Effects of Cardiac Surgery on Heart Rate Variability and Its Correlation with the Quality of Life

Objectives The purpose of this study is to explore the changes in HRV before and after cardiac surgery and the relationship between HRV and quality of life. Methods A total of 21 patients who received cardiac surgery were included in this study. All cases were conducted with a five-minute ECG uploaded by a Bluetooth signal three times. The ECGs were measured before the operation (1st), after the operation (2nd), and one month after the operation (3rd). The parameters of HRV included: standard deviation of normal to normal (SDNN), low frequency (LF), high frequency (HF), normalized low frequency (LF %), and LF/HF. In the third ECG measurement, the patients were also required to answer the World Health Organization Quality of Life Questionnaire (WHOQOL-BREF) in the concise Taiwanese version. The parameters of HRV were analyzed with Wilcoxon signed ranked test. The Spearman correlation test analyzed the correlations between the parameters of HRV and quality of life. Informed consent was obtained from all subjects and/or their legal guardian(s). Results Compared with the 1st ECG measurement, the SDNN, LF, and LF% decreased significantly in the 2nd ECG. There was a significant increase in SDNN in the 3rd ECG, but there was no significant difference compared with the 1st ECG. There was a significant positive correlation between HRV and the psychological category of quality of life. Conclusions Heart rate variability decreased after cardiac surgery, and the slight recovery of heart rate variability one month after surgery was mainly due to the recovery of sympathetic nerves. The psychological category of quality of life after surgery received the lowest score, which may be related to the incomplete recovery of parasympathetic nerve activity after surgery. The objective data of heart rate variability analysis can reflect the subjective psychological category of patients after heart surgery.