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Reflex syncope

Author
Brian Olshansky, MD
Section Editor
Leonard I Ganz, MD, FHRS, FACC
Deputy Editor
Brian C Downey, MD, FACC

INTRODUCTION

Reflex (neurally mediated) syncope is a transient loss of consciousness due to a reflex response that encompasses vasodilatation and/or bradycardia (rarely tachycardia), leading to systemic hypotension and cerebral hypoperfusion [1]. Types of reflex syncope include vasovagal syncope, situational syncope, carotid sinus syncope, and atypical forms (without apparent triggers and/or atypical presentation) (table 1).

Vasovagal syncope (also known as neurocardiogenic syncope) is the most common cause of syncope [2]. The diagnosis may be suggested or diagnosed by a specific history with well-known triggers, but a classic history is not required. The diagnosis can also be made by exclusion of other causes of syncope and by a characteristic response to upright tilt table testing during which the patient may pass out from bradycardia and/or hypotension.

The following discussion primarily applies to patients with recurrent syncope. Acute vasovagal reactions leading to syncope or presyncope are common also in a number of stressful settings, such as blood donation. They do not necessarily recur or require treatment. (See "Blood donor screening: Procedures and processes to enhance safety for the blood recipient and the blood donor", section on 'Vasovagal syncope'.)

Vasovagal syncope and situational syncope will be reviewed here. General discussions of the pathogenesis, etiology, and evaluation of syncope, and issues related to carotid sinus hypersensitivity and glossopharyngeal neuralgia, are discussed separately. (See "Pathogenesis and etiology of syncope" and "Syncope in adults: Clinical manifestations and diagnostic evaluation" and "Carotid sinus hypersensitivity" and "Overview of craniofacial pain", section on 'Glossopharyngeal neuralgia'.)

Vasovagal syncope is a cause of acute postural hypotension. Other causes of postural hypotension are discussed separately. (See "Mechanisms, causes, and evaluation of orthostatic hypotension" and "Postural tachycardia syndrome".)

                                   

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Literature review current through: Nov 2016. | This topic last updated: Thu Aug 14 00:00:00 GMT+00:00 2014.
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References
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