BJSM athletes are presented including congenital long and short QT syndromes (LQTS and SQTS), catecholaminergic polymorphic ventricular tachycardia (CPVT), Brugada syndrome (BrS), ventricular pre-excitation, supraventricular tachycardias (SVT), atrioventricular (AV) blocks and premature ventricular contractions (PVCs). Table 1 summarises a list of abnormal ECG findings unrelated to athletic training that may suggest the presence of a pathological cardiac disorder and should trigger additional evaluation in an athlete. Table 1. Abnormal ECG findings suggestive of primary electrical disease Abnormal ECG finding Definition Ventricular pre-excitation PR interval <120 ms with a delta wave (slurred upstroke in the QRS complex) and wide QRS (>120 ms) Long QT interval* Short QT interval* Brugada-like ECG pattern QTc ≥470 ms (male) QTc ≥480 ms (female) QTc ≥500 ms (marked QT prolongation) QTc ≤320 ms High take-off and downsloping ST segment elevation followed by a negative T wave in ≥2 leads in V1–V3 Profound sinus bradycardia Atrial tachyarrhythmias Premature ventricular contractions Ventricular arrhythmias <30 bpm or sinus pauses ≥3 s Supraventricular tachycardia, atrial-fibrillation, atrial-flutter ≥2 PVCs per 10 s tracing Couplets, triplets, and non-sustained ventricular tachycardia Note: These ECG findings are unrelated to regular training or expected physiological adaptation to exercise, may suggest the presence of pathological cardiovascular disease, and require further diagnostic evaluation. *The QT interval corrected for heart rate is ideally measured with heart rates of 60–90 bpm. Consider repeating the ECG after mild aerobic activity for borderline or abnormal QTc values with a heart rate <50 bpm. (SQTS). The pathophysiology of the QT syndromes is understood as either delayed ventricular repolarisation (LQTS) or accelerated ventricular repolarisation (SQTS) originating primarily from loss-of-function (LQTS) or gain-of-function (SQTS) mutations in genes encoding voltage-gated potassium channels (Kv7.1 and Kv11.1) that govern phase 3 repolarisation in the ventricular myocytes. Currently, 13 LQTS-susceptibility genes and 3 SQTS-susceptibility genes have been identified and account for over 75% of LQTS and <20% of SQTS.1 Prevalence SQTS is extremely uncommon affecting less than 1:10 000 individuals. Although once considered similarly rare, LQTS is now estimated to affect 1 in 2000 individuals and given the subpopulation of so-called ‘normal QT interval’ or ‘concealed’ LQTS, this may be an underestimate.13 Contribution as a cause of SCD Among individuals between 1 and 40 years of age, approximately 25–40% of sudden unexpected deaths are classified as autopsy negative sudden unexplained death (SUD) lacking necropsy findings to establish the cause and manner of death.14–16 Here, cardiac channelopathies such as LQTS, SQTS, CPVT and BrS are considered as possible culprits and have been implicated by postmortem genetic testing as the root cause for up to 25–35% of SUD in selected cohorts.17–19 LQTS is the most common channelopathy responsible for about 15–20% of SUD.20 SQTS is a very rare cause of autopsy negative SUD.14 In a series of young athletes with SCD from the USA (n=1049), a precise cause of death was identified in 690 cases.4 LQTS was implicated in less than 4% of cases (23/690) with an identified cause.4 However, this estimate does not inThe congenital QT syndromes Congenital long QT syndrome (LQTS) and short QT syndrome (SQTS) are potentially lethal, genetically mediated ventricular arrhythmia syndromes with the hallmark electrocardiographic feature of either QT prolongation (LQTS) or markedly shortened QT intervals (SQTS) (figures 1–3). Symptoms if present include arrhythmic syncope, seizures or aborted cardiac arrest/sudden death stemming from either torsades de pointes (LQTS) or ventricular fibrillation 22 Sport & Geneeskunde | november 2013 | nummer 5 clude one-third of the total cases in the series (359/1049) with no precise diagnosis but in whom post-mortem genetic testing was not documented. Thus, it is likely ion channelopathies or accessory electrical pathways represent a larger percentage of SCD in young athletes than previously reported. Diagnostic criteria Both QT syndromes are diagnosed based on a combination of symptoms, family history, electrocardiographic findings and genetic testing. The Gollob score is used for SQTS while the Schwartz-Moss score is used to invoke low, intermediate and high probability for LQTS.21–23 For LQTS, genetic testing is recommended for: (1) any patient where a cardi Pagina 21
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Sport & Geneeskunde nummer 5 | November 2013 Lees publicatie 26Home