Validation of the Canadian syncope risk score in a large prospective international multicenter study
Authors: Zimmermann T , Du Fay De Lavallaz J , Florez D , Widmer V , Freese M , Walter J , Lopez-Ayala P , Belkin M , Boeddinghaus J , Nestelberger T , Badertscher P , Lohrmann J , Twerenbold R , Kuehne M , Mueller C 
Published: November 2020

Abstract

Background
Management and risk stratification of patients with syncope in the emergency department (ED) is often challenging. In an effort to support ED physicians in disposition decisions, the Canadian Syncope Risk Score (CSRS) was developed to predict 30-day serious outcomes.

Methods
The CSRS was developed in a Canadian multicenter study and contains nine predictors: predisposition to vasovagal syncope, heart disease, systolic pressure &lt;90 or &gt;180mmHg in the ED, troponin level &gt;99th percentile, abnormal QRS axis, QRS duration &gt;130ms, QTc interval &gt;480ms and an ED diagnosis of vasovagal or cardiac syncope. Patients can achieve a CSRS score between −3 and +11 points. We validated the CSRS in a large prospective international multicenter study recruiting patients 40 years or older presenting to the ED with a syncopal event within the last 12 hours. Recruitment centers contained smaller provincial hospitals, as well as big University Hospitals in eight countries on three continents. Primary outcome measure were 30-day serious arrhythmic and non-arrhythmic adverse events, as defined by the authors of the original score.

Results
1581 patients were eligible for this analysis. The population in this validation cohort was older (mean age 68 vs 54 years) and had a considerably higher rate of serious outcomes compared to the derivation cohort (n=186 (11.8%) vs n=147 (3.6%)). The area under the receiver operating characteristic curve (AUC) for the CSRS was 0.88 (95% confidence interval (CI) 0.86–0.91) and significantly higher compared to the validated OESIL score (AUC 0.75, 95% CI 0.71–0.78, p&lt;0.001). Calibration curve analysis showed an underestimation of risk in patients with a low CSRS and an overestimation in patients with a high CSRS. The rate of observed serious outcomes within 30d increased from 0.8% in the very low risk group (CSRS equal to or below −2) to 48% in the (very) high risk group (CSRS equal to or above 4, Hazard ratio 79.4, 95% CI 11.1–570.9). A Kaplan-Meier plot was used to visualize rates of serious outcomes in three different risk groups (Figure).

Conclusion
This is the first validation of the Canadian Syncope Risk Score in a large international syncope cohort. The prognostic discrimination of the CSRS for 30-day serious outcomes was very good in our validation cohort and comparable to that of the Canadian derivation study. Despite suboptimal calibration, prognostic analysis showed a high rate of serious outcomes in the CSRS (very) high risk group and a low rate of serious outcomes in the very low risk group. Allowing the clinical judgement of the ED physician in the form of suspected syncope etiology to be a part of the score seems to largely contribute to the high performance of the CSRS. Additional validation studies might be needed to further increase the accuracy of the CSRS in different patient populations with a different incidence of outcomes in settings outside of Canada.
Figure 1

Funding Acknowledgement
Type of funding source: Public grant(s) – National budget only. Main funding source(s): Swiss National Science Foundation; Swiss Heart Foundation