[The Effect of Exercise Training on Heart Rate Variability in Patients With Hemodialysis: A Systematic Review]

More than 50% of hemodialysis patients exhibit autonomic dysfunction and impaired heart rate variability, which are linked to cardiovascular symptoms and poor health outcomes. While exercise training has been shown to positively affect heart rate variability in patients with chronic diseases, there is insufficient evidence to support similar effects in hemodialysis patients.

In order to give hemodialysis patients more objective information about exercise therapy, this study reviews the literature systematically to evaluate the effect of exercise training on heart rate variability in hemodialysis patients and establishes evidence-based recommendations for exercise training on heart rate variability in hemodialysis patients.

A systematic search of Cochrane Library, PubMed, CINAHL, MEDLINE, and CEPS was conducted. The keywords used in the search included "hemodialysis / haemodialysis", "exercise / exercise training / physical training / aerobic exercise / resistance exercise / strength training", and "heart rate variability / HRV / autonomic nervous system". Only randomized controlled trials (RCT) studies from the years 1990 to August 2018 were included. Non-adult ( ≤ 18 years) studies, non-English / non-Chinese language studies, and review studies were excluded.

Four studies were found and included in the analysis. Exercise training to hemodialysis patients improved the heart rate variability significantly to various degrees, including a medium to large effect for the standard deviation of all normal-to-normal intervals (SDNN), a large effect for the root mean square of the successive differences (RMSSD), a large effect for the proportion of differences of adjacent RR intervals > 50 ms (pNN50), a medium effect for the HRV triangular index, a medium effect for the low frequency/high frequency (LF/HF) ratio, and a small to medium effect for the mean RR interval. Based on the results of this systematic literature reviews recommendations emerged for exercise training on heart rate variability in hemodialysis patients. This recommendations regard to the exercise training time, frequency, intensity and contradictions.

The results of this systematic review support that the parasympathetic activity, sympathetic activity, and heart rate variability of hemodialysis patients increase close to the normal value after exercise training. Based on the results of systematic literature reviews, this study establishes four evidence-based recommendations for exercise training on heart rate variability in hemodialysis patients. These recommendations are valid, as all levels of evidences are 1++ and the grades of recommendations range from A to B.