Gradient model versus mosaic model of the sinoatrial node

Area of Science:

• Cardiac electrophysiology
• Computational biology
• Cardiovascular research

Background:

• The sinoatrial (SA) node's regional electrical differences are debated.
• The mosaic model proposes a mix of atrial and SA node cells.
• The gradient model suggests varying intrinsic properties of SA node cells.

Purpose of the Study:

• To computationally evaluate the SA node mosaic model.
• To compare the predictive power of the mosaic and gradient models.
• To determine the most accurate model for SA node function.

Main Methods:

• A computational mosaic model was built using a coupled ordinary differential equation network (CODE) in a 2D lattice.
• Lattice nodes were randomly assigned as atrial or SA node cells.
• Model predictions were compared to experimental observations of electrical activity.

Main Results:

• The mosaic model failed to predict observed differences in action potential rate and shape between SA node periphery and center.
• The gradient model successfully predicted these characteristic electrical differences.
• Computational simulations favored the gradient model over the mosaic model.

Conclusions:

• The mosaic model of the SA node is untenable.
• The gradient model adequately describes SA node function and regional electrical properties.
• The findings support the gradient model's explanation for SA node electrophysiology.