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Circulation. 2019 Jan 21. doi: 10.1161/CIRCULATIONAHA.118.036088. [Epub ahead of print]

Duration of Electrocardiographic Monitoring of Emergency Department Patients with Syncope.

Author information

Department of Emergency Medicine, University of Ottawa, Canada.
Department of Emergency Medicine, University of Alberta, Canada.
Emergency Medicine, Queen's University, Canada.
Emergency Medicine, University of Calgary, Canada.
Emergency Medicine Research Group, Ottawa Hospital Research Institute, Canada.
Clinical Epidemiology Program, Ottawa Hospital Research Institute, Canada.
Ottawa Hospital Research Institute, Canada.
Medicine/ Cardiology, University of British Columbia, Canada.
School of Epidemiology, University of Ottawa, Canada.
Clinical Epidemiology, Ottawa Hospital Research Institute, Canada.



The optimal duration of cardiac rhythm monitoring following emergency department (ED) presentation for syncope is poorly described. We sought to describe the incidence and time to arrhythmia occurrence to inform decisions regarding duration of monitoring based on ED risk-stratification.


We conducted a prospective cohort study enrolled adult (≥ 16 years) patients presenting within 24-hours of syncope at 6 EDs. We collected baseline characteristics, time of syncope and ED arrival, and the Canadian Syncope Risk Score (CSRS) risk category. We followed subjects for 30-days and our adjudicated primary outcome was serious arrhythmic conditions (arrhythmias, interventions for arrhythmias and unexplained death). After excluding patients with an obvious serious condition on ED presentation and those with missing CSRS predictors, we used Kaplan-Meier analysis to describe the time to serious arrhythmic outcomes.


5,581 patients (mean age 53.4 years, 54.5% females, 11.6% hospitalized) were available for analysis, including 346 (6.2%) for whom the 30-day follow-up was incomplete and were censored at the last follow-up time. 417 (7.5%) patients suffered serious outcomes of which 207 (3.7%; 95% CI 3.3%, 4.2%) were arrhythmic (161 arrhythmias, 30 cardiac device implantations, 16 unexplained death). Overall, 4123 (73.9%) were classified as CSRS low-risk, 1062 (19.0%) medium and 396 (7.1%) high-risk. The CSRS accurately stratified subjects as low (0.4% risk for 30-day arrhythmic outcome), medium (8.7% risk) and high-risk (25.3% risk). One-half of arrhythmic outcomes were identified within 2-hours of ED arrival in low-risk and within 6-hours in medium and high-risk patients and the residual risk after these cut-points were 0.2% for low-risk, 5.0% medium and 18.1% high-risk patients. Overall, 91.7% of arrhythmic outcomes among medium and high-risk patients including all ventricular arrhythmias were identified within 15-days. None of the low-risk patients suffered ventricular arrhythmia or unexplained death while 0.9% medium-risk and 6.3% of high-risk patients suffered them (p<0.0001).


Serious underlying arrhythmia was often identified within the first 2-hours of ED arrival for CSRS low-risk patients, and within 6-hours for CSRS medium- and high-risk patients. Outpatient cardiac rhythm monitoring for 15-days for selected medium-risk patientsand all high-risk patients discharged from the hospital should also be considered.


ED monitoring; acute management; cardiac rhythm monitoring; outpatient cardiac rhythm monitoring; risk stratification

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