BACKGROUNDS Ejection fraction and fractional shortening do not reflect the prognosis of patients with LVH. Midwall mechanics better represent the true function in LVH than endocardial indices. However, midwall fractional shortening (FSmw) interrogates a limited region of LV. We developed 3 dimensional (3D) method for determining midwall ejection fraction (3D EFmw). OBJECTIVES This study investigated the sensitivity of 3D EFmw to the presence of LVH in comparison with conventional echo indices for systolic function. METHODS This study compared 3D EFmw with 2D (endocardial EF [EFendo], endocardial FS [FSendo], FSmw, and systolic tissue velocity [TVs]) and 3D echo indices (3D endocardial EF [3D EFendo] and mitral annular motion [MAM]) in 28 patients with essential hypertension and LV mass index > 125 g/m2 versus 21 normal subjects. RESULTS Systolic function assessed by EFendo, FSendo, 3D EFendo, TVs did not differ between two groups, but MAM, FSmw, and 3D EFmw were significantly decreased in LVH compared to normal (Figure). FSmw (r= -0.74), 3D EFmw (r= -0.63), and MAM (r= -0.43) had significant negative correlation with LV mass index. Midwall indices FSmw (F = 40.4) and 3D EFmw (F = 26.5) better discriminated LVH and normal than MAM or endocardial indices. CONCLUSIONS 3D EFmw discriminates the systolic function of LVH and normal, and correlates with the degree of hypertrophy. By avoiding the limitations of FSmw or MAM, 3D EFmw provides a more comprehensive metric of systolic function in patients with LVH.