Effect of exercise training in patients with heart failure: a pilot study on autonomic balance assessed by heart rate variability

The effect of exercise training on heart rate variability in patients with hypertension: A systematic review and meta-analysis

We aimed to assess the effect of exercise training on heart rate variability (HRV) in hypertensive patients and to provide practical recommendations. We systematically searched seven databases for randomized controlled trials (RCTs) comparing the efficacy of exercise interventions vs. non-exercise control for HRV in adults with hypertension. HRV parameters, blood pressure (BP), and heart rate (HR) from the experimental and control groups were extracted to carry out meta-analysis. To explore the heterogeneity, we performed sensitivity analysis, sub-analysis, and meta-regression. Twelve RCTs were included, and the main results demonstrated exercise produced improvement in root mean square of successive RR-intervals differences (RMSSD) and high frequency (HF), and reductions in LF/HF, resting systolic blood pressure (SBP), and HR. The sub-analysis and meta-regression showed that AE improved more HRV indices and was effective in reducing BP compared with RE. Follow-up duration was also an important factor. Data suggests exercise training has ameliorating effects on HRV parameters, resting SBP, and HR in hypertensive patients, showing enhanced autonomic nervous system function and vagal activity. This effect may be better realized with exercise interventions of 4 weeks or more. Considering our results and the hypertension practice guidelines, we tend to recommend patients choose supervised AE.

Nine Months of Hybrid Intradialytic Exercise Training Improves Ejection Fraction and Cardiac Autonomic Nervous System Activity

Cardiovascular disease is the most common cause of death in hemodialysis (HD) patients. Intradialytic aerobic exercise training has a beneficial effect on cardiovascular system function and reduces mortality in HD patients. However, the impact of other forms of exercise on the cardiovascular system, such as hybrid exercise, is not clear. Briefly, hybrid exercise combines aerobic and strength training in the same session. The present study examined whether hybrid intradialytic exercise has long-term benefits on left ventricular function and structure and the autonomous nervous system in HD patients. In this single-group design, efficacy-based intervention, twelve stable HD patients (10M/2F, 56 ± 19 years) participated in a nine-month-long hybrid intradialytic training program. Both echocardiographic assessments of left ventricular function and structure and heart rate variability (HRV) were assessed pre, during and after the end of the HD session at baseline and after the nine-month intervention. Ejection Fraction (EF), both assessed before and at the end of the HD session, appeared to be significantly improved after the intervention period compared to the baseline values (48.7 ± 11.1 vs. 58.8 ± 6.5, p = 0.046 and 50.0 ± 13.4 vs. 56.1 ± 3.4, p = 0.054 respectively). Regarding HRV assessment, hybrid exercise training increased LF and decreased HF (p < 0.05). Both conventional Doppler and tissue Doppler imaging indices of diastolic function did not change after the intervention period (p > 0.05). In conclusion, long-term intradialytic hybrid exercise training was an effective non-pharmacological approach to improving EF and the cardiac autonomous nervous system in HD patients. Such exercise training programs could be incorporated into HD units to improve the patients’ cardiovascular health.

Impact of an exercise training program on cardiac neuronal function in heart failure patients on optimal medical therapy : A randomized Iodine-123 metaiodobenzylguanidine scintigraphy study

BACKGROUND

The syndrome of heart failure (HF) is characterized by left ventricular dysfunction and a compensatory chronic over activation of the sympathetic nervous system. We wanted to investigate if the beneficial effects of exercise training (ET) in HF patients on optimal medical therapy (OMT) are associated with alterations in cardiac sympathetic activity.

METHODS

Cardiac sympathetic activity was evaluated at baseline and after 12 weeks using metaiodobenzylguanidine scintigraphy in 23 patients with stable HF participating in the SmartEx trial. Patients with HF in New York Heart Association class II or III and left ventricular ejection fraction <35 % were randomized to three different ET groups.

RESULTS

We found no statistically significant changes in cardiac sympathetic activity after 12 weeks of ET. Heart to mediastinum (H/M) ratio at 15 minutes (0.00174 ± 0.0841, P = 0.922), H/M ratio at 4 hours (-0.00565 ± 0.1163, P = 0.818) and washout ratio (WR) (-1.2666 ± 16.5412, P = 0.717). A further group-wise analysis of the three ET groups did not show any difference between the groups.

CONCLUSION

A 12-week ET program did not alter the abnormal cardiac sympathetic activity in stable HF patients on modern OMT.

[The exercise training restores the heart rate variability in heart failure patients. A systematic review]

Cardiovascular diseases are a significant cause of morbidity and mortality in the general population. In this sense, the autonomic imbalance is the cornerstone of the pathophysiology underlying the development of these diseases. The aim of this study was to determine the efficacy of exercise training on heart rate variability (HRV) in adult patients with chronic heart failure.

METHODOLOGY

A systematic literature review was conducted in electronic databases. The considered studies were randomised clinical trials, quasi-experimental studies with non-randomised control group, quasi-experimental studies with analysis of pre- and post- intervention, and crossover studies with randomly assigned training and non-training periods. The standardised mean differences were calculated between pre- and post-intervention in both the control and experimental group.

RESULTS

Within-subject analysis of the control group showed no statistical significance in the standardised mean differences of HRV. In the experimental group, the standardised mean differences were positive for the root mean square of successive difference (+0.468±0.215; P=.032), high frequency band (HF) (0.934±0.256; P < .001) and low frequency band (LF) (< 0.415±0.096; P=.001). Moreover, the standardised mean difference was negative for LF/HF (-0.747±0.369, P=<.044). On the other hand, only 3 studies entered the comparative meta-analysis. The effect of exercise training was favourable for the experimental group in LF/HF (-2.21±95% CI: -3.83 to -0.60), HF, and LF.

CONCLUSION

The exercise training was effective in increasing HRV and restoring the autonomic balance in patients with heart failure.

Effect of physical exercise training in patients with Chagas heart disease: study protocol for a randomized controlled trial (PEACH study)

Background

The effects of exercise training on Chagas heart disease are still unclear. This study aimed to evaluate the effect of exercise training over functional capacity, cardiac function, quality of life, and biomarkers in Chagas heart disease.

Methods

The PEACH study is a superiority randomized clinical trial which will include subjects who meet the following criteria: Chagas heart disease with a left ventricular ejection fraction below 45 % with or without heart failure symptoms; clinical stability in the last 3 months; adherence to clinical treatment; and age above 18 years. The exclusion criteria are: pregnancy; neuromuscular limitations; smoking; evidence of non-chagasic heart disease; systemic conditions that limit exercise practice or cardiopulmonary exercise test; unavailability to attend the center three times a week during the intervention period; and practitioners of regular exercise. The intervention group will perform an exercise training intervention three times per week during 6 months and will be compared to the control group without exercise. Both groups will undergo the same monthly pharmaceutical and nutritional counseling as well as standard medical treatment according to the Brazilian consensus on Chagas disease. The primary outcome is functional capacity based on peak exercise oxygen consumption during cardiopulmonary exercise testing. Secondary outcomes are: cardiac function; body composition; muscle respiratory strength; microvascular reactivity; cardiac rhythm abnormalities; autonomic function; biochemical; oxidative stress and inflammatory biomarkers; and quality of life. Subjects will be evaluated at baseline, and at 3 and 6 months after randomization. Thirty patients will be randomly assigned into exercise or control groups at a ratio of 1:1.

Discussion

Findings of the present study will be useful to determine if physical exercise programs should be included as an important additional therapy in the treatment of patients with Chagas heart disease.

Trial registration

ClinicalTrials.gov ID: NCT02517632 (registered on 6 August 2015).

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-016-1553-4) contains supplementary material, which is available to authorized users.

Exercise training-induced modification in autonomic nervous system: An update for cardiac patients

Patients with cardiovascular disease show autonomic dysfunction, including sympathetic activation and vagal withdrawal, which leads to fatal events. This review aims to place sympathovagal balance as an essential element to be considered in management for cardiovascular disease patients who benefit from a cardiac rehabilitation program. Many studies showed that exercise training, as non-pharmacologic treatment, plays an important role in enhancing sympathovagal balance and could normalize levels of markers of sympathetic flow measured by microneurography, heart rate variability or plasma catecholamine levels. This alteration positively affects prognosis with cardiovascular disease. In general, cardiac rehabilitation programs include moderate-intensity and continuous aerobic exercise. Other forms of activities such as high-intensity interval training, breathing exercises, relaxation and transcutaneous electrical stimulation can improve sympathovagal balance and should be implemented in cardiac rehabilitation programs. Currently, the exercise training programs in cardiac rehabilitation are individualized to optimize health outcomes. The sports science concept of the heart rate variability (HRV)-vagal index used to manage exercise sessions (for a goal of performance) could be implemented in cardiac rehabilitation to improve cardiovascular fitness and autonomic nervous system function.

Influence of home-based telemonitored Nordic walking training on autonomic nervous system balance in heart failure patients

INTRODUCTION

Rehabilitation positively affects the modulation of the autonomic nervous system (ANS). There are no papers evaluating the influence of Nordic walking training (NW) on ANS activity among chronic heart failure (CHF) patients. The aim of study was to assess the influence of NW on ANS activity measured by heart rate variability (HRV) and heart rate turbulence (HRT) in CHF patients and its correlation with physical capacity improvement measured by peak oxygen consumption (peak VO2 [ml/kg/min]) in the cardiopulmonary exercise treadmill test (CPET).

MATERIAL AND METHODS

The study group comprised 111 CHF patients (NYHA class II-III; ejection fraction (EF) ≤ 40%). Patients were randomized (2 : 1) to 8-week NW (five times weekly) at 40-70% of maximal heart rate (training group - TG) (n = 77), or to a control group (CG) (n = 34). The effectiveness of NW was assessed by changes (delta (Δ)) in peak VO2, HRV and HRT as a result of comparing these parameters from the beginning and the end of the programme.

RESULTS

Eventually, 36 TG patients and 15 CG patients were eligible for HRV and HRT analysis. In the TG low/high frequency ratio (LF/HF) decreased (1.9 ±1.11 vs. 1.7 ±0.63, p = 0.0001) and peak VO2 increased (16.98 ±4.02 vs. 19.70 ±4.36 ml/kg/min, p < 0.0001). Favourable results in CG were not observed. The differences between TG and CG were significant: Δpeak VO2 (p = 0.0081); ΔLF/HF (p = 0.0038). An inverse correlation was found between the decrease in ΔLF/HF and the increase in Δpeak VO2 (R = -0.3830, p = 0.0211) only in the TG. Heart rate variability did not change significantly in either group.

CONCLUSIONS

Nordic walking positively affects the parasympathetic-sympathetic balance in CHF patients, which correlates with the improvement in Δpeak VO2. No significant influence of NW on HRT was observed.

Positive Effects of the Reversion of Depression on the Sympathovagal Balance after Telerehabilitation in Heart Failure Patients

BACKGROUND

Autonomic nervous system (ANS) dysfunction appears in the course of both chronic heart failure (CHF) and depression. Comprehensive cardiac rehabilitation (CCR), apart from improving physical capacity, can reduce depressive symptoms and leads to the restoration of ANS function among CHF patients. The purpose was to evaluate the influence of the reversion of depression (measured by Beck Depression Inventory [BDI] score, cut point <10) and the physical capacity improvement (measured by peak oxygen consumption [peak VO2 ; ml/kg per minute]) on the sympathovagal balance (measured by low/high frequency ratio [LF/HF]) after CCR in CHF patients.

METHODS

The study group comprised 111 CHF patients (New York Heart Association II-III; left ventricular ejection fraction ≤ 40%). Patients were randomized (2:1) to 8-week CCR based on Nordic walking training (five times weekly) at 40-70% of maximal heart rate, training group (TG) n = 77, or to control group (CG) n = 34. The effectiveness of CCR was assessed by changes-delta (Δ) in LF/HF, BDI score, and peak VO2 , as a result of comparing these parameters from the beginning and the end of the program.

RESULTS

Eventually, 46 patients in TG and 23 patients in CG were eligible for simultaneous ANS and psychological status analysis. Only in TG the LF/HF decreased 2.06 ± 1.14 versus 1.19 ± 0.80 (P < 0.0001) and peak VO2 increased 16.83 ± 3.72 versus 19.14 ± 4.20 ml/kg per minute (P < 0.0001). Favorable results in CG were not observed. The differences between TG and CG were significant: Δpeak VO2 (P < 0.0001); ΔLF/HF (P = 0.0001). Depressive symptoms were substantially reduced in both groups (TG, P = 0.0006; CG, P = 0.0490). Nevertheless, the greatest improvement of sympathovagal balance was observed in patients whose depression was reversed, thanks to the CCR in comparison to other patients from TG and the entire CG.

CONCLUSION

Positive effect of the sympatho-parasympathetic balance obtained during the home CCR based on Nordic walking training results from the additive effects of the reversion of depression and physical capacity improvement in CHF patients.

Effects of Exercise Training on Autonomic Function in Chronic Heart Failure: Systematic Review

Objectives. Cardiac autonomic imbalance accompanies the progression of chronic heart failure (CHF). It is unclear whether exercise training could modulate autonomic control in CHF. This study aimed to review systematically the effects of exercise training on heart rate recovery (HRR) and heart rate variability (HRV) in patients with CHF. Methods. Literatures were systematically searched in electronic databases and relevant references. Only published randomized controlled trials (RCTs) focusing on exercise training for CHF were eligible for inclusion. Outcome measurements included HRR and HRV parameters. Results. Eight RCTs were eligible for inclusion and provided data on 280 participants (186 men). The participants were 52–70 years of age with New York Heart Association functional class II-III of CHF. Each study examined either aerobic or resistance exercise. Two trials addressed outcome of HRR and six HRV among these studies. Two RCTs showed that moderate aerobic exercise could improve HRR at 2 minutes after exercise training in CHF. Five of six RCTs demonstrated positive effects of exercise training on HRV which revealed the increments in high frequency (HF) and decrements in LF (low frequency)/HF ratio after training. Conclusion. Participation in an exercise training program has positive effects on cardiac autonomic balance in patients with CHF.

Autonomic dysfunction assessed by EZSCAN and subclinical atherosclerosis

BACKGROUND

The present study aimed to explore the association between autonomic dysfunction and measurements of atherosclerosis in a middle-aged and elderly Chinese population.

METHODS

A population-based cross-sectional study was performed in Shanghai, China, from March to August 2010, with 5076 participants included in the analysis. Autonomic function was assessed by a novel EZSCAN test based on sudomotor function analysis. Carotid intima-media thickness (CIMT) was measured using B-mode ultrasonography and brachial-ankle pulse wave velocity (ba-PWV) was measured using an autonomic device. Participants were divided into three groups based on EZSCAN values: Group 1: EZSCAN 0-24; Group 2, EZSCAN 25-49; and Group 3, EZSCAN 50-100. These groups denoted autonomic dysfunction risk groups as follows: no risk, moderate risk and high risk, respectively.

RESULTS

The prevalence of elevated CIMT and ba-PWV increased markedly with increasing EZSCAN values (elevated CIMT 7.4%, 17.5%, and 29.7%, elevated ba-PWV 3.2%, 19.7%, and 36.5%, in Groups 1, 2, and 3, respectively; both Ptrend < 0.0001). Logistic regressions revealed that EZSCAN values ≥50 were associated with a non-significantly higher risk of elevated CIMT (odds ratio [OR] = 1.43; 95% confidence interval [CI] 0.98-2.07) and a significantly higher risk of elevated ba-PWV (OR = 2.16; 95% CI 1.25-3.71) compared with EZSCAN values <25, after controlling for conventional risk factors.

CONCLUSION

A higher EZSCAN value (≥50), an index of high autonomic dysfunction risk, was associated with an increased risk of elevated ba-PWV and CIMT. Such associations were partially explained by traditional atherosclerotic risk factors.

A randomized controlled trial of exercise training on cardiovascular and autonomic function among renal transplant recipients

BACKGROUND

There are conflicting data regarding the effects of renal transplantation (RT) on uraemic autonomic dysfunction. Moreover, no study has examined the impact of physical training on the cardiac autonomic function in RT patients. Thus, we studied the effects of exercise training on heart rate variability (HRV) and arterial baroreflex sensitivity (BRS), which are sensitive markers of cardiac autonomic outflow, in RT recipients.

METHODS

Eleven patients (Exercise group-aged 52.1 ± 5.6 years) were studied before and after 6 months of exercise training. Twelve age- and sex- matched RT patients (Sedentary) and 12 healthy sedentary individuals (Healthy), who remained untrained, served as controls. At baseline and follow-up, all the subjects underwent cardiopulmonary exercise testing for the evaluation of peak oxygen consumption (VO2peak), a tilt test for the evaluation of BRS and baroreflex effectiveness index (BEI) and an ambulatory 24-h Holter monitoring for time- and frequency-domain measures of HRV.

RESULTS

In the exercise group, VO2peak increased by 15.8% (P < 0.05) and all depressed HRV and BRS indices were significantly improved after training. Specifically, the standard deviation of all normal-to-normal (NN) intervals (SDNN) significantly increased by 92.5%, the root-mean-square of the differences between consecutive NN intervals by 45.4%, the percentage value of NN50 count by 58.2%, the high-frequency by 74.8% and low-frequency spectral power by 41.6%, BRS by 43.7% and BEI by 57.3%. None of the variables studied was altered over time in either control group.

CONCLUSIONS

The increased cardiorespiratory fitness by exercise training was associated with an improved BRS function and a modification of the sympathovagal control of HRV towards a persistent increase in parasympathetic tone. These alterations may lead to a better cardiovascular prognosis in RT recipients.

Exercise training improves heart rate variability in older patients with heart failure: a randomized, controlled, single-blinded trial

Reduced heart rate variability (HRV) in older patients with heart failure (HF) is common and indicates poor prognosis. Exercise training (ET) has been shown to improve HRV in younger patients with HF. However, the effect of ET on HRV in older patients with HF is not known. Sixty-six participants (36% men), aged 69±5 years, with HF and both preserved ejection fraction (HFPEF) and reduced ejection fraction (HFREF), were randomly assigned to 16 weeks of supervised ET (ET group) vs attention-control (AC group). Two HRV parameters (the standard deviation of all normal RR intervals [SDNN] and the root mean square of successive differences in normal RR intervals [RMSSD]) were measured at baseline and after completion of the study. When compared with the AC group, the ET group had a significantly greater increase in both SDNN (15.46±5.02 ms in ET vs 2.37±2.13 ms in AC, P=.016) and RMSSD (17.53±7.83 ms in ET vs 1.69±2.63 ms in AC, P=.003). This increase was seen in both sexes and HF categories. ET improved HRV in older patients with both HFREF and HFPEF.

Improvement of heart rate variability after exercise training and its predictors in COPD

BACKGROUND

Current literature lacks solid evidence on the improvement of heart rate variability (HRV) after exercise training in patients with COPD.

OBJECTIVES

We aimed to investigate changes in HRV after two exercise training programs in patients with COPD and to investigate the determinants of these eventual changes.

METHODS

Forty patients with COPD (FEV(1) 39 ± 13%pred) were randomized into high (n = 20) or low (n = 20) intensity exercise training (3-month duration), and had their HRV assessed by the head-up tilt test before and after either protocols. Baseline spirometry, level of daily physical activity, exercise capacity, body composition, functional status, health-related quality of life and muscle force were also assessed to investigate the determinants of improvement in HRV after the training program.

RESULTS

There was a significant improvement in HRV only after the high-intensity protocol (pre versus post; SDNN 29 ± 15 ms versus 36 ± 19 ms; rMSSD 22 ± 14 ms versus 28 ± 22 ms; p < 0.05 for both). Higher values of biceps brachialis strength, time spent walking in daily life and SDNN at baseline were determinants of improvement in HRV after the training program.

CONCLUSIONS

High-intensity exercise training improves HRV at rest and during orthostatic stimulus in patients with COPD. Better baseline total HRV, muscle force and daily physical activity level are predictors of HRV improvements after the training program.

The influence of physical activity level on heart rate variability among asthmatic adults

AIMS

The aim of the study was to evaluate the impact of physical activity levels on heart rate variability among asthmatic patients.

BACKGROUND

In recent years, heart rate variability is frequently used to assess the autonomic nervous system. The pathogenesis of asthma is probably related to autonomic dysfunction. Adequate exercise is considered beneficial to patients who suffer from asthma. However, the relationship between physical activity and the autonomic nervous system of adult asthmatic patients is still unknown.

DESIGN

A cross-sectional survey.

METHODS

A total of 54 subjects (27 healthy persons and 27 asthmatic patients matched by age and gender) were recruited for this study. Heart rate variability was determined by frequency analysis and measured in both resting and active states. The Seven-Day Physical Activity Recall was used to determine the subject's amount of weekly activity.

RESULTS

The results showed that the total power, low frequency (ms(2)), low frequency (nu) and low frequency/high frequency (nu) but not high frequency (nu) were significantly higher in healthy adults compared to asthmatic patients, no matter whether resting or exercising. In both groups, the greater the amount of moderate-to-vigorous physical activity, the higher the TP observed. However, a positive relationship between the amount of moderate-to-vigorous physical activity and low frequency (nu) and a negative relationship with high frequency (nu), respectively, was demonstrated only in asthmatic patients. There was no significant difference in heart rate variability between the asthmatic patients who engaged in more moderate-to-vigorous physical activity and the healthy patients.

CONCLUSIONS

Although the asthmatic patients had poor heart rate variability compared with healthy people, engaging in higher amounts of moderate-to-vigorous physical activity may result in a heart rate variability similar to that of healthy people.

RELEVANCE TO CLINICAL PRACTICE

The results of this study suggest that healthcare professionals should encourage asthmatic patients to take as much physical exercise as they can in their daily lives.

High-intensity interval exercise training improves heart rate variability in patients following percutaneous coronary intervention for angina pectoris

BACKGROUND

Low time domain measures of heart rate variability (HRV) have been shown to predict outcome after myocardial infarction (MI). The predictive value of HRV, when measured in patients with coronary artery disease (CAD) without MI is less clear. Further, little is known about the mechanisms of how autonomic imbalance affects outcome.

METHODS AND DESIGN

Forty patients following percutaneous coronary intervention (PCI) with stent implantation for angina pectoris were prospectively randomized to a six month supervised high-intensity interval training program (n=20) or to a control group (n=20). All patients underwent a 24-hour Holter monitoring to assess measures of HRV at baseline and at six months.

RESULTS

At baseline there were no significant differences between groups. In the training group all time domain indices and the frequency domain indices, total power and ultralow frequency of HRV, increased significantly during the training period. Mean heart rate decreased significantly. In the control group only the root mean square of differences between successive NN intervals (ln RMSSD) increased significantly. Changes in standard deviations of the average NN intervals (SDANN) and ln RMSSD were significantly correlated to changes in peak VO(2) (R=0.47 and 0.39; p<0.01 and p=0.03 respectively). HRV measures were not significantly correlated to endothelial function.

CONCLUSIONS

High-intensity exercise training over 6 months significantly improved time and frequency domain measures of HRV in patients following PCI with stent implantation. The effect on HRV was correlated to changes in peak VO(2), but not to changes in endothelial function.

Physical exercise improves the peripheral microcirculation of patients with chronic heart failure

PURPOSE

Patients with chronic heart failure (CHF) present with microcirculation alterations, partially attributed to endothelial dysfunction. Exercise training has been shown to induce beneficial effects in CHF patients. The aim of our study was to assess the effect of physical exercise on the microcirculation of CHF patients by near-infrared spectroscopy (NIRS).

METHODS

Sixteen consecutive stable CHF patients (men, n = 10; mean age = 50 +/- 12 years) participated in a 3-month rehabilitation program (3 sessions per week). All patients performed symptom-limited, ramp-incremental cardiopulmonary exercise testing on a cycle ergometer before and after the completion of the program. Measurements included peak oxygen uptake (VO2peak), VO2 at anaerobic threshold (AT), and first-degree slope of VO2 during the first minute of recovery (VO2/t slope). Tissue oxygen saturation was continuously measured by NIRS at the thenar muscle during a 3-minute vascular occlusion with a pneumatic cuff (occlusion technique) before and after the rehabilitation program.

RESULTS

The oxygen reperfusion rate (%/min) following the release of vascular occlusion increased significantly after the rehabilitation program (450 +/- 105 to 532 +/- 151, P = .004) as did vascular reactivity (from 27 +/- 13%/min to 39 +/- 21%/min, P = .006). In addition, there was a significant increase in VO2peak and AT (from 14.3 +/- 4.7 mL . kg . min to 16.7 +/- 6.3 mL . kg . min and from 9.5 +/- 3.6 mL . kg . min to 11.3 +/- 4 mL . kg . min, P = .007 and P = .012, respectively) as well as in VO2/t slope (from 0.35 +/- 0.17 to 0.51 +/- 0.07 mL . kg . min, P = .005).

CONCLUSIONS

Peripheral microcirculation of CHF patients measured by NIRS improved after the rehabilitation program. NIRS is a noninvasive technique that could be used to evaluate the effect of rehabilitation on the peripheral microcirculation of CHF patients.

Validity, prognostic value and optimal cutoff of respiratory muscle strength in patients with chronic heart failure changes with beta-blocker treatment

Background

Training studies frequently use maximum inspiratory mouth occlusion pressure (PImax) as a therapeutic target and surrogate marker. For patients on β-blocker (BBL), prognostic data allowing this extrapolation do not exist. Furthermore, the effects of BBL, mainstay of modern chronic heart failure therapy, on respiratory muscle function remain controversial. Finally, no proper separate cutoff according to treatment exists.

Design

Prospective, observational inclusion of patients with stable systolic chronic heart failure and recording of 1 year and all-time mortality for endpoint analysis.

Methods

In 686 patients, 81% men, 494 patients on BBL, PImax was measured along with clinical evaluation. The median follow-up was 50 months (interquartile range: 26–75 months).

Results

Patients with or without BBL did not differ significantly for PImax, percentage of predicted PImax or other marker of disease severity. PImax was a significant (hazard ratio: 0.925; 95% confidence interval: 0.879–0.975; χ2: 8.62) marker of adverse outcome, independent of BBL-status or aetiology. Percentage of predicted PImax was not independent of PImax. The cutoff identified through receiver-operated characteristics for 1-year mortality was 4.14 kPa for patients on BBL and 7.29 kPa for patients not on BBL. When separated accordingly, 1-year mortality was 8.5 versus 21.4%, P = 0.02, for patients not on BBL and 4.3 versus 16.2%, P < 0.001, for patients on BBL.

Conclusion

This study fills the gap between trials targeting respiratory muscle on a functional basis and the resultant prognostic information with regard to BBL. BBL lowered the optimal PImax cutoff values for risk stratification without changing the measured values of PImax. This should be considered at inclusion and evaluation of trials and interpretation of exercise parameters.

Aerobic exercise training improves autonomic nervous control in patients with COPD

OBJECTIVES

Autonomic modulation is adversely impacted in patients with chronic obstructive pulmonary disease (COPD). The purpose of the present investigation is to assess the effects of a 6-week aerobic exercise training program on autonomic modulation of heart rate in patients with COPD.

METHODS

Forty patients of both sexes with moderate-to-severe COPD were randomly allocated to aerobic exercise training (PT, n=20) or to usual care (Control, n=20). The training program consisted of lower and upper limb stretching and 30 min of treadmill exercise, 3 times per week for a 6-week period. Physiological data during symptom-limited exercise testing and the six-minute walk test (6MWT) were assessed. In addition, R-R intervals were obtained at rest and during the 6MWT. Heart rate variability was analyzed by time (rMSSD and SDNN index) and frequency domains (high frequency--HF, low frequency--LF and HF/LF ratio).

RESULTS

Peak oxygen consumption significantly improved in the training group only (p<0.05). Moreover, the training group demonstrated significant improvements (p<0.05) in blood lactate, minute ventilation, dyspnea at peak exercise, sympathetic activity, and parasympathetic activity at rest and during submaximal exercise. Lastly, a positive and significant correlation was found between change in 6MWT distance and rMSSD index (r=0.65 and p=0.001).

CONCLUSIONS

Neural control of heart rate, in addition to other clinically valuable measures, is positively altered in moderate-severe COPD patients following 6 weeks of aerobic exercise training. The improvement in submaximal performance after exercise training was associated with parasympathetic activity.

Is serial determination of inspiratory muscle strength a useful prognostic marker in chronic heart failure?

BACKGROUND

Little data exists on the prognostic role of inspiratory muscle strength (PImax) in chronic heart failure (CHF). Training studies, however, frequently use it as a therapeutic target and surrogate marker for prognosis. The prognostic value of changes of PImax that allow this extrapolation is unknown.

DESIGN

Patients with stable CHF were prospectively included and 1-year and all-time event rates recorded for endpoint analysis.

METHODS

In 158 patients (85% men; New York Heart Association functional class: 2.4+/-0.6), PImax was measured along with clinical evaluations at two visits, the initial visit and the second visit, 6.4+/-1.4 months apart. The mean follow-up was 59+/-34 months.

RESULTS

Overall, 59 patients (37%) reached the primary endpoint of death or hospitalization (endpoint positive), and overall mortality rate (secondary endpoint) was 26% (42 patients). PImax did not differ between endpoint-negative and endpoint-positive patients, both at the initial and at the second visit (8.3+/-5.6 vs. 7.3+/-3.4 kPa and 8.8+/-6.0 vs. 7.9+/-3.6 kPa, respectively; P=NS), and both groups showed increased PImax (0.6+/-2.6 vs. 0.6+/-2.8 kPa; P=NS). Cox analyses found neither the absolute nor the relative change of PImax to be significant predictors for the primary and secondary endpoints (P=NS for both), both for the 1-year and for the all-time event rates. Endpoint rates did not differ between patients showing increasing or decreasing PImax (P=NS; relative risk (RR): 0.77; 95% confidence interval: 0.47-1.27).

CONCLUSION

Trials focusing on inspiratory muscle function should use the actual levels of PImax as a surrogate marker to represent prognostic information, rather than relative or absolute changes. This is the first study to investigate the prognostic information of the changes of PImax over time, regarding both short-term and long-term morbidity and mortality in patients with stable CHF.

Effect of exercise training on autonomic derangement and neurohumoral activation in chronic heart failure

BACKGROUND

In chronic heart failure (CHF), persistent autonomic derangement and neurohumoral activation cause structural end-organ damage, decrease exercise capacity, and reduce quality of life. Beneficial effects of pharmacotherapy and of exercise training in CHF have been documented at various functional and structural levels. However, pharmacologic treatment can not yet reduce autonomic derangement and neurohumoral activation in CHF to a minimum. Various studies suggest that exercise training is effective in this respect.

METHODS AND RESULTS

After reviewing the available evidence we conclude that exercise training increases baroreflex sensitivity and heart rate variability, and reduces sympathetic outflow, plasma levels of catecholamines, angiotensin II, vasopressin, and brain natriuretic peptides at rest.

CONCLUSIONS

Exercise training has direct and reflex sympathoinhibitory beneficial effects in CHF. The mechanism by which exercise training normalizes autonomic derangement and neurohumoral activation is to elucidate for further development of CHF-related training programs aimed at maximizing efficacy while minimizing workload.

Effects of exercise training on heart rate and QT interval in healthy young individuals: are there gender differences?

AIMS

The aim of the present study was to assess the effects of exercise training on heart rate, QT interval, and on the relation between ventricular repolarization and heart rate in men and women.

METHODS AND RESULTS

A 24 h Holter recording was obtained in 80 healthy subjects (40 males) who differed for the degree of physical activity. Trained individuals showed a lower heart rate and a higher heart rate variability than sedentary subjects, independent of the gender difference in basal heart rate. Mean 24 h QTc was similar in trained and non-trained men, while a significant difference was observed between trained and non-trained women. Exercise training reduced the QT/RR slope in both genders. This effect on the QT/RR relation was more marked in women; in fact, the gender difference in the ventricular repolarization duration at low heart rate observed in sedentary subjects was no longer present among trained individuals.

CONCLUSION

The results of this study suggest that the cardiovascular response to exercise training may be different in men and women. Women may benefit more from interventions aimed to increase physical activity as a tool for prevention of cardiovascular morbidity and mortality.

Home-based exercise rehabilitation in addition to specialist heart failure nurse care: design, rationale and recruitment to the Birmingham Rehabilitation Uptake Maximisation study for patients with congestive heart failure (BRUM-CHF): a randomised controlled trial

BACKGROUND

Exercise has been shown to be beneficial for selected patients with heart failure, but questions remain over its effectiveness, cost-effectiveness and uptake in a real world setting. This paper describes the design, rationale and recruitment for a randomised controlled trial that will explore the effectiveness and uptake of a predominantly home-based exercise rehabilitation programme, as well as its cost-effectiveness and patient acceptability.

METHODS/DESIGN

Randomised controlled trial comparing specialist heart failure nurse care plus a nurse-led predominantly home-based exercise intervention against specialist heart failure nurse care alone in a multiethnic city population, served by two NHS Trusts and one primary care setting, in the United Kingdom.169 English speaking patients with stable heart failure, defined as systolic impairment (ejection fraction < or = 40%). with one or more hospital admissions with clinical heart failure or New York Heart Association (NYHA) II/III within previous 24-months were recruited.Main outcome measures at 1 year: Minnesota Living with Heart Failure Questionnaire, incremental shuttle walk test, death or admission with heart failure or myocardial infarction, health care utilisation and costs. Interviews with purposive samples of patients to gain qualitative information about acceptability and adherence to exercise, views about their treatment, self-management of their heart failure and reasons why some patients declined to participate. The records of 1639 patients managed by specialist heart failure services were screened, of which 997 (61%) were ineligible, due to ejection fraction>40%, current NYHA IV, no admission or NYHA II or more within the previous 2 years, or serious co-morbidities preventing physical activity. 642 patients were contacted: 289 (45%) declined to participate, 183 (39%) had an exclusion criterion and 169 (26%) agreed to randomisation.

DISCUSSION

Due to safety considerations for home-exercise less than half of patients treated by specialist heart failure services were eligible for the study. Many patients had co-morbidities preventing exercise and others had concerns about undertaking an exercise programme.

Is atherosclerosis a neurogenic phenomenon?

Identified risk factors for atherosclerosis include diet, age, gender, family history, stress, lifestyle, smoking, diabetes, dyslipidemias, hypertension, and HIV. The mechanistic rationale to explain these associations remains poorly understood. We believe that these seemingly unrelated entities may promote atherosclerosis through a common pathway by inducing adventitial autonomic dysfunction, specifically as an adventitial stress dysfunction of neurogenic origin. Atherosclerosis may represent a local vascular manifestation of the global autonomic dysfunction induced by age, smoking, hypertension, HIV, and diabetes. Atherosclerosis may also participate in a feed-forward cycle as aging, diabetes, dyslipidemia, and hypertension may also represent independent downstream consequences of global sympathetic bias. Chronic physiologic stress and behavioral stress can shift the autonomic balance towards a state of sympathetic predominance. The highly communicable nature of behavioral stress may partially implicate the familial association of atherosclerosis as an epigenetic phenomenon, independent of putative genetic mechanisms. Host stress, global autonomic dysfunction, and sympathetic bias may also arise from chronic maladaptive consumption of stressed foods, as organisms detect and assimilate the stress phenotypes of their dietary constituents through a process called xenohormesis. The benefits of exercise may operate through reduction of chronic physiologic stress associated with global sympathetic bias. The neurogenic adventitial stress response may explain the local tissue remodeling seen in atherosclerosis, including adventitial adipose dysfunction, inflammation, adventitial angiogenesis, thrombosis, and endothelial dysfunction. We believe that the locations of atherosclerotic lesions correspond to regions of neurogenic adventitial autonomic dysfunction, in similar fashion to the segmental patterns of involvement found in inflammatory bowel disease. The diffuse atherosclerosis exhibited in transplanted hearts may reflect a diffuse sympathetic bias of the donor heart, since tissues and organs exhibit an intrinsic sympathetic bias in the absence of an extrinsic source of autonomic hegemony. Once we regard atherosclerosis as a neurogenic phenomenon manifested in adventitial autonomic dysfunction, novel diagnostic and therapeutic paradigms become evident.

Electrocardiography of the failing heart

Structural heart disease, electrical instability, and increased sympathetic activity can generate a number of specific and nonspecific ECG changes and arrhythmias in patients with congestive heart failure (CHF). This review describes direct alterations of the P-QRS-T complex and ECG-derived parameters in CHF, together with the significance of cardiac arrhythmias, markers of atrial and ventricular electrical instability, and the parameters of sympathetic nervous system activity.

The role of exercise therapy in the treatment of patients with systolic heart failure

The predominant benefits of exercise training in systolic heart failure have been seen with aerobic training, although some information exists for the beneficial effects of resistive training as well. Although men clearly benefit from exercise training, the effects of exercise in women are less clear. Most of the studies have used supervised training 3 to 5 days a week for 8 weeks to 6 months, with 30 to 60 minutes of exercise per session. However, home exercise has been reported in a few studies, and appears to be safe and possibly efficacious. The effects of training on mortality are unknown at this time, although no study has demonstrated increased adverse events associated with training. Exercise training should be recommended for patients with stable New York Heart Association class II to III heart failure.

The dynamic range of biologic functions and variation of many environmental cues may be declining in the modern age: implications for diseases and therapeutics

We hypothesize that declining dynamic range and variation of environmental cues may contribute to health dysfunctions, and that judicious expansion of biologic dynamic ranges may be beneficial. Three disparate examples involving the endocrine, autonomic, and musculoskeletal systems are discussed. Daytime sheltering, optical shading, and nighttime use of artificial light may reduce circadian luminal variation. The resulting melatonin alterations may contribute to systemic dysfunctions. Loss of temporal variation of other hormones may contribute to biologic dysfunctions, especially those involving the hypothalamic-pituitary axis. Reduced variation of physical exertion, environmental stressors, and thermal gradients that characterize modern lifestyles may reduce the autonomic dynamic range resulting in lowered heart rate variability and a myriad of systemic dysfunctions. The health benefits of activities such as exercise, meditation, acupuncture, coitus, and laughter may operate through increasing autonomic variability. Reduced physical exertion also accounts for declining dynamic range of musculoskeletal function. The resulting muscle atrophy, fat infiltration, and sarcomere shortening may not only have deleterious local effects, but may also be involved in systemic metabolic dysfunctions such as insulin resistance. The extent to which our endogenous systems rely on environmental variation for self-tuning and the impact that under-utilization of compensatory mechanisms has on biologic function are not well understood. Modern therapeutic approaches generally result in reversion to the mean of physiologic functions and may buffer against variation. For example, beta-blockers are given to reduce adrenergic excess, insulin to treat insulin insufficiency, serotonin-reuptake inhibitors for depression, and refractive lenses for myopia. By undermining the demand for native compensatory functions, such therapeutic strategies may actually impair future ability to respond to biologic disequilibria. Generalizing from these observations, we anticipate benefits of therapeutic and lifestyle approaches that expand, rather than reduce, the dynamic range of many biologic experiences.

Paradoxical strategy for treating chronic diseases where the therapeutic effect is derived from compensatory response rather than drug effect

Reversing chronic conditions remains an elusive goal of medicine. The modern medical paradigm based on blocking overactive pathways or augmenting deficient pathways offers symptomatic benefit, but tolerance to therapy can develop and treatment cessation can produce rebound symptoms due to compensatory mechanisms. We propose a paradoxical strategy for treating chronic conditions based on harnessing compensatory mechanisms for therapeutic benefit. Many current drugs may be repurposed for a paradoxical indication where the therapeutic effect is derived from compensatory response, rather than drug effect. For example, although exercise is associated with acute adrenergia, paradoxical downregulation of baseline sympathovagal ratio occurs as a remodeling response. For conditions that manifest chronic sympathetic bias such as cardiovascular diseases, judicious administration of adrenergic agonists may induce compensatory downregulation of baseline sympathovagal ratio. The concept may generalize to many other diseases, especially those involving pathways which exhibit strong homeostatic tendencies such as the neurologic, immune, and endocrine systems. Careful consideration of chronobiologic features is necessary to optimize dosing strategies for modulating compensatory responses, and eccentric dosing schedules, shorter-acting formulations, or pulsatile delivery may be desirable in some cases. To what extent the effect of desensitization to current therapy is mistaken for disease progression in conditions such as diabetes, myopia, depression, and hypertension warrants investigation. The merits of combining behavioral and drug therapies such as diet-insulin therapy for diabetes and exercise-beta-blockade for cardiovascular disease should be revisited since there is a risk for exacerbating the underlying dysfunction. The reduced dynamic range of various environmental experiences and the tendency to revert to the mean through medical intervention, thermoregulation, and other modern lifestyle changes may play under-recognized roles in human diseases. Perhaps alternating agonists and antagonist may exercise the entire dynamic range of pathways and improve health.