[Role of the sympathetic nervous system in vasovagal syncope and rationale for beta-blockers and norepinephrine transporter inhibitors].

Vasovagal or neurocardiogenic syncope is a common clinical situation and, as with other entities associated with orthostatic intolerance, the underlying condition is a dysfunction of the autonomic nervous system. This article reviews various aspects of vasovagal syncope, including its relationship with orthostatic intolerance and the role of the autonomic nervous system in it. A brief history of the problem is given, as well as a description of how the names and associated concepts have evolved. The response of the sympathetic system to orthostatic stress, the physiology of the baroreflex system and the neurohumoral changes that occur with standing are analyzed. Evidence is presented of the involvement of the autonomic nervous system, including studies of heart rate variability, microneurography, cardiac innervation, and molecular genetic studies. Finally, we describe different studies on the use of beta-blockers and norepinephrine transporter inhibitors (sibutramine, reboxetine) and the rationality of their use to prevent this type of syncope.