Baroreflex activation therapy in advanced heart failure therapy: insights from a real-world scenario

Baroreflex activation therapy in patients with heart failure with reduced ejection fraction: a single-centre experience

AIMS

Heart failure with reduced ejection fraction (HFrEF) is associated with excessive sympathetic and impaired parasympathetic activity. The Barostim Neo™ device is used for electronical baroreflex activation therapy (BAT) to counteract autonomic nervous system dysbalance. Randomized trials have shown that BAT improves walking distance and reduces N-terminal prohormone of brain natriuretic peptide (NT-proBNP) levels at least in patients with only moderate elevation at baseline. Its impact on the risk of heart failure hospitalization (HFH) and death is not yet established, and experience in clinical routine is limited.

METHODS AND RESULTS

We report on patient characteristics and clinical outcome in a retrospective, non-randomized single-centre registry of BAT in HFrEF. Patients in the New York Heart Association (NYHA) Classes III and IV with a left ventricular ejection fraction (LVEF) <35% despite guideline-directed medical therapy were eligible. Symptom burden, echocardiography, and laboratory testing were assessed at baseline and after 12 months. Clinical events of HFH and death were recorded at routine clinical follow-up. Data are shown as number (%) or median (inter-quartile range). Between 2014 and 2020, 30 patients were treated with BAT. Median age was 67 (63-77) years, and 27 patients (90%) were male. Most patients (83%) had previous HFH. Device implantation was successful in all patients. At 12 months, six patients had died and three were alive but did not attend follow-up. NYHA class was III/IV in 26 (87%)/4 (13%) patients at baseline, improved in 19 patients, and remained unchanged in 5 patients (P < 0.001). LVEF improved from 25.5 (20.0-30.5) % at baseline to 30.0 (25.0-36.0) % at 12 months (P = 0.014). Left ventricular end-diastolic diameter remained unchanged. A numerical decrease in NT-proBNP [3165 (880-8085) vs. 1001 (599-3820) pg/mL] was not significant (P = 0.526). Median follow-up for clinical events was 16 (10-33) months. Mortality at 1 (n = 6, 20%) and 3 years (n = 10, 33%) was as expected by the Meta-Analysis Global Group in Chronic Heart Failure risk score. Despite BAT, event rate was high in patients with NYHA Class IV, NT-proBNP levels >1600 pg/mL, or estimated glomerular filtration rate (eGFR) <30 mL/min at baseline. NYHA class and eGFR were independent predictors of mortality.

CONCLUSIONS

Patients with HFrEF who are selected for BAT are in a stage of worsening or even advanced heart failure. BAT appears to be safe and improves clinical symptoms and-to a modest degree-left ventricular function. The risk of death remains high in advanced disease stages. Patient selection seems to be crucial, and the impact of BAT in earlier disease stages needs to be established.

Efficacy and safety of baroreflex activation therapy for heart failure with reduced ejection fraction: systematic review

Baroreflex activation therapy (BAT) is a possible adjuvant treatment for patients with heart failure with reduced ejection fraction (HFrEF) who remain symptomatic despite optimal medical therapy and may be an alternative therapy in patients with contraindications or drug intolerance. Our aim was to evaluate the efficacy and safety of BAT in patients with HFrEF. The protocol for this study was registered with PROSPERO (CRD42022349175). Searches were conducted using MEDLINE, preMedLine (via PubMed), EMBASE, Cochrane Library, Web of Science, Trip Medical Database, WHO International Clinical Trials Registry, and ClinicalTrials.gov. We included randomized controlled trials that compared the effects of BAT with pharmacological treatment. We assessed the risk of bias of each study using the Cochrane RoB2 tool and the certainty of the results using the GRADE approach. We performed a meta-analysis of treatment effects using a fixed-effects or random-effects model, depending on the heterogeneity observed. Two studies were included in the meta-analysis (HOPE4HF and BeAT-HF). The results showed that BAT led to statistically significant improvements in New York Heart Association functional class (relative risk 2.13; 95% confidence interval [CI, 1.65 to 2.76]), quality of life (difference in means -16.97; 95% CI [-21.87 to -12.07]), 6 min walk test (difference in means 56.54; 95% CI [55.67 to 57.41]) and N-terminal probrain natriuretic peptide (difference in means -120.02; 95% CI [-193.58 to -46.45]). The system- and procedure-related complication event-free rate varied from 85.9% to 97%. The results show that BAT is safe and improves functional class, quality of life and congestion in selected patients with HFrEF. Further studies and long-term follow-up are needed to assess efficacy in reducing cardiovascular events and mortality.

A Comparative Review of Vagal Nerve Stimulation Versus Baroreceptor Activation Therapy in Cardiac Diseases

Sympathetic imbalance coupled with impairment of baroreceptor control is a key factor responsible for hemodynamic abnormalities in congestive heart failure. Vagal nerve stimulation (VNS) and baroreceptor activation therapy (BAT) are two novel interventions for the same. In this paper, we review the role of sympathovagal alterations in cardiac diseases like heart failure, arrhythmia, hypertension (HTN), etc. Studies like neural cardiac therapy for heart failure (NECTAR-HF), autonomic regulation therapy to enhance myocardial function and reduce progression of heart failure (ANTHEM-HF), and baroreflex activation therapy for heart failure (BEAT-HF), which comprise the history, efficacy, limitations, and current protocols, were extensively analyzed in contrast to one another. Vagal nerve stimulation reverses the reflex inhibition of cardiac vagal efferent activity, which is caused as a result of sympathetic overdrive during the course for heart failure. It has shown encouraging results in certain pre-clinical studies; however, there is also a possibility of serious cardiovascular adverse events if given in higher than the recommended dosage. Attenuated baroreflex sensitivity is attributed to cardiac arrhythmogenesis during heart failure. Baroreceptor activation therapy reverses this phenomenon. However, the surgical procedure for baroreceptor stimulation can have unwarranted complications, including worsening heart failure and hypertension. Considering the effectiveness of the given modalities and taking into account the inconclusive evidence of their adverse events, more clinical trials are needed for establishing the future prospects of these interventional approaches.

Autonomic Regulation of Inflammation in Conscious Animals

Bioelectronic medicine is a novel field in modern medicine based on the specific neuronal stimulation to control organ function, cardiovascular, and immune homeostasis. However, most studies addressing neuromodulation of the immune system have been conducted on anesthetized animals, which can affect the nervous system and neuromodulation. Here, we review recent studies involving conscious experimental rodents (rats and mice) to better understand the functional organization of neural control of immune homeostasis. We highlight typical experimental models of cardiovascular regulation, such as electrical activation of the aortic depressor nerve or the carotid sinus nerve, bilateral carotid occlusion, the Bezold-Jarisch reflex, and intravenous administration of the bacterial endotoxin lipopolysaccharide. These models have been used to investigate the relationship between neuromodulation of the cardiovascular and immune systems in conscious rodents (rats and mice). These studies provide critical information about the neuromodulation of the immune system, particularly the role of the autonomic nervous system, i.e., the sympathetic and parasympathetic branches acting both centrally (hypothalamus, nucleus ambiguus, nucleus tractus solitarius, caudal ventrolateral medulla, and rostral ventrolateral medulla), and peripherally (particularly spleen and adrenal medulla). Overall, the studies in conscious experimental models have certainly highlighted to the reader how the methodological approaches used to investigate cardiovascular reflexes in conscious rodents (rats and mice) can also be valuable for investigating the neural mechanisms involved in inflammatory responses. The reviewed studies have clinical implications for future therapeutic approaches of bioelectronic modulation of the nervous system to control organ function and physiological homeostasis in conscious physiology.