Effects of isoproterenol infusions on heart rate variability in patients with panic disorder.

Some evidence suggests that patients with panic disorder have a decreased cardiac vagal and a relatively higher sympathetic activity. In this study, spectral analysis of the time series of heart rate before and after isoproterenol infusions was used to study heart rate variability in six panic disorder patients and 11 normal control subjects. These preliminary data reveal a significant increase of sympathovagal ratios only in the patient group after isoproterenol administration. The findings suggest a relative increase in cardiac sympathetic and a relative decrease in cardiac vagal function in patients with panic disorder during isoproterenol infusions.