ANALYSIS OF HEART RATE-BASED CONTROL OF ARTERIAL BLOOD-PRESSURE

Vagal control of the heart is the most rapidly responding limb of the arterial baroreflex. We created a mathematical model of the left heart and vascular system to evaluate the ability of heart rate to influenc e blood pressure. The results show that arterial pressure depends nonl inearly on rate and that changes in rate are of limited effectiveness, particularly when rate is increased above the basal level. A 10% chan ge in heart rate from rest causes a change of only 2.4% in arterial pr essure due to the reciprocal relation between heart rate and stroke vo lume; at higher rates, insufficient filling time causes stroke volume to fall. These findings agree well with published experimental data an d challenge the idea that changes in heart rate alone can strongly and rapidly affect arterial pressure. Possible implications are that vaga lly mediated alterations in inotropic and dromotropic state, which are not included in this model, play important roles in the fast reflex c ontrol of blood pressure or that the vagal limb of the baroreflex is o f rather limited effectiveness.