Physical training enhances sympathetic and parasympathetic control of heart rate and peripheral vessels in chronic heart failure

The ergoreflex: how the skeletal muscle modulates ventilation and cardiovascular function in health and disease

The control of ventilation and cardiovascular function during physical activity is partially regulated by the ergoreflex, a cardiorespiratory reflex activated by physical activity. Two components of the ergoreflex have been identified: the mechanoreflex, which is activated early by muscle contraction and tendon stretch, and the metaboreflex, which responds to the accumulation of metabolites in the exercising muscles. Patients with heart failure (HF) often develop a skeletal myopathy with varying degrees of severity, from a subclinical disease to cardiac cachexia. HF‐related myopathy has been associated with increased ergoreflex sensitivity, which is believed to contribute to dyspnoea on effort, fatigue and sympatho‐vagal imbalance, which are hallmarks of HF. Ergoreflex sensitivity increases significantly also in patients with neuromuscular disorders. Exercise training is a valuable therapeutic option for both HF and neuromuscular disorders to blunt ergoreflex sensitivity, restore the sympatho‐vagal balance, and increase tolerance to physical exercise. A deeper knowledge of the mechanisms mediating ergoreflex sensitivity might enable a drug or device modulation of this reflex when patients cannot exercise because of advanced skeletal myopathy.

Sympathetic neural responses in heart failure during exercise and after exercise training

The sympathetic nervous system coordinates the cardiovascular response to exercise. This regulation is impaired in both experimental and human heart failure with reduced ejection fraction (HFrEF), resulting in a state of sympathoexcitation which limits exercise capacity and contributes to adverse outcome. Exercise training can moderate sympathetic excess at rest. Recording sympathetic nerve firing during exercise is more challenging. Hence, data acquired during exercise are scant and results vary according to exercise modality. In this review we will: (1) describe sympathetic activity during various exercise modes in both experimental and human HFrEF and consider factors which influence these responses; and (2) summarise the effect of exercise training on sympathetic outflow both at rest and during exercise in both animal models and human HFrEF. We will particularly highlight studies in humans which report direct measurements of efferent sympathetic nerve traffic using intraneural recordings. Future research is required to clarify the neural afferent mechanisms which contribute to efferent sympathetic activation during exercise in HFrEF, how this may be altered by exercise training, and the impact of such attenuation on cardiac and renal function.

Isoflavone Supplementation Does Not Potentiate the Effect of Combined Exercise Training on Resting and Ambulatory Blood Pressure in Non-Obese Postmenopausal Women: A Randomized Double-Blind Controlled Trial-A Pilot Study

Physical exercise and isoflavone supplementation are potential strategies to prevent and treat cardiovascular diseases in postmenopausal women. The aim of this study was to investigate whether there are additive effects of isoflavone supplementation when associated with combined aerobic and resistance exercise on resting and ambulatory blood pressure monitoring (ABPM) and in blood pressure variability (BPV). Thirty-one non-obese postmenopausal women were randomly allocated into two groups: placebo and exercise (Placebo n = 19); and isoflavone supplementation (100 mg/day) and exercise (isoflavone n = 19). ABPM and BPV were evaluated before and after 10 weeks of moderate combined (aerobic and resistance) exercise training. Generalized Estimating Equation (GEE) with Bonferroni correction and intention-to-treat analysis was used to compare the effects of interventions on resting BP, ABPM and BPV. Combined exercise training decreased resting systolic (SBP) and diastolic blood pressure (DBP) and reduced 24 h and awake ambulatory SBP, DBP and mean blood pressure over time, with no additional effects of isoflavone supplementation. No changes were observed in sleep period, or in BPV indexes (Standard Deviation of 24 h (SD), daytime and nighttime interval (SDdn) and average real variability (ARV) in both groups. We conclude that isoflavone supplementation does not potentiate the effects of combined training on resting and ambulatorial systolic and diastolic blood pressure in non-obese postmenopausal women.

[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.

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.

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.

Effects of exercise and custom-made orthotics on blood pressure and heart rate variability: a randomized controlled pilot study

OBJECTIVE

The objective of this study is to use randomized controlled research design to investigate the effect of an exercise program and custom-made flexible orthotics on heart rate variability and blood pressure at varying stages of exercise over a 5-month period.

METHODS

Thirteen ping-pong players were recruited and randomly assigned into control and experimental groups. Both groups had the same exercise program, and only the experimental group wore custom-made flexible orthotics. Exercise effects were compared before and after the training using heart rate variability and blood pressure. The study lasted 5 months with 1 data collection per month except in the fourth month.

RESULTS

Ten male players (6 in the experimental group) completed the study. The average age of the participants was 44 +/- 16 years. The blood pressure in the experimental group significantly decreased after the 5-month study period and after each exercise session. The blood pressure did not change significantly after each exercise session in the control group. The heart rate was significantly increased immediately after exercise and remained at a higher level after the 20 minutes of rest at the end of each day's exercise session. The average resting heart rate decreased from 69.7 +/- 1.708 to 66.8 +/- 4.480 (P < .05) in the experimental group but increased from 69.7 +/- 1.708 to 90.7 +/- 2.808 (P > .05) in the control group. The total power reflecting the total autonomic activity was significantly decreased immediately after exercise and after the 20-minute rest period at the end of the exercise session in both the control and experimental groups.

CONCLUSIONS

There were positive changes in cardiac and vascular autonomic regulations with exercise training when combined with foot orthotics.

Effect of endurance training on blood pressure regulation, biomarkers and the heart in subjects at a higher age

We reported previously that two otherwise identical training programs at lower (LI) and higher intensity (HI) similarly reduced resting systolic blood pressure (BP) by approximately 4-6 mmHg. Here, we determined the effects of both programs on BP-regulating mechanisms, on biomarkers of systemic inflammation and prothrombotic state and on the heart. In this cross-over study (3 × 10 weeks), healthy participants exercised three times 1 h/week at, respectively, 33% and 66% of the heart rate (HR) reserve, in a random order, with a sedentary period in between. Measurements, performed at baseline and at the end of each period, involved blood sampling, HR variability, systolic BP variability (SBPV) and cardiac magnetic resonance imaging. Thirty-nine participants (18 men; mean age 59 years) completed the study. Responses were not different between both programs (P>0.05). Pooled data from LI and HI showed a reduction in HR (-4.3 ± 8.1%) and an increase in stroke volume (+11 ± 23.1%). No significant effect was seen on SBPV, plasma renin activity, basal nitric oxide and left ventricular mass. Our results suggest that the BP reduction observed appears to be due to a decrease in systemic vascular resistance; training intensity does not significantly affect the results on mechanisms, biomarkers and the heart.

Sympathetic nervous system activation in human heart failure: clinical implications of an updated model

Disturbances in cardiovascular neural regulation, influencing both disease course and survival, progress as heart failure worsens. Heart failure due to left ventricular systolic dysfunction has long been considered a state of generalized sympathetic activation, itself a reflex response to alterations in cardiac and peripheral hemodynamics that is initially appropriate, but ultimately pathological. Because arterial baroreceptor reflex vagal control of heart rate is impaired early in heart failure, a parallel reduction in its reflex buffering of sympathetic outflow has been assumed. However, it is now recognized that: 1) the time course and magnitude of sympathetic activation are target organ-specific, not generalized, and independent of ventricular systolic function; and 2) human heart failure is characterized by rapidly responsive arterial baroreflex regulation of muscle sympathetic nerve activity (MSNA), attenuated cardiopulmonary reflex modulation of MSNA, a cardiac sympathoexcitatory reflex related to increased cardiopulmonary filling pressure, and by individual variation in nonbaroreflex-mediated sympathoexcitatory mechanisms, including coexisting sleep apnea, myocardial ischemia, obesity, and reflexes from exercising muscle. Thus, sympathetic activation in the setting of impaired systolic function reflects the net balance and interaction between appropriate reflex compensatory responses to impaired systolic function and excitatory stimuli that elicit adrenergic responses in excess of homeostatic requirements. Recent observations have been incorporated into an updated model of cardiovascular neural regulation in chronic heart failure due to ventricular systolic dysfunction, with implications for the clinical evaluation of patients, application of current treatment, and development of new therapies.

Cardiac autonomic neural remodeling and susceptibility to sudden cardiac death: effect of endurance exercise training

Sudden cardiac death resulting from ventricular tachyarrhythmias remains the leading cause of death in industrially developed countries, accounting for between 300,000 and 500,000 deaths each year in the United States. Yet, despite the enormity of this problem, both the identification of factors contributing to ventricular fibrillation as well as the development of safe and effective antiarrhythmic agents remain elusive. Subnormal cardiac parasympathetic regulation coupled with an elevated cardiac sympathetic activation may allow for the formation of malignant ventricular arrhythmias. In particular, myocardial infarction can reduce cardiac parasympathetic regulation and alter beta-adrenoceptor subtype expression enhancing beta(2)-adrenoceptor sensitivity that can lead to intracellular calcium dysregulation and arrhythmias. As such, myocardial infarction can induce a remodeling of cardiac autonomic regulation that may be required to maintain cardiac pump function. If alterations in cardiac autonomic regulation play an important role in the genesis of life-threatening arrhythmias, then one would predict that interventions designed to either augment parasympathetic activity and/or reduce cardiac adrenergic activity would also protect against ventricular fibrillation. Recently, studies using a canine model of sudden death demonstrate that endurance exercise training (treadmill running) enhanced cardiac parasympathetic regulation (increased heart rate variability), restored a more normal beta-adrenoceptor balance (i.e., reduced beta(2)-adrenoceptor sensitivity and expression), and protected against ventricular fibrillation induced by acute myocardial ischemia. Thus exercise training may reverse the autonomic neural remodeling induced by myocardial infarction and thereby enhance the electrical stability of the heart in individuals shown to be at an increased risk for sudden cardiac death.

Trimetazidine potentiates the effects of exercise training in patients with ischemic cardiomyopathy referred for cardiac rehabilitation

BACKGROUND

Patients referred for cardiac rehabilitation may take advantage from combining trimetazidine (TMZ) with exercise training (ET), as both treatments produce similar effects in the cardiovascular system. It is, however, unknown whether the combination of TMZ with ET may determine greater improvements in functional capacity and endothelial function than ET alone.

DESIGN

A randomized longitudinal controlled study.

METHODS

We studied 116 patients (97 men and 19 women, mean age 58+/-9 years) with ischemic heart disease and left ventricular dysfunction who were referred for cardiac rehabilitation. Coronary risk factors were present in 82 patients (diabetes in 28 patients). Patients were randomized into three matched groups. A group (TMZ+training, TT, n=30) received TMZ at doses of 20 mg three times daily orally for 8 weeks in addition to standard medications and underwent a supervised program of ET at 60% of oxygen uptake at peak, three times a week for 8 weeks. A group (exercise, E, n=30) completed the ET program without receiving TMZ. A control group (C, n=26) was neither exercised nor received TMZ. A fourth group (TMZ, n=30) receiving TMZ 20 mg three times daily for 8 weeks was also studied. On study entry and at 8 weeks all patients underwent echocardiography, cardiopulmonary exercise testing, and vasomotor reactivity of the brachial artery.

RESULTS

Oxygen uptake at peak was significantly increased in the TT (25%), TMZ (15.1%), and E group (15.3%) (P<0.001 TT vs. C; P<0.05 vs. TMZ and E). Left ventricular ejection fraction was also improved in TT (18.4%), TMZ (15.7%), and E (12.9%) (P<0.001 TT vs. C; P<0.05 vs. TMZ and E), as a result of reduction in end-systolic volume. The endothelium-dependent dilation was similarly improved (P<0.001 TMZ vs. C; P<0.05 vs. TMZ and E). The most significant improvements were observed in the subgroup TT with multiple risk factors.

CONCLUSION

The addition of TMZ to ET determined greater improvements in functional capacity, left ventricular ejection fraction, and endothelium-dependent dilation than TMZ or ET given alone. No differences between improvements after TMZ and E as compared with controls were observed.

Central haemodynamics and peripheral muscle function during exercise in patients with chronic heart failure

In this narrative review of the current literature, we examine the central and peripheral mechanisms responsible for the exercise intolerance of chronic heart failure and highlight briefly the benefits of exercise training in the treatment of this debilitating disorder. Specifically, we identify the common finding of reduced cardiac output reserve during exercise conditions leading to decreased exercise tolerance. We also reveal that the stroke volume response to exercise varies depending on the individual patient, the presence of mitral regurgitation, and the aetiology of heart failure. Chronic heart failure patients with left ventricular systolic dysfunction appear able to use the Frank-Starling mechanism to compensate (in part) for their decreased contractile reserve. Patients with left ventricular diastolic dysfunction have normal contractile function; however, they are unable to make use of the Frank-Starling mechanism during exercise conditions. We also reveal that pericardial constraint may limit diastolic filling and exercise capacity in patients with chronic heart failure. It appears that interventions that reduce pericardial constraint and mitral regurgitation enhance diastolic filling and increase exercise tolerance. A series of peripheral muscle changes also occur, including changes in muscle mass, cellular structure, energy metabolism, and blood flow. Each of these factors is associated with decreased exercise capacity and the symptoms of chronic heart failure. Exercise training has been shown to improve both central haemodynamics and peripheral muscle function leading to improvements in exercise capacity, functional status, and overall quality of life in patients with chronic heart failure.

Improved exercise tolerance and cardiac function in severe chronic heart failure patients undergoing a supervised exercise program

BACKGROUND

Exercise intolerance is a widespread and serious problem in chronic heart failure (CHF) patients. However, the impact of a supervised exercise and rehabilitation program on exercise tolerance and cardiac performance in severe CHF patients has not yet been fully investigated.

METHODS

Of 56 consecutive patients with severe CHF (New York Heart Association functional class III, Stage D) 44 underwent a hospital-based supervised 18-week, cardiac exercise and rehabilitation program (exercise group), and 12 did not (control group). Cardiac performance was assessed by a 6-minute walk test, peak exercise VO(2), exercise duration time, resting and immediate post peak exercise stroke index (SI), cardiac index (CI) and systemic vascular resistance (SVR), before and after exercise.

RESULTS

Both groups were comparable regarding baseline clinical characteristics. Post exercise training, functional and hemodynamic parameters improved significantly in the exercise group compared to controls. A highly significant interaction between the groups and change was found in the 6-minute walk test (p<0.001), exercise test duration (p<0.001), METs during exercise (p<0.001), immediate post peak exercise CI (0.016), delta peak VO(2) (p=0.028), and immediate post peak exercise SVR (p=0.045).

CONCLUSIONS

A hospital-based supervised exercise and rehabilitation program significantly improves functional and hemodynamic parameters in severe CHF patients, and may partially contribute to better physical conditioning detected in these patients after exercise training.

Exercise training improves aortic depressor nerve sensitivity in rats with ischemia-induced heart failure

Exercise training improves arterial baroreflex control in heart failure (HF) rabbits. However, the mechanisms involved in the amelioration of baroreflex control are unknown. We tested the hypothesis that exercise training would increase the afferent aortic depressor nerve activity (AODN) sensitivity in ischemic-induced HF rats. Twenty ischemic-induced HF rats were divided into trained ( n = 11) and untrained ( n = 9) groups. Nine normal control rats were also studied. Power spectral analysis of pulse interval, systolic blood pressure, renal sympathetic nerve activity (RSNA), and AODN were analyzed by means of autoregressive parametric spectral and cross-spectral algorithms. Spontaneous baroreflex sensitivity of heart rate (HR) and RSNA were analyzed during spontaneous variation of systolic blood pressure. Left ventricular end-diastolic pressure was higher in HF rats compared with that in the normal control group ( P = 0.0001). Trained HF rats had a peak oxygen uptake higher than untrained rats and similar to normal controls ( P = 0.01). Trained HF rats had lower low-frequency [1.8 ± 0.2 vs. 14.6 ± 3 normalized units (nu), P = 0.0003] and higher high-frequency (97.9 ± 0.2 vs. 85.0 ± 3 nu, P = 0.0005) components of pulse interval than untrained rats. Trained HF rats had higher spontaneous baroreceptor sensitivity of HR (1.19 ± 0.2 vs. 0.51 ± 0.1 ms/mmHg, P = 0.003) and RSNA [2.69 ± 0.4 vs. 1.29 ± 0.3 arbitrary units (au)/mmHg, P = 0.04] than untrained rats. In HF rats, exercise training increased spontaneous AODN sensitivity toward normal levels (trained HF rats, 1,791 ± 215; untrained HF rats, 1,150 ± 158; and normal control rats, 2,064 ± 327 au/mmHg, P = 0.05). In conclusion, exercise training improves AODN sensitivity in HF rats.

Long-term versus intermediate-term supervised exercise training in advanced heart failure: Effects on exercise tolerance and mortality

AIM

To date there have been no studies exploring the effects of long-term versus intermediate-term and short-term supervised exercise training program in patients with severe chronic heart failure (CHF) on optimal medical therapy. We assessed exercise tolerance and mortality in CHF patients undergoing long- versus intermediate-term exercise training (ET).

METHODS

Forty-two consecutive severe CHF patients (New York Heart Association functional class III) were referred for a supervised exercise and cardiac rehabilitation program and were followed-up for 3 years: 20/42 (48%) patients discontinued ET after intermediate-term period of 1.6+/-0.8 years (Group A, intermediate-term ET), and 22/42 (52%) remained on the ET program for 3.0+/-0.3 years (Group B, long-term ET). Exercise duration, 6-min walked distance and metabolic equivalents (METs) assessed by modified Bruce protocol were recorded before, 4.5 months after, and 3 years after initiation of ET.

RESULTS

Both groups were comparable regarding age, gender, prevalence of ischemic etiology, mean ejection fraction and medications. Risk factors for ischemic heart disease were similar, except for the prevalence of diabetes, which was higher in Group A compared to Group B (11/20 versus 5/22, p=0.03). Significantly more Group A patients died after ET discontinuation (4/20 versus 0/22, p=0.01). At the end of follow-up a significant improvement could be seen in Group B patients compared to A in exercise duration, 6-min walked distance and metabolic equivalents (p<0.01 for all).

CONCLUSIONS

Higher survival rate was observed in severe CHF patients undergoing long-term versus intermediate-term exercise training. Long-term supervised exercise training is safe and improves exercise tolerance in these patients.

Exercise and the heart failure patient: aerobic vs strength training--is there a need for both?

Heart failure (HF) is characterized by general muscular weakness, muscle atrophy, and exercise intolerance that lead to reductions in functional capacity, ability to perform activities of daily living, and health-related quality of life. Until recently, exercise programs for patients with HF were centered on aerobic exercise training alone. Although many activities of daily living require significant muscle strength, the role of strength training for HF patients, either alone or in combination with aerobic exercise, has not been well studied. There is suggestive evidence that combined strength-aerobic exercise training may offer additional benefits in terms of health-related quality of life and functional capacity. Strength training can be targeted to reduce muscle atrophy to a greater extent than aerobic training. Further research is required to isolate the specific role of strength training regarding improvements in prognosis, HF-related morbidity and hospitalization, and health-related quality of life for patients with HF.

Clinical benefits of a metabolic approach in the cardiac rehabilitation of patients with coronary artery disease

Patients referred for cardiac rehabilitation may benefit from combining trimetazidine with exercise training because both treatments produce synergic benefits on the cardiovascular system. There is evidence that trimetazidine improves left ventricular (LV) function in patients with ischemic and diabetic cardiomyopathy by shifting the cellular energy substrate reference from fatty acids to glucose oxidation, and that this effect is associated with a better outcome. Recently, results have demonstrated that trimetazidine improves radial artery endothelium-dependent relaxation related to its antioxidant properties. Similarly, exercise training has been demonstrated to improve diastolic filling and systolic function in patients with ischemic cardiomyopathy, in relation to enhanced perfusion and contractility of dysfunctional myocardium. Patients with viable myocardium, in theory, should have the greatest benefits because trimetazidine improves contractility of dysfunctional hibernating/stunned myocardium, whereas exercise has documented efficacy in improving endothelial vasomotor response of coronary arteries, stimulating coronary collateral circulation and small vessel growth, improving LV function, and increasing functional capacity. At present, there are no published reports about the efficacy of the combination of trimetazidine with exercise training. In this article, we discuss the rationale for using trimetazidine in cardiac rehabilitation, the identification of patients referred for cardiac rehabilitation who might benefit the most from the addition of trimetazidine to standard therapy, and the documented benefits.

An alternative approach for exercise prescription and efficacy testing in patients with chronic heart failure: a randomized controlled training study

BACKGROUND

Prescription of endurance training and documentation of its efficacy in patients with chronic heart failure (CHF) is usually done with reference to maximal ergometric measurements which are subject to form on the day changes and motivational influences. However, the use of submaximal parameters might represent an alternative approach.

METHODS

This was tested in 54 patients with CHF (57 +/- 10 years, NYHA II: n = 40; NYHA III: n = 14) who were randomized into training (T; n = 26) or control group (CO; n = 28). Training consisted of 45 minutes cycling at an intensity corresponding to the anaerobic threshold (AT) and was conducted for 12 weeks, 4 to 5 times per week. Cardiorespiratory exercise testing was done before and after the experimental phase. Changes in well-being were investigated using a 5-point Likert scale.

RESULTS

A significant rightward shift in the heart rate curve was demonstrated in T compared with CO (P = .01; T: decrease in resting heart rate by 8 per minute, during exercise by 7 to 11/min; CO: -1 and -1 to -3 per minute, respectively). Anaerobic threshold increased significantly by 11.6% in T (+0.11 +/- 0.11 L min(-1) oxygen uptake) compared with CO (-0.02 +/- 0.10 L min(-1)). Positive changes in well-being were significantly larger in T (P < .01).

CONCLUSIONS

In patients with CHF, training can be prescribed and its efficacy can be evaluated by the exclusive use of submaximal parameters. Anaerobic threshold represents an appropriate training intensity in this population.

Exercise programmes for patients with chronic heart failure

The safety and efficacy of exercise training in patients with chronic heart failure (CHF) have been reported in a large number of scientific studies, with endurance training representing the most frequently applied training stimulus. Beneath the common continuous method of endurance training, the interval method (short bouts of intense exercise interspersed with pre-scheduled rest intervals), was also applied in some studies. Ergometric testing is a prerequisite for all individualised training prescription and is an appropriate method of efficacy documentation. However, there is a surprisingly large range of exercise intensities being prescribed to patients with CHF. Most of the prescription models refer to maximal ergometric measurements. Submaximal references from lactate and ventilatory curves represent an alternative method in measuring accuracy and efficacy of training. The course of heart rate during submaximal incremental exercise can be reliably used to indicate endurance gains in CHF. Some positive reports exist for carefully executed strength endurance training for patients with CHF and there are convincing arguments for the use of coordination and flexibility exercises; however, substantial scientific evidence is lacking.

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

BACKGROUND

Heart rate variability (HRV) is decreased in patients with congestive heart failure (CHF) and is a prognostic marker in this disease. Exercise training is now regarded as an important part of the treatment of patients with CHF, but the effect on HRV and the association between this effect and the effect on neurohormones are not well assessed.

METHODS

Heart rate recording was performed in 12 patients with CHF (mean age 67+/-8 years) with CHF NYHA functional class III, before and after 12 weeks of exercise training. The association with exercise capacity and serum levels of atrial natriuretic peptide was assessed. We also evaluated the correlation between HRV and survival at follow-up 87 months later.

RESULTS

At baseline there was a significant correlation between mean heart rate and work performed during max cycle test (r=0.650, P=0.022) and the HRV parameter standard deviation normal to normal (SDNN) (r=0.678, P=0.015). After exercise training there was a significant increase in work performed (30.3+/-14.2 versus 38.1+/-14.1 kJ), 6-min walk test (502+/-88 versus 552+/-59 m, P=0.006) and SDNN (117.3+/-40.7 versus 128.6+/-42.3 ms, P=0.028). At 87 months of follow-up, there was a borderline significant difference between survivors and non-survivors. Only the survivors had a significant increase in SDNN after exercise training.

CONCLUSION

This pilot study demonstrates an improvement with regard to parameters for HRV after exercise training in patients with CHF. The study suggests that the positive effect of exercise training in patients with CHF involves an attenuation of the reduced HRV response, and that this improvement might have prognostic significance.

Physical training and heart rate and blood pressure variability: a 5-yr randomized trial

We studied the effect of regular physical activity on cardiac and vascular autonomic modulation during a 5-yr controlled randomized training intervention in a representative sample of older Finnish men. Heart rate variability (HRV) and blood pressure variability (BPV) are markers of cardiac and vascular health, reflecting cardiac and vascular autonomic modulation. One hundred and forty randomly selected 53- to 63-yr-old men were randomized into two identical groups: an intervention (EX) group and a reference (CO) group, of which 89 men remained until the final analysis (EX: n = 47; CO: n = 42). The EX group trained for 30–60 min three to five times a week with an intensity of 40–60% of maximal oxygen consumption. The mean weekly energy expenditure of the training program for the 5-yr training period was 3.80 MJ, and 71% of the EX group exceeded the mean. The EX group had a significantly ( P < 0.01) higher oxygen consumption at ventilatory aerobic threshold (V̇o2VT) than the CO group at the 5-yr time point. V̇o2VT had a tendency to increase in the EX group and decrease in the CO group (interaction P < 0.001) from the baseline to the 5-yr time point. Peak performance did not change. Low-frequency power of R-R interval variability decreased in the EX group ( P < 0.01, by 6%) from the baseline to the 5-yr time point. BPV did not change. In conclusion, low-intensity regular exercise training did not prevent HRV from decreasing or change BPV in 5 yr in older Finnish men.

Neurohormonal abnormalities in heart failure: impact of exercise training

Endurance exercise training appears to beneficially alter the clinical course of chronic heart failure. The specific mechanisms responsible for exercise-induced benefits, however, are not completely understood. This review examines the impact of endurance exercise training on neurohormonal mechanisms, which play a central role in the progression of chronic heart failure. Few studies, however, have been specifically designed to elucidate exercise-induced mechanisms responsible for the suppression of neurohormonal activation in patients with chronic heart failure and the literature on this topic is derived from a limited number of small, single-center studies. The available data suggests that endurance exercise training programs of moderate duration (approximately 16 weeks) are efficacious in suppressing circulating levels of catecholamines, angiotensin II, arginine vasopressin, and aldosterone. Additionally, endurance exercise training improves baroreceptor sensitivity and heart rate variability, suggesting that exercise ameliorates the autonomic derangement in chronic heart failure by increasing the parasympathetically mediated component of heart rate variability. Pharmacologic suppression of sympathetic activity has proved, by and large, to be successful at reducing mortality in patients with chronic heart failure. Exercise-induced modulation of sympathetic activity may also be instrumental at reducing morbidity and mortality but this has not been carefully investigated and is a fertile area for further research.

Mortality, cardiac vagal control and physical training--what's the link?

There is little doubt that regular exercise results in increases in life expectancy and protects against adverse cardiac events in both healthy subjects and patients with cardiovascular disease. The mechanism of action of physical training remains unclear but a variety of evidence points towards an enhancement in cardiac vagal activity protecting against lethal arrhythmias. Just how physical training increases cardiac vagal activity is an area that is ill understood but plausible mechanisms include mediation via angiotensin II or NO. Further research is needed in this area. Exercise training is demanding and difficult, particularly for patients with cardiac disease. If the mechanism of increase in cardiac vagal activity with training can be determined it may be possible to use pharmacological approaches to mimic the effects of exercise with potentially beneficial effects.

Effects of endurance training on heart rate and blood pressure variability

PURPOSE

To study the influences of a 1-year controlled, randomized endurance exercise training period on heart rate (HR) and blood pressure variability in a representative sample of Finnish men in their late middle age.

METHODS AND RESULTS

Subjects were 140 sedentary men aged 53-63 years. The men were randomized into two identical groups: an intervention (EX) and a reference (CO) group. One hundred and twelve of them remained in the final analysis (EX: n=59, CO: n=53). EX trained for 30-60 min three to five times a week with the intensity of 40-60% of maximal oxygen consumption. In EX, 1 year of regular exercise training increased oxygen consumption at respiratory compensation threshold by 11% (P < or = 0.001) in a maximal cardiorespiratory test. Total power and very low frequency power of R-R interval variability (ms2) tended to increase in the EX group by 26 and 42% and to decrease in the CO group by 13 and 10% (interaction P<0.05 and P<0.01), respectively. There were no significant changes in blood pressure variability.

CONCLUSION

Regular low- to moderate-intensity exercise training could retard the declining tendency in cardiac autonomic nervous function in older men during 1 year.

Exercise and heart failure

Chronic heart failure (CHF) is a common condition with a poor prognosis, commonly associated with poor exercise tolerance and debilitation symptoms despite optimal modern therapy. Recent investigations have shown that the degree of exercise limitation may be related to pathophysiological changes that occur systemically in the patient with CHF. Exercise training in carefully selected stable patients with heart failure has been shown to be safe to correct many of these pathophysiological changes in the periphery and to lead to worthwhile improvements in exercise capacity. Recent studies have suggested a possible improvement in mortality and morbidity with exercise training in this patient group. This article discusses the factors limiting exercise capacity in CHF and reviews the controlled clinical trial of exercise testing in this condition.

Skeletal muscle training in chronic heart failure

Patients with heart failure are limited in their ability to tolerate exercise. Recent research has suggested that this limitation cannot be entirely attributed to cardiac or lung impairment but rather that changes in peripheral muscles may play an important role. There are objective similarities between heart failure and muscular deconditioning. Deficiencies in peripheral blood flow and skeletal muscle function, morphology, metabolism and function are present in both conditions. Moreover, an exaggerated activity of the receptors sensitive to exercise-derived metabolic signals (muscle ergoreceptors and peripheral and central chemoreceptors) leads to early and profound exercise-induced fatigue and dyspnoea. These muscle afferents contribute to the ventilatory, haemodynamic and autonomic responses to exercise both in physiological and pathological conditions, including chronic heart failure. Against this background, a skeletal muscle origin of symptoms in heart failure has been proposed. The protective effects of physical training have been described in many recent studies: training improves ventilatory control, skeletal muscle metabolism and autonomic nervous system activity. The exercise training appears to induce its beneficial effects on skeletal muscle both directly (on muscle function, histological and biochemical features) and indirectly (by reducing the activation of the muscle afferents). The metabolic mediators of these muscle afferents may become a potential target in the future therapy of heart failure symptoms.

Exercise training in heart failure

Chronic heart failure (CHF) is a common condition with a poor prognosis. It is associated with poor exercise tolerance and debilitating symptoms. These symptoms appear to be associated with pathophysiological changes that occur systemically in the patient with CHF. Exercise training in carefully selected patients has been shown to be safe and to improve exercise capacity. Many of the pathophysiological abnormalities of CHF are improved by training. Some studies have suggested a possible improvement in morbidity and mortality with training. This review analyzes the controlled clinical trials of exercise training in CHF published to date.

Automatic measurement of long-term heart rate variability by implanted single-chamber devices

Heart rate variability (HRV) measurement is an established technology for the assessment of cardiac autonomic status. Recently 24 h HRV has been shown to correlate with disease severity in heart failure. This potentially makes continuous 24 h HRV measurement suitable for monitoring of heart-failure patients. Day-to-day 24 h measurement of HRV is, in principle, feasible when implemented using implanted devices (pacemakers and defibrillators) used in patients who are predominantly in the sinus rhythm. However, a number of such devices used in heart-failure patients are single-chamber devices, in which the distinction between sinus rhythm beats and ectopic beats is problematic. The study investigates whether a reasonably accurate 24 h HRV measurement can be achieved by automatic algorithms, suitable for implementation using implanted devices, without the need for identification of ectopic beats. A set of 5321 nominal 24 h Holter recordings of cardiac patients are used. Each of the recordings contains at least one ectopic beat; approximately 30% of the recordings have more than 1% of ectopic beats. Conventional 24 h measures of HRV, that is the SDNN, HRV index, and SDANN indices, are obtained from each recording after elimination of the ectopic beats and are approximated by HRV measures computed by the same formulas without exclusion of the ectopic beats. The SDANN values are also approximated by the standard deviation of 5 min medians of all RR intervals (SDMRR measure). The errors introduced by including the ectopic beats in the HRV computation were evaluated using the Bland-Altman statistics and by Cohen's kappa statistics investigating the precision of identifying patients with depressed and preserved 24 h HRV. The SDNN measure is very sensitive to the quality of the RR interval sequence and cannot be reasonably used without distinction between sinus rhythm and ectopic beats. The HRV index measure is marginally more acceptable when used without ectopic elimination. The SDANN is rather insensitive, and its replacement by SDMRR values leads to relative errors in the region of 2-5% that are almost independent of the number of ectopic beats included. Even in recordings with a substantial proportion of ectopic beats, a practically acceptable (kappa > 0.9) identification of depressed and preserved SDANN values is possible without ectopic elimination. Thus, continuous monitoring of 24 h HRV is technically feasible within implanted devices, provided the SDANN measure is monitored and either computed from the sequence of all RR intervals or, potentially preferably, replaced by the SDMRR measure.

Autonomic control of heart rate variability in vasovagal syncope: a study of the nighttime period in 24-hour recordings

Patients experiencing vasovagal syncope have been claimed to show reduced vagal tone over 24-hour electrocardiography recordings. Assessment of sympathovagal balance in the absence of external stimuli, i.e., nighttime electrocardiography monitoring, might help to clarify if increased sympathetic activity is present in these patients. Heart rate variability was examined at nighttime in 40 patients with recurrent episodes of vasovagal syncope within the last 2 years (22 men; mean age, 37 years) and 20 comparable healthy volunteers. Time domain parameters (pNN50 [proportion of successive RR intervals difference >50 ms in %] and rMSSD [root-mean-square successive difference of RR intervals in ms]), indexes of vagal tone, and frequency domain parameters, expressing the overall heart rate variability, vagal (high frequency [HF]) and sympathetic (low frequency [LF]) activity, and autonomic balance (LF/HF ratio) were compared between groups by Mann-Whitney test. Significant (p<0.05) reduction of heart rate variability and vagal tone (pNN50 and rMSSD) were found for patients with vasovagal syncope, together with increased sympathetic activity (increased LF/HF ratio). These findings could open new insights in the pathogenesis of vasovagal syncope because of the shift of the autonomic balance toward sympathetic activation near the syncopal episode.