BJSM the presence of a delta wave (slurring of the initial QRS) and a wide QRS (>120 ms).55 (figure 10) WPW pattern Figure 10: ECG demonstrating the classic findings of Wolff–parkinson–White with a short PR interval (<120 ms), delta wave (slurred QRS upstroke) and prolonged QRS (>120 ms). This figure is only reproduced in colour in the online version. Figure 11: ECG demonstrating a low atrial rhythm with short PR interval. Since the impulse is initiated adjacent to the AV node the atrial conduction time is decreased and the PR interval shortened. The P wave is also negative in the inferior leads (II, III, aVF) which confirms this as a low atrial rhythm and differentiates it from Wolf–parkinson–White. This figure is only reproduced in colour in the online version. should be differentiated from a low atrial rhythm with a short PR interval that is a common finding in athletes (figure 11). The short PR is a result of the impulse being generated by an atrial focus outside the sinus node and closer to the AV node. Due to the proximity to the AV node, atrial conduction time is reduced and the PR interval is shortened. Findings that can help differentiate this from preexcitation include an atypical P wave axis (negative P wave in the inferior leads) suggesting the atrium is activated from bottom to top rather than top to bottom as in sinus rhythm (figure 11). No further evaluation is recommended for asymptomatic athletes with only a short PR interval and no other ECG abnormality. Evaluation of WPW The diagnostic evaluation of asymptomatic athletes with WPW pattern remains controversial and is conducted usually by an electrophysiologist. Stratification methods for the risk of sudden death include invasive and non-invasive tests. Non-invasive measures of a low-risk accessory pathway include intermittent pre-excitation during sinus rhythm and abrupt, complete loss of pre-excitation during an exercise stress test.56 57 If non-invasive testing is inconclusive, electrophysiology testing should be considered. Characteristics of a high-risk pathway are generally determined during an electrophysiology study by the shortest pre-excited RR interval during induced atrial fibrillation. If the shortest pre-excited RR interval is measured as ≤250 ms [240 beats/min (bpm)] then the pathway is deemed high risk.52 Young athletes with a shortest pre-excited RR interval ≤250 ms should proceed with transcatheter ablation.58 An echocardiogram should also be considered due to the association of WPW with Ebstein’s anomaly and cardiomyopathy. Figure 12: Paroxysmal supraventricular tachycardia (SVT) refers to narrow complex tachycardias including atrioventricular nodal re-entrant tachycardia (AVNRT), atrioventricular reciprocating tachycardia (AVRT), atrial tachycardia and other rare tachycardias. Atrial fibrillation and flutter are types of SVT but do not fall into the paroxysmal classification. Here, there is a narrow complex tachycardia at 240 bpm, which was later found to be AVRT. This figure is only reproduced in colour in the online version. 28 Sport & Geneeskunde | november 2013 | nummer 5 Supraventricular tachycardias SVT are heart rhythms >100 bpm, originating from the sinus node, atrial tissue or involving the AV node. The most common SVT is sinus tachycardia, seen during exercise, anxiety, fever, infection, dehydration, hyperthyroidism, anaemia, pulmonary disease, heart failure, stimulant use and other causes. Paroxysmal SVT includes AV nodal reentrant tachycardia (AVNRT), AV reciprocating tachycardia (AVRT), atrial tachycardia and other rare tachycardias (figure 12). AVNRT is a circuit involving a slow and fast pathway entering and exiting the AV node. The electrical cir Pagina 27
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