Patients with hereditary hemochromatosis (HH) have been reported to develop diastolic functional abnormalities detectable by echocardiography, but it is unknown whether these occur in asymptomatic subjects. Thus, this study tested whether echocardiographic left ventricular (LV) relaxation abnormalities are detectable in subjects with asymptomatic HH. Forty-three asymptomatic subjects with HH (C282Y homozygosity in the HFE gene) and 21 age- and gender-matched control subjects without known HFE mutations underwent echocardiography with comprehensive diastolic functional evaluations. Subjects with HH were in New York Heart Association functional class I and consisted of 22 newly diagnosed patients (group A) and 21 chronically phlebotomized subjects with stable iron levels (group B). Group A subjects showed significant iron overload compared with group B subjects and controls (group C) (ferritin 1,164 +/- 886 [p <0.05 vs groups B and C], 128 +/- 262, and 98 +/- 76 microg/L and transferrin saturation 79 +/- 19% [p <0.05 vs groups B and C], 42 +/- 21%, and 26 +/- 10% for groups A, B, and C, respectively). Echocardiographic evaluation revealed (1) no statistically significant abnormalities of Doppler LV relaxation in HH groups; (2) significant augmentation of atrial contractile function in subjects with HH compared with controls, which was not correlated with iron levels and treatment status; and (3) the preservation of overall LV systolic function in HH groups. In conclusion, the results of this study suggest that the augmentation of atrial contraction appears to be an early detectable echocardiographic cardiac manifestation of abnormal diastolic function in asymptomatic subjects with HH, which may reflect undetectable subclinical LV relaxation abnormalities.