Effects of Slow-paced Breathing on Heart Rate Variability in Patients With Heart Failure

Background:

Heart failure (HF) is a major global public health concern characterized by impaired cardiac function, high mortality, frequent hospital readmissions, and substantial healthcare burden. Autonomic nervous system (ANS) dysfunction plays a critical role in the pathophysiology of HF, typically presenting as increased sympathetic activity and reduced parasympathetic activity. Heart rate variability (HRV), a non-invasive marker of cardiac autonomic regulation, has been widely used to evaluate autonomic function and predict clinical outcomes in patients with HF. Reduced HRV is associated with increased risks of sudden cardiac death, cardiovascular events, and hospital readmission. Although cardiac rehabilitation (CR) has been demonstrated to improve exercise capacity, quality of life, and clinical outcomes in HF patients, its effects on autonomic modulation, particularly during Phase I cardiac rehabilitation, remain insufficiently investigated.

Slow-paced breathing (SPB) has emerged as a potential non-pharmacological intervention for enhancing autonomic regulation. By synchronizing respiratory rhythm with cardiovascular oscillations, SPB may enhance baroreflex sensitivity, increase vagal activity, and improve HRV. Previous studies have suggested beneficial effects of SPB on autonomic function; however, the findings remain inconsistent, and evidence regarding its short-term effects on HRV among hospitalized HF patients undergoing early cardiac rehabilitation is limited. Therefore, further investigation is warranted to determine whether SPB can provide additional autonomic benefits when incorporated into Phase I cardiac rehabilitation.

Objective:

This study aims to investigate the effects of slow-paced breathing combined with Phase I cardiac rehabilitation on autonomic nervous system function in patients with heart failure, using HRV as the primary outcome measure.

Methods:

This study will employ a parallel randomized controlled trial design. Hospitalized patients diagnosed with heart failure will be randomly allocated into either the SPB intervention group or the control group. Both groups will receive standard Phase I cardiac rehabilitation, while the intervention group will additionally receive slow-paced breathing training. The primary outcomes will include changes in HRV parameters, including time-domain indices (standard deviation of NN intervals \[SDNN\] and root mean square of successive differences \[RMSSD\]) and frequency-domain indices (low-frequency power \[LF\], high-frequency power \[HF\], and LF/HF ratio), to evaluate changes in cardiac autonomic regulation before and after intervention.