BJSM Introduction Sudden death from intrinsic cardiac conditions remains the leading cause of mortality in athletes during sport.12 A resting 12-lead ECG is utilised as a diagnostic tool in the evaluation of both symptomatic and asymptomatic athletes for conditions associated with sudden cardiac death (SCD). The purpose of pre-participation cardiovascular screening is to provide medical clearance for participation in sport through routine systematic evaluations intended to identify pre-existing cardiovascular abnormalities, and thereby reduce the potential for adverse cardiac events and loss of life.3 Many pre-participation screening programmes include an ECG. Physicians responsible for the cardiovascular care of athletes should be knowledgeable of the physiological cardiac adaptations to regular exercise that are manifested on the ECG. ECG changes in athletes are common and usually reflect the electrical and structural remodelling or autonomic nervous system adaptations that occur as a consequence of regular and sustained physical activity (ie, athlete’s heart). In fact, up to 60% of athletes demonstrate ECG changes (in isolation or in combination) such as sinus bradycardia, sinus arrhythmia, first-degree atrioventricular (AV) block, early repolarisation, incomplete right bundle branch block (IRBBB) and voltage criteria for left ventricular hypertrophy (LVH).4 The extent of these changes is also dependent on the athlete’s ethnicity, age, gender, sporting discipline and level of training and competition.5–7 Accordingly, the ability to identify an abnormal ECG suggestive of underlying cardiac disease is based on a sound understanding of ECG normality within a broad spectrum of athletic populations. Concerns for the physician when interpreting an athlete’s ECG include both missing a dangerous cardiac condition and generating false-positive interpretations that cause needless further investigations, increased economic cost and potentially unnecessary activity restriction for the athlete.8 This paper focuses on the physiological ECG adaptations commonly found in athletes to help physicians distinguish normal ECG changes from abnormal ECG findings related to a pathological cardiac condition associated with SCD. Abnormal ECG findings in athletes suggestive of underlying cardiac disease are presented separately.9,10 Overview of athlete’s heart Regular and long-term participation in intensive exercise (minimum of 4 h/week) is associated with unique electrical 26 Sport & Geneeskunde | mei 2013 | nummer 2 manifestations that reflect increased vagal tone and enlarged cardiac chamber size. These ECG findings in athletes are considered normal, physiological adaptations to regular exercise and do not require further evaluation (box 1). Box 1 Normal ECG findings in athletes 1. Sinus bradycardia (≥ 30 bpm) 2. Sinus arrhythmia 3. Ectopic atrial rhythm 4. Junctional escape rhythm 5. 1° AV block (PR interval > 200 ms) 6. Mobitz Type I (Wenckebach) 2° AV block 7. Incomplete RBBB 8. Isolated QRS voltage criteria for LVH  Except: QRS voltage criteria for LVH occurring with any non-voltage criteria for LVH such as left atrial enlargement, left axis deviation, ST segment depression, T-wave inversion or pathological Q waves 9. Early repolarisation (ST elevation, J-point elevation, J-waves or terminal QRS slurring) 10. Convex (‘domed’) ST segment elevation combined with T-wave inversion in leads V1–V4 in black/African athletes These common training-related ECG alterations are physiological adaptations to regular exercise, considered normal variants in athletes and do not require further evaluation in asymptomatic athletes. AV, atrioventricular; bpm, beats per minute; LVH, left ventricular hypertrophy; ms, milliseconds; RBBB, right bundle branch block. Increased vagal tone Common consequences of increased vagal tone include sinus bradycardia, sinus arrhythmia and early repolarisation (figure 1). Other, less common markers of increased vagal tone are first-degree AV block and Mobitz type I seconddegree AV block. Sinus bradycardia is defined as a heart rate of <60 beats/min and is present in up to 80% of highly trained athletes.6 11 Heart rates ≥30 beats/min are considered normal in highly trained athletes. Sinus arrhythmia is also common, particularly in younger athletes. Early repolarisation consists of concave ST segment elevation most commonly observed in the precordial leads and present in up to 45% of Caucasian athletes and 63–91% of black athletes of African-Caribbean descent (hereto referred to as ‘black/ African’ athletes).11–13 Black/African athletes also commonly demonstrate a repolarisation variant consisting of convex ST segment elevation in the anterior leads (V1– Pagina 25

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Sport & Geneeskunde nummer 2 | Mei 2013 Lees publicatie 21Home