BJSM tes ≥16 years.24 In a study of Italian adolescent athletes, incomplete pubertal development was an independent predictor for right precordial TWI.28 The prevalence of right precordial TWI decreased significantly with increasing age, 8.4% in children <14 years of age versus 1.7% in those ≥14 years.28 Figure 4. ECG from a 17-year-old black/African soccer player demonstrating ‘domed’ ST elevation followed by T wave inversion in leads V1–V4 (circles). This is a normal repolarisation pattern in black/African athletes and does not require further investigation in asymptomatic athletes. Note the T wave inversion does not extend to the lateral leads beyond V4. Biphasic T waves Biphasic Twaves create a challenge and currently there is no consensus regarding the definition of TWI when a large positive deflection precedes a negative portion below the isoelectric line. If the negative portion of the Twave is >1 mm in depth in two or more leads (excluding leads III, aVR, and V1), it is reasonable to consider this pattern as abnormal until more data are obtained. ST segment depression ST segment depression is a common abnormality in HCM but extremely rare in otherwise healthy athletes, making it a concerning indicator of disease if identified on an athlete’s ECG. ST segment depression is reported in 46–50% of patients with HCM, but in <1% of apparently healthy athletes or adolescents undergoing ECG screening.9 22–25 Any degree of ST depression beyond 0.5 mm in two or more leads is significant and requires further investigation for cardiomyopathy (figures 1 and 2). Figure 5. Abnormal ECG in a patient with hypertrophic cardiomyopathy. Note the abnormal Q waves (>3 mm in depth) in V5–V6, II and aVF. Pathological Q waves Q waves have been defined in different ways in different populations. In patients with overt HCM, pathological Q waves are reported in 32–42% of patients.19 22 In one series of asymptomatic patients with HCM, 42% demonstrated pathological Q waves.21 The consensus of this group is to define Q waves for HCM as >3mm in depth or >40 ms in duration in at least two leads (excluding leads III and aVR; figure 5). This detects HCM with a sensitivity of 35% and a specificity of 95% in patients with preclinical HCM based on molecular genetic diagnosis.29 Intraventricular conduction delay Left bundle branch block (LBBB) is an abnormal finding detected in 2% of patients with HCM but not reported in screening populations of athletes or adolescents.9 22 25 Figure 6. Abnormal ECG in a patient with hypertrophic cardiomyopathy showing complete left bundle branch block (QRS≥120 ms with predominantly negative QRS complex in lead V1). LBBB pattern with a QRS duration of 120 ms or greater should prompt further evaluation (figure 6). Right bundle branch block (RBBB) is found more commonly in HCM than in athletes but the frequency of incomplete and complete RBBB in athletes is felt to limit its differentiating value.23 30 The sig30 Sport & Geneeskunde | juli 2013 | nummer 3 Pagina 29
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