Acute effects of bilateral subthalamic stimulation implantation on heart rate variability of patients with Parkinson's disease

Objective: Impaired autonomic cardiovascular regulation and other autonomic nervous system dysfunctions have been reported in patients with Parkinson's disease (PD). These issues increase the long-term risk of morbidity and mortality in patients with PD. Deep brain stimulation of bilateral subthalamic nuclei (STN-DBS) is an effective treatment option in advanced PD with 'tetanic stimulation' silencing the subthalamic neurons. We hypothesized that the function of the hypothalamus and other autonomic centers are not affected by the surgery itself. Materials and Methods: In 2003, four Parkinson's patients were enrolled in this study. Under general anesthesia, we recorded the lead I ECG for a duration of 300 seconds for analysis of the heart rate variability (HRV) before (T1) and after (T2) STN-DBS were implanted. After the surgical procedures were completed, the STN-DBS was turned on to a frequency of 130 Hz, pulse width of 60 μs, and voltage of 1 V for 10 minutes. The third ECG records for analysis of the HRV were performed during the last 5 minutes of STN-DBS (T3). Then, the voltage was increased to 3 V for another 10 minutes. The fourth ECG records for analysis of the HRV were performed in the latter 5 minutes of 3 V-stimulation (T4). Frequency domain analysis was performed using the nonparametric method of fast Fourier transformation (FFT). The power spectrum was subsequently quantified into various frequency measurements as defined previously. A paired t-test was used for comparison within the groups at the four recording times. Results: The reductions from T1 to T2 were significantly demonstrated in the LF% and ratio LF/HF. However, the differences did not increase at the times of T3 and T4. The changes of the sympathetic indicators were due to the lesion effects of the surgery. There were no significant changes in the total autonomic or vagal indicators. Conclusions: STN-DBS surgery reduced the extent of sympathetic modulation upon the cardiovascular system in patients with Parkinson's disease. The results were achieved immediately by the lesion effects of the surgery itself.