Screening for cardiac and respiratory problems in elite sport – compare and contrast

KEYWORDS:

• Exercise
• asthma
• screening
• heart
• bronchoconstriction

The sudden death of a young athletic individual while participating in a sporting activity is a devastating event. Such occurrences have an immediate and profound impact on all involved, including family, team members, and coaching staff. This has driven a number of European countries [1], professional sporting organizations [2,3], and international cardiac societies [4–6] to recommend integration of screening for conditions that may predispose to sudden cardiac death (SCD), in pre-participation medical assessment. Indeed, although not universally accepted, this approach is promoted by a number of international sporting federations, across sporting disciplines [2,3,7] with a persuasive emphasis placed on the theory that detecting anomalies mitigates risk.

The success of any screening policy is dependent upon rigorous application of a series of widely accepted criteria [8]. For a screening program to be effective, it must identify a condition/disease state accurately and in a timely fashion, to allow initiation of a cost-effective intervention that has a beneficial impact on prognosis.

In this respect, the process of screening athletes for cardiac anomalies presents a number of challenges. First, a wide number of rare conditions have been associated with exercise-associated SCD [9]. For example, the estimated prevalence of hypertrophic cardiomyopathy, recognized as the commonest cause of SCD during exercise under 35 years of age, is just 1 in 500 [6,10]. Second, there is currently no single test, sufficient to identify all relevant conditions. Finally, intervention varies with diagnosis, but the relative risk and impact on prognosis is often uncertain. In general, any treatment begins with a recommendation to cease sporting activity.

In contrast, we now know that the prevalence of respiratory disease (specifically airway dysfunction) in elite athletes is extremely high [11], when compared to the general population. Indeed, asthma ± exercise-induced bronchoconstriction (EIB) is the most common chronic medical condition encountered in high-level athletes [12] and has often been identified in up to half of the members of large elite endurance teams [13].

Often considered a benign condition, asthma in young athletes is in fact associated with a recognized mortality. Specifically, Becker et al. found a high proportion of asthma-related deaths occur in elite or competitive athletes [14]. In addition, untreated airways disease in athletes has a potential detrimental impact on both their health (i.e. risk of exacerbations) and performance (i.e. limiting ability to both train and compete).

It is incorrect to assume that athletes with respiratory disease will always have symptoms and thus ‘self-present’. Intriguingly, the relationship between the presence of classical airway-centric symptoms (e.g. cough, wheeze, and dyspnea) and objective evidence of EIB in elite-athletic populations is actually weak [15,16]. Moreover, when athletic cohorts are ‘screened’, with surrogates of exercise (e.g. with the indirect bronchoprovocation test, eucapnic voluntary hyperpnoea [EVH]), there is almost always a ‘hidden’ prevalence signal; i.e. individuals with evidence of airway hyperreactivity but no or relatively few symptoms. Indeed in a study evaluating EIB screening in the Great British Olympic team, the prevalence of EIB was approximately 20% with seven individuals identified having no prior diagnosis of asthma [13].

Hence, when screening for occult respiratory disease is compared to the approach adopted, and often accepted, for the detection of cardiac anomalies in athletes [2–5], it seems intuitive to argue that consideration should also be given to commensurate respiratory screening.

A key consideration in any screening program concerns the test or diagnostic criteria that are employed. Any screening methodology should be simple, reproducible, and effective at detecting the target abnormality [8,17]. In cardiac screening, due to the wide number of potential cardiac diagnoses possible, no single test is sufficient. Current European Society of Cardiology recommendations rely upon the identification of subtle nonspecific abnormalities on clinical history, examination, and 12-lead ECG, initiating further more complex diagnostic investigations [2]. This approach differs from the current recommended by the AHA that relies purely on a clinical history and examination [18]. In addition, certain sporting organizations also mandate regular transthoracic echocardiography [5]. Interpretation can, therefore, be challenging, and should be undertaken by individuals with particular experience and expertise in this area.

In the context of airways disease screening, to date, most studies have employed indirect bronchoprovocation tests (e.g. EVH). The EVH test involves inhaling a dry gas stimulus for several minutes to elucidate and reveal an athlete’s tendency to airway narrowing [19]. The precision and reliability of this approach is yet to be proven and the use of any ‘screening test’ is entirely dependent on the cut-off value that is utilized to differentiate ‘normal from abnormal’. Indeed, at lower cut-off values, tests to detect EIB appear to have variable test–retest reliability (please see [20] for review).

The final common pathway or outcome from either a cardiac or a respiratory screening process is the initiation of effective treatment. If a potentially lethal cardiac condition is identified, then often the only common ‘therapy’ is advice regarding cessation of sporting activity. Further treatment depends on the condition identified and determined after a thorough clinical evaluation and risk assessment. Treatment strategies can include pharmacology, implantable devices (e.g. defibrillators), electrophysiological studies/ablation, and cardiac surgery.

Therapy for airways disease is well defined, efficacious, and generally associated with minimal side effects [21]. This acknowledged, it is not desirable to treat athletes with any unnecessary medication and at the current time the implications for health and performance [22] of detecting airway dysfunction in an asymptomatic athlete is yet to be fully established. Anecdotally, such athletes respond favorably to treatment with inhaled therapy, but robust objective evidence supporting the health and performance benefit of treating such individuals is currently lacking and mandates further research.

Finally, a key consideration in the assessment of any screening program is cost-effectiveness. With respect to cardiac screening, the assessment of true cost-effectiveness remains strongly debated within the literature and is beyond the scope of this article. In summary, the arguments hinge on the potential future contribution a young adult can make to society that is identified through screening and hence survives, and integrating this figure with the projected current incidence of cardiac death in a particular population. The calculation is also effected by the efficacy and cost of the screening modality employed, and differs in the USA and Europe (see [23–25]). In contrast, an estimation of the cost-effectiveness of screening for EIB is based upon the reversal of performance loss in a large number of individual athletes, using a screening test that remains relatively low cost, without any further complex investigations (often required in the diagnosis of a cardiac disorder) [17].

In summary, screening for occult cardiac or respiratory disorders is complex, and should be undertaken following due consideration of the application of a number of accepted ‘screening’ criteria. It is of interest to compare and contrast these criteria when applied separately to cardiac and respiratory disorders and certainly remarkable to observe that while the cardiac screening of athletes has an established place in many sporting pre-participation algorithms, respiratory screening programs remain rare. Indeed, based on the current best available evidence, there is a strong case to argue that respiratory screening should be included in any comprehensive physiological screening /pre-participation assessment in athletes and integrated cardiorespiratory assessment is likely to be indicated in certain groups of high-risk athletes (e.g. elite-level endurance athletes). In the meantime, while we await further research to guide the optimal approach in this area, certainly affording athletes close medical attention to their cardiorespiratory health is the least a responsible clinician can offer.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.