Sl. Cloherty et al., Inhomogeneity of action potential waveshape assists frequency entrainment of cardiac pacemaker cells, IEEE BIOMED, 48(10), 2001, pp. 1108-1115
In this paper, we have employed ionic models of sinoatrial node cells to in
vestigate the synchronization of a pair of coupled cardiac pacemaker cells
from central and peripheral regions of the sinoatrial node. The free-runnin
g cycle length of the cell models was perturbed using two independent techn
iques and the minimum coupling conductance required to achieve frequency en
trainment was used to assess the relative ease with which various cell pair
s achieve entrainment. The factors effecting entrainment were further inves
tigated using single-cell models paced with an artificial biphasic coupling
current.
Our simulation results suggest that dissimilar cell types, those with large
ly different upstroke velocities entrain more easily, that is, they require
less coupling conductance to achieve 1 :1 frequency entrainment. We, there
fore, propose that regional variation in action-potential waveshape within
the sinoatrial node assists frequency synchronization in vivo.