Left-heart fluid–structure interaction with aortic and mitral valves: Hemodynamic and energetic effects of ejection fraction and valve stiffening

Fully coupled fluid–structure interaction (FSI) modeling of the left heart (LH) remains computationally challenging, especially when the ventricle and its two valves are modeled together. Previous computational efforts have largely resorted to heavily simplified LH configurations, and a systematic quantification of the global energy budget has remained absent. To address these gaps, we present a fully coupled three-dimensional FSI model of the LH that incorporates both mitral and aortic valve geometries with variable tissue stiffness and prescribed wall kinematics under different ejection fractions (EFLV). Four conditions were compared: baseline (EFLV=40%, E=10 MPa), isolated aortic or mitral stiffening (E=20 MPa, EFLV=40%), and reduced EFLV (24%, E=10 MPa). The cases with EFLV=40% showed higher peak aortic flow rates (527 vs 404 ml/s) and larger geometric mitral orifice areas (0.50 vs 0.42 cm2). Aortic stiffening reduced the effective orifice area (0.81–0.69 cm2) and increased the maximum transvalvular pressure gradient (15.6–17.7 kPa), while mitral stiffening increased the diastolic leaflet forces (0.23–0.40 N). All cases exhibited competent valve closure with negligible regurgitation. Vortex analysis revealed that EF = 40% sustained high-helicity vortices in the left ventricle and atrium, which can reduce blood stasis, while EF = 24% led to markedly reduced vorticity. Energy analysis demonstrated that EF = 40% required substantially higher left ventricular work (0.84 vs 0.41 W), aortic kinetic energy flux (peak 4.3 vs 1.8 W), and energy dissipation (peak 1.08 vs 0.47 W) than EFLV=24%. Together, these findings quantify how EF and valve stiffness independently and interactively shape valvular dynamics, flow organization, and energetic efficiency in the failing LH, providing a biophysical framework for understanding LH failure. Our FSI platform offers a foundation for future parametric studies and holds translational potential for surgical planning and prosthetic valve design.