Syncope is a sudden and transient loss of consciousness that is associated with a loss of postural tone, and resolves spontaneously and completely without intervention. Precise incidence rates are difficult to determine and depend on the features of the population studied. In the United States, syncope accounts for approximately 0.8% of all emergency department visits and 2% of all hospital admissions from the emergency department.
Although the pathophysiology of syncope is related to a transient decrease in cerebral blood flow, the causes of syncope are myriad and range from the benign to the life threatening.
Physicians must identify patients with potentially life-threatening processes (e.g., dysrhythmias, pulmonary embolism, subarachnoid hemorrhage, acute coronary syndromes), patients who may require hospitalization and intervention (e.g., patients with bradycardia or medication-induced orthostatic hypotension), and those with a more benign cause of syncope who can be discharged.
The history and the physical examination may identify an underlying cause of syncope in many patients. However, the lack of accurate historical information, and the fact that patients are often asymptomatic at the time of evaluation, combine to fuel diagnostic uncertainty.
- Acute coronary syndrome
- Ventricular arrhythmias
- Atrioventricular block
- Acute atrial fibrillation
- Congestive heart failure
- Volume depletion
- Sinus node dysfunction
- Aortic stenosis
- Upper gastrointestinal bleeding
- Lower gastrointestinal bleeding
- Neurally mediated
- Orthostatic hypotension
- Wolff-Parkinson-White syndrome/preexcitation syndrome
- Cardiac tamponade
- Aortic dissection
- Pulmonary embolism
- Ruptured abdominal aortic aneurysm
- Brugada syndrome
- Long QT syndrome
- Hypertrophic cardiomyopathy
- Arrhythmogenic right ventricular cardiomyopathy
- Mitral stenosis
- Atrial myxoma
- Cardiac sarcoidosis
- Paroxysmal supraventricular tachycardia
- Subclavian steal syndrome
- Implantable cardiac device malfunction
- Ectopic pregnancy
- Addison disease
- Vertebrobasilar transient ischemic attack
- Subarachnoid hemorrhage
- Psychogenic pseudosyncope
Shamai Grossman, MD, MS
Associate Professor of Medicine and Emergency Medicine
Harvard Medical School Department
Vice Chair for Health Care Quality
Director, Observation Medicine
Beth Israel Deaconess Medical Center
SG is an author of a reference cited in this topic.
Christopher Fischer, MD
Chair, Assistant Professor
Mount Auburn Hospital
Harvard Medical School
CF is an author of a reference cited in this topic.
Dr Shamai Grossman and Dr Christopher Fischer would like to gratefully acknowledge Dr Sanjeev Wasson, Dr Sarabjeet Singh and Dr Nishant Kalra, the previous contributors to this topic. SS and NK declare that they have no competing interests.
David Leaf, MD, MPH
Professor of Medicine
VA Greater Los Angeles Healthcare System
UCLA School of Medicine
DL declares that he has no competing interests.
Sanjiv Petkar, MBBS, MD, DM (Cardiology), MRCP
Heart and Lung Centre
New Cross Hospital
SP has received funds for attending conferences, and fees for speaking and consultation, from Medtronic Inc. SP was also in receipt of funding for research, between 2007 and 2009, from Medtronic Inc. to the University of Manchester. SP was a Guideline Development Group member of the National Institute or Health and Care Excellence (formerly National Institute for Clinical Excellence) guidelines on transient loss of consciousness ('blackouts') management in adults and young people, published in August 2010.
Nicholas Gall, MSc, MD, FRCP
Department of Cardiology
King's College Hospital
NG declares that he has no competing interests.
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