In vivo assessment of MR elastography-derived effective end-diastolic myocardial stiffness under different loading conditions

Purpose: To compare magnetic resonance elastography (MRE) effective stiffness to end-diastolic pressure at different loading conditions to demonstrate a relationship between myocardial MRE effective stiffness and end-diastolic left ventricular (LV) pressure. Materials and Methods: MRE was performed on four pigs to measure the end-diastolic effective stiffness under different loading conditions. End-diastolic pressure was increased by infusing Dextran-40 (20% of blood volume). For each infusion of Dextran-40, end-diastolic pressure was recorded and end-diastolic effective stiffness was measured using MRE. In each pig, least-square linear regression was performed to determine the correlation between end-diastolic effective stiffness and end-diastolic LV pressure. Results: A linear correlation was found between end-diastolic LV pressure and end-diastolic effective stiffness with R² ranging from 0.73-0.9. A linear correlation with R² = 0.26 was found between end-diastolic LV pressure and end-diastolic effective stiffness when pooling data points from all pigs. Conclusion: End-diastolic effective myocardial stiffness increases linearly with end-diastolic LV pressure.