Baroreflex and oscillation of heart period at 0.1 Hz studied by alpha-blockade and cross-spectral analysis in healthy humans.

Unilateral percutaneous cervical cordotomy, performed in humans to relieve intractable cancer pain, elicits signs of ipsilateral sympathetic block. In patients undergoing right or left percutaneous cervical cordotomy (9 per group), changes in sympathovagal balance were evaluated by spectral analysis of heart rate to confirm the sympatholytic effect of this surgical procedure and to investigate the lateralization of sympathetic cardiac control. For these purposes, heart rate variability was recorded 1 hour before cordotomy and 24 hours later. Cordotomy significantly depressed the low frequency peak (LF) of heart rate variability and increased the high frequency component (HF), when measured as a percentage of total power. As a consequence, the LF/HF ratio decreased significantly (P =.001), particularly during standing. The effects of right or left cordotomies were not significantly different. In conclusion, in humans unilateral percutaneous cervical cordotomy depresses some sympathetic indexes (LF/total power ratio and LF/HF ratio) derived from heart rate variability, irrespective of side.