Synchronization-dissipation and the riddle of respiratory sinus arrhythmia

Since its first observation in 1733, the functional significance of respiratory sinus arrhythmia (RSA) has remained controversial. This is the mechanism by which the central nervous system modulates heart rate within the respiratory cycle. In healthy individuals, RSA causes the cardiac frequency to increase during each breadth intake. I will report on recent technological development in cardiac pacing where we built a neuromorphic pacemaker that emulates central nervous control of the heart to restore RSA modulation lost to cardiac disease. Restoring heart rate variability was found to increase cardiac pumping efficiency in three animal models of heart failure. It also produced a positive remodeling of the heart after several weeks pacing. In order to explain these experiments, we have modelled the dynamics of cardiorespiratory coupling through the pulmonary vasculature. We find that the role of respiratory sinus arrhythmia may be to improve cardiac pumping efficiency by reducing dynamic stress and viscoelastic power dissipation in the pulmonary vasculature.