The Effect of T\'ai Chi Exercise on Autonomic Nervous Function of Patients with Coronary Artery Disease

Abstract Objective: The objective of this study was to evaluate the effect of t\'ai chi (TC) on heart rate variability (HRV) from baseline to 9 months in patients with coronary artery disease (CAD). Design: A comparative trial was undertaken comparing the acute and long-term effect of TC on HRV in patients with CAD. Participants: Sixty-one (61) subjects with CAD undergoing percutaneous intervention or coronary bypass grafting for a period of more than 1 month were recruited from the clinics of cardiology and cardiovascular surgery at Chia-Yi Christian Hospital, Taiwan. Interventions: The experimental group (n = 22) practiced weekly 90-minute Yang\'s style TC for 9 months and the control group (n = 39) continued their normal daily physical activity. Main outcome measures: HRV was recorded at baseline, 3 months, 6 months, and 9 months in the control group. Resting HRV was recorded before TC exercise and recovery HRV was recorded 30 minutes post TC at the same four time points in the experimental group. Results: The change in the normalized low-frequency power, normalized high-frequency power, and the low-/high-frequency power ratio between resting and post-TC was significantly different at 9 months when compared with those at baseline, 3, and 6 months. The mean difference in normalized low-frequency power and the low/high-frequency power ratio changed from positive values at baseline, 3, and 6 months to negative values at 9 months. However, there were no significant differences in resting HRV between the patients in TC and control groups in either time domain or frequency domain HRV indices. Conclusion: The change in heart rate and HRV between resting and post-TC suggested that TC exercise could enhance vagal modulation. The potential beneficial effect of long-term regular TC exercise in patients with CAD merits further investigation.