Specialised cardiac screening of athletes

Screening of the elite athlete has been a controversial topic to date and emphasises the deep deficiencies in data with which to tailor broad-sweeping or population-wide recommendations. The debate also brings into focus some specific challenges related to guidelines and developments in the screening for sudden cardiac death from school sports assessment up to the elite athlete, where most of these disorders are rare. 

It must be remembered that it is always the arrhythmia that kills, and this can be caused by sudden arrhythmic death syndrome (SADS) or obvious or subtle structural cardiac abnormalities. 

Importance of ECGs and genetic testing

Ion channelopathies are rare genetic conditions. These include long QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia, progressive cardiac conduction defect, idiopathic ventricular fibrillation and sodium channel disease, which make the patient prone to arrhythmias and may be very difficult to diagnose by electrocardiography (ECG).

However, in a dedicated centre, ECGs may give us a hint as to which ion channel is involved. This is done by repeating them continuously, and including exercise ECG and Holter monitoring. The use of genetic testing is very useful but may have limitations. 

It must also be remembered that ECG as a screening tool can have its limitations outside a specialised centre. For example, the ECG is abnormal in most patients with hypertrophic cardiomyopathy (HCM), and is widely used in screening for the condition. 

However, Minnesota-based researchers report in the Journal of the American College of Cardiology 2009¹ that a normal ECG does not definitively rule out HCM. The researchers suggested that mass screening programmes for hypertrophic cardiomyopathy based on ECGs alone could inappropriately reassure a participant that they were free from disease when they were not. 

Very recent research published by the Hypertrophic Cardiomyopathy Center, Division of Cardiology, Tufts Medical Center, Boston, Massachusetts, in the American Journal of Cardiology 2012² showed that a substantial minority of young asymptomatic patients with hypertrophic cardiomyopathy with phenotypically expressed left ventricular hypertrophy have non-pathological ECG findings on the basis of the 2010 European Society of Cardiology guidelines. This high false-negative rate of 10% represents an important limitation in applying 12-lead electrocardiography to large, apparently healthy athletic populations for the detection of hypertrophic cardiomyopathy.

There are over 50 clinical indications for the use of echocardiography in a clinical setting and this figure is increased when you include all of this technique’s specialised modalities. Echocardiography is the imaging technique of choice when used in the overall assessment of the right and left heart and to rule out both subtle and obvious pathologies. However, routine basic echocardiography and Doppler without all of the technological advances in tissue Doppler imaging to include strain and strain imaging and contrast echocardiography may not be enough to reduce the number of false-positive results in a clinical setting.

Early screening in specialised centres

Remembering the alarming sight of Premier League player Fabrice Muamba collapsing on the pitch while playing football in an FA Cup match should act as a wake-up call for the overall assessment of the elite athlete’s heart. 

A total of five GAA players over the past year have died from SADS, and in April Italian footballer Piermario Morosini suffered a similar fate. This has highlighted yet again that the standards and practices in place right now have to be good enough to help identify both the problem that struck down these athletes and all other problems associated with sudden adult death.

We owe this type of care to every athlete from initial school sport assessments up to the adult high-end elite endurance athletes. Screening should not be performed outside specialised cardiac centres because of the risk of false-positive or false-negative results, or misdiagnosis by non-accredited personnel. This could lead to promising careers destroyed by a false-positive diagnosis or a misdiagnosis due to a false-negative result with fatal consequences. We need all the best equipment with all the different imaging modalities operated by accredited personnel to be confident of a diagnosis that reduces the risk of false-positive and negative results and therefore help to reduce the chance of missing subtle pathological abnormalities.

Athlete’s heart syndrome

Recently, compelling data suggested that some structural abnormalities of the right heart can be brought on by intense exercise over time and this can lead to arrhythmias and sudden death.^3,4

Presentation to a clinic by an athlete may be on foot of an abnormal electrocardiographic interpretation or the athlete themselves feel they have lost their proverbial ‘kick’ and this complaint may be accompanied by frequent arrhythmias.

Although there is compelling evidence for the cardiovascular benefits of regular physical exercise, these recent studies have shown that transient right ventricular myocardial damage may occur during intense training regimes and prolonged exercise, especially in amateur participants. 

The Heidbuchel group (2003) at the University of Leuven in Belgium demonstrated that mild RV dysfunction was common among athletes with complex ventricular arrhythmias and a significant number resulted in sudden death. 

Heidbuchel coined the term ‘exercise-induced right ventricular cardiomyopathy’ and subsequently demonstrated that endurance athletes with ventricular arrhythmias had a lower RV ejection fraction as determined by the gold standard of ventriculography than athletes without ventricular arrhythmias.⁵

We have known for years that habitual endurance exercise results in structural and functional cardiac changes which are termed ‘athlete’s heart syndrome’. We know that all chambers of the heart undergo remodelling which is believed to represent an adaptive response providing the means for enhanced cardiovascular performance during exercise. 

However, the differentiation between long-term loading-induced RV remodelling and reduced RV contractility may have important therapeutic and prognostic implications for the elite athlete. Recently a syndrome has been reported whereby the right ventricle in some high-end endurance elite athletes undergoes structural and electrical remodelling which may create substrate arrhythmias, including life-threatening arrhythmias.

 Additional clinical imaging modalities

Cardiovascular magnetic resonance imaging (MRI) is routinely used in the structural and functional assessment of patients with suspected cardiomyopathies to assess LV and RV volumes, ejection fraction, and regional wall abnormalities as well as myocardial perfusion. One additional benefit of this technique is the ability to detect characteristic patterns of myocardial fibrosis and scarring.⁸ The presence of scarring in addition to volumetric analysis has been shown to predict prognosis in conditions like hypertrophic cardiomyopathy. 

Recently it has become possible to reliably differentiate athlete’s heart from pathological forms of cardiac hypertrophy by means of geometric indices derived from cardiovascular MRI using geometric indices such as LV mass index, ejection fraction, end-diastolic, end-systolic and stroke volume index, diastolic wall thickness, wall thickness ratio and diastolic and systolic wall-to-volume ratios. Among 120 patients with different clinical conditions ranging from athlete’s heart, hypertrophic cardiomyopathy, wall-to-volume ratio of less than 0.15mm x m² ml^-1, athletes’ hearts could be differentiated from all other forms of pathological cardiac hypertrophy with 99% specificity.⁷ There was considerable overlap between the other pathological forms of cardiac hypertrophy.

Conclusion

In February 2012, Eagle Lodge Cardiology, Limerick, and Boston General Massachusetts combined clinical experiences of the health of the athletic heart in a lead editorial that appeared in the February edition of the Journal of the American Society of Echocardiography.⁶ The editorial concluded that the health benefits of moderate exercise are well established, but the health benefits of intense prolonged exercise are less certain. 

However, with careful specific evaluation in specialised centres incorporating all new modalities, we can be confident of a complete evaluation for the elite endurance athlete. 

All these tests should be consultant-led. Testing should be performed by accredited clinical physiologists in specialised centres.  

References

1. McLeod CJ, Ackerman MJ, Nishimura RA et al. Outcome of patients with hypertrophic cardiomyopathy and a normal electrocardiogram. J Am Coll Cardiol 2009; 54: 229-233
2. Rowin EJ, Maron BJ, Appelbaum E et al. Significance of false negative electrocardiograms in preparticipation screening of athletes for hypertrophic cardiomyopathy. Am J Cardiol 2012; 110(7): 1027-1032 
3. Neilan TG, Januzzi LJ, Lee-Lewandrowski E et al. Myocardial injury and ventricular dysfunction related to training levels among non-elite participants in the Boston marathon. Circulation 2006; 114: 2325-2333 
4. La Gerche A, Connelly KA, Mooney DJ et al. Biochemical and functional abnormalities of left and right ventricular function after ultra-endurance exercise. Heart 2008; 94: 860-866
5. Heidbüchel H, Hoogsteen J, Fagard R et al. High prevalence of right ventricular involvement in endurance athletes with ventricular arrhythmias. Role of an electrophysiological study in risk stratification. Eur Heart J 2003; 16: 1473-1480
6. King G, Wood MJ. The right ventricle of the elite high-end endurance athlete cannot be underestimated. J Am Soc Echocardiogr 2012; 25(3): 272-273