International audienceWe propose a methodology to estimate 3D+time maps of left ventricular (LV) fibre strain from human structural and dynamic MRI data. A biomechanical finite element model integrates fibre direction throughout the LV extracted from ex vivo human diffusion tensor MRI (DT-MRI) acquisition and motion tracked from tagged MRI (TMRI). This combination enables the estimation of fibre strain and its spatio-temporal variation throughout the cardiac cycle. The sensitivity of fibre strain estimation on the underlying fibre orientation is evaluated using a database of 7 DT-MRI and 1 TMRI datasets acquired on normal subjects. Our analysis indicates that the structure of the LV is designed for maximum homogeneity of fibre strain during ejection