BIFURCATIONS IN A NONLINEAR MODEL OF THE BARORECEPTOR-CARDIAC REFLEX

We investigate the dynamic properties of a nonlinear model of the huma n cardio-baroreceptor control loop. As a new feature we use a phase ef fectiveness curve to describe the experimentally well-known phase depe ndency of the cardiac pacemaker's sensitivity to neural activity. We s how that an increase of sympathetic time delays leads via a Hopf bifur cation to sustained heart rate oscillations. For increasing baroreflex sensitivity or for repetitive vagal stimulation we observe period-dou bling, toroidal oscillations, chaos, and entrainment between the rhyth ms of the heart and the control loop. The bifurcations depend cruciall y on the involvement of the cardiac pacemaker's phase dependency. We c ompare the model output with experimental data from electrically stimu lated anesthetized dogs and discuss possible implications for cardiac arrhythmias. Copyright (C) 1998 Published by Elsevier Science B.V.