Dysfunctional baroreflex regulation of sympathetic nerve activityin remitted patients with panic disorder

Background Many researchers have studied the abnormalities of autonomic nervous system (ANS) such as decreased heart rate variability, which is a risk factor for sudden cardiac death, in patients with panic disorder (PD). However, no consistent abnormality has been uncovered to date. One of the reasons for this controversy may be due to the fact that most of these conventional studies have analyzed each physiological variable independent of other indices. We examined the ANS in PD patients using a new method which can more directly investigate the function of the baroreflex by examining the relation between the blood pressure (BP) and heart rate (HR). Methods During rest and audiovisual stimulation (AS) as mental stress such as being exposed to video imaginary of experiences such as driving motor vehicles, cardiovascular parameters, HR and BP were consecutively measured in 13 remitted PD patients and twenty aged and gender–matched normal controls (NC). In this study, to assess the cardiovascular ANS function (baroreflex) in PD we used the power spectrum analysis as usual and the mean of lag time (τ) between the Mayer wave components, which was closely related to sympathetic nerve activity of vasomotor, of HR and BP variability as a new trial. Results The PD patients and NC did not differ with regard to the power spectrum analysis of the heart rate. We found that τ in the PD group was significantly shorter than that in the NC both before and after AS, especially before. Conclusions These findings suggest that remitted PD patients may have a dysfunctional baroreflex regulation of sympathetic nerve activity.