No accepted clinical method currently exists to measure myocardial (heart muscle tissue) stiffness. Increased myocardial stiffness, however, is a significant cardiac remodeling mechanism in heart failure. I’m developing a clinically viable approach to estimate myocardial stiffness, using magnetic resonance imaging (MRI) and finite element modeling (FEM). Validation of this framework is critical, but remains elusive as ground truth myocardial stiffness is unknown. To overcome this validation barrier, I have developed an MRI-compatible experimental setup that incorporates soft 3D-printed heart phantoms. Using the setup, I will acquire MRI data needed to evaluate the phantom’s material stiffness using FEM, and then compare MRI- and FEM-based stiffness estimates with ground truth phantom stiffness. I’ll use the validated myocardial stiffness estimation approach to characterize changes during heart failure progression. My overarching goal is to establish a comprehensively validated and clinically viable tool for estimating in vivo myocardial stiffness to better understand and manage heart failure.