The Different Mechanisms of Action Potential Propagation in the Heart

It was thought previously that cardiac muscle gap junctions provide low-resistance connections between cells and permit the local-circuit current to flow. Some evidences show that myocardial cells may not require low-resistance connections for successful propagation of the action potential (AP). It seems that some other types of mechanisms must be involved in AP propagation.

In this article, we study the different suggested mechanisms of AP propagation. We have calculated different conduction routes and hypothesized novel viewpoints on the mechanisms of conduction in myocyte. It seems that electric field and gap junctions are the main routes for propagation of action potential, but they are affected in different phases of action potential. Gap junction has a dynamic behavior in each cardiac cycle, managing different routes of propagation in the diverse moments. Gap junctions could be open in phases 0, 1, 3 and 4 and close in phase 2 (plateau) of action potential. Whenever gap junction is open, conduction can be fulfilled rapidly by current flow and whenever it is closed, the electrical field will be the main route of propagation.

This view on AP propagation may be useful for better exploitation of drugs or designing new remedies in arrhythmias and diseases that cause diminished cardiac contractility such as cardiac failure.