Echocardiographic evaluation of paediatric athlete’s heart

Cardiac remodelling induced by athletic conditioning, the so-called ‘athlete’s heart’, is considered a physiologic adaptation to training with no clinical consequences.1,2 Despite an increasing number of children being involved in competitive sports, the trend for more intensive training loads and the very young age at which pre-adolescents are being encouraged to start competitive events, most of the studies on athlete’s heart have been carried out in adults1,2 or, rarely, in adolescent individuals.3,4 Unfortunately, data derived from adults cannot be transferable to children, as they are physically less mature and exposed to a shorter intensity and duration of training, and, as a consequence, the magnitude of cardiac adaptation is less than that described in adult athletes.5 Recently, studies on paediatric athlete’s heart have been published, demonstrating that the physiological adaptation of athlete’s heart can be observed also in children practising competitive sports6–8 and refuting the notion of a ‘maturational threshold’ that must be surpassed for significant cardiac dimensional influences of training to be manifested. Accordingly, these preliminary data suggest that the application of normative reference values derived from the general population could be a potential source of misdiagnosis and should be applied with caution in children practising sport. Although the distinction between training-induced remodelling and life-threatening cardiac pathologies is crucial, differentiating between paediatric athlete’s heart and cardiovascular abnormalities remains a clinical challenge, particularly in children engaged in a high-intensity/high-volume training programme. Therefore, studies aimed to establish normative references values are welcome. A recent meta-analysis describes structural and functional manifestations of paediatric athlete’s heart by electrocardiogram and echocardiography, providing relevant clinical information about means and 95% confidence intervals of echocardiographic data of left ventricular size and function on more than 14,000 children practising competitive sports.9 In the study by Cavarretta and collaborators 2151 consecutive, healthy, peri-pubertal male athletes practising soccer (mean age 12.4 ± 1.4 years, range 8–18 years; training volume: 7.2 ± 1.1 h/week) were retrospectively evaluated in order to establish normal echocardiographic measurements of left heart (aortic root, left atrium and left ventricular dimensions and mass) in relation to age, weight, height, body mass index, body surface area and training hours.10 In this paper, the authors offer a promising tool in the echocardiographic evaluation of the tricky grey zone between athlete’s heart and pathology in children, providing equations for calculating Z scores for left ventricular, left atrial and aortic size in paediatric athlete’s heart. Calculation of Z scores involves assessment of the distribution of measurement values across a range of body sizes in the normal population and, specifically for athletes, in the normal population of subjects practising competitive sports. The Z score of a measurement is the number of standard deviations of that value from the mean value at a particular body surface area (BSA). In other words, a Z score of zero corresponds to a measurement equal to the population mean for that particular BSA, a Z score of +2 or a measurement that is two standard deviations above or below the mean for that particular BSA, thresholds that usually represent the upper or lower limits of normal. Z scores can be converted to percentiles, though the magnitude of an abnormality is much easier to appreciate with Z scores than with percentiles. Given the widely recognised impact of chronological age and somatic growth on paediatric echocardiographic variables, Z scores – accounting for the effect of body size and chronological age – are useful for differential diagnosis when normative data are available. Indeed, the recommendations for quantification methods of paediatric echocardiography, endorsed by the writing group of the American Society of Echocardiography Paediatric and Congenital Heart Disease Council,11 suggest that, when normative data are available, the measurements of cardiovascular structures should be expressed as Z scores using the Haycock formula to calculate BSA. The article by Cavarretta and collaborators provides both normative values and Z-score equations to be applied in children practising soccer. These data can be very useful in the clinical practice for the characterisation of paediatric athlete’s heart. According to the recognised gender-, ethnicity- and sport-specific manifestations of training-induced cardiac remodelling, further studies are needed in order to provide normative data and the respective Z-score equations for the specific populations of children. Furthermore, to achieve greater clarity regarding cardiac remodelling in preadolescent athletes, there is a need for future studies using novel echocardiographic techniques and defining also training-induced normative data for right ventricular morphology and function in this specific population, as done for adult athletes.12,13 Availability of such data would provide greater confidence for distinguishing physiological adaptation induced by exercise from pathological findings identified in the early phase of a disease, and aid in screening the paediatric population of athletes for cardiovascular disorders with echocardiographic imaging. The author declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. The author received no financial support for the research, authorship, and/or publication of this article.