Lack of circadian variation and reduction of heart rate variability in women with breast cancer undergoing lumpectomy: a descriptive study

Changes in the autonomic nervous system with increased sympathetic tone may be a cause of postoperative short-, and long-term cardiovascular complications. Heart rate variability (HRV) is assessed by Holter monitoring as a measure of autonomic tone and has not been investigated in patients with breast cancer undergoing surgery. We aimed to investigate evening- and night-time HRV after lumpectomy. Twelve patients were included in this descriptive study. HRV was measured the night before surgery (PREOP), the night after surgery (PO1) and 14 days after surgery (PO14) from 1900 to 0700 h. For calculation of HRV, time domain parameters (SDNN-standard deviation of all normal-to-normal (NN) intervals around the mean NN for the period of measurement, pNN50-percentage of beats where the change from one beat to the next is more than 50 ms, rMSSD-root mean square of successive differences) were used. We analyzed the variation of the overall time period and the circadian variation between evening and night (sympathetic vs. parasympathetic tonus). Mean heart rate increased from PREOP to PO1 (p