BJSM Figure 18: ECG showing third-degree (complete) AV block and a junctional escape rhythm. With third-degree AV block, there are more P waves than QRS complexes and the ventricular rhythm is perfectly regular due to an undisturbed junctional pacemaker. Complete heart block is not an expression of athlete’s heart and requires additional evaluation. This figure is only reproduced in colour in the online version. disease (figure 19). However, excluding pathology may be difficult and the extent of the evaluation is controversial. At a minimum, a 24 Holter monitor, echocardiogram and exercise stress test should be done. If the Holter and echocardiogram are normal and the PVCs suppress with exercise, some experts recommend no further evaluation for an asymptomatic athlete. However, in cases with >2000 PVCs per 24 h or episodes of non-sustained ventricular tachycardia, and depending on the level of clinical concern, morphology of the PVCs and type of sport, additional evaluation may also include cardiac MRI and more extensive electrophysiological (EP) evaluation with signal averaged ECG, long-term ECG recording, invasive EP study and/or cardiac biopsy.65 66 Therefore, many such cases require referral to a heart rhythm specialist. Considerations in high-level endurance athletes with PVCs In high-level adult endurance athletes (such as cyclists, triathlon athletes, marathon runners and rowers), concern has been raised about right ventricular changes that may resemble familial arrhythmogenic right ventricular cardiomyopathy (ARVC), but in the absence of demonstrable desmosomal mutations or a familial history.66 67 There is evolving evidence that persistent high volume and pressure load on the right ventricle from such long-term endurance exercise may result in ‘exercise-induced’ ARVC in such athletes.68 Its prognosis is not benign and may result in Figure 19: ECG of a 35-year-old cyclist shows two premature ventricular contractions which should trigger further evaluation for underlying structural heart disease and/or more complex arrhythmias. This asymptomatic athlete had inducible ventricular tachycardia during EP study, and later received appropriate shocks from an implanted ICD. major ventricular arrhythmias or sudden death, although many athletes with exercise-induced ARVC initially present with minor arrhythmias or symptoms. PVCs originating from the right ventricle typically show a left bundle branch block (LBBB) pattern with a predominantly negative QRS complex in V1. Therefore, in high-level adult endurance athletes, it may be reasonable to consider a single PVC, especially with LBBB morphology and superior axis, sufficient to warrant further investigation similar to that discussed above. lifethreatening ventricular arrhythmias was found in 30% of cases, compared to only 3% of athletes with 100–2000 PVCs, and 0% of athletes with <100 PVCs on a 24 h Holter.64 Over half of the athletes with >2000 PVCs also had bursts of nonsustained ventricular tachycardia. Therefore, a structural cardiac abnormality should be ruled out in athletes with >2000 PVCs per 24 h.64 Evaluation Documentation of ≥2 PVCs on baseline ECG should prompt more extensive evaluation to exclude underlying cardiac 32 Sport & Geneeskunde | november 2013 | nummer 5 Conclusions The ECG plays an important role in the cardiovascular assessment of athletes given its capacity to detect inherited primary arrhythmia syndromes and other diseases of disturbed cardiac conduction. As outlined in this paper, there is a concise list of ECG findings that are associated with the presence of a primary cardiac channelopathy or other disorder predisposing to ventricular arrhythmias. Clinicians charged with the cardiovascular care of athletes should be familiar with abnormal ECG findings indicative of primary Pagina 31
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