You passed out, Eh?- The Canadian Syncope Risk Score and its use in the ED
/
Tired of reading? Prefer to absorb your MedEd through your wonderful powers of hearing? Check out our podcast by clicking HERE.
Background:
The chief complaint of syncope as a symptom has many possible causes. Syncope is defined as a transient loss of consciousness, followed by a complete recovery. Often times the etiology of syncope is not found in patients presenting to the emergency department (ED). However, there are many worrisome underlying conditions that can manifest as syncope, including deadly arrhythmias, cardiac ischemia, pulmonary embolism, or internal hemorrhage (1, 2). For this reason, one of the important aspects of evaluation in the ED is to observe and exclude these underlying conditions.
Several tools in the past have been developed to risk stratify syncope patients in the ED. One tool is the Canadian Syncope Risk Score (CSRS; Figure 1), which the authors of this study developed previously (3). Other tools that have been developed in the past include the San Francisco Syncope Rule (SFSR), Evaluation of Guidelines in Syncope Study (EGSYS), and Osservatorio Epidemiologico sulla Sincope del Lazio Score (OESIL) for Syncope (4, 5). Unfortunately, these clinical decision tools have been shown to have poor external validity (6).
In theory, the goal of a risk stratifying tool for syncope is to identify which patients can be safely discharged versus those which warrant admission and further work up. Previous literature suggests that one-third to one-half of these serious conditions are missed in the ED (3, 7). In addition, there has been no definitive duration of time for which these patients should be observed (8). For this reason, the authors of this paper (9) attempted to assess the effectiveness of their decision-making tool in predicting the appropriate time to monitor patients in the ED who present with syncope.
Duration of Electrocardiographic Monitoring of Emergency Department Patients with Syncope
Thiruganasambandamoorthy V et al. Duration of Electrocardiographic Monitoring of Emergency Department Patients With Syncope. Circulation. 2019 Mar 12;139(11):1396-1406 [pubmed]
Study Design
With the goal of informing decisions regarding duration of monitoring for patients presenting to the ED with syncope, the authors designed a prospective observational study in which they enrolled adult patients (≥16 years old) presenting within 24 hours of syncope at 6 large EDs in Canada. Exclusion criteria were: prolonged LOC [>5 minutes], mental status changes from baseline, obvious witnessed seizure, or head trauma causing LOC. Also excluded from the study were patients with major trauma requiring hospitalization and patients who could not provide an accurate history (e.g. language barrier, intoxication). The primary outcome was the incidence of serious arrhythmic outcomes (defined as serious arrhythmias, interventions for arrhythmias, and unexplained death) within the 30 days following ED visit. One of the secondary outcomes was to determine the optimal duration and location of electrocardiographic monitoring based on the time and place that the serious arrhythmia was identified.
Results
● Patients enrolled between September 2010 to March 2015
● 5,719 patients enrolled, 78.9% eligibility
● Median time to ED after syncopal episode was 1.1 hours
● 417 patients (7.5%; CI 6.8-8.2%) suffered serious outcomes
● Of these 417 patients, 207 (3.7%, 95% CI 3.3-4.2%) had serious arrhythmic outcomes
● For the purposes of this study, patients were classified as low-risk with a CSRS score between -3 and 0, medium risk for score of 1 to 3, and high risk for scores greater than or equal to 4
o 4,123 patients (73.9%) were classified as low-risk
o 1,062 (19.0%) were classified as medium-risk
o 396 (7.1%) were classified as high-risk
● The proportion of patients who suffered any serious outcome or arrhythmic outcomes increases significantly with the CSRS risk (log rank p<0.0001)
● After analysis, the authors found that 2 hours for low-risk, and 6 hours for medium and high-risk patients were the optimal cut-points for ED monitoring
● Half of serious arrhythmic outcomes occurred within 6 hours of ED arrival, regardless of CSRS score
● Of low-risk CSRS patients, 0.2% experienced arrhythmic outcomes beyond 2 hours of observation
Key Limitations
● Approximately one-fifth of potentially eligible patients were not enrolled
● Approximately one-fourth of patients did not have a recorded time of syncope
Figure 1. The Canadian Syncope Risk Score (CSRS)
* Triggered by being in a warm, crowded place, prolonged standing, fear, emotion or pain
† Includes coronary or valvular heart disease, cardiomyopathy, congestive heart failure and non-sinus rhythm (electrocardiogram evidence during index visit, documented history of ventricular or atrial arrhythmias, or device implantation).
‡ Includes blood pressure values from triage until disposition from the emergency department
§Shrinkage-adjusted expected risk
Author’s conclusions
“In this large multicenter prospective study, among ED patients presenting with syncope who did not have an obvious serious condition identified on arrival, underlying arrhythmia is most often identified in the first 2-hours for CSRS low-risk patients, and in the first 6-hours for CSRS medium and high-risk patients. A short course of hospitalization may be appropriate for high-risk patients. Outpatient cardiac rhythm monitoring for 15 days should be considered for medium-risk patients and all high-risk patients discharged from the hospital. Such a strategy appears to represent an appropriate trade-off between diagnostic yield for arrhythmia and health resource utilization and will lead to improved detection of underlying important arrhythmias.”
Our conclusions:
Risk stratifying syncope patients in the ED remains a difficult task. However, the results of this study illustrate the utility of the CSRS and its ability to differentiate low-risk and high-risk patients, giving a guide to observation practices. Overall, I would say the low-risk patient data was most useful in that only 0.2% of patients experienced an arrhythmic event after the 2 hour mark, well within an acceptable threshold in my opinion. The medium and high-risk patient data is less useful in determining an appropriate ED observation duration as 5% of medium risk and 18% of high-risk patients experienced serious arrhythmic outcomes after the 6 hour cut point suggested in the study. These numbers exceed an acceptable threshold of risk. I think, in general, the score will likely need some more external validation in different practice environments. However, I would consider using the CSRS in the appropriate setting for syncope patients, keeping in mind that no risk stratifying tool is perfect. Importantly, it must be remembered that this study focused only on serious arrhythmic outcomes, not all serious outcomes associated with syncope. While the CSRS may be a useful tool to guide observation for arrhythmic outcomes, the other serious conditions that can manifest with syncope must also be investigated as part of the emergency department evaluation.
To hear a more detailed discussion of our analysis and conclusions, please listen to the podcast below:
References:
[1] Thiruganasambandamoorthy V, Taljaard M, Stiell IG, et al. Emergency department management of syncope: need for standardization and improved risk stratification. Intern Emerg Med. 2015;10:619-27. [pubmed]
[2] Thiruganasambandamoorthy V, Hess EP, Turko E, Perry JJ, Wells GA, Stiell IG. Outcomes in Canadian emergency department syncope patients--are we doing a good job? J Emerg Med. 2013;44:321-8. [pubmed]
[3] Thiruganasambandamoorthy V, Kwong K, Wells GA, et al. Development of the Canadian Syncope Risk Score to predict serious adverse events after emergency department assessment of syncope. CMAJ. 2016;188:E289-E98. [pubmed]
[4] Del Rosso A, Ungar A, Maggi R, et al. Clinical predictors of cardiac syncope at initial evaluation in patients referred urgently to a general hospital: the EGSYS score. Heart. 2008;94:1620-6. [pubmed]
[5] Ammirati F, Colivicchi F, Santini M. Diagnosing syncope in clinical practice. Implementation of a simplified diagnostic algorithm in a multicentre prospective trial - the OESIL 2 study (Osservatorio Epidemiologico della Sincope nel Lazio). Eur Heart J. 2000;21:935-40. [pubmed]
[6] Costantino G, Casazza G, Reed M, et al. Syncope risk stratification tools vs clinical judgment: an individual patient data meta-analysis. The American journal of medicine. 2014;127:1126.e13-25. [pubmed]
[7] Quinn J, McDermott D, Stiell I, Kohn M, Wells G. Prospective validation of the San Francisco Syncope Rule to predict patients with serious outcomes. Ann Emerg Med. 2006;47:448-54. [pubmed]
[8] Solbiati M, Bozzano V, Barbic F, et al. Outcomes in syncope research: a systematic review and critical appraisal. Intern Emerg Med. 2018;13:593-601. [pubmed]
[9] Thiruganasambandamoorthy V et al. Duration of Electrocardiographic Monitoring of Emergency Department Patients With Syncope. Circulation. 2019 Mar 12;139(11):1396-1406. [pubmed]
Authors: Mike Burla MD and Jason Hine MD
Peer Review: Lauren Wendell MD
