«Results: After screening 2,873 potential articles, two studies met the inclusion criteria. Studies were composed of 153 patients with chronic low back pain and 62 healthycontrols. An electrocardiogram was used to record HRV and linear methods (time and frequency) were used to analyze the results. The main findings indicate that patients with chronic low back pain have a significant reduction in HRV, with sympathetic predominance compared to healthycontrols.
Conclusions: There is limitedevidence suggesting that chronic low back painpatients presented a lower vagal activity evidenced by HRV, when compared to healthycontrols. The results of this systematic review should be interpreted with caution due to the restricted number of included studies, small sample sizes and different protocols used to measure HRV. The limitedevidence about HRV alterations in low back pain also suggests the need of future studies to investigate if HRV parameters can be a useful measure in chronic pain samples or even if it can be used as an outcome in clinical trials aiming to investigate the effectiveness of interventions based on emotion regulation.»