Responses of plasma norepinephrine and renin-angiotensin-aldosterone system to dynamic exercise in patients with congestive heart failure

Effects of exercise training on neurovascular control and skeletal myopathy in systolic heart failure

Neurohormonal excitation and dyspnea are the hallmarks of heart failure (HF) and have long been associated with poor prognosis in HF patients. Sympathetic nerve activity (SNA) and ventilatory equivalent of carbon dioxide (VE/VO2) are elevated in moderate HF patients and increased even further in severe HF patients. The increase in SNA in HF patients is present regardless of age, sex, and etiology of systolic dysfunction. Neurohormonal activation is the major mediator of the peripheral vasoconstriction characteristic of HF patients. In addition, reduction in peripheral blood flow increases muscle inflammation, oxidative stress, and protein degradation, which is the essence of the skeletal myopathy and exercise intolerance in HF. Here we discuss the beneficial effects of exercise training on resting SNA in patients with systolic HF and its central and peripheral mechanisms of control. Furthermore, we discuss the exercise-mediated improvement in peripheral vasoconstriction in patients with HF. We will also focus on the effects of exercise training on ventilatory responses. Finally, we review the effects of exercise training on features of the skeletal myopathy in HF. In summary, exercise training plays an important role in HF, working synergistically with pharmacological therapies to ameliorate these abnormalities in clinical practice.

Effects of exercise training on circulating and skeletal muscle renin-angiotensin system in chronic heart failure rats

BACKGROUND

Accumulated evidence shows that the ACE-AngII-AT1 axis of the renin-angiotensin system (RAS) is markedly activated in chronic heart failure (CHF). Recent studies provide information that Angiotensin (Ang)-(1-7), a metabolite of AngII, counteracts the effects of AngII. However, this balance between AngII and Ang-(1-7) is still little understood in CHF. We investigated the effects of exercise training on circulating and skeletal muscle RAS in the ischemic model of CHF.

METHODS/MAIN RESULTS

Male Wistar rats underwent left coronary artery ligation or a Sham operation. They were divided into four groups: 1) Sedentary Sham (Sham-S), 2) exercise-trained Sham (Sham-Ex), sedentary CHF (CHF-S), and exercise-trained CHF (CHF-Ex). Angiotensin concentrations and ACE and ACE2 activity in the circulation and skeletal muscle (soleus and plantaris) were quantified. Skeletal muscle ACE and ACE2 protein expression, and AT1, AT2, and Mas receptor gene expression were also evaluated. CHF reduced ACE2 serum activity. Exercise training restored ACE2 and reduced ACE activity in CHF. Exercise training reduced plasma AngII concentration in both Sham and CHF rats and increased the Ang-(1-7)/AngII ratio in CHF rats. CHF and exercise training did not change skeletal muscle ACE and ACE2 activity and protein expression. CHF increased AngII levels in both soleus and plantaris muscle, and exercise training normalized them. Exercise training increased Ang-(1-7) in the plantaris muscle of CHF rats. The AT1 receptor was only increased in the soleus muscle of CHF rats, and exercise training normalized it. Exercise training increased the expression of the Mas receptor in the soleus muscle of both exercise-trained groups, and normalized it in plantaris muscle.

CONCLUSIONS

Exercise training causes a shift in RAS towards the Ang-(1-7)-Mas axis in skeletal muscle, which can be influenced by skeletal muscle metabolic characteristics. The changes in RAS circulation do not necessarily reflect the changes occurring in the RAS of skeletal muscle.

β3-Adrenergic receptor antagonist improves exercise performance in pacing-induced heart failure

In heart failure (HF), the impaired left ventricular (LV) arterial coupling and diastolic dysfunction present at rest are exacerbated during exercise. We have previously shown that in HF at rest stimulation of β3-adrenergic receptors by endogenous catecholamine depresses LV contraction and relaxation. β3-Adrenergic receptors are activated at higher concentrations of catecholamine. Thus exercise may cause increased stimulation of cardiac β3-adrenergic receptors and contribute to this abnormal response. We assessed the effect of L-748,337 (50 μg/kg iv), a selective β3-adrenergic receptor antagonist (β3-ANT), on LV dynamics during exercise in 12 chronically instrumented dogs with pacing-induced HF. Compared with HF at rest, exercise increased LV end-systolic pressure (PES), minimum LV pressure (LVPmin), and the time constant of LV relaxation (τ) with an upward shift of early diastolic portion of LV pressure-volume loop. LV contractility decreased and arterial elastance (EA) increased. LV arterial coupling (EES/EA) (0.40 vs. 0.51) was impaired. Compared with exercise in HF preparation, exercise after β3-ANT caused similar increases in heart rate and PES but significantly decreased τ (34.9 vs. 38.3 ms) and LVPmin with a downward shift of the early diastolic portion of LV pressure-volume loop and further augmented dV/dtmax. Both EES and EES/EA (0.68 vs. 0.40) were increased. LV mechanical efficiency improved from 0.39 to 0.53. In conclusion, after HF, β3-ANT improves LV diastolic filling; increases LV contractility, LV arterial coupling, and mechanical efficiency; and improves exercise performance.

Oxygen uptake kinetics in chronic heart failure: clinical and physiological aspects

One of the hallmark symptoms of patients with chronic heart failure (CHF) is exercise intolerance. Therefore, exercise testing has become an important tool for the evaluation and monitoring of heart failure. Whereas the maximal aerobic capacity (peak VO(2)) is a reliable indicator of the severity and prognosis of heart failure, submaximal exercise parameters may be more closely related to the ability to perform daily activities. As such, oxygen (O(2)) uptake kinetics, describing the rate change of O(2) uptake during onset or recovery of submaximal constant-load exercise (O(2) onset and recovery kinetics, respectively), have been shown to be useful parameters for objectively evaluating the functional capacity of CHF patients. However, their evaluation in this population is not a routine part of daily clinical practice. Possible reasons for this include a lack of standardisation of the assessment methodology and a limited number of studies evaluating the clinical use of O(2) uptake kinetics in CHF patients. In addition, the pathophysiological mechanisms underlying the delay in O(2) uptake kinetics in these patients are not completely understood. This review discusses the current literature on the clinical potency and physiological determinants of O(2) uptake kinetics in CHF patients and provides directions for future research. (Neth Heart J 2009;17:238-44.Neth Heart J 2009;17:238-44.).

Hormonal responses to the 6-minute walk test in women and men with coronary heart disease: a pilot study

BACKGROUND

Women with coronary heart disease (CHD) are more likely than men to develop congestive heart failure (CHF). Dysregulation of sympathetic and volume-regulatory hormones may contribute to the onset of symptomatic CHF. We hypothesized that this hormonal dysregulation develops at an earlier stage of CHD in women than in men.

OBJECTIVES

The study goals were (1) to determine the effect of gender on basal and exercise-induced plasma concentrations of catecholamines and volume-regulatory hormones in patients diagnosed with CHD, New York Heart Association class I and (2) to determine efficacy of the 6-minute walk test as a stimulus for release of these hormones.

METHODS

Study participants were 9 women and 9 men with normal left ventricular ejection fraction (>50%) and CHD confirmed by arteriography. Data were collected under resting conditions, and after the 6-minute walk test, in the general clinical research center of a northeastern university medical center.

RESULTS

Basal plasma vasopressin (VP) concentration was significantly higher in men than in women (P = .018). Exercise, for women and men combined, significantly increased atrial natriuretic peptide (P < .0005), VP (P = .04), norepinephrine (P < .0005), and epinephrine (P = .038) but not plasma renin activity (P = .09). No further gender differences were detected for basal levels, or for the magnitude of exercise-induced increases, for any of the hormones measured.

CONCLUSIONS

The 6-minute walk test is an exercise of sufficient intensity and duration to initiate the release of hormones associated with sympathetic activation and fluid-electrolyte regulation in both women and men with CHD. It appears that a gender difference was detected only for basal VP levels.

Neurohumoral profiles in patients with hypertrophic cardiomyopathy: differences to hypertensive left ventricular hypertrophy

BACKGROUND

Patients with hypertrophic cardiomyopathy (HCM) or hypertensive heart disease (HHD) have increased concentrations of various neurohumoral factors. Thus, the aim of the present study was to evaluate the differences in the neurohumoral profiles of HCM and HHD.

METHODS AND RESULTS

Plasma concentrations of epinephrine, norepinephrine, atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), angiotensin II and endothelin-1 were measured in 40 patients with HCM, 35 with HHD, and 15 controls. Additionally, the concentrations of these neurohumoral factors in the coronary sinus and aortic root were measured in 12 HCM patients and 10 controls. Plasma concentrations of norepinephrine, ANP and BNP were significantly higher in HCM than HHD and controls. In HCM, there was no significant correlation between the left ventricular mass index and any neurohumoral factor. The plasma BNP concentration significantly correlated with left intraventricular pressure gradient in HCM. There were significant differences in the plasma concentrations of ANP and BNP between HCM with and without left ventricular diastolic dysfunction. Transcardiac production of BNP was significantly higher in patients with obstructive HCM than in those with non-obstructive HCM.

CONCLUSIONS

The significant neurohumoral differences between HCM and HHD were the plasma concentrations of norepinephrine, ANP and BNP. In HCM patients, the plasma BNP concentration may reflect the intraventricular pressure gradient and left ventricular diastolic dysfunction whereas the plasma ANP concentration reflects only the left ventricular diastolic dysfunction.

Basal and exercise-induced neuroendocrine activation in patients with heart failure and in normal subjects

BACKGROUND

Neuroendocrine activation is a pathophysiological response and an important prognostic marker in patients with chronic heart failure (CHF). Although chronic activation is well described, data on the responsiveness of the hormone systems are more limited. Most previous studies have looked at activation during maximal exercise, whereas we believe that activation at a submaximal level might be more pathophysiologically relevant.

AIM

To compare exercise-induced neurohormonal activation between CHF patients and normal subjects using the same relative and submaximal workload.

SUBJECTS

Twenty-three newly-diagnosed CHF patients and 18 age- and gender-matched healthy subjects were exercised at two workloads, which were calculated to correspond to 50 and 75% of each individual's heart rate response.

RESULTS

In CHF patients, baseline levels of ANP, BNP, AVP, PRA and ET-1 were elevated compared to healthy subjects. Exercise induced an increase in ANP, A and NA in both CHF patients and in normal subjects, however BNP was only increased in CHF patients and not in normal subjects.

CONCLUSION

When CHF patients exercise at the same relative and submaximal level as age-matched healthy subjects, the relative increases in ANP, A and NA were similar, however, BNP levels only increased in the CHF group.

Low-level exercise echocardiography identifies contractile reserve in patients with a recent myocardial infarction: comparison with dobutamine stress echocardiography

Contractile reserve (CR) during dobutamine stress echocardiography (DSE) identifies patients with coronary artery disease whose left ventricular function and prognosis may improve after revascularization. To test the hypothesis that the early stages of upright bicycle-exercise echocardiography (LLEx) result in CR comparable with DSE, 30 patients 1 week after myocardial infarction underwent multistage LLEx and DSE. At low and peak LLEx, heart rate and systolic blood pressure were higher than DSE. Identification of CR by LLEx was concordant with DSE when analyzed by infarct zone or by individual patient. We conclude that CR can be demonstrated during LLEx that correlates with DSE in patients with a recent MI. Low-level exercise is a promising alternative to DSE for identifying contractile reserve after MI.

Attenuation of angiotensin II-mediated coronary vasoconstriction and vasodilatory action of angiotensin-converting enzyme inhibitor in pacing-induced heart failure in dogs

OBJECTIVES

We investigated the changes in coronary vascular resistance caused by angiotensin II, angiotensin-converting enzyme (ACE) inhibition and angiotensin II type 1 or 2 receptor (AT(1)R and AT(2)R, respectively) antagonists in chronic heart failure (CHF).

BACKGROUND

Angiotensin II is an intense vasoconstrictor, and increased angiotensin II in CHF might exert significant vasoconstriction.

METHODS

Eleven dogs were studied. Before and after three and five weeks of rapid pacing, coronary flow dynamics were evaluated by the coronary pressure-flow relationship (PFR) in long diastole, before and after intracoronary injection of angiotensin II, the ACE inhibitor enalaprilat, the AT(1)R antagonist L158,809 or the AT(2)R antagonist PD123319.

RESULTS

Before rapid pacing, angiotensin II reduced the slope of PFR (1.16 +/- 0.08 to 0.81 +/- 0.07 ml/min/100 g left ventricular mass per mm Hg; p < 0.01) and increased the perfusion pressure at which coronary flow ceased (zero-flow pressure [P(f) = 0]), whereas enalaprilat did not change either of them. After rapid pacing, angiotensin II did not change the slope or P(f) = 0. In contrast, enalaprilat increased the slope (three weeks: 1.20 +/- 0.05 to 1.50 +/- 0.03; five weeks: 1.25 +/- 0.19 to 1.37 +/- 0.08; both p < 0.05) and decreased P(f) = 0 after three weeks of pacing, but not after five weeks. Pretreatment with the bradykinin antagonist HOE-140 attenuated the enalaprilat-induced increase in coronary blood flow. L158,809 and PD123319 had no effect both before and after rapid pacing.

CONCLUSIONS

This suggests that the coronary vasoconstrictive effect of angiotensin II would disappear and the vasodilatory effect of the ACE inhibitor, partly through bradykinin, would be enhanced in the early stage of CHF.

Neurohumoral blockade in CHF management

Is heart failure an endocrine disease? Historically, congestive heart failure (CHF) has often been regarded as a mechanical and haemodynamic condition. However, there is now strong evidence that the activation of neuroendocrine systems, like the renin-angiotensin-aldosterone system (RAAS) and sympathetic nervous system, as well as the activation of natriuretic peptides, endothelin and vasopressin, play key roles in the progression of CHF. In this context, agents targeting neurohormones offer a highly rational approach to CHF management, with ACE inhibitors, aldosterone antagonists and beta-adrenergic blockade improving the prognosis for many patients. Although relevant improvements in clinical status and survival can be achieved with these drug classes, mortality rates for patients with CHF are still very high. Moreover, most patients do not receive these proven life-prolonging drugs, partially due to fear of adverse events, such as hypotension (with ACE inhibitors), gynaecomastia (with spironolactone) and fatigue (with beta-blockers). New agents that combine efficacy with better tolerability are therefore needed. The angiotensin II type 1 (AT(1))-receptor blockers have the potential to fulfil both these requirements, by blocking the deleterious cardiovascular and haemodynamic effects of angiotensin II while offering placebo-like tolerability. As shown with candesartan, AT(1)-receptor blockers also modulate the levels of other neurohormones, including aldosterone and atrial natriuretic peptide (ANP). Combined with its tight, long-lasting binding to AT(1)-receptors, this characteristic gives candesartan the potential for complete blockade of the RAAS-neurohormonal axis, along with the great potential to improve clinical outcomes.

Augmented responses of angiotensin I and II in patients with ischemic heart disease: relation to left ventricular function

To evaluate the effects of left ventricular (LV) dysfunction upon the sympathetic nervous and renin-aldosterone-angiotensin systems, neurohormonal factors were measured in patients with ischemic heart disease. Eleven patients were divided into two groups by their LV ejection fraction based on previous catheterization; preserved (EF > or = 60%) and impaired (EF < 60%) LV systolic function groups. They performed supine ergometer exercise and blood samples were drawn at rest and at peak exercise. After dynamic exercise, plasma norepinephrine was significantly (p < 0.05) increased in patients with preserved LV function, whereas it was not altered in patients with impaired LV function (norepinephrine 20.8 +/- 20.5 vs 45.8 +/- 41.9, respectively). We observed no differences in basal or peak levels of neurohormonal factors, including plasma renin activity, aldosterone, and brain natriuretic peptide (BNP), between the groups. Although the plasma levels of angiotensin I and II were not different in the two groups at rest or at peak exercise, their increasing ratios from rest to peak exercise were significantly higher in patients with impaired LV function compared to those with preserved LV function (angiotensin I; -18.6 +/- 31.0% vs 64.8 +/- 66.5%, p < 0.05, angiotensin II; -5.9 +/- 41.2% vs 60.7 +/- 40.4% , p < 0.05). These results suggest that the increasing ratios of angiotensin I and II are superior to BNP as predictors of LV dysfunction, and that the sympathetic nervous system has already been activated even at rest and did not respond to dynamic exercise in patients with LV dysfunction in ischemic heart disease.

Responses of catecholamines, renin-angiotensin system, and atrial natriuretic peptide to exercise in untrained men and women

1. Plasma norepinephrine (NE), epinephrine (E), renin activity (PRA), angiotensin II (ATII), aldosterone (ALD), and atrial natriuretic peptide (ANP) were measured in 20 male and 15 female subjects during submaximal treadmill test. 2. Exercise duration was not different between the two groups (male vs. female: 13.4 +/- 0.8 min vs. 11.6 +/- 0.7 min, ns). Female subjects had higher heart rate during exercise, while systolic blood pressure at peak exercise was higher in male subjects. 3. Plasma NE, E, ANP, and ATII responses were comparable between male and female subjects, but PRA both at rest and during exercise and ALD at rest were significantly higher in male subjects. 4. Cardiac responses to submaximal exercise were different between male and female subjects, but neurohormonal responses were comparable between the two groups except for the high PRA at rest and during exercise and high plasma ALD at rest in male subjects.