EffecTs of tRanscutaneous vAgus Nerve Stimulation in Heart Failure Patients With Moderately rEduced or preseRved Left Ventricular Function

The autonomic nervous system (ANS), through the interaction between the sympathetic and vagal systems, plays a key role in modulating the cardiovascular system. Multiple experimental data and clinical studies have shown that alterations in the activity of the ANS - characterized by a predominant sympathetic modulation associated with reduced vagal modulation - are implicated in the onset and progression of numerous cardiovascular diseases. For example, both an increase in sympathetic activity and a reduction in vagal activity are associated with an increased risk of death after myocardial infarction and heart failure, and a further reduction in vagal activity has been shown to precede the phases of hemodynamic instability (1 -2).

Over the last few years, the modulation of the ANS through the implantation of devices has emerged as a new frontier for the treatment of heart failure (3). Although there is a wide interest in the scientific community for the potential represented by this therapeutic modality, nevertheless the different devices for neuromodulation therapy are implantable devices (whose application requires an invasive procedure) and therefore not free from risks and complications.

Direct stimulation of the vagus nerve by means of a sleeve positioned around the vagus nerve in its right or left cervical portion and controlled by a pacemaker, represents one of the methods proposed in the field of neuromodulation (4).

As for vagal stimulation, this can also be achieved non-invasively by applying an external stimulator in the ear (5). Transcutaneous nerve stimulation is a widely used procedure for the treatment of refractory epilepsy, while there is still limited experience evaluating its cardiovascular effects. Preliminary data in healthy volunteers have shown that: a) transcutaneous vagal stimulation, through the auricle, is able to activate the afferent vagal pathway up to the nucleus of the solitary tract (6), b) non-invasive stimulation of the vagus nerve is able to reduce sympathetic outflow (7). Recent clinical experience suggests its role also in the control of paroxysmal atrial fibrillation (8).

Therefore, non-invasive vagus nerve stimulation could be a promising therapeutic option in the cardiovascular field.