Pre-participation screening for athletes in the UK.14 June 2012
By: Robin Taylor
The sudden cardiac death (SCD) of a young, apparently healthy individual is one of the most difficult tragedies for family and friends to accept, and the outbreak of emotions spreads deep into local communities. Earlier this year, when an elite premiership footballer had an aborted episode of SCD during a live televised match, the ensuing events were played out through the national media. The favourable outcome was testament to advances in the immediate recognition of cardiac arrest, prompt delivery of CPR, and the recognition of the importance of widespread access to defibrillation.
An apparent paradox for the public to deal with is that we, the medical communities, extol the virtues of exercise, in terms of its ability to maintain fitness and prevent cardiovascular disease, diabetes and obesity; yet exercise could potentially contribute to the death of an athlete. The inevitable question raised in lay and medical communities alike is how best to prevent similar future events, and the role of pre-participation screening. Some countries have national screening programmes, but at present in the UK this remains in the realm of professional sport teams who deal with it in an ad-hoc way.
27% of all episodes of SCD in the 12-35 yr old population occur during competitive athletics. Screening aims to identify athletes who have a cardiovascular disorder for which intense athletic activity could either accelerate progression, or act as a trigger for a potentially fatal arrhythmia . Any suspicion will require further diagnostic testing and thorough specialist assessment. Once a diagnosis of a cardiovascular disease is confirmed there are effective means to prevent mortality. Many will need medical, electrophysiological or device therapy, and depending on the diagnosis, there is clear advice as to which competitive or recreational sports are safe for that individual [3, 4] These disqualification criteria are an important part of a robust screening programme.
Unrecognised cardiac disease is responsible for over 80% of sudden cardiac deaths in athletes;  In those under 35 years, the most common is Hypertrophic Cardiomyopathy with an incidence of 1 in 500. The other main conditions are comparatively rare and include congenital coronary artery anomalies, Dilated cardiomyopathy, Arrhythmogenic right ventricular dysplasia, ion channelopathies (such as LQTS and Brugada syndrome) and Marfan syndrome. In athletes over the age of 35 years previously silent coronary disease is the major culprit.
Drawbacks to Screening
There is an argument that pre-participation screening doesn’t meet Wilson’s criteria for validity. The incidence of SCD in athletes is low, about 1 in 50,000. Furthermore, we would be screening for a varied group of diseases which each require a variety of different diagnostic tests, and even then a diagnosis cannot always be categorically made or excluded immediately. This all reduces the cost efficiency of a screening programme. In addition, some of the physiological cardiac adaptations to exercise can be difficult to differentiate from partially expressed disease phenotypes; the consequences of false positives include not only psychological harm, but inappropriate investigations and at worst unnecessary disqualification. It must also be appreciated that cardiovascular screening will not reduce the death rate for non-cardiac events such as bronchial asthma, cerebral aneurysms or illicit drug use.
What should a screening programme include?
Logically screening should commence at the start of competitive athletic activity which in most disciplines is 12-14 years, and be repeated at regular intervals; the ESC suggests biannually. History and examination form an integral part of the screening programme. A positive history is any cardiovascular symptoms, or fatigue that is disproportionate to the level of exercise. The other important part of the history is the family history, as the majority of these conditions are inherited in Mendelian fashion. SCD or a confirmed diagnosis of one of the common aetiologies in any first degree relative warrants further investigation.
On clinical examination particular attention should be paid to BP measurement; ensuring no diminished or delayed femoral pulses to suggest coarctation; auscultation for added heart sounds or murmurs; and observation for any of the physical stigmata of Marfans. Further diagnostic testing depends on the anomalies found.
The most contentious issue for any screening programme is whether to compliment history and examination with an ECG. The American screening programme does not, primarily due to financial restrictions. The poor specificity of the ECG would greatly increase the amount of further investigations. However, without an ECG the sensitivity of screening is low as many athletes are not aware of symptoms prior to a SCD, and a positive family history is seldom recognised due to variable penetrance and low event rates. Furthermore, family history is of no use in those affected due to de novo mutations. Based on the Italian experience both the European Society of Cardiology (ESC) and the International Olympic Committee advocate incorporating the use of the ECG into screening. In Italy national screening of competitive athletes aged 12-35 years has been ongoing since 1982. The annual incidence of SCD in athletes has been reduced from 3.6/100,000 years to 0.4/100,000 years. This reduction was predominantly driven by a reduction of deaths from cardiomyopathies.
Athletic training induces structural and electrical cardiac remodelling which are manifest in the ECG. These changes can be difficult to distinguish from abnormalities that reflect underlying cardiac pathology. Until recently most physicians will have based their interpretation of an athlete’s ECG on their personal experience and on their knowledge of the norms of the general population. The ESC have produced criteria to help cardiologists and sports physicians to differentiate common ECG abnormalities which are training related from those which are uncommon, training unrelated, and worthy of further investigation. 
Sinus bradycardia and AV block are the consequence of autonomic adaption and increased influence of the parasympathetic nervous system. Diurnal pauses of greater than 3 seconds or heart rates less than 30 will need differentiating from sinus node disease. A normal heart rate response with exercise is often sufficient, although the effect of a reduction in training may be sought. Although first degree and second degree (Mobitz I) block are common in athletes, Mobitz type II and complete heart block require further investigation.
Early repolarisation, another manifestation of high vagal tone, is present in at least half of athletes. In Caucasians it is most commonly associated with raised, concave, ST segments and peaked tall t waves. In Afro-Caribbean athletes the elevated ST segments are often convex and followed by T wave inversion, and this requires the exclusion of Brugada syndrome. Demonstrating exercise resolution is often sufficient, although Ajmaline testing is occasionally warranted.
Incomplete RBBB is common in endurance athletes as the enlarged RV has a longer conduction time. Auscultation is particularly apt to ensure the absence of a widely split second heart sound signifying an ASD. However, if this pattern is associated with T wave inversion beyond lead V2, or ventricular ectopics of right ventricular origin, then Arrythmogenic Right Ventricular Cardiomyopathy is possible. Care must also be taken not to confuse incomplete RBBB with a Brugada type pattern.
LV hypertrophy is common in athletes, and isolated increase in QRS voltages that meet the criteria for LVH do not independently warrant further investigation, but association with axis deviation or a strain pattern are suggestive of cardiac pathology.
The extent of physiological ECG changes should be consistent with the athlete’s gender, race and sport; female athletes usually have normal hearts. Afro-Caribbean athletes have the most marked structural and autonomic cardiac response to training. 20% have LV wall thickness >12mm - compared to 4% of Caucasian athletes - and a minority have > 15mm. High endurance sports such as rowing and cycling are associated with a greater frequency and magnitude of ECG changes than sports that require speed and strength.
About 5% of those screened would likely have ECG changes which cannot be attributed to training (Table 1), and would require further diagnostic testing.
Table 1 : ECG changes seen on an Athlete’s ECG
Translating the results of the Italian screening program to estimate the public health implications of a national screening program for young athletes in the UK, we could prevent 40 of the 196 SCDs that are expected each year. For each death prevented, 40,000 individuals would need screening and 791 athletes would be disqualified. This net good/harm ratio does not compare favourably with other national screening processes such as for colon or breast cancer, but may still be considered worthwhile in view of the consequences of SCD in this young population. Before such a scheme could be introduced in the UK further cost-effectiveness analysis would be necessary, and the infra-structure and funding would need to be put in place to provide trained experts to conduct screening, analyse the ECGs, and deal with the significant number of further specialist consultations that would be generated.
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