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 < 0.001) and also increased between PREOP and PO14 (p < 0.05). SDNN (p < 0.001) and PNN50 (p < 0.001) decreased from PREOP to PO1. There was also a significant decrease between PREOP and PO14 for both parameters (p < 0.005 and p = 0.05 respectively). SDNN increased from PO1 to PO14 (p < 0.005). rMSSD decreased from PREOP to PO1 (p < 0.001). A circadian variation was found in the mean heart rate for all three monitoring periods (p < 0.005). Circadian variation was also present on PREOP for pNN50 (p ≤ 0.05) and rMSSD (p < 0.05). This variation was missing for both PO1 and PO14. Patients had a shift of autonomic tone with reduced parasympathetic activity and lack of circadian variation 14 days after lumpectomy.