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Chapter 4

Did Canada Crack the Syncope Code?

Rob Orman, MD and Clay Smith, MD

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Figuring out a decision tool or even consistent clinical approach to syncope has been like finding peace in the Middle East. Lots of people thought that they have had the answer but, let's face it, they haven't. Now, a research team from Canada may have found the right formula for emergency department evaluation: using a combination of the Canadian Syncope Risk Score and a few hours of cardiac monitoring.



  • A low-risk Canadian Syncope Risk Score (CSRS) combined with 2 hours of negative ECG monitoring can identify patients that have a 0.2% risk of a serious arrhythmic event within 30 days of syncope.

  • Medium-risk CSRS patients with 6 hours of negative ECG monitoring have a 5% risk of a serious arrhythmia.  

  • A troponin and PE workup are only necessary in syncope patients if the history and exam raise sufficient clinical concern.


  • Syncope and presyncope have similar risks of future adverse events.  

    • Syncope:  “An abrupt, transient, complete loss of consciousness associated with inability to maintain postural tone with rapid and spontaneous recovery.”  

    • Presyncope:  “The symptoms before syncope which could include extreme lightheadedness, visual sensations, and variable degrees of altered consciousness without complete loss of consciousness.”

    • One study showed that the 30-day risk of death or adverse event was the same in patients over age 60 whether they had syncope or presyncope.

  • Parsing out whose syncopal episode is due to a life threat can be tricky.  Syncope decision instruments have been developed, but suffer due to lack of consistency, variables which aren’t always intuitive, and poor diagnostic accuracy.

    • San Francisco Syncope Rule 2006.  This rule uses history of CHF, Hct<30%, ECG abnormalities, shortness of breath, and a SBP<90 to distinguish high vs. low risk patients.  While the internal validation study yielded a sensitivity of 98%, the results of external validation studies were not as positive In fact, 10% of San Francisco Syncope Rule negative patients were found to have a serious adverse event within a week of the syncopal episode and 1 in 250 died.

    • The ROSE Rule (2010).  Predictors of adverse sequelae include elevated BNP, bradycardia, chest pain, positive fecal occult blood testing, Hgb<9g/dL, oxygen saturation <94%, and a Q wave on presenting ECG. This instrument had a sensitivity of 87% and specificity of 65%.

    • The Canadian Syncope Risk Score (CSRS) 2016. Variables include predisposition to vasovagal symptoms, elevated troponin, SBP<90 or >180 mmHg,  heart disease history, and specific ECG changes. The rule has additive and subtractive factors. Initial study had a  sensitivity of 99% and specificity of 26% for 30 day adverse outcomes . Not yet externally validated.

  • The addition of ECG monitoring to the CSRS tool may be the right formula for the ED evaluation of syncope.  

    • The researchers that developed CSRS published a second study in 2019. The objective was to determine the optimal duration of ECG monitoring for ED syncope patients who were risk stratified using CSRS.

    • Methods:  

      • Prospective, multi-center study of 5,581 patients with syncope who were risk stratified with the CSRS.  ¾ of the patients were low-risk.

      • Subjects were followed for 30 days.

      • Primary outcome was a serious arrhythmic event (death, intervention for arrhythmia, or arrhythmia).

    • Results:  

      • 3.7% of the patients had a serious arrhythmic outcome.  

      • The CSRS rule performed fairly well at predicting who was at risk for a serious arrhythmia. As the CSRS  risk increased, so did the arrhythmic risk (low risk=0.4%, medium risk=9%, high risk=25%).

      • Adding ECG monitoring to CSRS greatly improved the prediction of serious arrhythmias.  

        • ½ of arrhythmic outcomes were picked up within 2 hours of  monitoring for low-risk patients and within 6 hours for medium or high-risk patients.  

        • For medium and high-risk patients, the overwhelming majority of arrhythmias occurred within 15 days of the syncopal event.

        • For low-risk CSRS patients, 2 hours of monitoring dropped the percentage of arrhythmic outcomes to 0.2%, translating to a negative predictive value of 99.8%. None of the arrhythmic outcomes were ventricular arrhythmia or death.

        • For medium and high-risk patients, 6 hours of monitoring dropped the arrhythmic outcome rate from 9 to 5% and 25 to 18%, respectively.

    • Bottom line and interpretation:  

      • If CSRS low-risk patients have 2 hours of negative ECG monitoring, you can identify 99.8% of the patients who are unlikely to have a 30-day bad outcome and are likely safe for discharge.  

      • For medium-risk patients being discharged from the ED after 6 hours of monitoring, outpatient rhythm monitoring for 15 days should be considered.  

      • Rob and Clay agree they would recommend admission for  most CSRS high-risk patients.

  • The CSRS rule includes a troponin which is not routinely ordered on all syncope patients.  Can we still use the rule without a troponin? Yes.

    • In the original 2016 CSRS study, troponin levels weren’t measured in 52% of patients. Those that did not have a troponin were younger, had fewer comorbidities, and fewer serious adverse events.  Study authors made the assumption in this (as well as in the 2019) study that missing troponin values were within the normal range.

  • Beware of a patient with syncope who has an elevated troponin or BNP.

    • While the decision to order a troponin or BNP on a patient with syncope should be driven by the history and exam, pay attention when they return elevated.

    • A recent study showed that a high-sensitivity troponin and natriuretic peptide are independent predictors of 30-day death and serious cardiac outcomes in patients >60 years presenting to the ED with syncope.

  • There is no need to do a PE workup in every patient who presents to the ED with syncope.

    • A 2016 study of 560 patients admitted for syncope found that 17.3% had a PE.  This study was fraught with issues, most significantly that it only included hospitalized patients.  Had it not excluded the 2000 other patients who had been discharged for syncope during the same time period, the PE rate would have been 3.8%.

    • A multi-center, multi-country retrospective study of 1.6 million people presenting to the ED with syncope found a PE prevalence of <1%.

    • A recent prospective study showed that PE prevalence in syncope patients was 0.6%.



Bastani A, et al. Comparison of 30-Day Serious Adverse Clinical Events for Elderly Patients Presenting to the Emergency Department With  Near-Syncope Versus Syncope. Ann Emerg Med. 2019 Mar;73(3):274-280. PMID: 30529112..


Quinn JV, et al. Derivation of the San Francisco Syncope Rule to predict patients with short-term serious outcomes. Ann Emerg Med. 2004 Feb;43(2):224-32.PMID: 14747812.


Reed MJ, et al. The ROSE (risk stratification of syncope in the emergency department) study. J Am Coll Cardiol. 2010 Feb 23;55(8):713-21. PMID: 20170806.


Thiruganasambandamoorthy V, et al. Development of the Canadian Syncope Risk Score to predict serious adverse events after emergency department assessment of syncope. CMAJ. 2016 Sep 6;188(12):E289-E298. PMID: 27378464.


Thiruganasambandamoorthy V, et al. Duration of Electrocardiographic Monitoring of Emergency Department Patients with Syncope. Circulation. 2019 Jan 21. PMID: 30661373.


Clark CL, et al. Do High-sensitivity Troponin and Natriuretic Peptide Predict Death or Serious Cardiac Outcomes After Syncope? Acad Emerg Med. 2019 Feb 5. PMID: 30721554.


Prandoni P, et al; PESIT Investigators. Prevalence of Pulmonary Embolism among Patients Hospitalized for Syncope. N Engl J Med. 2016 Oct 20;375(16):1524-1531. PMID: 27797317.


Thiruganasambandamoorthy V,et al; North American Syncope Consortium. Prevalence of Pulmonary Embolism Among Emergency Department Patients With Syncope: A Multicenter Prospective Cohort Study. Ann Emerg Med. 2019 Jan 25. [Epub ahead ofprint] PubMed PMID: 30691921.


Costantino G, et al. Prevalence of Pulmonary Embolism in Patients With Syncope. JAMA InternMed. 2018 Mar 1;178(3):356-362.PMID: 29379959.


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