BJSM stress. CPVT is a primary electrical disease involving cardiac channels, particularly the RYR2-encoded cardiac ryanodine receptor/ calcium release channel, and typically occurs in patients with structurally normal hearts. Exercise or acute emotion can lead to progressive ventricular ectopy eventually causing a fast ventricular tachycardia. This tachycardia may lead to syncope and in some cases ventricular fibrillation and sudden death. The average age of presentation of CPVT is between 7 and 9 years old, but onset as late as the fourth decade of life has been reported.37 If untreated, approximately 30% of individuals experience cardiac arrest and up to 80% have at least one episode of syncope.38 Figure 7: 15-year-old boy undergoing exercise stress test for evaluation of CPVT. Polymorphic ventricular ectopy is evident late in stage 3 of the exercise stress test. Heart rate 148 bpm. This figure is only reproduced in colour in the online version. Prevalence and contribution as a cause of SCD The prevalence of CPVT is estimated to be around 1 in 10 000 people, although the true prevalence of this condition is not known.39 The incidence of SCD in athletes from CPVT is also not known. However, one study showed a prevalence of 9.4% in adults with sudden unexplained death and a pooled analysis found 4–10% of autopsy negative SCD could be attributed to CPVT.20 40 41 Figure 8: Brugada pattern ECGs. Type 1 Brugada pattern ECG is defined as a high-take off and downsloping ST segment elevation ≥2 mm followed by a negative T-wave in at least two contiguous leads (V1–V3). Type 2 and 3 Brugada pattern ECGs have a ‘saddleback’ appearance with J-point elevation American Typewriter 2 mm, ST segment elevation >1 mm in type 2 and ≤1 mm in type 3, and either a positive or biphasic T-wave. Diagnostic criteria and ECG findings in CPVT CPVT should be considered in any person who experiences syncope during exercise or extreme emotion, particularly in those who experience syncope during maximal exertion or have repeated episodes of syncope with exercise. CPVT cannot be diagnosed on the basis of a resting ECG, as the resting ECG is normal. An echocardiogram is also typically normal. As ventricular ectopy occurs only in the face of increased emotion or exercise, exercise stress testing is the key test in the evaluation CPVT. As exercise workload increases, there is typically an increase in the amount of ventricular ectopy which ultimately may result in polymorphic ventricular tachycardia42 (figure 7). This graded, exerciseFigure 9: Brugada type-1 ECG (left) should be distinguished from early repolarisation with ‘convex’ ST-segment elevation in a trained athlete (right). Vertical lines mark the J-point (STJ) and the point 80 ms after the J-point (ST80), where the amplitudes of the ST segment elevation are calculated. The ‘downsloping’ ST segment elevation in Brugada pattern is characterised by a STJ/ST80 ratio >1. Early repolarisation patterns in an athlete show an initial ‘upsloping’ ST segment elevation with STJ/ST80 ratio <1. induced ventricular ectopy differentiates CPVT from benign PVCs which typically suppress with exercise. The ventricular tachycardia in CPVT can be bidirectional with a 180° rotation of the QRS complex alternating from beat to beat. However, exercise-induced bidirectional ventricular tachycardia is uncommonly seen in patients with genetically proven CPVT. Instead, as heart rate increases during exercise there will be increasing ventricular ectopy initially with isolated PVC’s, then ventricular bigeminy, progressing to ventricular couplets and ventricular tachycardia if exercise persists.43 26 Sport & Geneeskunde | november 2013 | nummer 5 Pagina 25
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