MRI-based finite-element analysis of left ventricular aneurysm

Area of Science:

• Cardiovascular Mechanics
• Biomedical Engineering
• Medical Imaging

Background:

• Tagged MRI and finite-element (FE) analysis are essential for studying cardiac mechanics.
• Left ventricular (LV) aneurysm analysis requires accurate systolic material parameters in 3D stress-strain relationships.

Purpose of the Study:

• To validate FE models of LV aneurysm using tagged MRI data.
• To determine systolic material parameters for accurate 3D stress-strain relationships in LV aneurysm models.

Main Methods:

• Tagged MRI was used to obtain in vivo geometry and myocardial strain data from sheep with induced anteroapical myocardial infarction.
• Asymmetric FE models of the LV were created, incorporating material properties from biaxial stretching, LV pressure, and diffusion tensor MRI-derived myofiber angles.
• Systolic material parameters were determined by optimizing FE models to match experimental myocardial strains.

Main Results:

• FE models successfully reproduced midwall systolic myocardial strains from tagged MRI.
• Including contractile stress transverse to muscle fibers improved model-prediction agreement by 27%.
• Elevated end-systolic midwall stress was observed in the infarct border zone (BZ) in both fiber and cross-fiber directions.

Conclusions:

• Active cross-fiber stress development is integral to LV systole, challenging previous assumptions.
• FE analysis requires more than uniaxial contracting stress for accurate LV mechanics modeling.
• Increased fiber and cross-fiber stress in the BZ may contribute to LV remodeling.