The differential diagnosis between physiological remodeling of the athlete's heart and cardiomyopathies responsible for sudden death is sometimes difficult.

Describe the difference between physiological dilatation of cardiac cavities in athletes with pathological dilatation by comparing a group of high-level athletes (athlete group) to a subject group followed for dilated cardiomyopathy (DCM group).

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

Left ventricular systolic function in MRI by left ventricular ejection fraction (LVEF) study, LV shortening fraction and MAPSE (Mitral annular plane systolic excursion) study were normal in the athlete group and impaired in the DCM group.

Left and right ventricular dilatation in the athlete group was proportionate with a ratio of LV tele diastolic volume indexed to RV tele-diastolic volume (LV TDVi/RV TDVi) at 1.1±0.1 versus disproportionate dilatation in the patient DCM group (LV TDVi/RV TDVi) at 2±0.8). The ROC curve was used to identify the threshold value of the LV TDVi/RV TDVi ratio. This threshold value corresponds to 1.21 with a 90% sensitivity and a 90.3% specificity. The correlation between the LV TDVi/RV TDVi ratio and the LV ejection fraction (LVEF) was negative (correlation coefficient=−0.55, P<0.0001). There is no late enhancement of the myocardium in the athlete group against 30% in the DCM group.

Cardiac MRI is a major contributor to the Athlete Heart distinction from the DCM. LV TDVi/RV TDVi ratio represents a discriminating role between a normal proportional adaptation of the two ventricles and a pathological dilatation.