Syncope Monitoring in ED: 2 Hours Okay for Low-Risk Patients

Nicola M. Parry, DVM

February 13, 2019

A 2-hour period of electrocardiogram (ECG) monitoring appears to be sufficient for low-risk patients who present to the emergency department (ED) with syncope, a study published online January 21 in Circulation shows.

"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 [Canadian Syncope Risk Score] low-risk patients, and in the first 6-hours for CSRS medium and high-risk patients," Venkatesh Thiruganasambandamoorthy, MBBS, University of Ottawa, Ontario, Canada, and colleagues write.

Syncope is a common reason for ED visits. Because of its wide-ranging causes, evaluation of syncope patients in the ED aims to rule out serious underlying conditions, such as arrhythmia.

However, research has suggested that ED evaluation fails to identify up to one half of serious conditions, particularly arrhythmias, which become evident only after discharge.

The optimal duration of cardiac rhythm monitoring for these patients, both in the ED and after discharge from the ED, is unknown.

With this in mind, Thiruganasambandamoorthy and colleagues conducted a study to determine the incidence and time to arrhythmia occurrence among patients with syncope who present to the ED.

"The ultimate goal was to provide guidance for decision regarding the duration and location of cardiac rhythm monitoring," they say.

The prospective cohort study was conducted at six EDs in Canada and included 5581 adults aged 16 years and older who presented within 24 hours of experiencing syncope. The researchers used the CSRS to stratify all patients with regard to risk and followed them for 30 days. The primary outcome was the occurrence of serious arrhythmic conditions.

Overall, 417 (7.5%) patients experienced serious outcomes, of which 207 (3.7%; 95% confidence interval [CI], 3.3% – 4.2%) were arrhythmic (161 arrhythmias, 30 cardiac device implantations, and 16 unexplained deaths).

On the basis of CSRS, 4123 patients (73.9%) were classified as low risk, 1062 (19.0%) as medium risk, and 396 (7.1%) as high risk.

The CSRS accurately stratified syncope patients as having low (0.4%), medium (8.7%), and high (25.3%) risk for 30-day arrhythmic outcome.

The researchers found that for monitoring syncope patients in the ED, 2 hours was the optimal cut-point for low-risk patients and that 6 hours was optimal for medium- and high-risk patients.

Among the 417 patients who experienced serious outcomes, about one half (232; 55.6%) of these outcomes were identified within 2 hours of arrival at the ED for low-risk patients, and within 6 hours for medium- and high-risk patients.

Overall, 13.1% of medium- and high-risk patients experienced arrhythmic outcomes within 30 days of visiting the ED; 91.7% of these (176 of 192) were identified within 15 days.

"[V]ery few (0.6%) patients, and no CSRS low-risk patients, suffered ventricular arrhythmia or died from an unknown cause within 30 days," the authors write.

In the study, the residual risk for arrhythmic outcomes was very low (0.2%) among low-risk patients after 2 hours of monitoring; it was 4.4% among medium- and high-risk patients after 6 hours of monitoring.

"The results of our study support brief monitoring in the ED for 2 hours for [CSRS] low-risk patients, and 6 hours for medium and high-risk patients, followed by selective admission," Thiruganasambandamoorthy and colleagues conclude.

"Our results also support 15-day outpatient monitoring for medium-risk patients at a selected threshold and all high-risk patients."

The study was supported by the Physicians' Services Incorporated Foundation, the Innovation Fund for Academic Health Sciences Centers of Ontario through the Ottawa Hospital Academic Medical Organization, the Canadian Institutes of Health Research, the Heart and Stroke Foundation of Canada, and the Cardiac Arrhythmia Network of Canada as part of the Networks of Centers of Excellence. The authors have disclosed no relevant financial relationships.

Circulation. Published online January 21, 2019. Abstract

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