Objective: This study investigated the mechanisms responsible for increases in heart rate and blood pressure during psychological stress, which are incompletely understood. Since cardiac transplant patients have denervated hearts, they provide a unique model for isolating central versus peripheral influences on the cardiovascular response to stress.
Methods: The authors compared the responses to two laboratory stressors of 20 ambulatory heart transplant recipients and two groups of normal subjects, one whose ages were matched to the ages of the transplant patients (mean = 46 years) and one whose ages were matched to the ages of the heart donors (mean = 27 years). The three groups of subjects performed mental arithmetic and reaction time tasks.
Results: Heart rate increase during the mental arithmetic task was significantly attenuated in the transplant recipients. During stress, stroke volume increased in the transplant recipients but decreased in both groups of comparison subjects. The difference in age between the heart recipients and donors did not account for the difference in reactivity between the heart transplant patients and the normal subjects.
Conclusions: Direct neural stimulation of the heart is more important than peripherally circulating factors in producing tachycardia during psychological stress. Cardiac but not vascular responses to psychological stress are altered by cardiac denervation.