Cardiovascular protection and mounting evidence for the benefits of intradialytic exercise

Effects of Acute Exercise on Cardiac Autonomic Response and Recovery in Non-Dialysis Chronic Kidney Disease Patients

Purpose: Heart rate variability (HRV) has gained acceptance as a key marker of cardiovascular health. We compared HRV responses after continuous moderate-intensity exercise (CMIE) and high-intensity interval exercise (HIIE) matched for intensity and duration in individuals with midspectrum chronic kidney disease (CKD). Methods: Twenty men and women (age 62.0 ± 10 yrs.) diagnosed with CKD stages G3a and G3b participated in a 2 (condition) x 4 (time point) repeated cross-over measures design study. HRV time-domain indices were based on the standard deviation of all NN intervals (SDNN) and the square root of the mean of the sum of the squares of differences between adjacent NN intervals (RMSSD) and frequency domain. High-frequency (HF), low-frequency (LF), total power (TP) were examined. CMIE consisted of treadmill walking for 30 minutes at a 2% incline and speed corresponding to 60%-65% of reserve volume of oxygen (VO2R). HIIE included five intervals of 3 minutes at 90% of VO2R and 2 minutes at 20% VO2R intervals. Conditions were designed to be of the same average intensity (60% to 65% of VO2R) and caloric expenditure (~144 kcal). Results: Immediately following exercise SDNN, RMSSD, HF, LF, and TP were significantly lower compared to before exercise (p <.05). HRV responses were not different between conditions and conditions X time (p >.05). Conclusions: Thirty minutes of either CMIE or HIIE decreased HRV indices, pointing to an autonomic imbalance favoring vagal mediation. HRV's responses regarding HIIE were no different from CMIE, therefore, from an autonomic function point of view this similarity may be useful for CKD exercise prescription and programming.

A single bout of hybrid intradialytic exercise did not affect left-ventricular function in exercise-naïve dialysis patients: a randomized, cross-over trial

INTRODUCTION

Cardiovascular diseases are the leading cause of mortality in end-stage renal disease (ESRD) patients, especially those receiving hemodialysis (HD) therapy. HD has many side effects that are related to patients' hearts, such as recurrent myocardial ischemia and global or segmental left-ventricular dysfunction, which is associated with intradialytic hypotension, long-term loss of systolic function, and high incidence of cardiovascular events and death. Systematic exercise training has a beneficial effect on measures of cardiovascular fitness and reducing cardiovascular risk factors in ESRD. Whether there is an acute benefit of exercise during HD on left-ventricular function is not well known. The current study aimed to investigate whether a single bout of hybrid (aerobic and resistance) intradialytic exercise could affect left-ventricular function during HD sessions.

METHODS

Twenty-one exercise naïve and clinically stable HD patients participated in the study. All participants completed two different HD trials on two different days, separated by 1 week: (1) standard HD and (2) HD including a single bout of hybrid intradialytic exercise. Hybrid intradialytic training included the usual intradialytic cycling followed by resistance training using elastic bands and dumbbells. Echocardiographic assessment of left-ventricular function was completed before HD, half an hour before the end of HD, and 30 min after the end of HD.

RESULTS

Cohort data for left-ventricular function indices were not different between trials and did not change across time in either the standard HD or HD plus exercise trial. Cohort data for the change in ejection fraction from baseline to during HD did mask considerable inter-individual variability (HD - 0 ± 15; HD plus exercise (- 2 ± 20). Despite this, the variability was not mediated by the addition of intradialytic hybrid exercise.

CONCLUSION

A single bout of hybrid intradialytic exercise did not affect left-ventricular function during the HD therapy. It is important to determine whether chronic exercise training could beneficially affect left-ventricular function abnormalities often observed during the HD therapy.

TRIAL REGISTRATION NUMBER

The study is registered at ClinicalTrials.gov (NCT01721551) as a clinical trial.

Exercise in patients on chronic hemodialysis: current evidence, knowledge gaps and future perspectives

PURPOSE OF REVIEW

Physical inactivity is common in hemodialysis patients, and is associated with disability and poor outcomes. We summarize the effects of aerobic, resistance or mixed exercise training on aerobic capacity, muscle mass and strength, dialysis efficiency, quality of life and cardiovascular adaptation according to clinical studies on this population, also focusing on knowledge gaps as topics for future research. Finally, we put evidence into clinical context deriving practical indications for exercise implementation in these patients.

RECENT FINDINGS

In hemodialysis patients, aerobic or mixed exercise training increases predominantly aerobic capacity, whereas resistance training seems more effective in increasing muscle strength. Data concerning dialysis efficiency are equivocal, although phosphate and potassium clearances seem to be improved. There is also inconclusive evidence concerning changes in cardiovascular risk factors. All types of exercise improve patients' quality of life. However, there is a need for protocol standardization and selection of easily measurable endpoints. In clinical practice, it is advised that exercise implementation be performed gradually, and goals be tailored to individual pretraining fitness levels to maximize patient adherence and clinical benefits.

SUMMARY

The overall evidence suggests that exercise training is beneficial and well tolerated in hemodialysis patients, although heterogeneity across studies hinders generalization of results. In any case, a gradual and individualized approach should be used to implement exercise in these patients.

Cardiac stunning during haemodialysis: the therapeutic effect of intra-dialytic exercise

Background

Cardiovascular risk is elevated in end-stage renal disease. Left ventricular (LV) dysfunction is linked to repetitive transient ischaemia occurring during haemodialysis (HD). Cardiomyocyte ischaemia results in ‘cardiac stunning’, evidenced by regional wall motion abnormalities (RWMAs). Ischaemic RWMA have been documented during HD resulting in maladaptive cardiac remodelling and increased risk of heart failure. Intra-dialytic exercise is well tolerated and can improve quality of life and functional capacity. It may also attenuate HD-induced cardiac stunning.

Methods

This exploratory study aimed to assess the effect of intra-dialytic cycle ergometry on cardiac stunning. Twenty exercise-naïve participants on maintenance HD (mean ± SD, 59 ± 11 years) underwent resting echocardiography and maximal cardiopulmonary exercise testing. Subsequently, cardiac stunning was assessed with myocardial strain-derived RWMAs at four time points during (i) standard HD and (ii) HD with 30 min of sub-maximal intra-dialytic cycle ergometry at a workload equivalent to 90% oxygen uptake at the anaerobic threshold (VO₂AT). Central haemodynamics and cardiac troponin I were also assessed.

Results

Compared with HD alone, HD with intra-dialytic exercise significantly reduced RWMAs after 2.5 h of HD (total 110 ± 4, mean 7 ± 4 segments versus total 77 ± 3, mean 5 ± 3, respectively; P = 0.008). Global cardiac function, intra-dialytic haemodynamics and LV volumetric parameters were not significantly altered with exercise.

Conclusions

Intra-dialytic exercise reduced cardiac stunning. Thirty minutes of sub-maximal exercise at 90% VO₂AT was sufficient to elicit acute cardio-protection. These data potentially demonstrate a novel therapeutic effect of intra-dialytic exercise.