Impact of Yoga Nidra on Heart Rate Variability in Coronary Artery Disease Patients Undergoing Coronary Artery Bypass Grafting: A Comparative Study

Background This study aimed to assess the changes in heart rate variability (HRV) before and after coronary artery bypass grafting (CABG) in patients with coronary artery disease (CAD) and evaluate the effect of Yoga Nidra as a postoperative intervention on autonomic function during recovery. Methodology A prospective study was conducted among 32 patients diagnosed with CAD and scheduled for elective CABG. Preoperative and postoperative HRV measurements were recorded. After discharge, participants were randomly divided into the following two groups: the case group received the Yoga Nidra intervention (guided sessions, two sessions daily for three months), while the control group received standard care without Yoga Nidra. HRV was assessed again three months postoperatively. Parameters such as high-frequency (HF) power, low-frequency (LF) power, and LF/HF ratio were analyzed to evaluate autonomic nervous system (ANS) modulation. Results In the case group, a significant decrease in HF (normalized units) was observed two weeks after surgery (from 40.38 to 30.85), reflecting a transient reduction in parasympathetic activity due to surgical stress. However, by the end of the three-month Yoga Nidra intervention, HF values improved significantly to 40.98, indicating a parasympathetic rebound. A decrease in the values of LF and the LF/HF ratio was noted, suggesting a restoration of autonomic balance in the Yoga Nidra group compared to the controls. In other words, at the end of three months, the HF component showed a statistically significant improvement in the Yoga Nidra group compared to controls (p = 0.003). The 95% confidence interval for the group difference (4.80, 21.50) did not cross zero, and the effect size (r = 0.61) indicated a large effect. Conclusions This study demonstrates that while CABG initially disrupts autonomic function, as evidenced by reduced parasympathetic markers, regular Yoga Nidra practice contributes to modulating the balance of the ANS during recovery periods, facilitating a favorable shift toward parasympathetic dominance. This shift, as assessed by HRV parameters, suggests improved autonomic recovery and enhanced myocardial electrical stability during the postoperative period.