The relationship between post-operative time and cardiac autonomic modulation in breast cancer survivors

Background/objectives: Breast cancer survivors present autonomic dysfunction when evaluated by their heart rate variability (HRV). The purpose of this study is to investigate the relationship between post-operative time and cardiac autonomic modulation in breast cancer survivors and compare these values to those of women without cancer. Methods: This is a cross-sectional study consisting of 45 women from 35 to 70 years old. These women were divided into two after breast cancer groups (BCG1 and BCG2) and a control group (CG). Group BCG1 consisted of women who had undergone breast cancer surgery within the last 18 months and BCG2 those whose postoperative periods were more than 18 months. The control group was formed by cancer-free women. HRV indices were used in the time and the frequency domain and geometric indexes. Results: The indices in millisecond, RMSSD (BCG1 = 19.83; BCG2 = 14.99; CG = 31.46), SD1 (BCG1 = 14.03; BCG2 = 10.61; CG = 22.27), SD2 (BCG1 = 39.17; BCG2 = 35.28; CG = 61.16), SDNN (BCG1 = 29.58; BCG2 = 26.12; CG = 46.36) and HF in milliseconds squared (BCG1 = 194.2; BCG2 = 91.07; CG = 449.4) showed statistically significant reductions in the breast cancer groups compared to the CG (p ≤ 0.0001). Lower SD1 index values were observed when comparing BCG2 to BCG1. Conclusions: Breast cancer survivors regardless of their postoperative period exhibited a decrease in overall variability and both sympathetic and parasympathetic activity when compared to women without the disease. The group with the longer postoperative period manifested more pronounced autonomic modulation changes.