20% in the control group (HR: .50, 95% CI: .33-.78). Additionally, symptom severity improved at 6 months and peak oxygen consumption increased in the exercise group at 6 and 12 months. Although there were several limitations, including the possibility of recruitment bias, performance bias, and external generalizability, these findings should encourage exercise prescription in all patients with AF.
SCD
In young athletes, the incidence of SCD is a rare yet tragic event, with an estimated 1 per 100,000 person-years.16 The fatal events attract significant media attention and spark debate regarding prevention through preparticipation screening. In early January, Damar Hamlin, a professional football player for the Buffalo Bills, suffered a sudden cardiac arrest on a nationally televised game immediately after a tackle play. While the official diagnosis has not been released, the suspected cause was thought to be due to commotio cordis, an event that occurs an estimated 10-20 times annually in the United States.17 Commotio cordis is a phenomenon in which sudden blunt impact to the chest, usually with a small ball, causes sudden cardiac arrest in the absence of cardiac damage.18 The impact must occur during the vulnerable moment of cardiac repolarization on a narrow window of 10-20 milliseconds on the upslope of the T wave directly over the left ventricle, leading to ventricular fibrillation. Resuscitation with early defibrillation remains the primary treatment.17
Classically, hypertrophic cardiomyopathy was thought to be the most common cause of SCD in the young athlete, followed by arrhythmogenic right ventricular cardiomyopathy, anomalous coronary artery, or myocarditis.19 More contemporary data has demonstrated that sudden arrhythmic death syndrome is actually the most common cause, as defined by athletes who have had an autopsy with no abnormal findings, with an incidence rate of 25%-42%.20,21 These studies led to the promotion of preparticipation screening programs to diagnose asymptomatic athletes with cardiac diseases. For instance, a decline in SCD incidence was observed in Italy after implementation of electrocardiogram (ECG)-based preparticipation screening, presumably due to identification of cardiomyopathies; however, these results have not been replicated.22-25 The likelihood of detecting cardiovascular conditions is significantly improved with the addition of an ECG. For example, the discovery rate of cardiovascular conditions associated with sudden death was .24% with an ECG/history/physical vs .04% with history/physical alone (P=.02). In addition, the cost per diagnosis was $61,712 in the ECG group and $312,407 in the history/physical group.26 Furthermore, a recent study suggested that nearly half of cardiovascular conditions were identified on serial annual evaluations among young Italian athletes (n = 44/69, 44%), emphasizing that screening should not be a one-time activity.27 In addition, false-positives on screening can lead to inappropriate disqualification if there is inadequate workup. Finally, identification of a condition associated with risk of SCD does not equate to a life saved, as many of the identified conditions would not have led to SCD if left undetected.
The American Heart Association/American College of Cardiology (AHA/ACC) 2014 Scientific Statement on ECG screening provides a weak recommendation (class IIb, level of evidence C) on the use of ECG screening along with comprehensive history-taking and physical examination in healthy people aged 12-25 years not necessarily limited to competitive athletes.28 The updated 2022 European Society of Cardiology (ESC) Guidelines for the Management of Patients with Ventricular Arrhythmias and the Prevention of SCD provide a higher recommendation (class IIa, level of evidence C) on preparticipation screening with a history, physical examination, and ECG.16
Familiarity with interpretation of the athlete’s ECG is also key to reduce false-positive rates.29 Beyond the cost and resource limitations of mass screening, some cases of SCD still occur and there are issues that remain in screening. Perhaps screening programs or routine screening throughout adolescence may reliably identify cardiomyopathies or genetic arrhythmia syndromes, while other causes of SCD become more frequent that are difficult to detect on routine screening, such as coronary disease. While preparticipation screening is an imperfect tool in the prevention of SCD, emphasis on the efforts to recognize and perform immediate cardiopulmonary resuscitation (CPR) as well as the use and improvement of availability of the external defibrillator need to be the focus to achieve high survival rates. A comprehensive emergency action plan throughout schools and sporting events is critical to facilitate a rapid and effective response.30
Furthermore, given the increased participation in endurance sports among the middle-aged and elderly, screening efforts to reduce the risk of SCD in older athletes are also of interest. It has been shown that the primary cause of SCD in those over 35 years is coronary artery disease, with those who are previously sedentary participating in vigorous exercise at the highest risk.31-33 The international ECG criteria has not been validated in those over 35 years and does not apply to evaluations in this age group. A strategy proposed by the 2020 ESC Guidelines on Sports Cardiology suggests those patients who are deemed to have cardiovascular risk who plan to participate in high-intensity exercise should undergo a maximal exercise test or functional imaging to further risk stratify, even if asymptomatic, prior to engaging in high levels of activity.34 Limited data supports this approach, and as in younger asymptomatic athletes, undergoing routine ECG testing may lead to false-positives and unnecessary cascade testing that may carry risk; therefore, shared decision-making is key.
Inherited Arrhythmia Syndromes
In the last half decade, there has been a paradigm shift in the recommendations for athletes with inherited arrhythmia syndromes, such as long QT syndrome (LQTS), to RTP. LQTS affects approximately 1 in 2000 people and can lead to SCD in select individuals (Figure).35 Due to the perceived high risk of death with exercise, automatic disqualification from competition was recommended by the 2005 ESC guidelines, while other expert task forces limited those with inherited arrhythmia syndromes to only low-intensity sports.36,37 Based on a study of 130 athletes with LQTS who returned to play after a full evaluation, in which only one patient had 2 ICD shocks while not taking medical therapy, the AHA/ACC introduced the concept of shared decision-making in a 2015 scientific statement with consideration of allowing patients to RTP.38,39
Recent data from the experience of 494 patients with LQTS from Mayo Clinic between 2000-2020 who were given RTP approval provide additional results. Seventy-nine of 494 athletes with LQTS (16%) were symptomatic prior to diagnosis and 58 (11.7%) had an implantable cardioverter-defibrillator. Over a mean follow-up of 4.2 years, there was no sports-related mortality and only 29 (5.9%) of patients with LQTS had a nonlethal, LQTS-associated breakthrough event.40 Although most data on RTP is with LQTS, Mayo Clinic also described their experience with 63 patients with catecholaminergic polymorphic ventricular tachycardia. Overall, 31 (49%) were athletes at some point in their lives and 21 (33.3%) exercised after diagnosis. During follow-up, 3 (14%) and 7 (14%) arrhythmic events occurred in the athlete and nonathlete group, with no deaths.41 While these data may support the decision to RTP in select patients, limitations to these studies include the single-center retrospective design and referral bias to an expert center. Access to experts in the field who are capable of risk stratification to provide a safe exercise plan may limit RTP decision-making in this group. Multicenter, prospective experiences will be highly informative. Still, these findings continue to challenge the prior exercise restriction recommendations based on expert opinion in certain arrhythmic syndromes.
Allowing an athlete with an inherited arrhythmia syndrome to RTP requires a complex conversation to adequately convey risk, promote autonomy, avoid paternalistic decision-making, and restrain fear or influence from medical liability to cloud medical-decision making.42 These decisions are not binary and depend on a multitude of factors, including the athlete’s desire to remain in competitive sport, appropriate risk stratification, compliance with medications and treatment plan, and availability of an external defibrillator. In addition, there can be pressures from family, friends, agents, coaches, and teams to influence the decision.
Conclusion
The field of sports cardiology and EP have substantial overlap, and the evidence base continues to build. Extreme levels of exercise achieved by only a small subset of the population may increase the risk of AF; however, exercise should be recommended as an important therapy for the treatment of AF. Future study results will help inform discussions regarding the role of exercise for AF as a culprit or treatment. RTP recommendations continue to liberalize for those with inherited arrhythmia syndromes, with emphasis on shared decision-making. While preparticipation screening continues to be a source of controversy, increasing awareness, education, and planning for CPR and early defibrillation continues to be the key to long-term survival.
Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Drs Darden and Prutkin report no conflicts of interest regarding the content herein.
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