Objectives: To establish cardiac MRI reference values for endurance athletes and nonathletes, and study the impact of variables related to ventricular volumes and wall-mass.
Methods: Three hundred and thirty-six prospectively recruited healthy individuals aged 18-39 years (mean age 26+/-6 years, 46% women) underwent cardiac MRI: 79 elite athletes (exercising >18 h/week), 143 regular athletes (9-18 h/week), and 114 matched nonathletes (< or =3 h/week).
Results: Body surface area corrected right (RV) and left ventricular (LV) end-diastolic volume (EDV ml/m2) and wall mass (g/m2) were significantly higher (P<0.0005) in regular/elite athletes than in nonathletes (nonathlete/regular-athlete/elite-athlete; men RV-EDV 111/136/144, RV-wall mass 12/14/15, LV-EDV 101/123/129, LV-wall mass 48/62/69; women RV-EDV 96/115/118, RV-wall mass 10/13/14, LV-EDV 90/107/107, LV-wall mass 34/46/50). Male sex, body surface area, and training hours/week increase ventricular volume and wall mass. In elite athletes, short-axis RV diameter exceeded 50 mm in 49/16% (men/women), and LV diameter exceeded 60 mm in 55/16% (men/women). Interventricular septal-wall thickness was 13-15 mm in 5% regular and 15% elite male athletes.
Conclusion: Cardiac MRI reference values show increased ventricular volumes, diameters, wall mass, and wall thickness for endurance athletes compared with nonathletes. High training hours/week and male sex result in an increased overlap with standard thresholds for cardiomyopathy. To help prevent inconclusive reports, the 95th percentile reference values can be used as an alternative to standard upper limits used for the general population.