Background: Syncope is a common symptom with rising incidence, often leading to emergency department (ED) visits. Early determination of diagnosis is often difficult in patients with syncope and there is an unmet clinical need for tools that can support physicians in their decision making. We hypothesized that an electrocardiogram (ECG)-based cardiac syncope risk calculator might create a simple and attractive clinical decision tool for the diagnosis and risk stratification of patients with syncope.

Methods: Based on a large prospective diagnostic international multicenter study enrolling patients who presented to the ED with syncope, we derived a cardiac syncope risk calculator by penalized stepwise backward-selection and multivariable logistic regression utilizing predefined ECG criteria. Primary diagnostic endpoint was cardiac syncope, as adjudicated by two independent physicians taking into account all available information including cardiac work-up and 12-month follow-up. Major adverse cardiac events (MACE) including life-threatening arrhythmias, myocardial infarction, pulmonary embolism, stroke, transient ischemic attack, valvular surgery, and death within 30 days were the prognostic endpoint.

Results: Median age in our cohort was 71 years and 40% of patients were women. Of all 2007 patients enrolled, 1696 patients were eligible for the prognostic analysis and 1550 patients were eligible for the diagnostic analysis.

We identified seven ECG criteria (rhythm, heart rate, corrected QT-interval, ST-segment depression, atrioventricular-block, bundle-branch-block and ventricular extrasystole/non-sustained ventricular tachycardia) as significant predictors for cardiac syncope and combined them into the bAseL Ecg Risk calculaTor for Cardiac Syncope (ALERT-CS). Diagnostic accuracy for cardiac syncope, as quantified by the area under the receiver operating characteristic curve (AUC), was high (AUC 0.80, 95%-confidence interval (CI) 0.77 to 0.83), and significantly higher compared to that of the EGSYS score (AUC 0.73, 95%-CI 0.70 to 0.76, p<0.001). Prognostic verification of the ALERT-CS to predict 30-day overall MACE showed similar accuracy (AUC 0.75, 95%-CI 0.71 to 0.79).

Conclusion: Combining seven ECG criteria within a simple risk calculator for cardiac syncope may aid physicians in the diagnosis and risk stratification of patients presenting to the ED with syncope.