Exercise and Heart Disease

From Athletes and Arrhythmias to Hypertrophic Cardiomyopathy and Congenital Heart Disease

Abbas Zaidi; Sanjay Sharma


Future Cardiol. 2013;9(1):119-136. 

In This Article

Sudden Cardiac Death in Athletes & the Role of Pre-participation Screening

Sudden Cardiac Death in Young Athletes

The vast majority of sudden deaths in young athletes (≤35 years of age) are due to cardiovascular pathology. Estimates for the incidence of sudden cardiac death (SCD) in this group range between 1 in 50,000[6] to 1 in 200,000 per year.[7] Observational data indicate that physical exercise may behave as a trigger for life-threatening ventricular arrhythmias in individuals harboring harmful cardiac conditions. As such, the risk of SCD in young athletes is increased 2.8-fold compared with non-athletes of similar age.[6] In up to 80% of cases, SCD may be the first presentation. Most of these sudden deaths are the result of hereditary or congenital disorders affecting the structural, functional and electrical properties of the myocardium. Prompt intervention by means of automated external defibrillators during sudden cardiac arrest has been demonstrated to improve survival rates in young athletes.[8] On-site access and training in the implementation of these devices is therefore recommended for all individuals working within a sporting environment.[9]

The distribution of cardiovascular causes of SCD in 1435 young competitive athletes is shown in Figure 1, as reported by Maron et al..[10] Definite or possible hypertrophic cardiomyopathy (HCM) is the most common cause of SCD (44%) in young athletes worldwide. Coronary artery anomalies are the second most common underlying pathology (17%). A variety of acquired conditions, including acute myocarditis (6%) and premature coronary atherosclerosis (3%), are also implicated. Arrhythmogenic right ventricular cardiomyopathy (ARVC) accounts for the greatest number of fatalities (23%) in Italian athletes,[6] a figure much greater than that reported in other studies. This might in part represent a unique genetic substrate, but may also be a consequence of the Italian program of mandatory pre-participation cardiovascular screening (PPS) of all young competitive athletes that has been in place since 1982. During this time, there has been a 90% mortality reduction in young Italian athletes[11] with the near-eradication of deaths due to HCM.[12]

Figure 1.

Causes of sudden cardiac death in young athletes.
HCM: Hypertrophic cardiomyopathy.
Data taken from [10].

Recommendations for Pre-participation Screening

Based largely on the evidence from the Italian screening program, The European Society of Cardiology (ESC) advocates PPS of all young competitive athletes, by means of 12-lead electrocardiogram (ECG), personal and family history, and physical examination.[13] Proponents of screening cite the highly visible nature of the sudden death of any young, fit individual, with the resultant loss of many life-years. Further support is derived from the existence of simple, acceptable screening protocols which lead to effective interventions to prevent sudden death (primarily abstinence from competitive sport and in some cases implantation of a defibrillator). Among the proponents of screening, internal debate exists regarding the optimal protocol, with the model supported by the American Heart Association utilizing health questionnaire and physical examination alone. The addition of the ECG has been demonstrated to increase the sensitivity of PPS for detecting underlying cardiovascular disease, since around 80% of young athletes experiencing SCD are asymptomatic prior to presentation.[14] As a result, cost–effectiveness analyses adjusting for life-years saved are in favor of incorporating the ECG into screening protocols.[15]

Opponents of PPS argue that sudden death is a rare event in young athletes, with evidence for the efficacy of screening derived only from population-based observational studies. The conditions that screening aims to identify are diverse and rare, with highly variable and sometimes poorly understood natural histories. It is also argued that in most cases, the relatively benign prognosis in conditions such as HCM results in a low-risk profile for adverse events, even in athletes identified to have the condition. Furthermore, studies demonstrating high false-positive rates of PPS are cited,[16] resulting in expensive and disruptive investigation and, in some cases, erroneous disqualification. Additional criticism of PPS is directed at the potential for false-negative results: ECG-based screening protocols will fail to identify conditions such as coronary artery anomalies and premature atherosclerotic disease, which constitute a significant proportion of SCD in young athletes.

Nonetheless, the ESC screening guidelines have been endorsed by organizations including the International Olympic Committee as well as international soccer governing bodies. Despite this, most countries have not instituted systematic state-sponsored PPS of young athletes, often due to a lack of expertise, resources and infrastructure.

Sudden Death in the Older Athlete

Research and debate in relation to PPS has largely focused on young professional athletes (≤35 years of age). However, recent years have borne witness to a dramatic increase in amateur participation in endurance events, such as half marathons, marathons and triathlons, with the average age of London Marathon entrants being 49 years. In such individuals, the etiology of SCD differs greatly in comparison to young athletes, in whom inherited and congenital causes predominate. In a large observational study by Kim et al. assessing 10.9 million marathon and half-marathon runners over a 10-year period, 59 fatal and nonfatal cardiac arrests were documented, yielding a remarkably low SCD incidence of 1 in 259,000.[17] HCM remained the most important underlying etiology, followed by coronary atherosclerosis, which was documented in almost a third of cases. Our own experience of the London Marathon is an SCD rate of 1 in 80,000, the vast majority due to coronary atherosclerosis.[18] The major implication of this finding for the screening of older individuals lies in the fact that the resting ECG will fail to detect quiescent coronary artery disease in the absence of prior myocardial infarction.

The ESC has therefore issued guidelines for the cardiovascular evaluation of middle-aged and senior individuals engaging in leisure-time sporting activity.[19] In such cases, risk should be assessed by means of a questionnaire aimed at eliciting symptoms of cardiac ischemia, as well as assessment of cardiovascular risk factors or established atherosclerotic disease. In individuals deemed to have a high likelihood of atherosclerosis, maximal exercise testing is recommended before eligibility for moderate- or high-intensity physical activity. However, even this strategy may have its limitations, since exercise testing can fail to detect vulnerable, non-obstructive plaques that might theoretically become unstable under the stress of intense exertion. In the London Marathon experience, only one runner that died of coronary artery disease had previously reported anginal symptoms. A pre-race exercise test had been unremarkable, although post-mortem examination subsequently revealed stenotic disease of the left anterior descending coronary artery. Such reports have led some to advocate computed tomography (CT) calcium scoring or CT coronary angiography in the assessment of middle-aged athletes with adverse cardiovascular risk profiles, although availability, cost and radiation exposure are currently limiting factors for such a strategy.