Effects of an 18-Week Integrated Yoga Program on Cardiac Autonomic Function in Breast Cancer Patients Undergoing Adjuvant Chemotherapy: A Randomized Controlled Trial

BACKGROUND: Cardiotoxicity is a commonly observed adverse effect seen in breast cancer (BC) patients undergoing chemotherapy with attributes toward cardiac autonomic dysfunction (CAD). Yoga, a mind-body system of medicine that has been shown to improve cardiac autonomic nervous system (ANS) activity in various health conditions, could be an effective adjuvant approach in addressing CAD. OBJECTIVE: This study aims to investigate the protective effects of Integrated Yoga Therapy (IYT) on ANS functioning, assessed using Heart rate variability (HRV) in breast cancer patients undergoing chemotherapy. METHODS: A total of 68 (stage I-III) BC patients were randomly assigned into 2 groups: Treatment as Usual group (TAU) and TAU with Yoga Therapy group (TAUYT). All patients underwent anthracycline-based adjuvant chemotherapy for a total of 6 cycles with 21 days/cycle. During chemotherapy, the TAUYT group received IYT 5 days a week for 18 weeks, compared with usual care alone in the TAU group. Resting heart rate (RHR) and HRV, measured in both the time and frequency domains, were used to assess the cardiac ANS function of each patient before and after 6 cycles of chemotherapy. RESULTS: A total of 30 subjects in the TAU group and 29 subjects in the TAUYT group were included in the analysis. At baseline (before chemotherapy), there were no significant differences between the TAU and TAUYT groups in terms of RHR and HRV indices. However, after chemotherapy, patients in the TAU group had a significantly higher average RHR (P < .02) and lower HRV indices with reduced parasympathetic indices: RMSSD (P < .01), pNN50% (P < .04), high-frequency power (P < .001) and increased sympathetic indices: low-frequency power (P < .001) with sympathovagal imbalance: LF/HF (P < .001) compared with patients in the TAUYT group. CONCLUSION: The study showed the protective effects of yoga therapy on CAD in patients receiving anthracycline-based chemotherapy for BC, proposing yoga as a potential adjuvant intervention in improving cardiac health and preventing cardiovascular-related morbidities. TRIAL REGISTRATION: This trial is registered with the Clinical Trials Registry-India (CTRI) database (CTRI/2020/10/028446; October 16, 2020).