11/28 7/6/23, 2:38 PM Syncope in adults: Epidemiology, pathogenesis, and etiologies - UpToDate apparent TLOC (often many minutes), absence of physical injury, and absence of evidence pointing toward a cause for syncope or evidence of seizure activity [39-41]. (See "Psychogenic nonepileptic seizures: Etiology, clinical features, and diagnosis".) Metabolic and/or toxic abnormalities Metabolic or toxic abnormalities are rarely associated with an abrupt onset or complete brisk recovery; syncope is therefore rare in this setting. Hypoglycemia and encephalitis can cause coma, stupor, and confusion, but rarely the transient loss of consciousness characteristic of syncope. Although metabolic abnormalities (such as hypoglycemia or hypoxia) infrequently cause syncope, they can cause impaired consciousness that may be difficult to distinguish from syncope. Metabolic abnormalities, anemia, and hypovolemia can be effectively managed by specific therapy to correct these abnormalities. SOCIETY GUIDELINE LINKS Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Syncope".) INFORMATION FOR PATIENTS UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." th th The Basics patient education pieces are written in plain language, at the 5 to 6 grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more th th sophisticated, and more detailed. These articles are written at the 10 to 12 grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon. Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword[s] of interest.) Basics topic (see "Patient education: Syncope (fainting) (The Basics)") Beyond the Basics topic (see "Patient education: Syncope (fainting) (Beyond the Basics)") SUMMARY AND RECOMMENDATIONS https://www.uptodate.com/contents/syncope-in-adults-epidemiology-pathogenesis-and-etiologies/print 12/28 7/6/23, 2:38 PM Syncope in adults: Epidemiology, pathogenesis, and etiologies - UpToDate Epidemiology Syncope is a common clinical problem, which is one of the many causes of transient loss of consciousness (TLOC). Syncope has a lifetime prevalence in the population as a whole of approximately 20 percent. Syncope is responsible for between 1 and 3 percent of all emergency department visits and 1 percent of all hospital admissions. (See 'Epidemiology' above.) Causes The possible causes of TLOC resulting in true syncope are generally grouped into four major categories ( table 1): reflex syncope (neurally-mediated), orthostatic syncope, cardiac arrhythmias, and structural cardiopulmonary disease. (See 'Causes of syncope' above.) Causes of nonsyncopal attacks In the evaluation of a patient with TLOC in whom syncope is suspected, the clinician must necessarily consider and exclude conditions that mimic TLOC/syncope but are not true syncope ( algorithm 1). The most common of these conditions are seizures, sleep disturbances, accidental falls, and some psychiatric conditions (eg, conversion reactions resulting in psychogenic nonepileptic seizures, previously called psychogenic pseudoseizures). (See 'Causes of nonsyncopal attacks' above and "Evaluation and management of the first seizure in adults" and "Classification of sleep disorders" and "Psychogenic nonepileptic seizures: Etiology, clinical features, and diagnosis".) Atherosclerotic disease of the cerebral arteries is almost never the cause of true syncopal symptoms, as the brain has a very redundant blood supply. Instead, stroke and transient ischemia attacks cause focal neurologic deficits that do not recover rapidly or completely. (See 'Cerebrovascular disease' above.) Syncope of unknown origin When the initial evaluation, including history, physical examination, and ECG, is nondiagnostic in a patient with suspected syncope, the patient is considered to have syncope with an unexplained diagnosis (ie, syncope of unknown origin). The frequency of an "unknown" cause was previously approximately one-third of cases, but is now closer to 10 percent as syncope experts and specialized syncope diagnostic clinics have become more widely available. As a rule, syncope of unknown cause is generally associated with a good prognosis, suggesting that most are likely "reflex" in origin. (See 'Syncope of unknown origin' above.) Use of UpToDate is subject to the Terms of Use. REFERENCES https://www.uptodate.com/contents/syncope-in-adults-epidemiology-pathogenesis-and-etiologies/print 13/28 7/6/23, 2:38 PM Syncope in adults: Epidemiology, pathogenesis, and etiologies - UpToDate 1. Chen LY, Shen WK, Mahoney DW, et al. Prevalence of syncope in a population aged more than 45 years. Am J Med 2006; 119:1088.e1. 2. Shen WK, Sheldon RS, Benditt DG, et al. 2017 ACC/AHA/HRS Guideline for the Evaluation and Management of Patients With Syncope: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines, and the Heart Rhythm Society. J Am Coll Cardiol 2017. 3. Soteriades ES, Evans JC, Larson MG, et al. Incidence and prognosis of syncope. N Engl J Med 2002; 347:878. 4. Lipsitz LA. Syncope in the elderly. Ann Intern Med 1983; 99:92. 5. Freed LA, Eagle KA, Mahjoub ZA, et al. Gender differences in presentation, management, and cardiac event-free survival in patients with syncope. Am J Cardiol 1997; 80:1183. 6. Kapoor WN. Evaluation and outcome of patients with syncope. Medicine (Baltimore) 1990; 69:160. 7. Manolis AS, Linzer M, Salem D, Estes NA 3rd. Syncope: current diagnostic evaluation and management. Ann Intern Med 1990; 112:850. 8. Costantino G, Sun BC, Barbic F, et al. Syncope clinical management in the emergency department: a consensus from the first international workshop on syncope risk stratification in the emergency department. Eur Heart J 2016; 37:1493. 9. Colivicchi F, Ammirati F, Melina D, et al. Development and prospective validation of a risk stratification system for patients with syncope in the emergency department: the OESIL risk score. Eur Heart J 2003; 24:811. 10. Zimmermann T, du Fay de Lavallaz J, Nestelberger T, et al. International Validation of the Canadian Syncope Risk Score : A Cohort Study. Ann Intern Med 2022; 175:783. 11. Anand V, Benditt DG, Adkisson WO, et al. Trends of hospitalizations for syncope/collapse in the United States from 2004 to 2013-An analysis of national inpatient sample. J Cardiovasc Electrophysiol 2018; 29:916. 12. Kadri AN, Abuamsha H, Nusairat L, et al. Causes and Predictors of 30-Day Readmission in Patients With Syncope/Collapse: A Nationwide Cohort Study. J Am Heart Assoc 2018; 7:e009746. 13. Alboni P, Brignole M, Menozzi C, et al. Diagnostic value of history in patients with syncope with or without heart disease. J Am Coll Cardiol 2001; 37:1921. 14. Mathias CJ, Deguchi K, Schatz I. Observations on recurrent syncope and presyncope in 641 patients. Lancet 2001; 357:348. https://www.uptodate.com/contents/syncope-in-adults-epidemiology-pathogenesis-and-etiologies/print 14/28 7/6/23, 2:38 PM Syncope in adults: Epidemiology, pathogenesis, and etiologies - UpToDate 15. Linzer M, Yang EH, Estes NA 3rd, et al. Diagnosing syncope. Part 1: Value of history, physical examination, and electrocardiography. Clinical Efficacy Assessment Project of the American College of Physicians. Ann Intern Med 1997; 126:989. 16. Linzer M, Yang EH, Estes NA 3rd, et al. Diagnosing syncope. Part 2: Unexplained syncope. Clinical Efficacy Assessment Project of the American College of Physicians. Ann Intern Med 1997; 127:76. 17. Olshansky B, Mazuz M, Martins JB. Significance of inducible tachycardia in patients with syncope of unknown origin: a long-term follow-up. J Am Coll Cardiol 1985; 5:216. 18. Benditt DG, Adkisson WO, Sutton R, et al. Ambulatory diagnostic ECG monitoring for syncope and collapse: An assessment of clinical practice in the United States. Pacing Clin Electrophysiol 2018; 41:203. 19. Narkiewicz K, Cooley RL, Somers VK. Alcohol potentiates orthostatic hypotension : implications for alcohol-related syncope. Circulation 2000; 101:398. 20. Rutan GH, Hermanson B, Bild DE, et al. Orthostatic hypotension in older adults. The Cardiovascular Health Study. CHS Collaborative Research Group. Hypertension 1992; 19:508. 21. Ray CA, Monahan KD. Aging attenuates the vestibulosympathetic reflex in humans. Circulation 2002; 105:956. 22. Kontny F, Dale J. Self-terminating idiopathic ventricular fibrillation presenting as syncope: a 40-year follow-up report. J Intern Med 1990; 227:211. 23. Benditt DG. Syncope risk assessment in the emergency department and clinic. Prog Cardiovasc Dis 2013; 55:376. 24. Leitch JW, Klein GJ, Yee R, et al. Syncope associated with supraventricular tachycardia. An expression of tachycardia rate or vasomotor response? Circulation 1992; 85:1064. 25. Doi A, Miyamoto K, Uno K, et al. Studies on hemodynamic instability in paroxysmal supraventricular tachycardia: noninvasive evaluations by head-up tilt testing and power spectrum analysis on electrocardiographic RR variation. Pacing Clin Electrophysiol 2000; 23:1623. 26. Brembilla-Perrot B, Beurrier D, Houriez P, et al. Incidence and mechanism of presyncope and/or syncope associated with paroxysmal junctional tachycardia. Am J Cardiol 2001; 88:134. 27. Hamer AW, Rubin SA, Peter T, Mandel WJ. Factors that predict syncope during ventricular tachycardia in patients. Am Heart J 1984; 107:997. 28. Landolina M, Mantica M, Pessano P, et al. Impaired baroreflex sensitivity is correlated with hemodynamic deterioration of sustained ventricular tachycardia. J Am Coll Cardiol 1997; https://www.uptodate.com/contents/syncope-in-adults-epidemiology-pathogenesis-and-etiologies/print 15/28 7/6/23, 2:38 PM Syncope in adults: Epidemiology, pathogenesis, and etiologies - UpToDate 29:568. 29. Menozzi C, Brignole M, Garcia-Civera R, et al. Mechanism of syncope in patients with heart disease and negative electrophysiologic test. Circulation 2002; 105:2741. 30. Kapoor W, Karpf M, Levey GS. Issues in evaluating patients with syncope. Ann Intern Med 1984; 100:755. 31. Krahn AD, Andrade JG, Deyell MW. Selecting appropriate diagnostic tools for evaluating the patient with syncope/collapse. Prog Cardiovasc Dis 2013; 55:402. 32. Grech ED, Ramsdale DR. Exertional syncope in aortic stenosis: evidence to support inappropriate left ventricular baroreceptor response. Am Heart J 1991; 121:603. 33. Goliasch G, Kammerlander AA, Nitsche C, et al. Syncope: The Underestimated Threat in Severe Aortic Stenosis. JACC Cardiovasc Imaging 2019; 12:225. 34. WAYNE HH. Syncope. Physiological considerations and an analysis of the clinical characteristics in 510 patients. Am J Med 1961; 30:418. 35. Badertscher P, du Fay de Lavallaz J, Hammerer-Lercher A, et al. Prevalence of Pulmonary Embolism in Patients With Syncope. J Am Coll Cardiol 2019; 74:744. 36. Kenny RA, Brignole M, Dan GA, et al. Syncope Unit: rationale and requirement the European Heart Rhythm Association position statement endorsed by the Heart Rhythm Society. Europace 2015; 17:1325. 37. Brignole M, Moya A, de Lange FJ, et al. 2018 ESC Guidelines for the diagnosis and management of syncope. Eur Heart J 2018; 39:1883. 38. Sheldon R, Rose S, Ritchie D, et al. Historical criteria that distinguish syncope from seizures. J Am Coll Cardiol 2002; 40:142. 39. Heyer GL, Harvey RA, Islam MP. Comparison of Specific Fainting Characteristics Between Youth With Tilt-Induced Psychogenic Nonsyncopal Collapse Versus Reflex Syncope. Am J Cardiol 2017; 119:1116. 40. Walsh KE, Baneck T, Page RL, et al. Psychogenic pseudosyncope: Not always a diagnosis of exclusion. Pacing Clin Electrophysiol 2018; 41:480. 41. Tannemaat MR, van Niekerk J, Reijntjes RH, et al. The semiology of tilt-induced psychogenic pseudosyncope. Neurology 2013; 81:752. Topic 1049 Version 37.0 https://www.uptodate.com/contents/syncope-in-adults-epidemiology-pathogenesis-and-etiologies/print 16/28 7/6/23, 2:38 PM Syncope in adults: Epidemiology, pathogenesis, and etiologies - UpToDate GRAPHICS Major cardiovascular causes of syncope Reflex-mediated* Vasovagal Orthostatic vasovagal syncope: usually after prolonged standing, frequently in a warm environment, etc Emotional vasovagal syncope: secondary to fear, pain, medical procedure, etc Unknown trigger Situational Micturition, defecation Swallowing Coughing/sneezing Carotid sinus syndrome Orthostatic hypotension* Medication-related Diuretics (eg, thiazide or loop diuretics) Vasodilators (eg, dihydropyridine calcium channel blockers, nitrates, alpha blockers, etc) Antidepressants (eg, tricyclic drugs, SSRIs, etc) Volume depletion Hemorrhage Gastrointestinal losses (ie, vomiting or diarrhea) Diminished thirst drive (primarily in older patients) Autonomic failure Primary: pure autonomic failure, Parkinson disease, multiple system atrophy, Lewy body dementia Secondary: diabetes mellitus, amyloidosis, spinal cord injuries, autoimmune neuropathy (eg, Guillain-Barr ), paraneoplastic neuropathy Cardiac Tachyarrhythmias Ventricular tachycardia Supraventricular tachycardias Bradyarrhythmias (with inadequate ventricular response) Sinus node dysfunction https://www.uptodate.com/contents/syncope-in-adults-epidemiology-pathogenesis-and-etiologies/print 17/28 7/6/23, 2:38 PM Syncope in adults: Epidemiology, pathogenesis, and etiologies - UpToDate Atrioventricular block Structural disease Severe aortic stenosis Hypertrophic cardiomyopathy Cardiac tamponade Prosthetic valve dysfunction Congenital coronary anomalies Cardiac masses and tumors (eg, atrial myxoma) Cardiopulmonary/vascular Pulmonary embolus Severe pulmonary hypertension Aortic dissection SSRI: selective serotonin reuptake inhibitor. Reflex-mediated syncope and syncope due to orthostatic hypotension are more likely to occur, or are more severe, when other factors may also be contributing, such as medication(s) causing low blood pressure, volume depletion, pulmonary diseases causing reduction in brain oxygen supply, alcohol use, and/or environmental factors (excessive heat or humidity). Adapted from: Brignole M, Moya A, de Lange FJ, et al. 2018 ESC Guidelines for the diagnosis and management of syncope. Eur Heart J 2018; 39:1883. Graphic 118175 Version 4.0 https://www.uptodate.com/contents/syncope-in-adults-epidemiology-pathogenesis-and-etiologies/print 18/28 7/6/23, 2:38 PM Syncope in adults: Epidemiology, pathogenesis, and etiologies - UpToDate Incidence rates of syncope according to age and sex The incidence rates of syncope per 1000 person-years of follow-up increased with age among both men and women. The increase in the incidence rate was steeper starting at the age of 70 years. Syncope rates were similar among men and women. Soteriades ES, Evans JC, Larson MG, et al. Incidence and prognosis of syncope. N Engl J Med 2002; 347:878. Graphic 82449 Version 2.0 https://www.uptodate.com/contents/syncope-in-adults-epidemiology-pathogenesis-and-etiologies/print 19/28 7/6/23, 2:38 PM Syncope in adults: Epidemiology, pathogenesis, and etiologies - UpToDate Causes of syncope in pooled data from five population-based studies Cause Mean prevalence, percent Neurally mediated Vasovagal 18 Situational (eg, cough, micturition, defecation, swallow) 5 Carotid sinus syncope 1 Orthostatic hypotension 8 Medications 3 Psychiatric 2 Neurologic 10 Cardiac Organic heart disease 4 Arrhythmia 14 Unknown 34 Data from Linzer M, Yang EH, Estes M, et al. Ann Intern Med 1997; 126:989. Includes 1002 unselected patients with syncope, including those from hospital-based referrals, emergency departements, and outpatient clinics between 1984 and 1990. Graphic 55289 Version 2.0 https://www.uptodate.com/contents/syncope-in-adults-epidemiology-pathogenesis-and-etiologies/print 20/28 7/6/23, 2:38 PM Syncope in adults: Epidemiology, pathogenesis, and etiologies - UpToDate Causes of syncope in Framingham cohort Prevalence, percent Cause Men Women Cardiac 13.2 6.7 Stroke or transient ischemic attack 4.3 4.0 Seizure disorder 7.2 3.2 Vasovagal 19.8 22.2 Orthostatic hypotension 8.6 9.9 Medication 6.3 7.2 Other 9.5 6.1 Unknown 31.0 40.7 Includes data from 727 patients. Data from Soteriades ES, Evans JC, Larson MG, et al. N Engl J Med 2002; 347:878. Graphic 68080 Version 2.0 https://www.uptodate.com/contents/syncope-in-adults-epidemiology-pathogenesis-and-etiologies/print 21/28 7/6/23, 2:38 PM Syncope in adults: Epidemiology, pathogenesis, and etiologies - UpToDate Overall survival of patients with syncope Survival was worst for patients with a cardiovascular cause of syncope. p<0.001 for the comparison between participants with and those without syncope. The category "Vasovagal and other causes" includes vasovagal, orthostatic, medication-induced, and other, infrequent cause of syncope. Sorteriades ES, Evans JC, Larson MG, et al. Incidence and prognosis of syncope. N Engl J Med 2002; 347:878. Graphic 53302 Version 4.0 https://www.uptodate.com/contents/syncope-in-adults-epidemiology-pathogenesis-and-etiologies/print 22/28 7/6/23, 2:38 PM Syncope in adults: Epidemiology, pathogenesis, and etiologies - UpToDate Conditions incorrectly diagnosed as syncope Disorders with partial or complete LOC but without global cerebral hypoperfusion Epilepsy Metabolic disorders including hypoglycaemia, hypoxia, hyperventilation with hypocapnia Intoxication Vertebrobasilar TIA Disorders without impairment of consciousness Cataplexy Drop attacks Falls Functional (psychogenic pseudosyncope) TIA or carotid origin LOC: loss of consciousness; TIA: transient ischaemic attack. Reproduced with permission from: European Heart Rhythm Association (EHRA), Heart Failure Association (HFA), Heart Rhythm Society (HRS), et al. Guidelines for the diagnosis and management of syncope (version 2009): the Task Force for the Diagnosis and Management of Syncope of the European Society of Cardiology (ESC). Eur Heart J 2009; 30:2631. Copyright 2009 Oxford University Press. Graphic 76023 Version 6.0 https://www.uptodate.com/contents/syncope-in-adults-epidemiology-pathogenesis-and-etiologies/print 23/28 7/6/23, 2:38 PM Syncope in adults: Epidemiology, pathogenesis, and etiologies - UpToDate Algorithm for syncope/collapse This algorithm poses key questions about a collapse episode, including whether and when LOC occurred. However, in the absence of a credible witness, information about such episodes is often limited, as the affected individual may not have accurate recall of the event. Some causes have more than one possible type of presentation. LOC: loss of consciousness; BLS: basic life support; ACLS: advanced cardiac life support; SAH: subarachnoid hemorrhage; TIA: transient ischemic attack. This includes actual LOC as well as apparent LOC. Accidental falls without LOC often have multiple causes, including gait, posture, or balance impairment, environmental hazard, vertigo, focal seizure, TIA, stroke, and presyncope. These conditions result in apparent transient LOC, although consciousness may be preserved. https://www.uptodate.com/contents/syncope-in-adults-epidemiology-pathogenesis-and-etiologies/print 24/28 7/6/23, 2:38 PM Syncope in adults: Epidemiology, pathogenesis, and etiologies - UpToDate Other causes of collapse may cause secondary head trauma. Most TIAs and strokes are not associated with LOC. An SAH may cause transient or prolonged LOC. A rare cause of LOC is a brainstem stroke. Graphic 131146 Version 1.0 https://www.uptodate.com/contents/syncope-in-adults-epidemiology-pathogenesis-and-etiologies/print 25/28 7/6/23, 2:38 PM Syncope in adults: Epidemiology, pathogenesis, and etiologies - UpToDate Differentiation of generalized tonic-clonic seizures from pseudoseizures and syncope Generalized Characteristic seizure tonic- Pseudoseizure Syncope clonic Circumstances Situation Awake or sleep Awake Usually upright; any position if cardiogenic Precipitating Sleep loss, alcohol Emotion Emotion, injury, heat, factors withdrawal, flashing crowds; none if lights cardiogenic Presence of others Variable Usual Variable Motor phenomena Vocalization At onset, if any During course None Location of motor component (if present) Proximal limb Proximal limb None Generalized motor Tonic, then clonic Tonic; flailing; struggling or thrashing, or both Usually atonic; if syncope lasts >20 seconds: tonic, then clonic Tonic posture Partial flexion or straight Opisthotonic Head movements To one side or none Side to side Clonus/limb jerks Bilaterally Asynchronous Bilaterally synchronous synchronous Purposeful movements Absent Occasional, including avoidance Absent Biting Tongue, inside Lips, arms, other people Tongue biting rare mouth Babinski's sign Present Absent Absent Autonomic features Micturition Frequent Rare Occasional Eyes Open Closed Open Pupils Dilated or hippus during attacks Normal Dilated https://www.uptodate.com/contents/syncope-in-adults-epidemiology-pathogenesis-and-etiologies/print 26/28 7/6/23, 2:38 PM Syncope in adults: Epidemiology, pathogenesis, and etiologies - UpToDate Colour Cyanotic or grey Rubor or normal Pale Pulse Rapid, strong Normal Slow if vasovagal, weak if vasodepressor; that of arrhythmias if cardiogenic Timing Usual duration 1 to 5 min 5 to 60 min 1 to 2 min Onset Sudden Gradual Gradual; possibly sudden if cardiogenic Sequence of Stereotyped Variable Stereotyped symptoms Termination Spontaneous Spontaneous or induced Rapid by supraorbital pressure, suggestion Sequelae Injury Frequent, mild; scalp, face, common Rare, but multiple bruises possible; scalp, face, rare If sudden onset Postictal Tired, confused, sleepy Alert, emotional outburst Regains consciousness in 2 to 3 min; alert but tired Reproduced with permission from: Blume WT. Diagnosis and management of epilepsy. CMAJ 2003; 168:441. Copyright 2003 Canadian Medical Association. Graphic 73515 Version 2.0 https://www.uptodate.com/contents/syncope-in-adults-epidemiology-pathogenesis-and-etiologies/print 27/28 7/6/23, 2:38 PM Syncope in adults: Epidemiology, pathogenesis, and etiologies - UpToDate Contributor Disclosures David Benditt, MD Equity Ownership/Stock Options: Medtronic [Pacemakers/event recorders and defibrillators]. Grant/Research/Clinical Trial Support: Medtronic [Pacemakers/event recorders and defibrillators]; St Jude Medical [Pacemakers/event recorders and defibrillators]. Consultant/Advisory Boards: Medtronic [Pacemakers/event recorders and defibrillators]; Zoll [Pacemakers/event recorders and defibrillators]. Other Financial Interest: Advanced CPR Solutions [Outside director]. All of the relevant financial relationships listed have been mitigated. Peter Kowey, MD, FACC, FAHA, FHRS Equity Ownership/Stock Options: VuMedi [Arrhythmias]. Consultant/Advisory Boards: Abbvie [Arrhythmias]; Acesion Pharma [Arrhythmias]; Allergan [Arrhythmias, cardiac safety of non-cardiac drugs]; Anthos [Anticoagulants]; Boehringer-Ingelheim [Arrhythmias]; Bristol-Meyers-Squibb [Arrhythmias]; Daiichi Sankyo [Arrhythmias]; Gilead [Arrhythmias]; Huya [Arrhythmias]; InCarda Therapeutics [Arrhythmias]; INSTA [Arrhythmias]; Johnson & Johnson [Arrhythmias]; Medtronic [Arrhythmias]; Milestone [Arrhythmias]; Novartis [Arrhythmias, cardiac safety of non-cardiac drugs]; Pfizer [Arrhythmias]; Sanofi [Arrhythmias]; Takeda [Arrhythmias]. All of the relevant financial relationships listed have been mitigated. Susan B Yeon, MD, JD, FACC No relevant financial relationship(s) with ineligible companies to disclose. Contributor disclosures are reviewed for conflicts of interest by the editorial group. When found, these are addressed by vetting through a multi-level review process, and through requirements for references to be provided to support the content. Appropriately referenced content is required of all authors and must conform to UpToDate standards of evidence. Conflict of interest policy https://www.uptodate.com/contents/syncope-in-adults-epidemiology-pathogenesis-and-etiologies/print 28/28