Impact of 6 months of therapy with carvedilol on muscle sympathetic nerve activity in heart failure patients

Abnormal neurovascular control during central and peripheral chemoreceptors stimulation in heart failure patients with preserved ejection fraction

PURPOSE

Central and peripheral chemoreceptors are hypersensitized in patients with heart failure with reduced ejection fraction. Whether this autonomic alteration occurs in patients with heart failure with preserved ejection fraction (HFpEF) remains little known. We test the hypothesis that the central and peripheral chemoreflex control of muscle sympathetic nerve activity (MSNA) is altered in HFpEF.

METHODS

Patients aged 55-80 years with symptoms of heart failure, body mass index ≤ 35 kg/m2, left ventricular ejection fraction > 50%, left atrial volume index > 34 mL/m2, left ventricular early diastolic filling velocity and early diastolic tissue velocity of mitral annulus ratio (E/e' index) ≥ 13, and BNP levels > 35 pg/mL were included in the study (HFpEF, n = 9). Patients without heart failure with preserved ejection fraction (non-HFpEF, n = 9), aged-paired, were also included in the study. Peripheral chemoreceptors stimulation (10% O2 and 90% N2, with CO2 titrated) and central chemoreceptors stimulation (7% CO2 and 93% O2) were conducted for 3 min. MSNA was evaluated by microneurography technique, and forearm blood flow (FBF) by venous occlusion plethysmography.

RESULTS

During hypoxia, MSNA responses were greater (p < 0.001) and FBF responses were lower in patients with HFpEF (p = 0.006). Likewise, MSNA responses during hypercapnia were higher (p < 0.001) and forearm vascular conductance (FVC) levels were lower (p = 0.030) in patients with HFpEF.

CONCLUSIONS

Peripheral and central chemoreflex controls of MSNA are hypersensitized in patients with HFpEF, which seems to contribute to the increase in MSNA in these patients. In addition, peripheral and central chemoreceptors stimulation in patients with HFpEF causes muscle vasoconstriction.

Ischemia and no obstructive coronary arteries (INOCA): A narrative review

Myocardial ischemia with no obstructive coronary arteries (INOCA) is a chronic coronary syndrome condition that is increasingly being recognized as a substantial contributor to adverse cardiovascular mortality and outcomes, including myocardial infarction and heart failure with preserved ejection fraction (HFpEF). While INOCA occurs in both women and men, women are more likely to have the finding of INOCA and are more adversely impacted by angina, with recurrent hospitalizations and a lower quality of life with this condition. Abnormal epicardial coronary vascular function and coronary microvascular dysfunction (CMD) have been identified in a majority of INOCA patients on invasive coronary function testing. CMD can co-exist with obstructive epicardial coronary artery disease (CAD), diffuse non-obstructive epicardial CAD, and with coronary vasospasm. Epicardial vasospasm can also occur with normal coronary arteries that have no atherosclerotic plaque on intravascular imaging. While all predisposing factors are not clearly understood, cardiometabolic risk factors, and endothelium dependent and independent mechanisms that increase oxidative stress and inflammation are associated with microvascular injury, CMD and INOCA. Cardiac autonomic dysfunction has also been implicated in abnormal vasoreactivity and persistent symptoms. INOCA is under-recognized and under-diagnosed, partly due to the heterogenous patient populations and mechanisms. However, diagnostic testing methods are available to guide INOCA management. Treatment of INOCA is evolving, and focuses on cardiac risk factor control, improving ischemia, reducing atherosclerosis progression, and improving angina and quality of life. This review focuses on INOCA, relations to HFpEF, available diagnostics, current and investigational therapeutic strategies, and knowledge gaps in this condition.

Sympathoinhibitory effect of sacubitril-valsartan in heart failure with reduced ejection fraction: A pilot study

Chronic sympathetic nervous system (SNS) overactivity, characteristic of heart failure (HF) with reduced ejection fraction (HFrEF), is associated with poor prognosis and contributes to increased mortality risk. Sacubitril-valsartan is a recently approved, first-in-class, angiotensin receptor neprilysin inhibitor (ARNI) drug that markedly reduces the risks of death from cardiovascular causes and hospitalization for HF in patients with HFrEF, but the physiological mechanisms underlying these benefits are not fully understood. This single-arm, open-label, prospective study sought to test the hypothesis that short-term treatment with sacubitril-valsartan reduces SNS activity, measured directly via muscle sympathetic nerve activity (MSNA), in patients with HFrEF. MSNA, heart rate (HR), and arterial blood pressure (BP) were assessed in stable Class II and III patients with HFrEF (n = 9, 69 ± 8 yrs.; 28.6 ± 3.6 kg/m²) on contemporary, guideline-directed medical treatment who were subsequently started on sacubitril-valsartan. These measurements were repeated after two months of treatment with sacubitril-valsartan. Sacubitril-valsartan reduced MSNA burst frequency (baseline: 43 ± 10 bursts/min; 2-month: 36 ± 10 bursts/min, p = 0.05) and burst incidence (baseline: 68 ± 16 bursts/100 heartbeats; 2-month: 55 ± 16 bursts/100 heartbeats, p = 0.02), while HR and BP were unchanged following of treatment (p > 0.05). These preliminary findings provide new evidence regarding the ability of sacubitril-valsartan to rapidly reduce SNS activity in patients with HFrEF, suggesting the presence of a novel sympathoinhibitory effect of this new drug class.

Sympathetic neural overdrive in congestive heart failure and its correlates: systematic reviews and meta-analysis

BACKGROUND AND OBJECTIVES

Sympathetic neural activation occurs in congestive heart failure (CHF). However, the small sample size of the microneurographic studies, heterogeneity of the patients examined, presence of comorbidities as well as confounders (including treatment) represented major weaknesses not allowing to identify the major features of the phoenomenon, particularly in mild CHF. This meta-analysis evaluated 2530 heart failure (CHF) patients recruited in 106 microneurographic studies. It was based on muscle sympathetic nerve activity (MSNA) quantification in CHF of different clinical severity, but data from less widely addressed conditions, such as ischemic vs. idiopathic, were also considered.

METHODS

Assessment was extended to the relationships of MSNA with venous plasma norepinephrine, heart rate (HR) and echocardiographic parameters of cardiac morphology [left ventricular (LV) end-diastolic diameter] and function (LV ejection fraction) as well.

RESULTS

MSNA was significantly greater (1.9 times, P < 0.001) in CHF patients as compared with healthy controls, a progressive significant increase being observed from New York Heart Association classes I-IV in unadjusted and adjusted analyses. MSNA was significantly greater in both untreated and treated CHF (P < 0.001 for both), related to left ventricular (LV) end-diastolic diameter and to a lesser extent to LV ejection fraction (r = 0.24 and -0.05, P < 0.001 and <0.01, respectively), and closely associated with HR (r = 0.66, P < 0.001) and plasma norepinephrine (r = 0.68, P < 0.001).

CONCLUSION

CHF is characterized by sympathetic overactivity which mirrors the degree of LV dysfunction independently of the stage of CHF, its cause and presence of confounders or pharmacological treatment. plasma norepinephrine and HR represent potentially valuable surrogate markers of sympathetic activation in the clinical setting.

Sympathetic and baroreflex alterations in congestive heart failure with preserved, midrange and reduced ejection fraction

AIM

Although abnormalities in reflex sympathetic neural function represent a hallmark of heart failure, no information is available on the neuroadrenergic and baroreflex function in heart failure with preserved, midrange and reduced ejection fraction. The current study was designed to assess muscle sympathetic nerve traffic (MSNA) and baroreflex function in the clinical classes of heart failure defined by the new European Society of Cardiology/American College of Cardiology Foundation/American Heart Association guidelines.

METHODS

In 32 treated heart failure patients aged 69.3 ± 1.1 (mean ± SEM) classified according to new heart failure guidelines, we measured MSNA (microneurography), spontaneous baroreflex sensitivity and venous plasma norepinephrine (HPLC). Fourteen age-matched healthy individuals represented the control group.

RESULTS

MSNA was progressively and significantly increased from controls to heart failure conditions characterized by preserved, midrange and reduced ejection fraction (40.4 ± 2.5, 55.6 ± 2.1, 70.4 ± 3 and 78.6 ± 2.6 bursts/100 heart beats, P < 0.01). In contrast, plasma norepinephrine was significantly increased in heart failure with reduced ejection fraction only. Baroreflex sensitivity was significantly reduced in the latter two clinical conditions and almost unaltered in heart failure with preserved ejection fraction. There was an inverse relationship between different markers of adrenergic activity (MSNA, heart rate and plasma norepinephrine), left ventricular ejection fraction and baroreflex function. Brain natriuretic peptides were directly and significantly related to MSNA and plasma norepinephrine.

CONCLUSION

Thus clinical categories of heart failure patients defined by the new European Society of Cardiology/American College of Cardiology Foundation/American Heart Association classification share as a common pathophysiological link the marked overactivity of the sympathetic nervous system, whose magnitude is significantly and strongly related to the impairment of the left ventricular ejection fraction. A baroreflex dysfunction accompanies in the more severe heart failure state the neuroadrenergic activation.

Cardiac and Peripheral Autonomic Responses to Orthostatic Stress During Transcutaneous Vagus Nerve Stimulation in Healthy Subjects

Previous studies showed that transcutaneous vagus nerve stimulation (tVNS) modulates the autonomic nervous system (ANS) in resting condition. However, the autonomic regulation in response to an orthostatic challenge during tVNS in healthy subjects remains unknown. We tested the hypothesis that tVNS reduces heart rate (HR) and alters the responsivity of ANS to orthostatic stress in healthy subjects. In a randomized and cross-over trial, thirteen healthy subjects underwent two experimental sessions on different days: (1) tVNS and (2) control. Using a tVNS device, an auricular electrode was placed on the left cymba conchae of the external ear; an electric current with a pulse frequency of 25 Hz and amplitude between 1 and 6 mA was applied. For the assessment of ANS, the beat-to-beat HR and systolic arterial pressure (SAP) were analyzed using linear and nonlinear approaches during clinostatic and orthostatic conditions. In clinostatic conditions, tVNS reduced HR (p < 0.01), SAP variability (p < 0.01), and cardiac and peripheral sympathetic modulation (p < 0.01). The responsivity of the peripheral sympathetic modulation to orthostatic stress during tVNS was significantly higher when compared to the control session (p = 0.03). In conclusion, tVNS reduces the HR and affects cardiac and peripheral autonomic control and increases the responses of peripheral autonomic control to orthostatic stress in healthy subjects.

Transcatheter Aortic Valve Implantation Improves Cardiac Sympathetic Nerve Activity on 123I-Metaiodobenzylguanidine Myocardial Scintigraphy in Severe Aortic Valve Stenosis

BACKGROUND

There is a consensus that overactivation of the cardiac sympathetic nervous system (CSN) proportionately increases the severity of heart failure and is accompanied by worse prognosis. Because it is unknown whether patients with aortic valve stenosis (AS) have similar CSN activation, we investigated the effect of transcatheter aortic valve implantation (TAVI).Methods and Results:We enrolled 31 consecutive patients with AS treated by TAVI. ¹²³I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy was performed at baseline and at 2 weeks after TAVI. At baseline, the early heart-mediastinum ratio (H/M) was within normal limits (3.0±0.5), but the delayed H/M was low (2.6±0.6) and the washout rate (WR) was high (34±13%). WR negatively correlated with aortic valve area (r=-0.389, P<0.01) and cardiac output (r=-0.595, P<0.01) and positively correlated with norepinephrine (r=0.519, P<0.01) and log NT-proBNP level (r=0.613, P<0.01). After TAVI, there were significant decreases in the norepinephrine level (366±179 ng/mL vs. 276±125 ng/mL, P<0.01) and WR (34±13 vs. 26±11%, P<0.01).

CONCLUSIONS

The WR of MIBG was a useful marker of CSN activity and severity of AS. Immediate improvement of CSN activity after TAVI implied that AS hemodynamics per se enhanced CSN.

Lipophilic Statin Versus Rosuvastatin (Hydrophilic) Treatment for Heart Failure: a Meta-Analysis and Adjusted Indirect Comparison of Randomised Trials

OBJECTIVES

This study aims to compare lipophilic and hydrophilic statin therapy on clinical outcomes of heart failure (HF) using a systematic review and an adjusted indirect comparison meta-analysis. Outcomes were all-cause mortality, cardiovascular mortality, cardiovascular hospitalization and hospitalization for worsening HF.

METHODS

We conducted a search of PubMed, EMBASE and Cochrane databases until 31st December 2014 for randomized control trials (RCTs) in HF evaluating statins versus placebo. Identified RCTs and their respective abstracted information were grouped according to statin type evaluated and analyzed separately. Outcomes were initially pooled with the Peto's one-step method, producing odd ratios (OR) and 95 % confidence intervals (CI) for each statin type. Using these pooled estimates, we performed adjusted indirect comparisons of lipophilic versus hydrophilic statin for each outcome.

RESULTS

Thirteen studies involving 10,966 patients were identified and analyzed. Lipophilic statins were superior to hydrophilic rosuvastatin regarding all-cause mortality (OR 0 · 50; 95 % CI, 0 · 11-0 · 89; p = 0 · 01), cardiovascular mortality (OR 0 · 61; 0 · 25-0 · 97; p = 0 · 009), and hospitalization for worsening HF (OR 0 · 52; 0 · 21-0 · 83; p = 0 · 0005). However, both statins were comparable with regards to cardiovascular hospitalization [OR 0 · 80 (0 · 31, 1 · 28); p = 0 · 36].

CONCLUSIONS

Lipophilic statin treatment shows significant decreases in all-cause mortality, cardiovascular mortality and hospitalization for worsening HF compared with rosuvastatin treatment. This meta-analysis provides preliminary evidence that lipophilic statins offer better clinical outcomes in HF till data from head to head comparisons are available.

Effect of Heart Rate and Use of Beta Blockers on Mortality After Heart Transplantation

Heart transplantation (HT) recipients may have tachycardia secondary to cardiac denervation. As higher heart rate predicts worse outcomes in cardiovascular disease, we hypothesized that tachycardia and nonuse of β blockers are associated with increased mortality after HT. All patients who underwent HT at our institution from 1987 to 2010 were included. The association of heart rate 3 months after HT and β-blocker use during follow-up to mortality was assessed using Kaplan-Meier and multivariate Cox proportional hazards regression analyses adjusting for clinically relevant baseline variables. From 1987 to 2010, there were 493 HT. After excluding 29 who died within 3 months and 3 with follow-up <3 months, 461 HT recipients (50 ± 2 years; 20% women) were included. Over a follow-up of 12 ± 7 years, selected important univariate predictors of post-HT mortality were older age, male gender, higher body mass index, ischemic cardiomyopathy, longer post-HT intensive care unit stay, and hospitalization and at 3 months, increased mean pulmonary artery pressure, right atrial pressure and pulmonary capillary occlusion pressure, higher heart rate, and nonuse of β blockers during follow-up. In multivariate analysis, older ager, longer hospitalization, higher mean pulmonary artery pressure, higher heart rate at 3 months (hazard ratio 1.02 per beat, 95% confidence interval 1.008 to 1.035, p = 0.02) and nonuse of β blockers (hazard ratio 1.43, 95% confidence interval 1.002 to 2.031, p <0.05) were associated with mortality. In conclusion, in a large single-center cohort of HT recipients, higher heart rate and nonuse of β blockers were independently associated with higher mortality.

Chronic Kidney Disease As a Potential Indication for Renal Denervation

Renal denervation is being used as a blood pressure lowering therapy for patients with apparent treatment resistant hypertension. However, this population does not represent a distinct disease condition in which benefit is predictable. In fact, the wide range in effectiveness of renal denervation could be a consequence of this heterogeneous pathogenesis of hypertension. Since renal denervation aims at disrupting sympathetic nerves surrounding the renal arteries, it seems obvious to focus on patients with increased afferent and/or efferent renal sympathetic nerve activity. In this review will be argued, from both a pathophysiological and a clinical point of view, that chronic kidney disease is particularly suited to renal denervation.

Aerobic Exercise and Pharmacological Therapies for Skeletal Myopathy in Heart Failure: Similarities and Differences

Skeletal myopathy has been identified as a major comorbidity of heart failure (HF) affecting up to 20% of ambulatory patients leading to shortness of breath, early fatigue, and exercise intolerance. Neurohumoral blockade, through the inhibition of renin angiotensin aldosterone system (RAS) and β-adrenergic receptor blockade (β-blockers), is a mandatory pharmacological therapy of HF since it reduces symptoms, mortality, and sudden death. However, the effect of these drugs on skeletal myopathy needs to be clarified, since exercise intolerance remains in HF patients optimized with β-blockers and inhibitors of RAS. Aerobic exercise training (AET) is efficient in counteracting skeletal myopathy and in improving functional capacity and quality of life. Indeed, AET has beneficial effects on failing heart itself despite being of less magnitude compared with neurohumoral blockade. In this way, AET should be implemented in the care standards, together with pharmacological therapies. Since both neurohumoral inhibition and AET have a direct and/or indirect impact on skeletal muscle, this review aims to provide an overview of the isolated effects of these therapeutic approaches in counteracting skeletal myopathy in HF. The similarities and dissimilarities of neurohumoral inhibition and AET therapies are also discussed to identify potential advantageous effects of these combined therapies for treating HF.

Restoration of Pulsatile Flow Reduces Sympathetic Nerve Activity Among Individuals With Continuous-Flow Left Ventricular Assist Devices

Background—

Current-generation left ventricular assist devices provide circulatory support that is minimally or entirely nonpulsatile and are associated with marked increases in muscle sympathetic nerve activity (MSNA), likely through a baroreceptor-mediated pathway. We sought to determine whether the restoration of pulsatile flow through modulations in pump speed would reduce MSNA through the arterial baroreceptor reflex.

Methods and Results—

Ten men and 3 women (54±14 years) with Heartmate II continuous-flow left ventricular assist devices underwent hemodynamic and sympathetic neural assessment. Beat-to-beat blood pressure, carotid ultrasonography at the level of the arterial baroreceptors, and MSNA via microneurography were continuously recorded to determine steady-state responses to step changes (200–400 revolutions per minute) in continuous-flow left ventricular assist device pump speed from a maximum of 10 480±315 revolutions per minute to a minimum of 8500±380 revolutions per minute. Reductions in pump speed led to increases in pulse pressure (high versus low speed: 17±7 versus 26±12 mm Hg; P <0.01), distension of the carotid artery, and carotid arterial wall tension ( P <0.05 for all measures). In addition, MSNA was reduced (high versus low speed: 41±15 versus 33±16 bursts per minute; P <0.01) despite a reduction in mean arterial pressure and was inversely related to pulse pressure ( P =0.037).

Conclusions—

Among subjects with continuous-flow left ventricular assist devices, the restoration of pulsatile flow through modulations in pump speed leads to increased distortion of the arterial baroreceptors with a subsequent decline in MSNA. Additional study is needed to determine whether reduction of MSNA in this setting leads to improved outcomes.

Acute electromyostimulation decreases muscle sympathetic nerve activity in patients with advanced chronic heart failure (EMSICA Study)

Background

Muscle passive contraction of lower limb by neuromuscular electrostimulation (NMES) is frequently used in chronic heart failure (CHF) patients but no data are available concerning its action on sympathetic activity. However, Transcutaneous Electrical Nerve Stimulation (TENS) is able to improve baroreflex in CHF. The primary aim of the present study was to investigate the acute effect of TENS and NMES compared to Sham stimulation on sympathetic overactivity as assessed by Muscle Sympathetic Nerve Activity (MSNA).

Methods

We performed a serie of two parallel, randomized, double blinded and sham controlled protocols in twenty-two CHF patients in New York Heart Association (NYHA) Class III. Half of them performed stimulation by TENS, and the others tested NMES.

Results

Compare to Sham stimulation, both TENS and NMES are able to reduce MSNA (63.5 ± 3.5 vs 69.7 ± 3.1 bursts / min, p < 0.01 after TENS and 51.6 ± 3.3 vs 56.7 ± 3.3 bursts / min, p < 0, 01 after NMES). No variation of blood pressure, heart rate or respiratory parameters was observed after stimulation.

Conclusion

The results suggest that sensory stimulation of lower limbs by electrical device, either TENS or NMES, could inhibit sympathetic outflow directed to legs in CHF patients. These properties could benefits CHF patients and pave the way for a new non-pharmacological approach of CHF.

Integrative effect of carvedilol and aerobic exercise training therapies on improving cardiac contractility and remodeling in heart failure mice

The use of β-blockers is mandatory for counteracting heart failure (HF)-induced chronic sympathetic hyperactivity, cardiac dysfunction and remodeling. Importantly, aerobic exercise training, an efficient nonpharmacological therapy to HF, also counteracts sympathetic hyperactivity in HF and improves exercise tolerance and cardiac contractility; the latter associated with changes in cardiac Ca²⁺ handling. This study was undertaken to test whether combined β–blocker and aerobic exercise training would integrate the beneficial effects of isolated therapies on cardiac structure, contractility and cardiomyocyte Ca²⁺ handling in a genetic model of sympathetic hyperactivity-induced HF (α_2A/α_2C- adrenergic receptor knockout mice, KO). We used a cohort of 5–7 mo male wild-type (WT) and congenic mice (KO) with C57Bl6/J genetic background randomly assigned into 5 groups: control (WT), saline-treated KO (KOS), exercise trained KO (KOT), carvedilol-treated KO (KOC) and, combined carvedilol-treated and exercise-trained KO (KOCT). Isolated and combined therapies reduced mortality compared with KOS mice. Both KOT and KOCT groups had increased exercise tolerance, while groups receiving carvedilol had increased left ventricular fractional shortening and reduced cardiac collagen volume fraction compared with KOS group. Cellular data confirmed that cardiomyocytes from KOS mice displayed abnormal Ca²⁺ handling. KOT group had increased intracellular peak of Ca²⁺ transient and reduced diastolic Ca²⁺ decay compared with KOS group, while KOC had increased Ca²⁺ decay compared with KOS group. Notably, combined therapies re-established cardiomyocyte Ca²⁺ transient paralleled by increased SERCA2 expression and SERCA2:PLN ratio toward WT levels. Aerobic exercise trained increased the phosphorylation of PLN at Ser¹⁶ and Thr¹⁷ residues in both KOT and KOCT groups, but carvedilol treatment reduced lipid peroxidation in KOC and KOCT groups compared with KOS group. The present findings provide evidence that the combination of carvedilol and aerobic exercise training therapies lead to a better integrative outcome than carvedilol or exercise training used in isolation.

Muscle reflex in heart failure: the role of exercise training

Exercise evokes sympathetic activation and increases blood pressure and heart rate (HR). Two neural mechanisms that cause the exercise-induced increase in sympathetic discharge are central command and the exercise pressor reflex (EPR). The former suggests that a volitional signal emanating from central motor areas leads to increased sympathetic activation during exercise. The latter is a reflex originating in skeletal muscle which contributes significantly to the regulation of the cardiovascular and respiratory systems during exercise. The afferent arm of this reflex is composed of metabolically sensitive (predominantly group IV, C-fibers) and mechanically sensitive (predominately group III, A-delta fibers) afferent fibers. Activation of these receptors and their associated afferent fibers reflexively adjusts sympathetic and parasympathetic nerve activity during exercise. In heart failure, the sympathetic activation during exercise is exaggerated, which potentially increases cardiovascular risk and contributes to exercise intolerance during physical activity in chronic heart failure (CHF) patients. A therapeutic strategy for preventing or slowing the progression of the exaggerated EPR may be of benefit in CHF patients. Long-term exercise training (ExT), as a non-pharmacological treatment for CHF increases exercise capacity, reduces sympatho-excitation and improves cardiovascular function in CHF animals and patients. In this review, we will discuss the effects of ExT and the mechanisms that contribute to the exaggerated EPR in the CHF state.

Statin therapy lowers muscle sympathetic nerve activity and oxidative stress in patients with heart failure

Despite standard drug therapy, sympathetic nerve activity (SNA) remains high in heart failure (HF) patients making the sympathetic nervous system a primary drug target in the treatment of HF. Studies in rabbits with pacing-induced HF have demonstrated that statins reduce resting SNA, in part, due to reductions in reactive oxygen species (ROS). Whether these findings can be extended to the clinical setting of human HF remains unclear. We first performed a study in seven statin-naïve HF patients (56 ± 2 yr; ejection fraction: 31 ± 4%) to determine if 1 mo of simvastatin (40 mg/day) reduces muscle SNA (MSNA). Next, to control for possible placebo effects and determine the effect of simvastatin on ROS, a double-blinded, placebo-controlled crossover design study was performed in six additional HF patients (51 ± 3 yr; ejection fraction: 22 ± 4%), and MSNA, ROS, and superoxide were measured. We tested the hypothesis that statin therapy decreases resting MSNA in HF patients and this would be associated with reductions in ROS. In study 1, simvastatin reduced resting MSNA (75 ± 5 baseline vs. 65 ± 5 statin bursts/100 heartbeats; P < 0.05). Likewise, in study 2, simvastatin also decreased resting MSNA (59 ± 5 placebo vs. 45 ± 6 statin bursts/100 heartbeats; P < 0.05). In addition, statin therapy significantly reduced total ROS and superoxide. As expected, cholesterol was reduced after simvastatin. Collectively, these findings indicate that short-term statin therapy concomitantly reduces resting MSNA and total ROS and superoxide in HF patients. Thus, in addition to lowering cholesterol, statins may also be beneficial in reducing sympathetic overactivity and oxidative stress in HF patients.

β-Blockers in heart failure: benefits of β-blockers according to varying male proportions of study patients

BACKGROUND

In patients with heart failure (HF), b-blockers reduce mortality. It's not known whether the beneficial effects of the b-blockers were associated with the differing male proportions of study patients. It also remains to be clarified regarding the true beneficial effects of the 3 b-blockers recommended by the guideline on mortality in the real world.

HYPOTHESIS

The benefits of b-blockers in HF patients were sex-related different.

METHODS

Randomized, placebo controlled clinical trials were included if they evaluated the beneficial effects of the three b-blockers on mortality and on hospital admissions on an intention-to-treat basis, and lasted at least 3 months.

RESULTS

Twenty-eighty trials with 14,829 patients were included. The b-blockers significantly reduced all cause mortality by 29.6%, cardiac death by 29.8%, sudden death by 49.4%, respectively. The magnitude of benefits of b-blockers in HF patients was increased with the increased male proportion. A similar magnitude of reduction in all cause mortality was observed among the three b blockers. A trend toward to reduced cardiac death was observed among the three b blockers, but only in bisoprolol was this statistically different (RR, 0.72; 95%CI, [0.59-0.87]). Metoprolol was significantly superior to carvedilol (P = 0.008) or bisoprolol (P = 0.034) in reduced sudden death.

CONCLUSIONS

In patients with HF, the 3 commonly used b-blockers significantly reduced mortality. Greater benefits of b-blockers were observed in the higher male proportion studies. The metoprolol was significantly superior to carvedilol or bisoprolol in reduced sudden death. Additional trials are required to determine whether the benefits of b-blockers will be observed in female HF patients.

Statins do not significantly affect muscle sympathetic nerve activity in humans with nonischemic heart failure: a double-blind placebo-controlled trial

BACKGROUND

Hydroxymethylglutaryl-coenzyme A reductase inhibitors (statins) have been shown to reduce sympathetic nervous system (SNS) activation in experimental heart failure (HF). However, this potential mechanism of action of statins in HF has not been well studied in humans.

METHODS AND RESULTS

Twenty-six patients with nonischemic systolic HF (left ventricular ejection fraction [LVEF] ≤35%) were randomized to atorvastatin (10 mg) or placebo for 3 months. Pre- and posttreatment testing included echocardiography, laboratory assays, quality of life (QOL) questionnaires, and peroneal nerve muscle sympathetic nerve activity (MSNA) via microneurography. Eighteen subjects had technically adequate MSNA tracings before and after treatment. The cohort was 65% male, 81% New York Heart Association functional class II, LVEF 26 ± 6%, and low-density lipoprotein cholesterol (LDL-C) 108 ± 26 mg/dL. Baseline MSNA was 41 ± 2 bursts/min. LDL-C significantly decreased in the atorvastatin (-36.8%) versus the placebo (-0.1%) group (P < .0001). However, there was no significant change in MSNA (-16.2% vs -2.5%), LVEF, B-type natriuretic peptide, or QOL score in the atorvastatin compared with the placebo group.

CONCLUSIONS

Short-term statin therapy in patients with nonischemic HF does not result in a significant decrease in SNS activation as measured by MSNA. These findings are consistent with the neutral outcomes of large clinical trials of statins in HF.

A randomised, placebo-controlled trial of carvedilol in early familial dilated cardiomyopathy

BACKGROUND

Screening of asymptomatic relatives of patients with dilated cardiomyopathy (DCM) has identified a population of individuals with left ventricular dilatation and/or minimally impaired contraction who are believed to have early disease. A proportion of these individuals with early disease progress to overt cardiomyopathy, however to our knowledge there have been no studies that have examined the impact of early intervention on disease progression.

METHODS

We evaluated 424 asymptomatic relatives in 110 families of probands with DCM and identified 102 individuals (24%) with suspected "early disease" (EDCM). Thirty-two EDCM subjects were randomised into a six-month placebo-controlled trial of the β-blocker, carvedilol. Transthoracic echocardiography and plasma nt-proBNP levels were measured at baseline and repeated at six months. The primary trial endpoint was change in left ventricular end-systolic diameter after six months. Subjects completing six months of blinded trial therapy were offered open-label carvedilol and then observed over an extended period with repeated clinical evaluation and echocardiography.

RESULTS

At baseline, left ventricular dimensions, systolic function and plasma nt-proBNP levels were similar in carvedilol and placebo groups. There were no significant changes observed in these parameters in either treatment group after six months, however reductions in end-diastolic diameter (% predicted) were observed in carvedilol-treated subjects (P=0.002) during an open-label median follow-up of 32 months (range: 13-56 months).

CONCLUSIONS

In an asymptomatic population of individuals with EDCM, treatment with carvedilol for six months had no effect on echocardiographic left ventricular dimensions or systolic function, however longer-term treatment may reverse left ventricular remodelling (Australian Clinical Trials Registry N012605000204640).

Is kidney ischemia the central mechanism in parallel activation of the renin and sympathetic system?

In chronic kidney disease simultaneous activation of the renin-angiotensin and sympathetic systems occurs. Kidney ischemia seems to play a key role in the pathogenesis. This review firstly summarizes experimental and clinical evidence in chronic kidney disease supporting this idea and addresses the possibility that this mechanism is also relevant in some other disease conditions.

Microvascular oxygen delivery-to-utilization mismatch at the onset of heavy-intensity exercise in optimally treated patients with CHF

Impaired muscle blood flow at the onset of heavy-intensity exercise may transiently reduce microvascular O(2) pressure and decrease the rate of O(2) transfer from capillary to mitochondria in chronic heart failure (CHF). However, advances in the pharmacological treatment of CHF (e.g., angiotensin-converting enzyme inhibitors and third-generation beta-blockers) may have improved microvascular O(2) delivery to an extent that intramyocyte metabolic inertia might become the main locus of limitation of O(2) uptake (Vo(2)) kinetics. We assessed the rate of change of pulmonary Vo(2) (Vo(2)(p)), (estimated) fractional O(2) extraction in the vastus lateralis (approximately Delta[deoxy-Hb+Mb] by near-infrared spectroscopy), and cardiac output (Qt) during high-intensity exercise performed to the limit of tolerance (Tlim) in 10 optimally treated sedentary patients (ejection fraction = 29 + or - 8%) and 11 controls. Sluggish Vo(2)(p) and Qt kinetics in patients were significantly related to lower Tlim values (P < 0.05). The dynamics of Delta[deoxy-Hb+Mb], however, were faster in patients than controls [mean response time (MRT) = 15.9 + or - 2.0 s vs. 19.0 + or - 2.9 s; P < 0.05] with a subsequent response "overshoot" being found only in patients (7/10). Moreover, tauVo(2)/MRT-[deoxy-Hb+Mb] ratio was greater in patients (4.69 + or - 1.42 s vs. 2.25 + or - 0.77 s; P < 0.05) and related to Qt kinetics and Tlim (R = 0.89 and -0.78, respectively; P < 0.01). We conclude that despite the advances in the pharmacological treatment of CHF, disturbances in "central" and "peripheral" circulatory adjustments still play a prominent role in limiting Vo(2)(p) kinetics and tolerance to heavy-intensity exercise in nontrained patients.

Effects of exercise training in patients with chronic heart failure and sleep apnea

STUDY OBJECTIVES

To test the effects of exercise training on sleep and neurovascular control in patients with systolic heart failure with and without sleep disordered breathing.

DESIGN

Prospective interventional study.

SETTING

Cardiac rehabilitation and exercise physiology unit and sleep laboratory.

PATIENTS

Twenty-five patients with heart failure, aged 42 to 70 years, and New York Heart Association Functional Class I-III were divided into 1 of 3 groups: obstructive sleep apnea (n=8), central sleep apnea (n=9) and no sleep apnea (n=7). INTERVENTIONS Four months of no-training (control) followed by 4 months of an exercise training program (three 60-minute, supervised, exercise sessions per week).

MEASURES AND RESULTS

Sleep (polysomnography), microneurography, forearm blood flow (plethysmography), peak VO2, and quality of life were evaluated at baseline and at the end of the control and trained periods. No significant changes occurred in the control period. Exercise training reduced muscle sympathetic nerve activity (P < 0.001) and increased forearm blood flow (P < 0.01), peak VO2( P < 0.01), and quality of life (P < 0.01) in all groups, independent of the presence of sleep apnea. Exercise training improved the apnea-hypopnea index, minimum 0O saturation, and amount stage 3-4 sleep (P < 0.05) in patients with obstructive sleep apnea but had no significant effects in patients with central sleep apnea.

CONCLUSIONS

The beneficial effects of exercise training on neurovascular function, functional capacity, and quality of life in patients with systolic dysfunction and heart failure occurs independently of sleep disordered breathing. Exercise training lessens the severity of obstructive sleep apnea but does not affect central sleep apnea in patients with heart failure and sleep disordered breathing.

Altered firing pattern of single-unit muscle sympathetic nerve activity during handgrip exercise in chronic heart failure

Sympathetic activation in chronic heart failure (CHF) is greatly augmented at rest but the response to exercise remains controversial. We previously demonstrated that single-unit muscle sympathetic nerve activity (MSNA) provides a more detailed description of the sympathetic response to physiological stress than multi-unit nerve recordings. The purpose of this study was to determine whether the reflex response and discharge properties of single-unit MSNA are altered during handgrip exercise (HG, 30% of maximum voluntary contraction for 3 min) in CHF patients (New York Heart Association functional class II or III, n = 16) compared with age-matched healthy control subjects (n = 13). At rest, both single-unit and multi-unit indices of sympathetic outflow were augmented in CHF compared with controls (P < 0.05). However, the percentage of cardiac intervals that contained one, two, three or four single-unit spikes were not different between the groups. Compared to the control group, HG elicited a larger increase in multi-unit total MSNA (Delta1002 +/- 50 compared with Delta636 +/- 76 units min(-1), P < 0.05) and single-unit MSNA spike incidence (Delta27 +/- 5 compared with Delta8 +/- 2 spikes (100 heart beats)(-1)), P < 0.01) in the CHF patients. More importantly, the percentage of cardiac intervals that contained two or three single-unit spikes was increased (P < 0.05) during exercise in the CHF group only (Delta8 +/- 2% and Delta5 +/- 1% for two and three spikes, respectively). These results suggest that the larger multi-unit total MSNA response observed during HG in CHF is brought about in part by an increase in the probability of multiple firing of single-unit sympathetic neurones.

Potential autonomic nervous system effects of statins in heart failure

Sympathetic nervous system activation in heart failure, as indexed by elevated norepinephrine levels, higher muscle sympathetic nerve activity and reduced heart rate variability, is associated with pathologic ventricular remodeling, increased arrhythmias, sudden death, and increased mortality. Recent evidence suggests that 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor (statin) therapy may provide survival benefit in heart failure of both ischemic and nonischemic etiology, and one potential mechanism of benefit of statins in heart failure is modulation of the autonomic nervous system. Animal models of heart failure demonstrate reduced sympathetic activation and improved sympathovagal balance with statin therapy. Initial human studies have reported mixed results. Ongoing translational studies and outcomes trials will help delineate the potentially beneficial effects of statins on the autonomic nervous system in heart failure.

Comparison of muscle sympathetic activity in ischemic and nonischemic heart failure

BACKGROUND

The magnitude of sympathetic activation in chronic heart failure is assumed to be independent of its cause. However, because a higher sympathetic component of heart rate variability (HRV) in patients with ischemic cardiomyopathy (ICM) has been reported, we hypothesized that patients with ICM would have a higher resting muscle sympathetic nerve activity (MSNA) than patients with nonischemic dilated cardiomyopathy (DCM).

METHODS AND RESULTS

Resting MSNA was assessed by microneurography and HRV concurrently by coarse-graining spectral analysis in 30 treated normotensive patients with chronic heart failure (12 with ICM and 18 with DCM), matched for age and left ventricular ejection fraction, and 23 healthy normal control subjects, matched for age and blood pressure. Peak oxygen uptake was determined during graded cycling (17 W/min) to maximum effort. MSNA was significantly different between groups (P < .001; ICM 60 +/- 3; DCM 47 +/- 3; control subjects 35 +/- 3 bursts/min). Compared with control subjects, the total spectral power and the high-frequency component of HRV were lower in both ICM and DCM groups, but fractal and low-frequency power were lower only in the ICM group (P < .05). Peak oxygen uptake (milliliters per kilogram of body weight per minute) was significantly less in the ICM group than in the DCM group (P = .04) and lower in both groups than in the control subjects (P < .001).

CONCLUSIONS

These observations suggest an additional ischemic stimulus to sympathetic activation in heart failure, which may impair exercise capacity reflexively.

Exercise training reduces sympathetic nerve activity in heart failure patients treated with carvedilol

BACKGROUND

Evidence suggests that carvedilol decreases muscle sympathetic nerve activity (MSNA) in patients with heart failure (HF) but carvedilol fails to improve forearm vascular resistance and overall functional capacity. Exercise training in HF reduces MSNA and improves forearm vascular resistance and functional capacity.

AIMS

To investigate whether the beneficial effects exercise training on MSNA are maintained in the presence of carvedilol.

METHODS AND RESULTS

Twenty seven HF patients, NYHA Class II-III, EF <35%, peak VO(2) <20 ml/kg/min, treated with carvedilol were randomly divided into two groups: exercise training (n=15) and untrained (n=12). MSNA was recorded by microneurography. Forearm blood flow (FBF) was measured by venous occlusion plethysmography. The four-month training program consisted of three 60-min exercise/week on a cycloergometer. Baseline parameters were similar between groups. Exercise training reduced MSNA (-14+/-3.3 bursts/100 HB, p=0.001) and increased forearm blood flow (0.6+/-0.1 mL/min/100 g, p<0.001) in HF patients on carvedilol. In addition, exercise training improved peak VO(2) in HF patients (20+/-6%, p=0.002). MSNA, FBF and peak VO(2) were unchanged in untrained HF patients on carvedilol.

CONCLUSION

Exercise training reduces MSNA in heart failure patients treated with carvedilol. In addition, the beneficial effects of exercise training on muscle blood flow and functional capacity are still realized in patients on carvedilol.

Blunted muscle vasodilatation during chemoreceptor stimulation in patients with heart failure

Chemoreflex control of sympathetic nerve activity is exaggerated in heart failure (HF) patients. However, the vascular implications of the augmented sympathetic activity during chemoreceptor activation in patients with HF are unknown. We tested the hypothesis that the muscle blood flow responses during peripheral and central chemoreflex stimulation would be blunted in patients with HF. Sixteen patients with HF (49 +/- 3 years old, Functional Class II-III, New York Heart Association) and 11 age-paired normal controls were studied. The peripheral chemoreflex control was evaluated by inhalation of 10% O(2) and 90% N(2) for 3 min. The central chemoreflex control was evaluated by inhalation of 7% CO(2) and 93% O(2) for 3 min. Muscle sympathetic nerve activity (MSNA) was directly evaluated by microneurography. Forearm blood flow was evaluated by venous occlusion plethysmography. Baseline MSNA were significantly greater in HF patients (33 +/- 3 vs. 20 +/- 2 bursts/min, P = 0.001). Forearm vascular conductance (FVC) was not different between the groups. During hypoxia, the increase in MSNA was significantly greater in HF patients than in normal controls (9.0 +/- 1.6 vs. 0.8 +/- 2.0 bursts/min, P = 0.001). The increase in FVC was significantly lower in HF patients (0.00 +/- 0.10 vs. 0.76 +/- 0.25 units, P = 0.001). During hypercapnia, MSNA responses were significantly greater in HF patients than in normal controls (13.9 +/- 3.2 vs. 2.1 +/- 1.9 bursts/min, P = 0.001). FVC responses were significantly lower in HF patients (-0.29 +/- 0.10 vs. 0.37 +/- 0.18 units, P = 0.001). In conclusion, muscle vasodilatation during peripheral and central chemoreceptor stimulation is blunted in HF patients. This vascular response seems to be explained, at least in part, by the exaggerated MSNA responses during hypoxia and hypercapnia.

Effect of adrenergic blockade on plasma adrenomedullin concentration during static handgrip in patients with heart failure

Our previous study showed that static handgrip caused increases in the plasma adrenomedullin (ADM) both in patients with heart failure (HF) and healthy subjects. The present study was designed to determine the role of the sympathetic nervous system in mediating plasma ADM changes during handgrip in patients with HF. Twelve male HF patients (II class NYHA) treated with carvedilol, a non-selective adrenergic blocker (TC) and 12 patients untreated with carvedilol (UC) performed two 3-min bouts of static handgrip at 30% of maximal voluntary contraction, alternately with each hand. At the end of both exercise bouts and in 5 min of the recovery period, plasma ADM and catecholamines were determined. In addition, heart rate, blood pressure and stroke volume (SV) were measured. The baseline plasma ADM, noradrenaline (NA) and adrenaline (A) levels were similar in the two groups of patients, while SV was higher (P<0.05) in TC than in UC. During exercise plasma ADM concentrations were lower (P<0.05) in TC than in UC, but the handgrip-induced increases in plasma ADM did not differ between the groups. Plasma ADM correlated with NA concentrations (r = 0.764) and with SV (r = -0.435) and increases in plasma ADM expressed as percentage of baseline values correlated with those of plasma NA (r = 0.499), diastolic BP (r = 0.550) and total peripheral resistance (r = 0.435). The study suggests that the sympathetic nervous system may be involved in the stimulation of ADM secretion during static exercise either directly or by changes in the haemodynamic response.

Sympathetic control after cardiac resynchronization therapy: responders versus nonresponders

Cardiac resynchronization therapy (CRT) decreases muscle sympathetic nerve activity (MSNA) in patients with severe congestive heart failure (CHF) and cardiac asynchrony. Whether this affects equally patients who clinically respond or not to CRT is unknown. We tested the hypothesis that the favorable effects of CRT on MSNA disappear on CRT interruption only in those who respond to CRT. Twenty-three consecutive CHF patients participated in the study, among whom 16 presented a symptomatic improvement by one or more New York Heart Association (NYHA) functional classes 15 ± 5 mo after CRT (responders), and seven had not improved after 12 ± 4 mo of CRT (nonresponders). MSNA and echocardiographic recordings were obtained in random order during atrio-right ventricular pacing (ARV), without stimulation in patients who were not pacemaker dependent (OFF, n = 17), and during atrio-biventricular pacing (BIV). Responders had a longer 6-min walking distance, a lower NYHA class and brain natriuretic peptide levels, and a better quality of life than did nonresponders (all P < 0.05). MSNA increased by 25 ± 7% in the responders, whereas it remained unchanged in the nonresponders, when shifting from the BIV mode to a nonsynchronous condition (ARV and OFF modes) ( P < 0.01). Cardiac output decreased by 0.7 ± 0.2 l/min in the responders but did not change when shifting from the BIV mode to the nonsynchronous pacing mode in the nonresponders ( P < 0.01). In conclusion, reversible sympathoinhibition is a marker of the clinical response to CRT.