BACKGROUND: Left ventricular hypertrophy (LVH) is traditionally classified as concentric or eccentric, based on the ratio of LV wall thickness to chamber dimension. We propose a 4-tiered LVH classification based on LV concentricity(0.67) (mass/end-diastolic volume(0.67)) and indexed LV end-diastolic volume (EDV). METHODS AND RESULTS: Cardiac MRI was performed in 2803 subjects and LVH (n=895) was defined by increased LV mass/height(2.7). Increased concentricity(0.67) and indexed EDV were defined at the 97.5th percentile of a healthy subpopulation. Four geometric patterns resulted: increased concentricity without increased EDV ("thick hypertrophy," n=361); increased EDV without increased concentricity ("dilated hypertrophy," n=53); increased concentricity with increased EDV ("both thick and dilated hypertrophy," n=13); and neither increased concentricity nor increased EDV ("indeterminate hypertrophy," n=468). Compared with subjects with isolated thick hypertrophy, those with both thick and dilated hypertrophy had a lower LV ejection fraction and higher NT-pro-BNP and BNP levels (P