Syncope is common presenting complaint in the emergency department. Over 40% of adults will experience a syncopal episode, and syncope accounts for approximately 1% of all ED visits (1).
Because syncope can result from a variety of etiologies, both life-threatening and benign, the syncopal patient is diagnostically challenging and can be especially daunting for learners. A consistent framework helps learners avoid missing a potentially serious underlying problem. The SVNCOPE mnemonic is a useful reminder of the most common causes of syncope. Prevalence of each noted in brackets (2).
- Situational (5%)
- Syncope associated with a triggering event, often occurring post-micturition, post-tussive, or with GI stimulation or defecation. A thorough history of the event will yield information about situational causes.
- Vasovagal (a.k.a. neurocardiogenic; 18%)
- A transient stimulation of parasympathetic activity resulting in hypotension. This is generally triggered by noxious stimuli, stress, fear, or heat. Has a typical prodrome of lightheadedness, dizziness, diaphoresis, and blurred vision.
- Neurogenic (10%)
- Cerebrovascular events such as TIA/stroke, or a subclavian steal syndrome can cause syncope. Generally associated with abnormal neurological examination.
- Cardiogenic (18%)
- This type can result from structural pathology (such as aortic stenosis, cardiomyopathy, tamponade, acute MI) or from arrhythmias. Cardiogenic syncope is generally unprovoked and is more common in older patients.
- Orthostatic (8%)
- Sudden decrease in blood pressure on standing. Often described by the 30/20/10 rule – after standing for 2 minutes, an increase in heart rate of 30 beats per minute, decrease in systolic blood pressure by 20 mmHg, or decrease diastolic blood pressure by 10 mmHg.
- Psychogenic (2%)
- May occur in patients with panic disorders, somatization disorders, and anxiety. Can be difficult to identify, as examination and investigations are often unremarkable. This is a diagnosis of exclusion.
- Always consider hypoglycemia as a possible cause.
It is important to keep in mind that approximately 34% of syncope cases have no identifiable etiology(1). The mnemonic is useful to avoid forgetting possible etiologies of syncope, but will not necessarily lead to a definitive diagnosis.
For a more in-depth review of syncope, head over to LITFL(3) or check out the EM Basic podcast(4) and associated show notes(5).
- Moya A, Sutton R, Ammirati F, et al. Guidelines for the diagnosis and management of syncope (version 2009). Eur Heart J. 2009;30(21):2631-71.
- Gauer RL. Evaluation of syncope. Am Fam Physician. 2011;84(6):640-50.
- Syncope. Life In the Fast Lane Blog. Accessed June 10, 2015. Available at: http://lifeinthefastlane.com/ccc/syncope/
- Syncope. EM Basic. Accessed June 10, 2015. Available at: http://embasic.org/syncope/
- Syncope Show Notes. EM Basic. Accessed June 10, 2015. Available at: http://embasic.org/wp-content/uploads/2012/01/13-syncope-show-notes1.pdf
Reviewing with the Staff | @TChanMD
Dr. Chan is an assistant professor at McMaster University. She is also one of our editors here at BoringEM.org.
An approach to syncope is a key concept that any emergency medicine learner should have in his/her back pocket. That being said, sometimes on history it might not be remarkably clear as to whether the incident was truly a syncopal event or if it might have been due to other causes (e.g. seizure, trauma, narcolepsy, etc..). It is, therefore, important to broaden your clinical assessment to consider other causes of sudden loss of consciousness that may not classically be considered within the “syncope” differential.
A careful collateral history from bystanders or first responders may be key in revealing differences in etiology, so make sure you hop on the phone and try to see if someone else can give you information about the circumstances of the loss of consciousness.