Syncope in adults: Clinical manifestations and diagnostic evaluation
- David Benditt, MD
David Benditt, MD
- Professor of Medicine
- Director, Cardiac Arrhythmia Center
- University of Minnesota Medical School
- Section Editors
- Peter Kowey, MD, FACC, FAHA, FHRS
Peter Kowey, MD, FACC, FAHA, FHRS
- Section Editor — Arrhythmias
- Professor of Medicine and Clinical Pharmacology
- Jefferson Medical College, Philadelphia, PA
- Robert S Hockberger, MD, FACEP
Robert S Hockberger, MD, FACEP
- Section Editor — Adult Signs and Symptoms
- Emeritus Professor of Medicine
- David Geffen School of Medicine at UCLA
Syncope is a clinical syndrome in which transient loss of consciousness (TLOC) is caused by a period of inadequate cerebral nutrient flow, most often the result of an abrupt drop of systemic blood pressure. Typically, the inadequate cerebral nutrient flow is of relatively brief duration (8 to 10 seconds), and, in syncope, is by definition spontaneously self-limited.
Loss of postural tone is inevitable with loss of consciousness, and consequently syncope usually is associated with collapse, which may trigger injury due to a fall (such as may occur if the person is standing) or other type of accident (eg, if syncope occurs while driving). Recovery from true syncope is usually complete and rapid, with episodes rarely lasting more than a minute or two. Longer periods of real or apparent loss of consciousness suggest that the event is not syncope or is not syncope alone (eg, syncope resulting in a head injury, thereby prolonging the event).
Syncope is only one on the many potential causes of TLOC. Examples of non-syncopal causes of TLOC, or apparent TLOC, include seizure disorders, traumatic brain injury (ie, concussion), intoxications, metabolic disturbances, and conversion disorders (ie, psychogenic "pseudo-syncope" or "pseudo-seizures"). Distinguishing these conditions from true syncope may be challenging, but it is crucial in order to determine appropriate management.
True syncope itself has many possible causes (table 1). Consequently, after the syncopal event has resolved and the patient is hemodynamically stable, the essential next step is establishing the etiology in order to initiate an appropriate diagnostic and treatment strategy to prevent future events as well as to determine prognosis. The initial evaluation of suspected syncope relies heavily on obtaining of a comprehensive history, performing a physical examination (which may include careful carotid sinus massage in older patients), and reviewing an electrocardiogram; these steps should guide the subsequent diagnostic evaluation and help limit unnecessary testing and treatment.
Issues relating to the evaluation of syncope in adults will be reviewed here. The approach to the adult patients with syncope in the emergency department, as well as the pathogenesis, etiology, and management of syncope in adults, are discussed elsewhere. (See "Approach to the adult patient with syncope in the emergency department" and "Syncope in adults: Epidemiology, pathogenesis, and etiologies" and "Reflex syncope in adults: Clinical presentation and diagnostic evaluation" and "Syncope in adults: Management".)
- 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.
- Calkins H, Shyr Y, Frumin H, et al. The value of the clinical history in the differentiation of syncope due to ventricular tachycardia, atrioventricular block, and neurocardiogenic syncope. Am J Med 1995; 98:365.
- Task Force for the Diagnosis and Management of Syncope, European Society of Cardiology (ESC), European Heart Rhythm Association (EHRA), et al. Guidelines for the diagnosis and management of syncope (version 2009). Eur Heart J 2009; 30:2631.
- 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.
- Sarasin FP, Junod AF, Carballo D, et al. Role of echocardiography in the evaluation of syncope: a prospective study. Heart 2002; 88:363.
- Pires LA, Ganji JR, Jarandila R, Steele R. Diagnostic patterns and temporal trends in the evaluation of adult patients hospitalized with syncope. Arch Intern Med 2001; 161:1889.
- Sivakumaran S, Krahn AD, Klein GJ, et al. A prospective randomized comparison of loop recorders versus Holter monitors in patients with syncope or presyncope. Am J Med 2003; 115:1.
- Krahn AD, Klein GJ, Yee R, Skanes AC. Randomized assessment of syncope trial: conventional diagnostic testing versus a prolonged monitoring strategy. Circulation 2001; 104:46.
- Brignole M, Sutton R, Menozzi C, et al. Early application of an implantable loop recorder allows effective specific therapy in patients with recurrent suspected neurally mediated syncope. Eur Heart J 2006; 27:1085.
- Kapoor WN. Evaluation and outcome of patients with syncope. Medicine (Baltimore) 1990; 69:160.
- Bachinsky WB, Linzer M, Weld L, Estes NA 3rd. Usefulness of clinical characteristics in predicting the outcome of electrophysiologic studies in unexplained syncope. Am J Cardiol 1992; 69:1044.
- 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.
- Kapoor WN, Hammill SC, Gersh BJ. Diagnosis and natural history of syncope and the role of invasive electrophysiologic testing. Am J Cardiol 1989; 63:730.
- Teichman SL, Felder SD, Matos JA, et al. The value of electrophysiologic studies in syncope of undetermined origin: report of 150 cases. Am Heart J 1985; 110:469.
- Krol RB, Morady F, Flaker GC, et al. Electrophysiologic testing in patients with unexplained syncope: clinical and noninvasive predictors of outcome. J Am Coll Cardiol 1987; 10:358.
- European Heart Rhythm Association, Heart Rhythm Society, Zipes DP, et al. ACC/AHA/ESC 2006 guidelines for management of patients with ventricular arrhythmias and the prevention of sudden cardiac death: a report of the American College of Cardiology/American Heart Association Task Force and the European Society of Cardiology Committee for Practice Guidelines (Writing Committee to Develop Guidelines for Management of Patients With Ventricular Arrhythmias and the Prevention of Sudden Cardiac Death). J Am Coll Cardiol 2006; 48:e247.
- CAUSES OF SYNCOPE
- CLINICAL PRESENTATION
- INITIAL EVALUATION
- Medical history
- - Number, frequency, and duration of episodes
- - Onset of syncope
- - Position
- - Provocative factors
- - Associated symptoms preceding the event
- - Associated symptoms following the event
- - Witnessed signs
- - Pre-existing medical conditions
- - Medications
- - Family history
- Physical examination
- Risk stratification
- - High risk patients
- - Intermediate risk patients
- - Low risk patients
- OUTCOMES OF THE INITIAL EVALUATION
- Certain diagnosis
- Suspected diagnosis
- Unexplained diagnosis
- SELECTED ADDITIONAL TESTING
- Ambulatory ECG monitoring
- Orthostatic blood pressure measurement
- Exercise testing
- Carotid sinus massage
- Electrophysiology study
- Neurologic testing
- FREQUENTLY ASKED QUESTIONS
- SOCIETY GUIDELINE LINKS
- INFORMATION FOR PATIENTS
- SUMMARY AND RECOMMENDATIONS