Differential diagnosis between athlete’s heart (AH) and hypertrophic cardiomyopathy (HC) remains one of the most challenging territories in the field of sports cardiology. In a recent report, Kansal et al addressed the usefulness of 2-dimensional and speckle-tracking echocardiography in differentiating AH from HC in “gray zone” left ventricular hypertrophy. The investigators state that especially relative wall thickness (measured as the ratio of septal plus posterior wall thickness to left ventricular end-diastolic diameter) and longitudinal endocardial strain by relative wall thickness have shown sufficient accuracy to clinically differentiate physiologic from pathologic hypertrophy in athletes. The study certainly opens new perspectives, but some major concerns are also raised.

“Gray-zone left ventricular hypertrophy” as a term does not just describe a septal wall thickness of 12 to 16 mm. It represents a group of usually highly trained athletes who present with similar hypertrophy features due either to training or to sarcomeric gene mutations, while they share clinical and echocardiographic characteristics that make case ascertainment at least difficult if not impossible. The patients with HC enrolled in the study of Kansal et al do not really conform to the former definitions. Their range of maximum septal wall thickness significantly differed compared to that of involved athletes; they presented with left ventricular outflow tract obstruction, which easily differentiates the cause of observed hypertrophy; and finally, their involvement in any sport discipline (even until their diagnoses with HC) and their symptomatic status are not described. It is evident that comparing groups that are not well within the gray zone limits the accuracy of any differential diagnostic approach suggested as well as the generalizability of the findings.

Review of the published research has suggested that athletes of African or Caribbean descent more frequently (compared to Caucasian athletes) exhibit gray-zone hypertrophy, while they present different morphologic and functional echocardiographic characteristics compared to age- and gender-matched Caucasian athletes. Furthermore, isometric and isotonic conditioning leads to differences in the athletic remodeling achieved, differences recorded in the geometric characteristics and function of left ventricle. Therefore, the sports in which they participate and the race of athletes participating in a study of gray-zone hypertrophy have importance in the cut-off values of echocardiographic indexes suggested (in the present study, the race of involved athletes is not described).

Finally, many standard 2-dimensional echocardiographic and tissue Doppler parameters have been found to significantly differ between athletes and patients with HC, including relative wall thickness, left ventricular end-diastolic diameter, isovolumic relaxation time, and septal E′-wave velocity. The combination of those parameters and brain natriuretic peptide (which also was found to significantly differ) may provide an easier approach to differential diagnosis compared to speckle tracking, which might be much more time-consuming and cost ineffective. Of course, newer echocardiographic modalities offer a more objective assessment of the gray zone; nonetheless, in many cases and despite different laboratory and clinical indexes used, the dilemma regarding AH or HC remains.