A large body of evidence exists indicating that autonomic imbalance is characteristic of heart failure, with several parameters of autonomic function associated with adverse clinical outcomes. The aim of this systematic review and meta-analysis was to investigate the effects of exercise training on parameters of autonomic function in patients with heart failure and where possible quantify the size of the effect. We conducted database searches (PubMed, EMBASE and Cochrane Trials Register to 31 March 2017) for exercise-based rehabilitation trials in heart failure; using search terms, exercise training, autonomic function, heart rate recovery, heart rate variability and muscle sympathetic nerve activity. Pooled data indicated a statistically significant increase in heart rate recovery at 1 min (HRR) in exercise compared to control groups mean difference 5.90 bpm (95%CI 5.12, 6.69; p < 0.00001). Pooled data also indicated that exercise training improved the short-term heart rate variability (HRV) parameters of root mean square of successive differences between normal heart beats (RMSSD (ms)) [mean difference 10.44 (95%CI 0.60, 20.28, p = 0.04)] and high-frequency normalised units (HF) [mean difference 7.72 (95%CI 3.32, 12.12, p = 0.0006), which are predominantly reflective of parasympathetic activity. Analyses also indicated a statistically significant decrease in muscle sympathetic nerve activity (MSNA) bursts/minute (mean difference - 11.09 (95%CI - 16.18, - 6.00; p < 0.0001) and MSNA bursts/100 heart beats (mean difference - 15.44 (95%CI - 20.95, -9.92; p < 0.00001) in exercise groups compared to controls. With improvements in HRR, HRV and MSNA, exercise training appears to facilitate an improvement in parasympathetic tone and reduction in sympathetic activity.
ObjectiveThe aim of this study was to undertake a contemporary review of the impact of exercise-based cardiac rehabilitation (CR) targeted at patients with atrial fibrillation (AF).MethodsWe conducted searches of PubMED, EMBASE and the Cochrane Library of Controlled Trials (up until 30 November 2017) using key terms related to exercise-based CR and AF. Randomised and non-randomised controlled trials were included if they compared the effects of an exercise-based CR intervention to a no exercise or usual care control group. Meta-analyses of outcomes were conducted where appropriate.ResultsThe nine randomised trials included 959 (483 exercise-based CR vs 476 controls) patients with various types of AF. Compared with control, pooled analysis showed no difference in all-cause mortality (risk ratio (RR) 1.08, 95% CI 0.77 to 1.53, p=0.64) following exercise-based CR. However, there were improvements in health-related quality of life (mean SF-36 mental component score (MCS): 4.00, 95% CI 0.26 to 7.74; p=0.04 and mean SF-36 physical component score: 1.82, 95% CI 0.06 to 3.59; p=0.04) and exercise capacity (mean peak VO2: 1.59 ml/kg/min, 95% CI 0.11 to 3.08; p=0.04; mean 6 min walk test: 46.9 m, 95% CI 26.4 to 67.4; p<0.001) with exercise-based CR. Improvements were also seen in AF symptom burden and markers of cardiac function.ConclusionsExercise capacity, cardiac function, symptom burden and health-related quality of life were improved with exercise-based CR in the short term (up to 6 months) targeted at patients with AF. However, high-quality multicentre randomised trials are needed to clarify the impact of exercise-based CR on key patient and health system outcomes (including health-related quality of life, mortality, hospitalisation and costs) and how these effects may vary across AF subtypes.
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