[Effects of spinal cord stimulation implantation on heart rate variability in patients with postherpetic neuralgia]

Postherpetic neuralgia (PHN) is a severe and distressing complication in elderly patients with herpes zoster and is associated with increased sympathetic nervous system activity. Spinal cord stimulation (SCS) implantation has been shown to effectively relieve PHN. In recent years, heart rate variability (HRV) analysis, as a reliable and objective indicator of autonomic nervous system (ANS) activity, has been widely used in the assessment of chronic pain. This study aims to investigate the clinical effects of SCS implantation on HRV in patients with PHN and its correlation with pain outcomes.

A total of 28 patients who met the inclusion criteria and were treated in the Department of Pain Medicine, the Third Xiangya Hospital of Central South University between November 2023 and March 2024 were retrospectively included. All patients underwent SCS implantation. HRV parameters before and after SCS implantation were collected, including the standard deviation of all normal-to-normal intervals over 24 hours (SDNN), root mean square of successive differences (RMSSD), standard deviation of successive differences (SDSD), percentage of adjacent normal-to-normal intervals differing by more than 50 milliseconds (PNN50), low-frequency power (LF), high-frequency power (HF), the LF/HF ratio, and total power (TP) within 5 minutes across all frequency bands. Univariate linear regression analysis was performed to explore the correlations among HRV parameters before and after SCS treatment.

After SCS implantation, the HRV time-domain indices SDNN, RMSSD, SDSD, and PNN50, as well as the frequency-domain indices LF, HF, and TP, were significantly increased (all P<0.05), while the change in LF/HF ratio was not statistically significant (P>0.05). SCS treatment also had positive effects on pain relief, improvement of negative emotions, and reduction of psychological stress (all P<0.05). Differences were observed among implantation segments. In patients receiving SCS implantation below the T8 thoracic segment, SDNN, LF, and HF decreased significantly (all P<0.05). Correlation analysis revealed that pain scores were significantly correlated with SDNN. Significant correlations were also observed among the HRV time-domain indices SDSD, RMSSD, and PNN50 (all P<0.05), whereas correlations among frequency-domain indices were relatively weak. The changes in time-domain and frequency-domain HRV indices showed a synergistic trend.

Pain outcomes in patients with PHN are accompanied by synchronous changes in autonomic nervous system activity. SCS implantation can improve HRV stability in patients with PHN and contribute to better cardiac rhythm regulation. HRV measurement may serve as evidence reflecting ANS activity in patients with PHN.