Baroreflex activation for the treatment of heart failure

Antiarrhythmic effects of baroreceptor activation therapy in chronic heart failure: a case report

Background

Autonomic imbalance represents a keystone of chronic heart failure (HF) with substantial clinical and prognostic implications. Baroreceptor activation therapy (BAT) is a new therapeutic strategy to target the autonomic dysbalance by electrical stimulation of carotid baroreceptors. Besides its known beneficial effects on HF parameters, BAT is also supposed to trigger potential antiarrhythmic effects, which may additionally contribute to HF improvement.

Case summary

We report on a 70-year-old male with progredient shortness of breath and advanced HF in the context of an extensive cardiovascular history. After optimization of pharmacologic and device-related therapy, the decision was made to implant a BAT system (Barostim Neo, CVRx) to improve functional cardiac parameters and support symptomatic improvement. Implantation was associated with an overall clinical improvement assessed during outpatient visits every 6 months. Frequency of ventricular arrhythmic events declined, and atrial fibrillation ceased spontaneously. Echocardiography revealed an amelioration in left ventricular systolic function. Numbers of HF hospitalization decreased after Barostim implantation.

Discussion

We present a patient with an extensive cardiovascular history and fully exploited pharmacologic and device-related therapy, who showed improvement in New York Heart Association (NYHA) functional classification, left ventricular systolic function, and reduction of arrhythmic events following implantation of the BAT device. This case presents an additional positive potential of BAT for HF patients in terms of reduction of arrhythmia burden. These results should be confirmed by further clinical trials.

Baroreflex activation therapy with the Barostim™ device in patients with heart failure with reduced ejection fraction: a patient level meta-analysis of randomized controlled trials

AIMS

Heart failure with reduced ejection fraction (HFrEF) remains associated with high morbidity and mortality, poor quality of life (QoL) and significant exercise limitation. Sympatho-vagal imbalance has been shown to predict adverse prognosis and symptoms in HFrEF, yet it has not been specifically targeted by any guideline-recommended device therapy to date. Barostim™, which directly addresses this imbalance, is the first Food and Drug Administration approved neuromodulation technology for HFrEF. We aimed to analyse all randomized trial evidence to evaluate the effect of baroreflex activation therapy (BAT) on heart failure symptoms, QoL and N-terminal pro-brain natriuretic peptide (NT-proBNP) in HFrEF.

METHODS AND RESULTS

An individual patient data (IPD) meta-analysis was performed on all eligible trials that randomized HFrEF patients to BAT + guideline-directed medical therapy (GDMT) or GDMT alone (open label). Endpoints included 6-month changes in 6-min hall walk (6MHW) distance, Minnesota Living With Heart Failure (MLWHF) QoL score, NT-proBNP, and New York Heart Association (NYHA) class in all patients and three subgroups. A total of 554 randomized patients were included. In all patients, BAT provided significant improvement in 6MHW distance of 49 m (95% confidence interval [CI] 33, 64), MLWHF QoL of -13 points (95% CI -17, -10), and 3.4 higher odds of improving at least one NYHA class (95% CI 2.3, 4.9) when comparing from baseline to 6 months. These improvements were similar, or better, in patients who had baseline NT-proBNP <1600 pg/ml, regardless of the cardiac resynchronization therapy indication status.

CONCLUSION

An IPD meta-analysis suggests that BAT improves exercise capacity, NYHA class, and QoL in HFrEF patients receiving GDMT. These clinically meaningful improvements were consistent across the range of patients studies. BAT was also associated with an improvement in NT-proBNP in subjects with a lower baseline NT-proBNP.

Nonpharmacologic Treatment for Heart Failure: A Review of Implantable Carotid Baroreceptor Stimulators As a Therapeutic Option

There has been significant interest in research for the development of device-based therapy as a treatment option of heart failure (HF), whether it is with reduced or preserved ejection fraction. This is due to the high morbidity and mortality rate in patients with HF despite recent advances in pharmacologic treatment. Following the success of cardiac resynchronization therapy, baroreceptor activation therapy has emerged as another novel device-based treatment for HF. The Barostim neo was developed by CVRx Minneapolis, MN for the treatment of mild to severe HF. The device works by electrically activating the baroreceptor reflex with the goal to restore the maladaptive autonomic imbalance that is seen in patients with HF. Preliminary clinical investigations have given promising results with an encouraging safety profile. Baroreceptor activation therapy as a treatment option is still investigational at this time; however, several trials in different patient populations have already shown benefit with a very good safety profile. In this review, we will summarize the current state of technology and the available literature of the use of baroreceptor activation therapy in patients with different comorbidities, with a focus on this device-based therapy in patients with HF.

Benefits of pharmacological and electrical cholinergic stimulation in hypertension and heart failure

Systemic arterial hypertension and heart failure are cardiovascular diseases that affect millions of individuals worldwide. They are characterized by a change in the autonomic nervous system balance, highlighted by an increase in sympathetic activity associated with a decrease in parasympathetic activity. Most therapeutic approaches seek to treat these diseases by medications that attenuate sympathetic activity. However, there is a growing number of studies demonstrating that the improvement of parasympathetic function, by means of pharmacological or electrical stimulation, can be an effective tool for the treatment of these cardiovascular diseases. Therefore, this review aims to describe the advances reported by experimental and clinical studies that addressed the potential of cholinergic stimulation to prevent autonomic and cardiovascular imbalance in hypertension and heart failure. Overall, the published data reviewed demonstrate that the use of central or peripheral acetylcholinesterase inhibitors is efficient to improve the autonomic imbalance and hemodynamic changes observed in heart failure and hypertension. Of note, the baroreflex and the vagus nerve activation have been shown to be safe and effective approaches to be used as an alternative treatment for these cardiovascular diseases. In conclusion, pharmacological and electrical stimulation of the parasympathetic nervous system has the potential to be used as a therapeutic tool for the treatment of hypertension and heart failure, deserving to be more explored in the clinical setting.

Cost-impact analysis of baroreflex activation therapy in chronic heart failure patients in the United States

Background

The study evaluated the cost of baroreflex activation therapy plus guideline directed therapy (BAT + GDT) compared to GDT alone for HF patients with reduced ejection fraction and New York Heart Association Class III or II (with a recent history of III). Baroreflex activation therapy (BAT) is delivered by an implantable device that stimulates the baroreceptors through an electrode attached to the outside of the carotid artery, which rebalances the autonomic nervous system to regain cardiovascular (CV) homeostasis. The BeAT-HF trial evaluated the safety and effectiveness of BAT.

Methods

A cost impact model was developed from a U.S. health care payer or integrated delivery network perspective over a 3-year period for BAT + GDT versus GDT alone. Expected costs were calculated by utilizing 6-month data from the BeAT-HF trial and existing literature. HF hospitalization rates were extrapolated based on improvement in NT-proBNP.

Results

At baseline the expected cost of BAT + GDT were $29,526 per patient more than GDT alone due to BAT device and implantation costs. After 3 years, the predicted cost per patient was $9521 less expensive for BAT + GDT versus GDT alone due to lower rates of significant HF hospitalizations, CV non-HF hospitalizations, and resource intensive late-stage procedures (LVADs and heart transplants) among the BAT + GDT group.

Conclusions

BAT + GDT treatment becomes less costly than GDT alone beginning between years 1 and 2 and becomes less costly cumulatively between years 2 and 3, potentially providing significant savings over time. As additional BeAT-HF trial data become available, the model can be updated to show longer term effects.

The protective role of SOD1 overexpression in central mediation of bradycardia following chronic intermittent hypoxia in mice

Obstructive sleep apnea (OSA) is a highly prevalent sleep disorder that is associated with many cardiovascular complications. Similar to OSA, chronic intermittent hypoxia (CIH) (a model for OSA) leads to oxidative stress and impairs baroreflex control of the heart rate (HR) in rodents. The baroreflex arc includes the aortic depressor nerve (ADN), vagal efferent, and central neurons. In this study, we used mice as a model to examine the effects of CIH on baroreflex sensitivity, aortic baroreceptor afferents, and central and vagal efferent components of the baroreflex circuitry. Furthermore, we tested whether human Cu/Zn Superoxide Dismutase (SOD1) overexpression in transgenic mice offers protection against CIH-induced deficit of the baroreflex arc. Wild-type C57BL/6J and SOD1 mice were exposed to room air (RA) or CIH and were then anesthetized, ventilated, and catheterized for measurement of mean arterial pressure (MAP) and HR. Compared with wild-type RA control, CIH impaired baroreflex sensitivity but increased maximum baroreceptor gain and bradycardic response to vagal efferent stimulation. Additionally, CIH reduced the bradycardic response to ADN stimulation, indicating a diminished central regulation of bradycardia. Interestingly, SOD1 overexpression prevented CIH-induced attenuation of HR responses to ADN stimulation and preserved HR responses to vagal efferent stimulation in transgenic mice. We suggest that CIH decreased central mediation of the baroreflex and SOD1 overexpression may prevent the CIH-induced central deficit.

Chronic heart failure: a disease of the brain

The underlying mechanism for clinical and biochemical manifestations of chronic heart failure (HF) may be due in part to neurohumoral adaptations, such as activation of the renin-angiotensin-aldosterone and sympathetic nervous systems in the periphery and the brain. Internet search and discussion with colleagues are the methods for this study. Since chronic HF is associated with autonomic imbalance with increased sympathetic nerve activity and a withdrawal of parasympathetic activity, it may be considered a brain disease. This phenomenon may be the result of an increased systemic and cerebral angiotensin II signaling because plasma angiotensin II is increased in humans and animals with chronic HF. The increase in angiotensin II signaling enhances sympathetic nerve activity through actions on both central and peripheral sites during chronic HF. Activation of angiotensin II signaling in different brain sites such as the paraventricular nucleus (PVN), rostral ventrolateral medulla (RVLM), and area postrema (AP) may increase the release of norepinephrine, oxidative stress, and inflammation leading to increased cardiac contractility. It is possible that blocking angiotensin II type 1 receptors decreases sympathetic nerve activity and cardiac sympathetic afferent reflex when therapy is administered to the PVN. The administration of an angiotensin receptor blocker by injection into the AP activates the sympatho-inhibitory baroreflex indicating that receptor blockers act by increasing parasympathetic activity. In chronic HF, in peripheral regions, angiotensin II elevates both norepinephrine release and synthesis and inhibits norepinephrine uptake at nerve endings, which may contribute to the increase in sympathetic nerve activity. Increased circulating angiotensin II during chronic HF may enhance the sympatho-excitatory chemoreflex and inhibit the sympatho-inhibitory baroreflex resulting in worsening of HF. Increased circulating angiotensin II signaling can directly act on the central nervous system via the subfornical organ and the AP to increase sympathetic outflow resulting in to neurohumoral dysfunction, resulting in to heart failure.

Safety and efficacy of baroreflex activation therapy for heart failure with reduced ejection fraction: a rapid systematic review

To retrieve and assess the available data in the literature about the safety and efficacy of baroreflex activation therapy (BAT) in heart failure with reduced ejection fraction (HFrEF) patients, through a rapid systematic review of clinical studies. Rapid systematic review of literature. Searched electronic databases included PubMed, EMBASE, CENTRAL, Scopus, and Web of Science using Mesh and free terms for heart failure and BAT. No language restriction was used for the searches. We included full peer reviewed publications of clinical studies (randomized or not), including patients with HFrEF undergoing BAT, with or without control group, assessing safety and efficacy outcomes. One reviewer conducted the analysis of the selected abstracts and the full‐text articles, performed data extraction, and evaluated the methodological quality of the selected articles. The methodological quality was assessed according to the Cochrane Collaboration instruments. A descriptive summary of the results is provided. Of the 441 citations screened, 10 publications were included (three were only conference abstracts), reporting data from three studies. Only one study was a randomized clinical trial. Two studies reported a 6 month following, and the other study analysed outcomes up to 41 months. The procedure seems to be safe when performed by a well‐trained multi‐professional team. An 86% rate of system and procedure‐related complication‐free was reported, with no cranial nerve injuries. Improvements in New York Heart Association class of heart failure, quality of life, 6 min walk test, and hospitalization rates, as well as in muscle sympathetic nerve activity. No meta‐analysis was conducted because of the lack of homogeneity across studies; the results from each study are reported individually. BAT procedure seems to be safe if appropriate training is provided. Improvements in clinical outcomes were described in all included studies. However, several limitations do not allow us to make conclusive statements on the efficacy of BAT for HFrEF. New well‐designed trials are still needed.

Aortic stiffness and central systolic pressure are associated with ambulatory orthostatic BP fall in chronic kidney disease

OBJECTIVE

Orthostatic hypotension (OH) has a significant association with cardiovascular disease. OH becomes more common in older age, as does arterial stiffness, shown to be independently associated with impaired baroreflex sensitivity and OH. Measurement of arterial compliance and central blood pressures are increasingly important, with evidence that central BP more closely correlates to end-organ damage and mortality than peripheral measurements. Patients with chronic kidney disease (CKD) are high risk for cardiovascular events, which can be predicted through measures of arterial compliance. We hypothesised that OH is associated with arterial stiffness and central blood pressure in CKD patients.

DESIGN/SETTING

We tested this hypothesis within the arterial compliance and oxidant stress as predictors of loss of renal function, morbidity and mortality in chronic kidney disease (ACADEMIC) study, a single-centre prospective observational study of the progression of arterial stiffness and renal function.

PARTICIPANTS

One hundred and forty-six patients with CKD 3 or 4.

MEASUREMENTS

Twenty-four-hour ambulatory BP monitoring with postural sensing (DIASYS Integra 2, Novacor France); central systolic and diastolic BP (cSBP and cDBP) and aortic Augmentation Index using Sphygmocor^® (Atcor, Australia); Carotid-femoral pulse wave velocity (cfPWV) using Complior^® (ALAM Medical, France).

RESULTS

Twenty-three patients had a postural SBP fall (prevalence 15.8%), with mean drop 7 mmHg. Patients with OH had higher cfPWV (15.2 m/s vs 12.7 m/s in patients without OH, p < 0.001) and central SBP (147.5 vs 135.7, p = 0.012). Regression analysis gave an odds ratio (OR) of orthostatic SBP fall for cfPWV of 1.46 (95% CI 1.16-1.84, p = 0.001) and 1.03 for cSBP (95% CI 1.004-1.06, p = 0.024) after adjustment for cardiovascular risk factors.

CONCLUSION

Aortic stiffness and central SBP are independently associated with orthostatic SBP fall in CKD patients. This suggests that enhanced arterial stiffness may be an underlying mechanism in baroreflex dysfunction, and may partly explain the vascular risk in CKD patients.

Carotid baroreceptor stimulation suppresses ventricular fibrillation in canines with chronic heart failure

Carotid baroreceptor stimulation (CBS) has been shown to improve cardiac dysfunction and pathological structure remodelling. This study aimed to investigate the effects of CBS on the ventricular electrophysiological properties in canines with chronic heart failure (CHF). Thirty-eight beagles were randomized into control (CON), CHF, low-level CBS (LL-CBS), and moderate-level CBS (ML-CBS) groups. The CHF model was established with 6 weeks of rapid right ventricular pacing (RVP), and concomitant LL-CBS and ML-CBS were applied in the LL-CBS and ML-CBS groups, respectively. After 6 weeks of RVP, ventricular electrophysiological parameters and left stellate ganglion (LSG) neural activity and function were measured. Autonomic neural remodelling in the LSG and left ventricle (LV) and ionic remodelling in the LV were detected. Compared with the CHF group, both LL-CBS and ML-CBS decreased spatial dispersion of action potential duration (APD), suppressed APD alternans, reduced ventricular fibrillation (VF) inducibility, and inhibited enhanced LSG neural discharge and function. Only ML-CBS significantly inhibited ventricular repolarization prolongation and increased the VF threshold. Moreover, ML-CBS inhibited the increase in growth-associated protein-43 and tyrosine hydroxylase-positive nerve fibre densities in LV, increased acetylcholinesterase protein expression in LSG, and decreased nerve growth factor protein expression in LSG and LV. Chronic RVP resulted in a remarkable reduction in protein expression encoding both potassium and L-type calcium currents; these changes were partly amended by ML-CBS and LL-CBS. In conclusion, CBS suppresses VF in CHF canines, potentially by modulating autonomic nerve and ion channels. In addition, the effects of ML-CBS on ventricular electrophysiological properties, autonomic remodelling, and ionic remodelling were superior to those of LL-CBS.

Orthostatic hypotension and the risk of atrial fibrillation and other cardiovascular diseases: An updated meta-analysis of prospective cohort studies

The relationships between orthostatic hypotension (OH) and some kinds of cardiovascular disease are inconsistent among studies. This updated meta-analysis was conducted in hopes of producing progress on this topic. A systematic database search was performed in electronic databases, including the Chinese Biomedical Database (CBM), PubMed, Web of Science, and the Cochrane Library. Summary hazard ratio (HR) estimates with 95% confidence intervals (CIs) were calculated by a random-effects model. Statistical heterogeneity was assessed with Cochran's Q test and the I2 statistic. From 1462 potentially eligible records, 15 studies met the inclusion criteria. Subjects with OH had a high risk of heart failure (HF) and atrial fibrillation (AF) (pooled HR 1.34, 95% CI 1.17-1.52, P < 0.001 and pooled HR 1.51, 95% CI 1.28-1.79, P < 0.001, respectively). This meta-analysis also showed significant associations between OH and the risks of developing coronary heart disease (CHD) (pooled HR 1.44, 95% CI 1.18-1.75, P < 0.001) and myocardial infarction (MI) (pooled HR 1.52, 95% CI 1.12-2.06, P = 0.008). Our study suggests that OH is positively associated with high risks of HF and AF. Moreover, it may be related to high risks of CHD and MI.

First granted example of novel FDA trial design under Expedited Access Pathway for premarket approval: BeAT-HF

BACKGROUND

The Food and Drug Administration (FDA) initiated the Expedited Access Pathway (EAP) to accelerate approval of novel therapies targeting unmet needs for life-threatening conditions. EAP allows for the possibility of initial FDA approval using intermediate end points with postapproval demonstration of improved outcomes.

OBJECTIVE

Describe the EAP process using the BeAT-HF trial as a case study.

METHODS

BeAT-HF will examine the safety and effectiveness of baroreflex activation therapy (BAT) in heart failure patients with reduced ejection fraction using an Expedited and Extended Phase design. In the Expedited Phase, BAT plus guideline-directed medical therapy (GDMT) will be compared at 6 months postimplant to GDMT alone using 3 intermediate end points: 6-minute hall walk distance, Minnesota Living with Heart Failure Questionnaire, and N-terminal pro-B-type natriuretic peptide. The rate of heart failure morbidity and cardiovascular mortality will be compared between the arms to evaluate early trending using predictive probability modeling. Sample size of 264 patients randomized 1:1 to BAT + GDMT versus GDMT alone provides 81% power for the Expedited Phase intermediate end points. For the Extended Phase, the heart failure morbidity and cardiovascular mortality end point is based on an expected event rate of 0.4 events/patient/year in the GDMT arm. With an adaptive sample size selection design for robustness to inaccurate assumptions, a sample size of 480-960 randomized patients followed ≥2 years allows detecting a 30% reduction in the primary end point with a power of 97.5%.

CONCLUSION

Through a unique collaboration with FDA under the EAP, the BeAT-HF trial design allows for the possibility of approval of BAT, initially for symptom relief and subsequently for outcomes improvement.

Earliest effects of sudden occlusions on pressure profiles in selected locations of the human systemic arterial system

We have developed a numerical simulation method for predicting the time dependence (wave form) of pressure at any location in the systemic arterial system in humans. The method uses the matlab-Simulink environment. The input data include explicitly the geometry of the arterial tree, treated up to an arbitrary bifurcation level, and the elastic properties of arteries as well as rheological parameters of blood. Thus, the impact of anatomic details of an individual subject can be studied. The method is applied here to reveal the earliest stages of mechanical reaction of the pressure profiles to sudden local blockages (thromboses or embolisms) of selected arteries. The results obtained with a purely passive model provide reference data indispensable for studies of longer-term effects due to neural and humoral mechanisms. The reliability of the results has been checked by comparison of two available sets of anatomic, elastic, and rheological data involving (i) 55 and (ii) 138 arterial segments. The remaining arteries have been replaced with the appropriate resistive elements. Both models are efficient in predicting an overall shift of pressure, whereas the accuracy of the 55-segment model in reproducing the detailed wave forms and stabilization times turns out dependent on the location of the blockage and the observation point.

Baroreflex Activation Therapy in Heart Failure With Reduced Ejection Fraction: Available Data and Future Perspective

Progression of heart failure with reduced ejection fraction (HFrEF) is promoted by sympathovagal imbalance. Baroreflex activation therapy, i.e., electrical stimulation of baroreceptors at the carotid sinus, can restore sympathovagal balance. Large animal studies of baroreflex activation therapy revealed improvements in cardiac function, susceptibility to ventricular arrhythmias, and a survival benefit as compared to untreated controls. Recently, the first randomized and controlled trial of optimal medical and device therapy alone or plus baroreflex activation therapy in patients suffering from HFrEF was published. It demonstrated a reasonable safety profile in this severely ill patient population. Moreover, the study found significant improvements in New York Heart Association class, quality of life, 6-min walk distance, and NT-proBNP levels. This review provides an overview on baroreflex activation therapy for the treatment of HFrEF-from the concept and preclinical findings to most recent clinical data and upcoming trials.

[Baroreflex activation therapy. A novel interventional approach to treat heart failure with reduced ejection fraction]

Sympathovagal imbalance plays an important role in the progression of heart failure with reduced ejection fraction. Baroreflex activation therapy (BAT), i. e. electrical stimulation of baroreceptors located at the carotid sinus, can reduce sympathetic and enhance parasympathetic tone. Large animal studies on BAT demonstrated improvements in cardiac function, arrhythmogenic risk and a survival benefit compared to untreated controls. The recently published Neo Randomized Heart Failure Study, the first multicenter, randomized and controlled trial of optimal medical and device therapy alone or plus BAT in patients with a left ventricular ejection fraction ≤ 35 %, demonstrated a reasonable safety profile of BAT in this severely ill patient population and no relevant interactions with other devices. The study found significant improvements in the New York Heart Association (NYHA) class of heart failure, quality of life as well as 6 min walking distance and data pointed to a reduction in hospitalization rates. Moreover, N-terminal pro-brain natriuretic peptide (NT-proBNP) levels were significantly reduced. This review gives an overview on BAT for the treatment of heart failure with reduced ejection fraction, from the rationale and animal experiments to the most recent clinical data and future perspectives.

Angiotensin II-superoxide-NFκB signaling and aortic baroreceptor dysfunction in chronic heart failure

Chronic heart failure (CHF) affects approximately 5.7 million people in the United States. Increasing evidence from both clinical and experimental studies indicates that the sensitivity of arterial baroreflex is blunted in the CHF state, which is a predictive risk factor for sudden cardiac death. Normally, the arterial baroreflex regulates blood pressure and heart rate through sensing mechanical alteration of arterial vascular walls by baroreceptor terminals in the aortic arch and carotid sinus. There are aortic baroreceptor neurons in the nodose ganglion (NG), which serve as the main afferent component of the arterial baroreflex. Functional changes of baroreceptor neurons are involved in the arterial baroreflex dysfunction in CHF. In the CHF state, circulating angiotensin II (Ang II) and local Ang II concentration in the NG are elevated, and AT1R mRNA and protein are overexpressed in the NG. Additionally, Ang II-superoxide-NFκB signaling pathway regulates the neuronal excitability of aortic baroreceptors through influencing the expression and activation of Na_v channels in aortic baroreceptors, and subsequently causes the impairment of the arterial baroreflex in CHF. These new findings provide a basis for potential pharmacological interventions for the improvement of the arterial baroreflex sensitivity in the CHF state. This review summarizes the mechanisms responsible for the arterial baroreflex dysfunction in CHF.

Intermittent electrical stimulation of the right cervical vagus nerve in salt-sensitive hypertensive rats: effects on blood pressure, arrhythmias, and ventricular electrophysiology

Hypertension (HTN) is the single greatest risk factor for potentially fatal cardiovascular diseases. One cause of HTN is inappropriately increased sympathetic nervous system activity, suggesting that restoring the autonomic nervous balance may be an effective means of HTN treatment. Here, we studied the potential of vagus nerve stimulation (VNS) to treat chronic HTN and cardiac arrhythmias through stimulation of the right cervical vagus nerve in hypertensive rats. Dahl salt-sensitive rats (n = 12) were given a high salt diet to induce HTN. After 6 weeks, rats were randomized into two groups: HTN-Sham and HTN-VNS, in which VNS was provided to HTN-VNS group for 4 weeks. In vivo blood pressure and electrocardiogram activities were monitored continuously by an implantable telemetry system. After 10 weeks, rats were euthanized and their hearts were extracted for ex vivo electrophysiological studies using high-resolution optical mapping. Six weeks of high salt diet significantly increased both mean arterial pressure (MAP) and pulse pressure, demonstrating successful induction of HTN in all rats. After 4 weeks of VNS treatment, the increase in MAP and the number of arrhythmia episodes in HTN-VNS rats was significantly attenuated when compared to those observed in HTN-Sham rats. VNS treatment also induced changes in electrophysiological properties of the heart, such as reduction in action potential duration (APD) during rapid drive pacing, slope of APD restitution, spatial dispersion of APD, and increase in conduction velocity of impulse propagation. Overall, these results provide further evidence for the therapeutic efficacy of VNS in HTN and HTN-related heart diseases.

Cardiovascular morbidity and mortality related to orthostatic hypotension: a meta-analysis of prospective observational studies

BACKGROUND

Whether orthostatic hypotension (OH) is a risk factor for cardiovascular morbidity and death is uncertain. Currently available evidence derives from non-homogeneous and partly ambiguous studies.

OBJECTIVE

We aimed at assessing the relationship between OH and death or major adverse cardiac and cerebrovascular events (MACCEs) by integrating results of previous studies.

METHODS

We performed a meta-analysis of prospective observational studies reporting on the association between prevalent OH, mortality, and incident MACCE, published from 1966 through 2013. Mantel-Haenszel pooled estimates of relative risk (RR) and 95% confidence intervals (CIs) for all-cause death were assessed as the primary endpoint at the longest follow-up; incident coronary heart disease (CHD), heart failure (HF), and stroke were assessed as secondary endpoints. We also performed post hoc subgroup analyses stratified by age and a meta-regression analysis.

RESULTS

We identified a total of 13 studies, including an overall population of 121 913 patients, with a median follow-up of 6 years. Compared with the absence of OH, the occurrence of OH was associated with a significantly increased risk of all-cause death (RR 1.50; 95% CI 1.24-1.81), incident CHD (RR 1.41; 95% CI 1.22-1.63), HF (RR 2.25; 95% CI 1.52-3.33), and stroke (RR 1.64; 95% CI 1.13-2.37). When analysed according to age, pooled estimates of RR (95% CI) for all-cause death were 1.78 (1.25-2.52) for patients <65 years old, and 1.26 (0.99-1.62) in the older subgroup.

CONCLUSION

Orthostatic hypotension is associated with a significantly increased risk of all-cause death, incident CHD, HF, and stroke.

Carotid Baroreceptor Stimulation in Resistant Hypertension and Heart Failure

A significant number of hypertensive subjects fail to achieve adequate blood pressure control despite adherence to maximal doses of several antihypertensive drugs. In the same way although medical and device therapies continue to improve the clinical course of heart failure patients, morbidity, mortality and healthcare costs remain high. Electrical stimulation of the carotid sinus is a new interesting approach for the treatment of resistant hypertension and heart failure. The purpose of this paper is to overview the argument starting from physiological background and evaluating the clinical results obtained with this approach in these pathophysiological conditions.

The interplay between sympathetic overactivity, hypertension and heart rate variability (review, invited)

The control of arterial pressure is a complex interaction of the long- and short-term influences of hormones, local vascular factors, and neural mechanisms. The autonomic nervous system and its sympathetic arm play important roles in the regulation of blood pressure, and overactivity of sympathetic nerves may have an important role in the development of hypertension and related cardiovascular disorders. The baroreceptor system opposes either increases or decreases in arterial pressure, and the primary purpose of the arterial baroreflex is to keep blood pressure close to a particular set point over a relatively short period of time. The ability of the baroreflex to powerfully buffer acute changes in arterial pressure is well established, but the role of the arterial baroreceptor reflex in long-term control of arterial pressure has been a topic of many debate and controversy for decades. The sympathetic nervous system and arterial baroreceptor reflex control of renal sympathetic nerve activity has been proposed to play a role in long-term control of arterial pressure. The aim of this paper has been to review the postulated role of sympathetic activation.

Chronic baroreflex activation effects on sympathetic nerve traffic, baroreflex function, and cardiac haemodynamics in heart failure: a proof-of-concept study

Aims

Heart failure (HF) pathophysiology is believed to be mediated by autonomic dysfunction, including chronic sympathoexcitation and diminished baroreflex sensitivity, which correlate with mortality risk. Baroreflex activation therapy (BAT) is a device-based treatment providing chronic baroreflex activation through electrical stimulation of the carotid sinus. BAT chronically reduces sympathetic activity in resistant hypertension. The purpose of this investigation is to determine BAT effects in clinical HF.

Methods and results

In a single-centre, open-label evaluation, patients with NYHA class III HF, EF <40%, optimized medical therapy, and ineligible for cardiac resynchronization received BAT for 6 months. Efficacy was assessed with serial measurement of muscle sympathetic nerve activity (MSNA) and clinical measures of quality of life and functional capacity. Eleven patients participated in the trial. MSNA was reduced over 6 months from 45.1 ± 7.7 to 31.3 ± 8.3 bursts/min and from 67.6 ± 12.7 to 45.1 ± 11.6 bursts/100 heartbeats, decreases of 31% and 33%, respectively (P < 0.01). Concomitant improvements occurred in baroreflex sensitivity, EF, NYHA class, quality of life and 6 min hall walk (6MHW) distance (P ≤ 0.05 each). On an observational basis, hospitalization and emergency department visits for worsening HF were markedly reduced. One complication, perioperative anaemia requiring transfusion, occurred during the study.

Conclusion

BAT was safe and provided chronic improvement in MSNA and clinical variables. Based on present understanding of HF pathophysiology, these results suggest that BAT may improve outcome in HF by modulating autonomic balance. Prospective, randomized trials to test the hypothesis are warranted.

The baroreceptor as a therapeutic target for heart failure

Sympathoactivation is a prominent feature of heart failure (HF). Its role in cardiac remodeling and arrhythmogenesis is well-recognized today, although incomplete understanding of autonomic mechanisms was a barrier to development of contemporary medical therapies. Despite widespread availability of drugs and devices, mortality and morbidity in HF remain unacceptably high. Recognition of an additional phenotype, HF with preserved ejection fraction (EF), poses additional challenges. New treatment options are required. Electrical modulation of the central nervous system with baroreflex activation therapy offers a new approach. Activation of this afferent pathway induces the central nervous system to rebalance autonomic modulation of the cardiovascular system. Results in animal models of HF demonstrating increased survival and beneficial cardiac remodeling recently led to a clinical feasibility study in HF with reduced EF wherein the clinical course of patients dramatically improved. Results in resistant hypertension patients further suggest potential for benefit in HF with preserved EF.

Orthostatic hypotension and the risk of congestive heart failure: a meta-analysis of prospective cohort studies

BACKGROUND

Orthostatic hypotension (OH) has been related to the increased risk of future congestive heart failure (CHF) events. However, the overall quantitative estimate of predictive ability of OH for CHF has not been determined. We therefore performed a meta-analysis to investigate the association between OH and incident CHF.

METHODS

Prospective cohort studies relevant to the aim of the study were identified by searching of Medline and Embase databases up to December 25, 2012 without restrictions and by reviewing the reference lists from retrieved articles.

RESULTS

A total of 51270 subjects and 3603 incident CHF cases from 4 prospective cohorts were included in the meta-analysis. Using random effect model, the pooled result indicated that presence of OH at baseline was significantly associated with an increased risk for future CHF outcomes (adjusted hazard ratio: 1.30, 95% confidence interval 1.09-1.55; p = 0.004). Results of stratified analysis suggested that the association between OH and CHF incidence seemed to be significant in middle-age subjects, or the individuals with hypertension and diabetes at baseline, but did not significant in the elderly subjects or those without hypertension or diabetes.

CONCLUSIONS

Our meta-analysis confirmed that presence of OH is related to a significant increased risk for development of CHF in the future. Studies are needed to explore the potential mechanisms underlying this association. More importantly, screen for OH may be of great clinical significance for the early identification of subjects at higher risk for development of CHF.