Last reviewed: 10 Apr 2021
Last updated: 28 Apr 2021

Summary

Differentials

Common

  • 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
  • Migraine
  • Seizure

Uncommon

  • 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
  • Hypoglycemia
  • Addison disease
  • Vertebrobasilar transient ischemic attack
  • Subarachnoid hemorrhage
  • Psychogenic pseudosyncope

Contributors

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

Boston

MA

Disclosures

SG is an author of a reference cited in this topic.

Chair, Assistant Professor

Mount Auburn Hospital

Harvard Medical School

Boston

MA

Disclosures

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.

Peer reviewersVIEW ALL

Professor of Medicine

VA Greater Los Angeles Healthcare System

UCLA School of Medicine

Los Angeles

CA

Disclosures

DL declares that he has no competing interests.

Consultant Cardiologist

Heart and Lung Centre

New Cross Hospital

Wolverhampton

UK

Disclosures

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.

Consultant Cardiologist

Department of Cardiology

King's College Hospital

London

UK

Disclosures

NG declares that he has no competing interests.

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