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Prevention of stroke by means of non-invasive vagus nerve stimulation: a pilot randomised controlled trial

Abstract

Stroke is a leading cause of death and disability worldwide, and one of the main warning signs for stroke is the transient ischemic attack (TIA). Although neurological damage is not permanent, the main concern in TIA is the recurrence of stroke. One of the oldest and most challenging questions in the treatment of cerebrovascular diseases is how to manage blood pressure levels after a sudden event. It has been documented that the benefits of some antihypertensive drugs in stroke prevention are due to reduced blood pressure variability (BPV). However, it is noteworthy that patients after TIA with elevated BPV during antihypertensive treatment have a worse prognosis, despite the control of pressure levels. On the other hand, data from clinical and experimental studies direct attention to the stimulation of the transcutaneous vagus nerve stimulation (VNS-t) as an adjuvant approach in some clinical conditions refractory to the pharmacological approach. In addition, some studies also report the acute effects of VNS-t on the autonomic nervous system in healthy subjects. For example, our group recently demonstrated that VNS-t reduces heart rate, systolic BPV and cardiac and peripheral sympathetic modulation in healthy subjects. Given these data, we see a therapeutic potential for this non-invasive neuromodulation technique in patients with elevated BPV after TIA. However, the ideal energy density for VNS-t to control blood pressure levels and autonomic dysfunction, in patients with elevated BPV, after TIA remains unknown. Therefore, the point that underlies the proposal of this investigation, focuses on identifying the ideal VNS-t parameters to reduce heart rate, blood pressure, systolic BPV and muscle sympathetic nerve activity in patients with elevated BPV after TIA. For this, the present proposal consists of two studies. In the first study, we will explore the combination of some parameters of stimulation energy density settings based on previous studies with other populations. We hypothesize that the parameters of moderate energy density will be more effective and safe in inducing changes in peripheral autonomic control and encephalic and systemic hemodynamics, than more extreme combinations of energy density. Then, we will select the most efficient and safe protocol from the first study to conduct a pilot randomized controlled trial. For this, thirty patients with elevated BPV after TIA will be randomly allocated to two homogeneous groups, in which the best stimulation parameters will be applied in an active area or in a harmless area/placebo for 30 consecutive days to investigate their effects on the cerebral and systemic hemodynamics and autonomic function. This second study hypothesizes that only VNS-t in the active area will control brain hemodynamics, autonomic dysfunction and decrease BPV in patients after TIA. (AU)

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