eMedicine Specialties > Cardiology > Arrhythmias
Syncope: Differential Diagnoses & Workup
Updated: Aug 24, 2009
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
- Multimedia
Differential Diagnoses
Other Problems to Be Considered
The history findings usually allow differentiation of syncope from the following conditions:
Vertigo: A sensation of movement of the patient and/or the surroundings, vertigo is usually caused by a neurologic or otolaryngologic problem. Most commonly, the abnormality is in the inner ear. Vertigo may be reproduced with the Parinet maneuver.
Seizure: Epileptic disorders are caused by excessive electrical activity in the cortex or other area of the brain. Partial complex seizures may cause loss of consciousness without marked motor activity. Grand mal seizures are characterized by tonic-clonic motor activity. On the other hand, syncope can be accompanied by tonic posturing due to brainstem hypoxia. Syncope is rarely accompanied by incontinence or a prolonged period of confusion following the event (ie, postictal confusion).
Transient ischemic attack: While a vertebrobasilar transient ischemic attack can cause loss of consciousness, this is unusual in the absence of other vertebrobasilar symptoms (eg, dysarthria, difficulty swallowing).
Narcolepsy: This is an extreme tendency to fall asleep during the day. A patient who is found to have unexpectedly fallen asleep is sometimes diagnosed with syncope.
Pseudosyncope: This is a functional or psychiatric disorder in which episodes are fabricated or faked.
Cataplexy: This rare condition is characterized by transient loss of postural tone without loss of consciousness.
Workup
Laboratory Studies
- See Media file 1 for an algorithm for the evaluation of syncope.
An algorithm for the evaluation of syncope.
- No laboratory studies are routinely obtained in patients with syncope. Instead, tests should be ordered if they are indicated clinically. For example, perform (1) a serum electrolyte evaluation if concerned about dehydration, (2) a digoxin level measurement if the patient is on this medication, or (3) thyroid studies in patients with bradycardia.
Imaging Studies
- No imaging studies are routinely obtained in patients with syncope. Tests should be ordered if indicated clinically, especially in patients suspected of having cerebrovascular causes for loss of consciousness.
- A transthoracic echocardiogram is useful to screen for structural heart disease such as left ventricular dysfunction, aortic stenosis, and hypertrophic cardiomyopathy. An echocardiogram should be performed if any suggestion of structural heart disease is present, if the patient is not young, or if the history findings are inconsistent with neurocardiogenic syncope.
Other Tests
- Additional work-up based on the suspected etiology from history and physical examination may include the following:
- Cardiac causes - Electrocardiogram, exercise stress test, and echocardiogram followed by electrophysiological study in selected patients
- Neurally mediated syncope - Carotid sinus message in appropriate patients, tilt table test
- Unexplained syncope - Start with a carotid sinus message (if not contraindicated) and tilt table test followed by echocardiogram
- Electrocardiogram: A resting ECG should be performed on all patients who present with syncope. Relevant abnormalities include long QT syndrome, ventricular preexcitation, signs of ischemia/infarction, Brugada syndrome, and the suggestion of right ventricular cardiomyopathy.
- Exercise stress test: Stress testing should not be performed routinely in patients with syncope; testing should be performed only if coronary artery disease is suggested or if the syncope occurs during or after exercise. In the latter case, an echocardiogram should be performed first to exclude significant aortic stenosis and hypertrophic cardiomyopathy.
- Ambulatory monitoring: External endless loop recording is generally more useful than Holter monitoring because of the relative infrequency of syncopal episodes.
- Implantable loop recorder: For patients with extremely infrequent episodes, a device may be implanted subcutaneously that records (1) episodes of bradycardia and tachycardia and (2) patient-activated events for up to a year.
- Head-up tilt test: This noninvasive test assesses a patient's tendency for neurocardiogenic or vasovagal syncope. Protocols vary; one representative protocol includes tilting the patient at a 70° angle for 30 minutes. If the response after a baseline tilt is negative, it is typically repeated during pharmacologic provocation (eg, isoproterenol infusion, nitroglycerin). Several positive responses are possible with head-up tilt testing. A cardioinhibitory response involves severe bradycardia. In a vasodepressor response, the degree of hypotension is out of proportion to any bradycardia induced because of profound vasodilatation. Frequently, the response is mixed.
- Electrophysiologic study: Invasive electrophysiologic (EP) testing helps assess a patient's propensity for bradyarrhythmias and tachyarrhythmias. The yield on EP testing is greatest when evaluating the risk of ventricular tachyarrhythmias in patients with ischemic cardiomyopathy. The yield is lower in patients with nonischemic cardiomyopathy or possible bradycardia.
- Neurologic testing: Although brain MRI/CT scan, carotid studies, and electroencephalograms are performed frequently in patients with syncope, the yield on these studies is extremely low in patients who do not have focal neurologic deficits or witnessed seizure activity.
Procedures
Diagnostic EP studies may be necessary.
More on Syncope |
| Overview: Syncope |
 Differential Diagnoses & Workup: Syncope |
| Treatment & Medication: Syncope |
| Follow-up: Syncope |
| Multimedia: Syncope |
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References
Brignole M, Alboni P, Benditt DG, et al. Guidelines on management (diagnosis and treatment) of syncope--update 2004. Europace. Nov 2004;6(6):467-537.
Cannom DS. A critical appraisal of indications for the implantable cardioverter defibrillator (ICD). Clin Cardiol. May 1992;15(5):369-72. [Medline].
Chen-Scarabelli C, Scarabelli TM. Neurocardiogenic syncope. BMJ. Aug 7 2004;329(7461):336-41.
Connolly SJ, Sheldon R, Roberts RS, Gent M. The North American Vasovagal Pacemaker Study (VPS). A randomized trial of permanent cardiac pacing for the prevention of vasovagal syncope. J Am Coll Cardiol. Jan 1999;33(1):16-20. [Medline].
Grubb BP, Kosinski DJ. Syncope resulting from autonomic insufficiency syndromes associated with orthostatic intolerance. Med Clin North Am. Mar 2001;85(2):457-72. [Medline].
Kapoor WN. Syncope. N Engl J Med. Dec 21 2000;343(25):1856-62. [Medline].
Kapoor WN. Current evaluation and management of syncope. Circulation. Sep 24 2002;106(13):1606-9.
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. Jun 15 1997;126(12):989-96. [Medline].
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. Jul 1 1997;127(1):76-86. [Medline].
Soteriades ES, Evans JC, Larson MG. Incidence and prognosis of syncope. N Engl J Med. Sep 19 2002;347(12):878-85. [Medline].
Sutton R, Brignole M, Menozzi C, et al. Dual-chamber pacing in the treatment of neurally mediated tilt-positive cardioinhibitory syncope: pacemaker versus no therapy: a multicenter randomized study. The Vasovagal Syncope International Study (VASIS) Investigators. Circulation. Jul 18 2000;102(3):294-9. [Medline].
Further Reading
Keywords
syncope, loss of consciousness, loss of postural tone, decreased cerebral perfusion, brainstem hypoxia, carotid sinus pressure, coronary artery disease, nonischemic cardiomyopathy, non-ischemic cardiomyopathy, ventricular tachyarrhythmia, congenital long QT syndrome, Wolff-Parkinson-White syndrome, WPW syndrome, Brugada syndrome, hypertrophic cardiomyopathy, syncopal episode, blackout, dizzy spell, seizure, dizziness, aortic stenosis, pulmonary embolus, pulmonary hypertension, acute myocardial infarction, acute MI, tamponade, aortic dissection, atrial fibrillation, atrial flutter, supraventricular tachycardia, SVT, torsades de pointes, ventricular tachycardia, VT, ventricular fibrillation, AV block, atrioventricular block, A/V block, A-V block, sick sinus syndrome, implanted cardioverter/defibrillators, ICDs
