Effects of myocardial sheetlet sliding on left ventricular function.

Area of Science:

• Cardiovascular Biomechanics
• Cardiac Mechanics
• Computational Biology

Background:

• The left ventricle myocardium exhibits complex micro-architecture with laminar myocyte sheetlets.
• Sheetlet re-orientation and sliding occur during cardiac cycle deformations.
• Altered sheetlet dynamics are observed in cardiomyopathy, but their biomechanical effects are unclear.

Purpose of the Study:

• To investigate the biomechanical effects of sheetlet sliding on left ventricle function.
• To understand how sheetlet sliding influences cardiac mechanics in healthy and diseased states.

Main Methods:

• Finite element simulations of the left ventricle coupled with a windkessel model.
• Modeling sheetlet sliding as reduced shear stiffness in the sheet-normal direction.
• Utilizing cardiac MRI data from a healthy subject and incorporating geometric changes for hypertrophic and dilated cardiomyopathy.

Main Results:

• Sheetlet sliding impacts cardiac function when diastolic sheetlet orientations deviate from the LV wall plane.
• Sheetlet sliding modestly improved cardiac function (ejection fraction, stroke volume, systolic pressure) in healthy and dilated hearts.
• The effects of sheetlet sliding were amplified in hypertrophic cardiomyopathy and diminished in dilated cardiomyopathy, influenced by sheetlet angle and geometry.
• Sheetlet sliding increased tissue stresses, particularly in the myofiber direction, where it aided function.

Conclusions:

• Sheetlet sliding may be a tissue adaptation for easier left ventricle deformation, preventing excessive wall stiffness.
• This mechanism potentially balances cardiac function with tissue stress regulation.
• Further research is needed to explore micro-scale sheetlet mechanics and dynamics.