Syncope is a common presenting complaint to the emergency department. Estimates suggest that 1- 3 percent of ED visits are for syncope.(1) While the large majority of these episodes are often benign, they can suggest underlying life-threatening etiologies such as arrhythmias, pulmonary embolism, and stroke. The disposition of these patients can represent a difficult quandary at times. In fact, emergency physicians are only able to establish a clear underlying diagnosis in approximately 50% of syncope patients after obtaining an HPI, physical exam and ECG. (2)
Should these patients be observed in the ED? And, if so, for how long? Should they be admitted to the hospital for further workup and observation? Should they instead be discharged home with close follow-up?
Traditionally, the answer has been admission for many of these patients. From 1992-2010, admission rates for syncope visits remained stable at around 32%. (3) Additionally, rates of non-diagnostic admissions remained persistently high over these periods with over a third of patients being discharged with a diagnosis identical to their chief complaint. Strict adherence to guidelines has been ineffective: criteria from 3 major society guidelines including the European Society of Cardiology, Canadian Cardiovascular Society and American College of Emergency Physicians were used in a retrospective study, showing no decrease in the rate of low-risk admissions when compared with a non-standardized approach based on clinician gestalt. (4)
Overimaging (specifically CT/MRI head)
Unnecessary PE screening
Use of orthostatic vital signs (which are not diagnostic of syncope)
Overuse of troponin in workup
What about decision rules?
San Francisco Syncope Rule
The original study in 2004 deriving this clinical decision-making rule, was a single-center, prospective cohort study enrolling 592 patients. (9) The initial goals of the study were to decrease syncope-related admissions and identify patients at low risk of a short-term, serious clinical event. Specifically, these outcomes were defined as death, myocardial infarction, arrhythmia, pulmonary embolism, stroke, subarachnoid hemorrhage, significant hemorrhage, or any condition causing a return ED visit and hospitalization for a related event. Patients with any of the “CHESS” predictors were considered high risk for these serious outcomes at 7 or 30 days, and admission was recommended.
This decision rule has been controversial, because multiple external validation studies have been unable to reproduce the sensitivity (96%) and specificity (62%) of the original study. Specifically, in 2008 a study at Albert Einstein College of Medicine found that the rule had a sensitivity of 74% and specificity of 54% for predicting serious outcomes at 7 days. (10) Of note, serious outcomes in the study that the decision rule failed to identify included 1 death, 8 arrhythmias, 3 strokes and 1 subarachnoid hemorrhage, which were all deemed to be causally related to the syncope. A subsequent meta-analysis found that the rule had a sensitivity of 87% and specificity of 52%. (11)
Canadian Syncope Rule
This scoring rule is born out of the same medical center known for the other well-known clinical decision-making rules including the Canadian C-Spine, Head, and Ottawa Ankle Rules. Led by Dr. Thiruganasambandamoorthy, the goal of the derivation study in 2016 was initially to create a simple tool to identify syncope patients at greater risk for adverse events which may need increased monitoring in the emergency department or hospitalization. (12) Their prospective cohort study enrolled 4,030 patients with syncope. Of note, their definition of serious adverse events differed from the San Francisco syncope rule, specifying that only return visits within 30 days related to conditions causing syncope or procedural interventions for the treatment of syncope would qualify, rather than any return visit. Initial internal validation showed that scores of -2 or higher had 99% sensitivity and 26% specificity. Scores of -1 or higher had 98% sensitivity and 46% specificity. An external validation study has been performed pending publication.
What if I just use my own clinical judgment?
Emergency physician gestalt has been found to be 100% sensitive but poorly specific (30%) in identifying high-risk syncope. (13) Trust in your ability to rule out lower risk patients! For patients that you feel are higher risk, air on the side of observation, further workup and admission.
Verdict: Should I use these decision rules?
San Francisco Syncope rule:No. The literature has shown that it is not sufficiently accurate to replace clinical gestalt. It is simply insufficiently sensitive to safely augment cautious clinical judgment with high admission rates.
Canadian Syncope rule:Pending external validation, this has potential in that it quantifies the risk associated with various point values. It also qualifies specific ECG findings rather than the nebulous “abnormal ECG” criteria used in the San Francisco syncope rule. Pitfalls include the need for a troponin to fully score patient risk, and the subjective nature of the clinical diagnosis counting for a significant portion of the scoring.
Toarta C, Mukarram M, Diercks D, et al. Syncope Prognosis Based on Emergency Department Diagnosis: A Prospective Cohort Study. Academic Emergency Medicine (AEM)[serial online]. April 1, 2018;25(4):388-396.
Patel PR, Quinn JV.Syncope: a review of emergency department management and disposition. Clin Exp Emerg Med. 2015;2(2):67–74. Published 2015 Jun 30. doi:10.15441/ceem.14.049
Anand V, Benditt DG, Adkisson WO, Garg S, George SA, Adabag S.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(6):916-922.
Deif B, Kang S, Ismail A, Vanniyasingam T, Guzman JC, Morillo CA.Application of Syncope Guidelines in the Emergency Department Do Not Reduce Admission Rates: A Retrospective Cohort Study. Can J Cardiol. 2018;34(9):1158-1164.
Ozturk K, Soylu E, Bilgin C, Hakyemez B, Parlak M.Predictor variables of abnormal imaging findings of syncope in the emergency department. International Journal of Emergency Medicine. 2018;11:16. doi:10.1186/s12245-018-0180-0.
Costantino G, Ruwald M, Casazza G, et al.Prevalence of Pulmonary Embolism in Patients With Syncope. JAMA Internal Medicine[serial online]. n.d.;178(3):356-362. Available from: Biological Abstracts, Ipswich, MA. Accessed May 1, 2018.
Bloom A, Devlin J.Discriminatory Value of Orthostatic Vital Signs in the Emergency Department Evaluation of Syncope. Annals of Emergency Medicine[serial online]. September 1, 2017;70(3):438-439. Available from: E-Journals, Ipswich, MA. Accessed May 1, 2018
Thiruganasambandamoorthy V, Perry J. High-sensitivity cardiac troponin T in isolation has limited diagnostic utility in identifying cardiac causes of syncope. Evidence Based Medicine[serial online]. August 2015;20(4):146. Available from: CINAHL Complete, Ipswich, MA. Accessed May 1, 2018.
Quinn JV, Stiell IG, Mcdermott DA, Sellers KL, Kohn MA, Wells GA.Derivation of the San Francisco Syncope Rule to predict patients with short-term serious outcomes. Ann Emerg Med. 2004;43(2):224-32.
Birnbaum A, Esses D, Bijur P, Wollowitz A, Gallagher EJ. Failure to validate the San Francisco Syncope Rule in an independent emergency department population. Ann Emerg Med. 2008;52(2):151-9.
Saccilotto RT, Nickel CH, Bucher HC, Steyerberg EW, Bingisser R, Koller MT. San Francisco Syncope Rule to predict short-term serious outcomes: a systematic review. CMAJ. 2011;183(15):E1116–E1126. doi:10.1503/cmaj.101326
Venkatesh Thiruganasambandamoorthy, Kenneth Kwong, George A. Wells, Marco L.A. Sivilotti, Muhammad Mukarram, Brian H. Rowe, Eddy Lang, Jeffrey J. Perry, Robert Sheldon, Ian G. Stiell, Monica Taljaard. Development of the Canadian Syncope Risk Score to predict serious adverse events after emergency department assessment of syncope. CMAJ Sep 2016, 188 (12) E289-E298; DOI: 10.1503/cmaj.151469
Sun BC, Mangione CM, Merchant G, et al.External validation of the San Francisco Syncope Rule. Ann Emerg Med. 2007;49(4):420-7, 427.e1-4.
Written by Jonathan Chucko, MD - PGY-1 University of Cincinnati Department of Emergency Medicine
Peer Review and Editing by Jeffery Hill, MD MEd