A simulation of the SA node by a phase response curve-based model of a two-dimensional pacemaker cells array

This paper presents a simulation of the sino-atrial (SA) node by a two-dimensional pacemaker cells array model, based on phase response curve (PRC) interaction. This simple model of the cardiac pacemaker cells, involves only the most basic functional properties, which play a direct role in the determination of the SA node rhythm. The two most relevant functional properties of the pacemaker cells are: the intrinsic cycle length, an "internal" feature of each pacemaker cell, and the PRC, an "overall collective" function. The PRC contains the "information" about the type of interactions of each pacemaker cell with the outside world (i.e., interaction with neighboring cells, external stimulus, etc.), and "strength" of the interaction (strong, weak, etc.). The authors\´ studied the spatial interaction among a large number of pacemaker cells (15×15), as a function of the regional variation of cells properties, the "electrical" coupling between cells (the PRC), and the appearance of regions with abnormal cycle lengths. The authors investigated the influence of those parameters on the mutual interaction between the pacemaker cells, on the activation pattern and conduction time of the array, and on a pseudo-electrocardiogram (ECG) signal. This study demonstrates that by representing the pacemaker cells in the SA node by only two fundamental features, and by applying a simple physical-mathematical model, one can create a global picture of the SA node system. This enables one to explore physiological phenomena related to the genesis and maintenance of the SA node activity, and to gain insight into the conditions which predispose the SA node instability, and conduction disturbances.