The data derived from the CRY screening program has dramatically improved our understanding of electrocardiogram (ECG) patterns commonly present in young individuals and how these can vary for individuals of different ethnic backgrounds, genders, ages, sizes, levels of athletic activity and sporting disciplines.
Establishing what constitutes a normal pattern is crucial in order to accurately differentiate between traits attributed to the individual’s demographics and characteristics that may represent underlying cardiac pathology and should trigger further clinical evaluation. By devising clear, demographic-specific criteria CRY have reduced the false positive rate of the 12-lead ECG and utilise it as a useful screening tool in the context of a diverse, young population in the UK.
The quality and novelty of the data acquired from the CRY screening programme is underscored by the number of peer-reviewed publications it has informed, as well as the incorporation of our conclusions into guidelines relating to the interpretation of the 12-lead ECG from international scientific bodies such as the European Society of Cardiology and expert consensus panels such as the “Seattle Criteria”. Based on the CRY screening programme, the investigators have:
Reported the distribution of the corrected QT interval (QTc) in young athletes and the prevalence of prolonged QT interval, which may raise suspicion of long QT syndrome. (3)
Defined the effect of age on the 12-lead ECG. In this manuscript the author outlines what constitutes a normal ECG for an adolescent and how it should be interpreted in the context of preparticipation screening. (4)
Defined the effect of black ethnicity on the 12-lead ECG. The investigators identified ECG patterns that are highly suggestive of quiescent cardiomyopathy in white athletes but are a normal ethnic variant in individuals of African/Afro-Caribbean descent. (5–7)
Assessed the prevalence and significance of voltage ECG criteria for right ventricular hypertrophy (RVH), commonly considered to represent cardiac disease. This manuscript highlighted the relatively high prevalence of RVH on the ECG of young individuals and its poor predictive value for underlying cardiac pathology. (8)
Re-evaluated ECG indices, which by convention were considered to represent signs of cardiac disease, but our screening experience demonstrated were likely to be innocent bystanders. (9)
Based on our research we have been able to define structural adaptations in young athletic individuals. This is imperative to support an ECG screening programme given that echocardiography is commonly the first investigation performed in individuals who exhibit an abnormal 12-lead ECG. The investigators have:
Defined the physiological upper limits of the left atrial and ventricular size in young athletes, which are utilised to distinguish physiological adaptation to exercise versus heart disease. (10,11)
Addressed the effect of ethnicity in structural adaptation to exercise, and demonstrated that black athletes exhibit significantly more left ventricular hypertrophy, which is pivotal in order to ensure that no athlete with an abnormal ECG is falsely labelled with underlying cardiomyopathy based on imaging criteria derived from white athletes. (12,13)
Described the novel concept of increased myocardial trabeculations, which if misinterpreted can lead to a false diagnosis of left ventricular non-compaction, a fairly novel cardiomyopathy. (14)
CRY’s preliminary screening results in 2008 (15) demonstrated that the 12-lead ECG was able to identify young individuals with cardiac disease. Nine out of 2,750 (0.3%) young individuals were diagnosed with a condition predisposing to sudden cardiac death. All diagnoses were based on an abnormal ECG, as all individuals were asymptomatic with no significant family history. In order, however, to assess the value of the 12-lead ECG as a screening tool for identifying young, apparently healthy individuals with cardiac disease, the investigators evaluated the ability of the ECG to identify cardiac disease but also, very importantly, the ability of a normal ECG to exclude cardiac disease and offer reassurance. In a recent study published in the journal Circulation (16) it was demonstrated that by refining the ECG criteria utilised during screening it was possible to improve the ECG’s specificity without compromising its sensitivity. The results suggested that the ECG sensitivity remained close to 100% (with a negative predictive value of 100%) for major cardiac abnormalities while the specificity improved from 40% to 84% in black athletes and from 74% to 94% in white athletes.
During this research CRY have identified and treated a considerable number of individuals who harboured previously quiescent conditions predisposing to sudden cardiac death. Of 29,506 individuals (mean age 19.6 years, 68% male, 94% Caucasian) who recently underwent cardiovascular evaluation through CRY, 26,486 (89.8%) were cleared of cardiovascular disease on initial evaluation. A further 2,182 (7.4%) individuals were cleared after a transthoracic echocardiogram on-site. A recommendation for secondary evaluation on the basis of suspicion or diagnosis of a cardiac condition was made in 838 (2.8%) individuals. Of these 838 individuals, 76 were given a definitive cardiac diagnosis. Interestingly, our results indicate that the prevalence of hypertrophic cardiomyopathy (HCM), which published literature suggested a prevalence of 1 in 500 individuals, may be lower than 1 in 3,500 in certain groups such as adolescents and young athletes. (17)
CRY’s research demonstrates that ECG screening is feasible and the 12-lead ECG is a useful tool in identifying young, apparently healthy individuals with cardiac disease. It also demonstrates that symptoms and family history alone are a poor discriminator of pathology.
It is self-evident, based on the wealth of publications referenced, that CRY’s screening programme has contributed a considerable amount of knowledge to the international scientific arena.
- Basavarajaiah S et al. Prevalence and significance of an isolated long QT interval in elite athletes. Eur Heart J 2007;28:2944-2959.
- Papadakis M et al. Prevalence and significance of T-wave inversions in predominantly Caucasian adolescent athletes. Eur Heart J 2009;30:1728-1735.
- Rawlins J et al. Ethnic differences in physiological adaptation to intense physical exercise in highly trained female athletes. Circulation 2010;121:1078-1085.
- Papadakis M et al. The prevalence, distribution and clinical outcomes of electrocardiographic repolarisation patterns in male athletes of African/Afro-Caribbean origin. Eur Heart J 2011;32:2304-2313.
- Sheikh N et al. Cardiac adaptation to exercise in adolescent athletes of African ethnicity: an emergent elite athletic population. Br J Sports Med 2013;47:585-592.
- Zaidi A et al. Clinical significance of electrocardiographic right ventricular hypertrophy in athletes: Comparison with arrhythmogenic right ventricular cardiomyopathy and pulmonary hypertension. Eur Heart J 2013;34:3649-3656.
- Gati S et al. Should axis deviation or atrial enlargement be categorised as abnormal in young athletes? The athlete’s electrocardiogram: Time for re-appraisal of markers of pathology. Eur Heart J 2013;34:3641-3648.
- Makan J et al. Physiological upper limits of left ventricular cavity size in highly trained adolescent athletes. Heart 2005;91:495-499.
- Basavarajaiah S et al. Physiological upper limits of left atrial diameter in highly trained adolescent athletes. J Am Coll Cardiol 2006;47:2341-2342.
- Basavarajaiah S et al. Ethnic differences in left ventricular remodelling in highly-trained athletes: relevance to differentiating physiologic left ventricular hypertrophy from hypertrophic cardiomyopathy. J Am Coll Cardiol 2008;51:2256-2262.
- Zaidi A et al. Physiologic right ventricular adaptation in elite athletes of African and Afro-Caribbean origin. Circulation 2013;127:1783-1792.
- Gati S et al. Increased left ventricular trabeculation in highly trained athletes: do we need more stringent criteria for the diagnosis of left ventricular non-compaction in athletes? Heart 2013;99:6 401-408.
- Wilson M et al. Efficacy of personal symptom and family history questionnaires when screening for inherited cardiac pathologies: the role of electrocardiography Br J Sports Med 2008;42:207-211.
- Sheikh N et al. Comparison of electrocardiographic criteria for the detection of cardiac abnormalities in elite black and white athletes. Circulation 2014;129:1637-1649.
- Basavarajaiah S et al. Prevalence of hypertrophic cardiomyopathy in highly trained athletes: Relevance to pre-participation screening. J Am Coll Cardiol 2008;51:1033-1039.