A computer study of the effects of branching dimension on safety factor distribution and propagation in a cardiac conduction network

Branching conduction networks are responsible for coordinated distribution of activation throughout the heart, but the effects of branching geometry on the efficiency of distribution and the safety of propagation remain unclear. We have developed a simplified computer model to investigate this issue in a systemic fashion. A simplified 2D model that reproduces key features of the right atrial pectinate muscle network has been developed. This consists of a large main strand that gives rise to regularly spaced perpendicular branches. Safety factor (SF) and activation time (AT) within the network are estimated for a range of different branch dimensions. The SF is reduced as branch dimension is increased due to the larger current load and is least at the proximal edge of the junction between the main strand and branches. On the other hand, activation efficiency depends on appropriate balance between the load imposed by branching and source which they subsequently provide. With repeated stimulation at progressively decreasing coupling intervals, the SF and conduction fall within the network, but the locations of block varied with branching dimension, again reflecting spatial variation in the balance between current source and current load. We hypothesize that the observed geometry of the branching network optimizes distribution efficiency and propagation safety.