Neural influence is essential for synchronizing cardiac oscillators: A computational model

Introduction: Although the autorhythmic cells in the heart beat at a wide range of frequencies (80-15 bpm) in culture, in the whole heart they beat at a common frequency set by the normal sinus rhythm. Two nonlinear oscillators operating at different frequencies can synchronize only under special conditions which are expected to be more stringent for a large network of oscillators with a range of intrinsic frequencies. In this paper we investigate this problem using simulations involving Noble cardiac cell model. Methods and Materials: We conducted two sets of simulations. The first set involves cell-pair models of cardiac cells using the well-known Noble cell model, with and without neural feedback. The second set of experiments involves grid models of Noble cells with corner-to-corner variation of intrinsic frequencies. External input, representing neural influence, is presented at varied locations and is adjusted to produce best synchronization. Observations: Cardiac Cell pair without neural feedback: Lower resistance of coupling and lesser discrepancy in intrinsic frequencies improve synchronization. Innervated Cell Pair: A pair of cells that otherwise do not synchronize are made to synchronize by appropriate neural feedback. Grid of Cardiac Cells without neural feedback: Synchronization took longer with increasing frequency range and was never complete. Innervated Grid of cardiac cells: Improved synchronization was achieved by neural feedback applied at specific locations in the grid. Input location and feedback gain are crucial for obtaining rapid synchronization. Conclusion: Neural feedback seems to play a crucial role in forging the activities of cardiac oscillators to a unitary rhythm. © 2005 Indian Association of Cardiovascular-Thoracic Surgeons.