Normal basic 2D echocardiographic values to screen and follow up the athlete's heart from juniors to adults: What is known and what is missing. A critical review

In the last few years, multiple echocardiographic nomograms have been published. However, normal values calculated in the general population are not applicable to athletes, whose hearts may be enlarged and hypercontractile. Accordingly, athletes require specific nomograms. Our aim is to provide a critical review of echocardiographic nomograms on two-dimensional (2D) measures for athletes. We performed a systematic search in the National Library of Medicine for Medical Subject Headings and free text terms including echocardiography, athletes, normal values and nomograms. The search was refined by adding the keywords heart, sport, elite, master, children and young. Twenty-eight studies were selected for the final analysis. Our research revealed that currently available ranges of normality for athletes reported by different authors are quite consistent, with limited exceptions (e.g. atria, aorta). Numerical and methodological limitations, however, emerged. Numerical limitations included a limited sample size (e.g. < 450 subjects) of the population assessed and the paucity of data in women, non-Caucasian athletes, and junior and master athletes. Some data on M-mode measurements are available, while those for some specific structures (e.g. left atrial (LA) area and volumes, right ventricular diameters and aorta) are limited or rare (e.g. LA area). There was heterogeneity in data normalization (by gender, sport type and ethnicity) and their expression was limited to mean values (Z-scores have rarely been employed), while variability analysis was often lacking or incomplete. We conclude that comprehensive nomograms using an appropriate sample size, evaluating a complete dataset of 2D (and three-dimensional) measures and built using a rigorous statistical approach are warranted.