Using Systolic Local Mechanical Load to Predict Fiber Orientation in Ventricles

Area of Science:

• Computational Biology
• Biomechanical Engineering
• Cardiovascular Physiology

Background:

• Myofiber reorientation is crucial for cardiac function.
• Existing models do not fully capture the complex interplay of microscopic and macroscopic forces.
• Understanding fiber architecture is key to predicting heart disease progression.

Purpose of the Study:

• To develop a novel algorithm for myofiber reorientation based on microscopic myocyte branching.
• To model macroscopic active tension using a multidirectional active stress tensor.
• To reconstruct known cardiac structures and simulate fiber remodeling in infarcted ventricles.

Main Methods:

• A reorientation algorithm updating principal fiber direction towards greater active tension.
• Step-by-step updates after achieving mechanical equilibrium.
• Modeling active tension as a function of strain in branching directions.

Main Results:

• Reoriented fiber helix angles align with experimental observations.
• Successfully reconstructed Torrent-Guasp and Rushmer cardiac models.
• Simulated steeper helix angles near infarction sites in remodeled ventricles.

Conclusions:

• Microscopic branching and active tension drive myofiber reorientation.
• The force-velocity relationship is critical for active tension generation.
• The algorithm predicts near-optimal pumping performance but may degrade with inhomogeneous contractility.