Numerical evaluation of myofiber orientation and transmural contractile strength on left ventricular function

Area of Science:

• Cardiovascular Physiology
• Biomedical Engineering
• Cardiac Mechanics

Background:

• The left ventricle (LV) utilizes complex cardiac muscle fiber arrangements for blood pumping.
• Myofiber orientation and contractile strength vary transmurally across the ventricular wall.
• The interdependent impact of these factors on LV function is not fully understood.

Purpose of the Study:

• To investigate the hypothesis that transmural distributions of myofiber orientation and contractile strength interdependently impact LV pump function.
• To quantify the combined effects of myofiber orientation and contractile strength on the Starling relationship and LV apex twist.

Main Methods:

• A finite element (FE) model of the LV was developed incorporating transmural variations.
• Simulations assessed the influences of myofiber orientation and contractile strength on cardiac output parameters.
• Evaluated effects on the Starling relationship and end-systolic (ES) apex twist.

Main Results:

• Reductions in contractile strength within a transmural layer amplified the effects of altered myofiber orientation in that layer, significantly impacting stroke volume (SV).
• The greatest LV apex twist occurred when epicardial myofibers exhibited the strongest contraction, irrespective of their orientation.
• Demonstrated a critical interplay between transmural contractile strength distribution and myofiber orientation.

Conclusions:

• The transmural distribution of myocardial contractile strength and its interaction with myofiber orientation are crucial for LV pump function.
• This coupling may play a significant role in the pathophysiology of heart failure.
• Highlights the importance of considering both factors in cardiac modeling and understanding heart disease progression.