Momentary changes in the cardiovascular autonomic system during mental loading in patients with panic disorder: a new physiological index “ρmax”

Background: Although panic disorder (PD) is suggestive of autonomic nervous system dysfunction, especially in the cardiovascular autonomic system (CAS), the results in many previous studies are still controversial. Using a new physiological index which could well reflect emotional reaction to visual stimuli (Yoshizawa, M., Sugita, N., Tanaka, A., Abe, K., Yambe, T., Nitta, S., 2001. Quantiatative Physioligical Evaluation of Three Dimensional Images. The Seventh International Conference on Virtual Systems and Multumedia, 25-27.), we studied momentary changes in the CAS in patients with PD during audiovisual stimulation (AS) as mental loading. Methods: During AS, exposed to a video of imaginary experiences such as driving a motor vehicle or diving into the sea, blood pressure (BP) and heart rate (HR) were measured in 12 remitted patients with PD and 19 age- and sex-matched normal controls (NC). We used the maximum cross-correlation coefficient (ρmax) from the BP to the HR, whose frequency components were limited to around 0.1 Hz. Results: The ρmax was an available index which could detect the momentary changes in the CAS during AS in both groups. The two-way ANOVA disclosed significant group and time effects on the ρmax. The momentary response to emotional stimuli in the PD patients was slower than that in the NC subjects. Limitations: Antidepressants have a potential impact on the autonomic variables in this study. Conclusions: These findings suggest that there may be a dysfunction of the CAS in remitted PD patients and that the dysfunction may be one of the trait markers of PD. To confirm these findings, however, further studies with a large sample size are required.