The distinction between the athlete's heart and hypertrophic cardiomyopathy (HCM) is important because the HCM constitutes an absolute counter-indication to the practice of sport. Cardiac remodeling related to intense physical activity can sometimes make the distinction between athlete's heart and the HCM difficult. An inappropriate diagnosis of HCM can therefore lead to unnecessary exclusion from the practice of sport.

The objective of this work is to study in cardiac MRI the difference between the physiological hypertrophy of the myocardium of the athlete's heart and the hypertrophy of the pathological myocardium by comparing athletes (athlete group) to a group of subjects. non-athlete followed for HCM (HCM group).

We conducted a prospective comparative study including 61subjects. The group of athletes comprised 31subjects. TheHCM group consisted of 30subjects. All subjects were paired to age and body surface and had cardiac MRI with the late enhancement study.

The thickness of the LV wall (measured at the 17segments of AHA) in healthy athletes was lower than that in the HCM with a significant difference (P<0.0001 for mean thickness and P<0.0001 for the maximum thickness and P=0.02 for the minimum thickness).

Calculation of left ventricular mass indexed was similar between the athlete group and the HCM group (P=0.9)

The size of the left atrium was larger in the HCM group with a significant difference between the area of the left atrium indexed between the two groups (P=0.0001).

Cardiac MRI is of great benefit to the delicate differential diagnosis between myocardial hypertrophy of the athlete's heart and HCM.