ECG in the athlete, QRS voltage value never matters, really?

Sudden cardiac death (SCD) related to sport is a rare but always devastating event. SCD mainly affects men over 50 years of age who participate in recreational sport. In this population, SCD is almost always caused by coronary artery disease.1 Competing young athletes (≤35 years of age) are much less often affected by SCD. In this population the causes of SCD are varied and are dominated by genetic heart diseases.2 However, in young athletes, both autopsy and toxicological analysis are negative in almost 50% of SCD cases.3 The cause of SCD is then called ‘sudden arrhythmic death syndrome’, the probable aetiology of which is a genetic heart disease.3 A European consensus statement has recently been published to recommend a preparticipation cardiovascular evaluation (PPE) in young athletes.4 Its primary scope is to detect silent cardiac diseases which may otherwise be revealed by SCD. This PPE includes familial and personal histories, physical exam, and a 12-lead resting electrocardiogram (ECG). The place of the ECG in the PPE is the subject of a lively debate, which is out of the scope of this editorial. One of the main criticisms for the systematic use of ECG in PPE is the large number of false positives observed in athletes when using the classic ECG analysis derived from untrained populations. Since 2005, the date of the first recommendations published by the European Society of Cardiology, several evidence-based ECG classifications have been successively proposed. All these data have finally led to the international recommendations for electrocardiographic interpretation in athletes published in 2017.5,6 Thus, the specificity of the ECG standards for athletes has improved, lowering the rate of false positives (now 3% to 5%) while maintaining the sensitivity of ECG to identify serious disease. Therefore, the cost of screening has been reduced.7 Moreover, despite the specific ECG patterns reported in untrained children (i.e. mainly the T-wave inversions in right precordial leads) the value of these recommendations has also been validated in young athletes.8 The international recommendations for electrocardiographic interpretation in athletes should be applied in athletes who train regularly and intensively at least 4 hours per week.6 In these recommendations, ECG findings are divided into three groups: normal, borderline and abnormal.6 With regard to the voltage of the QRS, only an increased QRS voltage has been considered in this classification. The presence of isolated (i.e. without other associated ECG abnormality) increased QRS voltage classified as electrical left9 or right10 ventricular hypertrophy does not correlate with a pathology in asymptomatic athletes. Therefore, this observation should be considered as part of the normal spectrum of ECG findings in athletes and should not require further cardiac evaluation.6 The observation of low QRS voltage (LQRSV) was not considered in these recommendations.6 LQRSV is defined by a whole QRS amplitude of less than 0.5 mV in the frontal leads and/or less than 1.0 mV in all the precordial leads.11 Moreover, any significant attenuation of the QRS voltage observed on the comparison of two successive ECGs is also classified as LQRSV.11 LQRSV may be due to several cardiac and extracardiac causes. With regard to cardiac diseases, it has recently been reported that LQRSV may be present in patients with arrhythmogenic cardiomyopathy (ACM) in an early stage of the disease.12 ACM is a group of heart diseases characterised by a progressive fibro-fatty replacement of the ventricular myocardium.12 ACM predisposes to lethal ventricular arrhythmia that can occur at an early stage of the disease and thus reveals it.12 It has been suggested that ACMs may worsen with intense sports practice and may be complicated by sudden arrhythmic death in athletes.12 Their detection with an ECG during PPE would therefore be essential. Some previous publications have underlined the lower prevalence of LQRSV in athletes as compared to patients with arrhythmogenic right ventricular cardiomyopathy, which is classified today as an ACM.13,14 The article proposed by Pelliccia’s group seems very important because it is the first study that focuses on the prevalence of LQRSV in athletes and on their outcome.15 The authors retrospective study included 516 Caucasian Olympic Italian athletes, 60% men, aged 25±5 years.15 All had PPE with a clinical exam, ECG, echocardiography, maximal exercise test and 24-hour Holter recording with a training session. The follow-up duration was 5±2 years, based on serial clinical evaluations and/or structured telephone interviews. Only 4% of athletes presented with LQRSV on their ECG, associated with left atrial enlargement in 13% of cases. No gender difference was noted and the prevalence of LQRSV was slightly higher in athletes engaged in skilled sports disciplines. No correlation was observed between LQRSV and left ventricular morphological patterns. Premature ventricular beats were more frequent (39%) in athletes with LQRSV versus those with normal QRSV (7%). No cardiac event was reported during the follow-up of athletes with LQRSV. Despite this reassuring fact, the authors concluded that, due to a higher prevalence of ventricular arrhythmias in athletes with LQRSV, a long-term follow-up with clinical evaluations and serial imaging of these athletes was justified. The study provides important new data on the prevalence of LQRSV and the risk of cardiac events among elite Caucasian athletes. However, the study has some limitations. Firstly, while many of the athletes with LQRSV presented with arrhythmias coming from the right ventricle we have no information on the morphological and functional characteristics of this cardiac cavity. Secondly, no systematic cardiac magnetic resonance imaging (MRI) was performed either for the diagnosis nor for the follow-up of these athletes. Therefore, further prospective studies are required. Despite these limits, we think that the results of the Pelliccia group study should lead to the amendment of the international recommendations of ECG interpretation in athletes,6 and to the inclusion of the observation of LQRSV in the class of abnormal ECG findings.6 We believe that this finding requires the same cardiological evaluation as proposed in the case of abnormal negative T-waves in an athlete,16 that is, at least an echocardiogram, a maximum exercise test because of its confirmed value to detect adrenergic ventricular arrhythmias,17 a Holter with a training session and if all these examinations are normal, a cardiac MRI seems justified. Annual cardiological monitoring at least for the whole duration of the sports career also appears justified. The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. The author(s) received no financial support for the research, authorship, and/or publication of this article.