(Circulation. 2000;102:2898.)
© 2000 American Heart Association, Inc.
Current Perspective |
The Elusive Pathophysiology of Neurally Mediated Syncope
From the Division of Clinical Pharmacology, DuPont Pharmaceuticals, Wilmington, Del (R.M.-G., R.F.-V.); Centro Ricerche Cardiovascolari, CNR, Medicina Interna II, Ospedale "L. Sacco," Università di Milano, Italy (R.F.); and Clinic Bavaria Kreischa, Department of Diabetes and Endocrinology, Keischa, Germany (J.T.).
Correspondence and reprint requests to Dr Rogelio Mosqueda-Garcia, Dupont Pharmaceuticals Co, Chestnut Run Plaza, WR 2081, 974 Centre Road, Wilmington, DE 19805. E-mail Agustin.r.Mosqueda@Dupontpharma.com
Key Words: baroreceptors • catecholamines • nervous system, autonomic • syncope • microneurography
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Introduction |
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Syncope is defined as a sudden transient loss of consciousness and postural tone due to cerebral hypoperfusion. Although no permanent medical sequelae should result from syncope itself, isolated or recurrent events are often dramatic and disrupt the lifestyle of affected individuals. Syncope is a common clinical problem that affects up to 3.5% of the general population.1 Strikingly, in close to 40% of cases, the exact cause of syncope remains elusive, and
30% of affected patients will experience
recurrent episodes.1
Neurally mediated syncope (NMS) is a common type of syncope (Figure 1
); clinical descriptions of it have been
present in the medical literature for >100 years. Despite its
prevalence, significant gaps in our understanding of its
pathophysiology and treatment remain. The purpose of this review is to
critically evaluate proposed theories that attempt to explain the
pathophysiological mechanisms of NMS.
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Definition |
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The development of arterial vasodilation in the setting of relative or absolute bradycardia characterizes NMS. This syndrome has also been known as vasovagal reaction, neurocardiogenic syncope, emotional fainting, or reflex syncope. Related processes include situational fainting (ie, shaving syncope), hyperadrenergic and hypoadrenergic conditions, and hypotensive reactions resulting from drug administration.
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Classification |
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We have classified NMS into several categories. These include central (for example, occurring in response to strong emotional stimulation), postural (associated with the upright position), and situational (after the
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