Electrotonic influences on action potential duration dispersion in small hearts: a simulation study

Area of Science:

• Cardiac Electrophysiology
• Computational Biology
• Cardiovascular Research

Background:

• Spatial variations in heart repolarization currents create action potential duration (APD) gradients, potentially leading to conduction block and reentrant arrhythmias.
• Electrotonic influences in well-coupled myocardium modulate intrinsic APD heterogeneity, affecting gradients beyond propagation length constants.

Purpose of the Study:

• To investigate how heart size, tissue properties, and cell type distribution influence functional APD dispersion using computer simulations.
• To explore the role of electrotonic effects versus intrinsic cellular heterogeneity in APD dispersion across different heart sizes.

Main Methods:

• Utilized computer simulations with murine ventricular myocyte and Luo-Rudy mammalian models.
• Employed three-dimensional models representing mouse and rabbit ventricular geometries.
• Analyzed the relationship between heart size, tissue properties, cell type distribution, and functional APD dispersion.

Main Results:

• The spatial extent of APD dispersion correlates with dynamic changes in transmembrane resistance during cardiac recovery.
• In small hearts (mouse), electrotonic effects on APD are primary drivers of functional refractoriness dispersion, even with cellular heterogeneity.
• APD dispersion significantly increases in larger hearts (rabbit), unmasking intrinsic cell type variations.

Conclusions:

• Heart size is a critical factor in determining the dominance of electrotonic effects versus intrinsic cellular properties in shaping functional APD dispersion.
• Understanding these size-dependent electrophysiological behaviors is essential for modeling cardiac disease and developing targeted therapies.
• Simulation models reveal that larger hearts better represent the impact of intrinsic cellular heterogeneity on APD dispersion.