In patients with heart failure a series of pathophysiological mechanisms are activated, leading to an imbalance of the autonomic system. In particular, there is an increase in sympathetic activity and a reduction in parasympathetic activity.
These changes play a key role in the evolution of the disease, so much that the use of antiadrenergic drugs is a cornerstone in the treatment of patients with heart failure.
However, there are not only drug therapies capable of modulating the activity of the autonomic system. Electrical stimulators, acting on the carotid level, can counteract the prevalence of sympathetic activity. This new approach to heart failure treatment is defined as baroreflex activation therapy (BAT).
The Baroreflex Activation Therapy
Baroreflex Activation Therapy works by activating the parasympathetic system and inhibiting the sympathetic system thanks to an electrical stimulation delivered at the level of the carotid sinus baroreceptors. The impulses are generated by a device similar to a pacemaker or a neurostimulation device. The fact that BAT stimulates vagal activity, and at the same time inhibits sympathetic activity, characterizes it, compared to devices that induce only a vagal stimulation. The effect obtained is a reduction of vascular resistance. For this effect, BAT has shown in several studies to be effective in the treatment of resistant arterial hypertension.
Baroreflex Activation Therapy in heart failure
The effects of BAT in patients with heart failure have already been evaluated in some studies, showing that stimulation afferent to the brain, through the carotid sinus nerve, reduced sympathetic activity and increased parasympathetic activity, rebalancing the neurovegetative drive to the heart.
Research in this field has also shown that BAT induces a reduction of the pro-terminal N-type natriuretic peptide B (NT-proBNP), improves the quality of life of patients and increases the distance covered at the 6-minute walk test.
Baroreflex Activation Therapy and heart failure: the BAT-HF study
Recently, a new study has been published in the Journal of the American College of Cardiology: the BeAT-HF. The aim of this prospective, phase III, multicenter, randomized and controlled trial was to evaluate the safety and efficacy of BAT in patients with heart failure and reduced ejection fraction.
Patients enrolled in the study were randomized to receive BAT and optimal medical management, or optimal medical management alone. The stimulation device adopted was the BAROSTIM NEO system (CVRx, Minneapolis, Minnesota).
The inclusion criteria included a New York Heart Association class (NYHA) II or III, a left ventricular ejection fraction less than or equal to 35%, a 6-minute walk test distance between 150 and 400 meters and a stable medical management for 4 or more weeks.
Initially, a further eligibility criterion was the presence of NT-proBNP values greater than 1,600 pg/ml, in patients who had not had hospitalization for heart failure in the previous 12 months. This eligibility criterion was subsequently modified, excluding all patients with NTproBNP greater than 1,600 pg/ml.
There were no restrictions in case of atrial fibrillation or flutter.
The study endpoints assessed changes to the walk test distance, a quality of life score (Minnesota Living with HF Questionnaire quality-of-life) and NT-proBNP levels.
Baroreflex Activation Therapy and heart failure: tangible improvements
The results of the study showed that BAT induced an improvement in the walking test distance, in the levels of NT-proBNP and in the quality of life. More precisely, the group treated with BAT, compared to the control group, followed only with medical therapy, recorded a 25% reduction in NT-proBNP and an increase of 60 meters in the distance covered at the 6-minutes walk test.
Also, with regards to safety, the results were reassuring, with 97% of the patients free from major neurological or cardiovascular events related to the procedure.
In the six months of follow-up of the study, an additional interesting ancillary analysis of the results was performed. By evaluating drug management in patients in the two groups, it was seen that more drugs were added to the treatment regimen. In addition, this group of patients was more likely to have a new class of drugs added and more likely to receive a new angiotensin receptor-neprilysin inhibitor added.
Baroreflex Activation Therapy and heart failure: rebalance the neurovegetative system
The carotid baroreceptors work as a sort of safety sensors. If the blood pressure increases excessively, they send afferent signals through the glossopharyngeal nerve to the nucleus of the solitary tract. From here, efferent reflex signals are generated, direct to heart and vessels, that reduce sympathetic activity and increase vagal activity, reducing blood pressure and heart rate.
This new electrical stimulation system of the carotid sinus induces a “false” afferent signal, with the result of rebalancing a neurovegetative system which, due to heart failure, is oriented towards a sympathetic dominance.
This study therefore seems to highlight promising results for BAT, highlighting clear signs of clinical improvement in patients treated with this method.
But the BAT-HF study does not end here. After this first phase of the research, which led to the approval of the device by the FDA, a post-marketing evaluation will follow.
In this subsequent phase, the effects of BAT on hospitalization rates for heart failure and on cardiovascular mortality will be evaluated. If the results will be positive, a greater diffusion of this non-pharmacological approach to heart failure can be expected.
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